Mineralogy of Jadeitite and Related Rocks From Myanmar

Mineralogy of jadeitite and related rocks from Myanmar:

a review with new data

GUANGHAI SHI1,2,*, GEORGE E. HARLOW2, JING WANG1, JUN WANG1, ENOCH NG1, XIA WANG1, SHUMIN CAO3

and WENYUAN CUI4

1 State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences,Beijing 100083, PR China

2 Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY 10024-5192, USA*Corresponding author, e-mail: [email protected]; [email protected]

3 Guangdong Province Material Testing Center, Guangzhou 510080, PR China4 School of Earth and Space Sciences, Peking University, Beijing 100871, PR China

Abstract: The jadeitite from Myanmar is the most important commercial source on Earth, and its mineralogy perhaps the mostdiverse. More than thirty mineral species, including jadeite, omphacite, kosmochlor, Cr-bearing jadeite-omphacite, albite, celsian,banalsite, hyalophane, nyboite, eckermannite, magnesiokatophorite, glaucophane, richterite, winchite, analcime, natrolite, thomso-nite-Ca, pectolite, vesuvianite, titanite, grossular, uvarovite, allanite, phlogopite, cymrite, zircon, graphite, quartz, diaspore, kaolinite,pyrite, galena, chromite, and ilmenite have been documented from these jadeitites and related rocks, which we review and update.Phlogopite, natrolite, thomsonite-Sr, titanite and ilmenite are newly reported here. Amphiboles, kosmochlor and omphacite formedclosely related to the paragenetic sequence in the presence of jadeite; however, uvarovite is formed by replacement of chromite anddoes not require the presence of jadeite. At least two stages of jadeitization have been identified for Myanmar jadeitite. Late-stagezeolites, pectolite and hyalophane, banalsite, titanite and some celsian formed at lower P and T. The spectrum of minerals in Myanmarjadeitite indicates that the jadeite-forming fluids were rich in Na, Al, Ba, Sr, and Ca. Moreover, the variety of replacement texturessuggests that most rocks in the serpentinite melanges were subject to infiltration and potential replacement by jadeitite or reactionwith jadeitite. Serpentinite was replaced by sodic to sodic-calcic amphibole, chromite in ultramafic rock by kosmochlor and Cr-bearing jadeite, and the clinopyroxene in mafic rock by omphacite. Relict ilmenite replaced by titanite in omphacitite is evidence formetasomatism of mafic rock. Sodium-rich fluids were likely dominant throughout jadeitite crystallization and metasomatic reactions.A general mineralogical comparison of jadeitites world-wide indicates both similarities and distinctions; these could be used forinterpreting sources of the jadeite jade, particularly in archaeology.

Key-words: jadeitite, fluid-rock interaction, serpentinite, metasomatism, mineral diversity, subduction, Myanmar.

1. Introduction

Jadeitite is a rock composed almost entirely of jadeite andrelated pyroxene, which is found in serpentinite melangeassociated with high-pressure low-temperature (HP/LT)metamorphosed rock, such as eclogite and blueschist.Jadeitite is interpreted as a product of subduction; however,it is rare world-wide and found only at �19 locations (e.g.,Essene, 1967; Chihara, 1971; Harlow, 1994; Shi et al.,2001; Tsujimori, 2002; Tsujimori et al., 2005; Harlowet al., 2003, 2007, 2012; Harlow & Sorensen, 2005;Sorensen et al., 2006; Compagnoni et al., 2007; Garcia-Casco et al., 2009; Schertl et al., 2012; Tsujimori &Harlow, 2012), and much rarer than either HP/LT eclogiteor blueschist. Considerable progress has been maderecently in the interpretation of jadeitite petrogenesis anddiscovery of new occurrences, as noted in the citations

above. The largest and commercially most important sourceof jadeitite on the planet is the so-called Jade Mine Tract,Kachin State, northern Myanmar (a.k.a. Burma), wheresome classic relationships are preserved. However, it hasnot been as well documented recently as it deserves, largelyowing to the difficulty of obtaining access to the deposits.

Classic relationships were described over 100 years agoby Bauer (1895), Noetling (1893, 1896) and Bleeck (1907,1908), but the most important overall review is made byChhibber (1934). These works defined the basic lithologiesas jadeitite, albitite, amphibole-rich rocks and serpentinite.More recent studies of Myanmar jadeitite have identifiedmany minerals, some with unusual chemical compositionsand/or textures (e.g., Mevel & Kienast, 1986; Shi et al.,2005a, 2005b, 2009a, 2010, 2011; Nyunt et al., 2009), aswell as six species of amphibole, terrestrial kosmochlor andomphacite (Ou Yang, 1984; Harlow & Olds, 1987; Shi et al.,

Jadeitite:new occurrences, new data,

new interpretations

0935-1221/12/0024-2190 $ 11.70DOI: 10.1127/0935-1221/2012/0024-2190 # 2012 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart

Eur. J. Mineral.

2012, 24, 345–370

Published online January 2012

2003, 2005a; Yi et al., 2006). In a comparison of jadeititesworld-wide, Sorensen et al. (2006) argued that Myanmarjadeitite is most likely a crystallization product of subduc-tion channel fluids, as with jadeitite from other deposits theystudied. Methane (CH4) bearing fluid inclusions in theMyanmar jadeitite identified by Shi et al. (2005b) supporta channel origin and suggest a reducing characteristic of thefluid. Research on zircons in jadeitite from Myanmar (Shiet al., 2008), as well as those from Guatemala and Japan (Fuet al., 2010), indicate that they may be either inherited byrapid reworking of basaltic oceanic crust, based on thehighly depleted-mantle eHf(t) values (Qiu et al., 2009; Shiet al., 2009a), or be primary crystallization products from afluid as suggested by low Th/U ratios and fluid inclusions(Yui et al., 2010, 2012), or may even have multiple origins(Fu et al., 2010; Mori et al., 2010, 2011).

Our recent work on rocks associated with jadeitite inMyanmar reveals several occurrences of rare minerals thathave not been previously reported. In this paper we presentour new findings within the context of a mineralogicalreview and discuss mineral origins based on parageneticrelationships. Relevant mineral formulae and abbrevia-tions are list in Table 1.

2. Geological setting

Jadeitite is found along the western boundary of theSagaing fault zone as boulders in drainages and the Uruconglomerate and as tectonic blocks or veins in serpenti-nite melange at the Jade Mine Tract, near Hpakan, Kachinstate (Fig. 1a), where basement rocks are exposed throughthe sediments of the Chindwin, Irrawaddy and Hukawngbasins (Mitchell et al., 2007). The Tract is associated withfragments of an ophiolite or serpentinite melange that hasbeen interpreted as a Late Cretaceous (?) collision zonebetween the West Burma Plate and Shan-Thai block, butmore recently as an exhumation resulting from transpres-sional deformation of the Shan-Thai block and the trans-form-like motion along the Indus-Yardang suture adjacentto the Indo-Burman Range (cf. Morley, 2004). This Rangeto the west of the Jade Mine Tract covers an area betweenthe Myanmar Central Basin and the western border withIndia. The Sagaing fault is a major right-lateral strike-slipcontinental fault, extending over 1200 km, which reachesthe Andaman spreading centre at its southern end and is themodern expression of the transform motion. The rocks inthis range are progressively younger from east to west.

Dating of rocks from the Jade Mine Tract has been animportant goal for understanding both the evolution of thejadeitite and the history of the melange. Zircon crystalsoccurring in the Jade Tract jadeitites have been studied,including U-Pb dating by SHRIMP, to elucidate moreabout the geochronology (Shi et al., 2008). There are twoimportant groups of zircon grains with different interiorcharacteristics, cathodoluminescence, mineral inclusions,and chemical compositions. Group-I zircons generallyhave oscillatory zoning, high U and Th contents, and Na-

free, Mg-rich mineral inclusions, and a mean age of 163.2� 3.3 Ma. Group-II zircons have bright luminescencewithout oscillatory zoning, jadeite and jadeitic pyroxeneinclusions, lower U and Th contents and a mean age of146.5 � 3.4 Ma. Because of the oscillatory zoning, Mg-rich inclusions typical of a mafic to ultramafic association,Group I zircons were interpreted as igneous (oceanic crust)or hydrothermal (serpentinization and/or rodingitization)in origin from the oceanic crust during the Middle Jurassic.Group II with inclusions consistent with crystallizationcoeval with jadeitite thus formed during active subductionin the Late Jurassic. Thus, from this interpretation, somezircons are inherited while others are primary, crystallizedduring jadeitite crystallization. The average of all Group-Iand II ages of 157.4 � 3.8 Ma (Shi et al., 2008) is nearly

Table 1. Mineral formulae and abbreviations used in this paper.

Name Abbreviations Formulae

Aegirine Aeg NaFeSi2O6

Albite Ab NaAlSi3O8

Allanite Aln Ca(REE,Ca)Al2(Fe2þ,Fe3þ)(SiO4)(Si2O7)O(OH)

Amphibole Amp A B2 C5 T8 O22 W2

(generalized formula)Analcime Anl NaAlSi2O6�H2OAnorthite An CaAl2Si2O8

Augite Aug (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6

Banalsite Ban BaNa2Al4Si4O16

Celsian Cls BaAl2Si2O8

Chromite Chr FeCr2O4

Cymrite Cym BaAl2Si2O8.H2ODiopside Di CaMgSi2O6

Eckermannite Eck NaNa2(Mg4Al)Si8O22(OH)2

Glaucophane Gln &Na2(Mg3Al2)Si8O22(OH)2

Grossular Grs Ca3Al2Si3O12

Hyalophane Hy (K,Ba)Al(Si,Al)3O8

Ilmenite Ilm FeTiO3

Jadeite Jd NaAlSi2O6

Kosmochlor Kos NaCrSi2O6

Magnesiokatophorite Mkt Na(CaNa)(Mg4Al)Si7AlO22

(OH)2

Natrolite Ntr Na2(Al2Si3)O10�2(H2O)Nyboite Nyb NaNa2(Mg3Al2)Si7AlO22

(OH)2

Omphacite Omp (Ca,Na)(Mg,Fe2þ,Al)Si2O6

Orthoclase Or KAlSi3O8

Pectolite Pct NaCa2Si3O8(OH)Phlogopite Phl KMg3(Si3Al)O10(OH, F)2

Richterite Rct Na(CaNa)Mg5Si8O22(OH)2

Thomsonite-Ca Thm NaCa2Al5Si5O20�6H2OThomsonite-Sr Thm-Sr Na(Sr,Ca)2Al5Si5O20�6H2OTitanite Ttn CaTiSiO5

Uvarovite Uv Ca3Cr2(SiO4)3

Vesuvianite Ves (Ca,Na)19(Al,Mg,Fe)13

(SiO4)10(Si2O7)4

(OH,F,O)10

Winchite Wnc &(CaNa)(Mg4Al)Si8O22

(OH)2

Zircon Zrn ZrSiO4

Note: Mineral abbreviations mainly according to Whitney & Evans(2010).

346 G. Shi, G.E. Harlow, J. Wang, J. Wang, E. Ng, X. Wang, S. Cao, W. Cui

identical to the ungrouped U-Pb ages of 158 � 2 Ma forzircons in jadeitite from the same locality using LA-MC-ICPMS techniques by Qiu et al. (2009).

Primary jadeitite deposits occur as massive veins cross-cutting serpentinized peridotites that belong to theHpakan-Tawmaw serpentinite melange (Fig. 1b).Country rocks adjacent to the melange include phengite-bearing glaucophane schists and stilpnomelane-bearingquartzites, as well as amphibolite-facies rocks such asgarnet-bearing amphibolites and diopside-bearing marbles(Shi et al., 2001). The primary discontinuous veins ofjadeitite also occur in serpentinized peridotite at severalother areas (Chhibber, 1934). At Tawmaw, ‘‘dikes’’ areparallel to shear zones following northeasterly strikes withdips from 18� to 90�SE (Hughes et al., 2000, and refer-ences therein). Dike thicknesses are poorly reported, prob-ably because of weathering and their irregular swelling,pinching, and faulting-off; however Soe Win (1968) gave awidth of 1.5–2.5 m for the Khaisumaw dike at Tawmaw.Recently Nyunt (2009) described that jadeitite occurs asvein-like bodies about 15 � 6 � 9 m in the Natmaw area(Nantmaw #109 mine) and about 3 � 3 � 2 m at the JadeLand worksite at Tawmaw. The second author visited theNatmaw mine in 2002 and observed an ellipsoidal body,like a boudinage, tapering into a centimeters thick vein atone end (source of MJE02-3 samples). Nyunt (2009)described that jadeitite, albite-jadeite rocks, albitite, chlor-ite schist, actinolite schist and amphibole felses were foundwithin the serpentinized peridotite (mainly dunite), and

that some veins contain only jadeite and albite, whileothers have a boundary zone (on one or both sides) ofamphiboles, such as eckermannite and glaucophane (darkgray to blue-black) or actinolite (dark green). The bound-ary with serpentinite is marked by a soft, green border zonethat consists of a mixture of the adjacent vein minerals andchlorite, with or without calcite, actinolite, talc, and chertymasses (Chhibber, 1934; Soe Win, 1968), i.e., a blackwallassemblage. Serpentinite conglomerate units in fault con-tact with the serpentinite melanges contain jadeititeboulders, cobbles and pebbles that are also mined aroundHpakan and about 60 km west of Hpakan at Nansibon (AveLallemant et al., 2000; Goffe et al., 2000; Hughes et al.,2000; Harlow & Sorensen, 2005). Jadeitite-bearing con-glomerates also extend from Monhyn (Thin, 1985) toIndaw-Tigyaing (United Nations, 1979), �100–230 kmsouth of Hpakan, along the Sagaing fault.

In the classic work by Bleeck (1908) a jadeitite veinsystem (described then as a dike) at Tawmaw had a foot-wall boundary zone between the serpentinized peridotitebody and jadeitite-albitite vein (see fig. 7–2 and Plate 7-2cin Harlow et al., 2007). Located within or associated withthe amphibole boundary, kosmochlor, chromian jadeiteand some chromian omphacite occur as coronal aggregateswith or without a chromite core or as small blocks (Shiet al., 2005a). Small blocks of omphacitite have also beenfound (Yi et al., 2006). The jadeitite veins are crosscutlocally by thin late-stage albite veins, which are commonlyless than 5 mm wide. In addition, accessory minerals such

Fig. 1. (a) Geological overview of the Myanmar area, showing the Jade Mine Tract. (b) Geological sketch map of the Myanmar Jade MineTract (modified after Bender (1983), and Morley (2004)).

Mineralogy of jadeitite and related rocks from Myanmar 347

as zircon, pyrite and galena also occur in jadeitite (Harlowet al., 2007; Shi et al., 2008). Jadeitite-related rocks in thepresent investigation refer to rocks adjacent to jadeititeveins or blocks within the serpentinized ultramafic rocks,including amphibole rock, omphacitite, kosmochlor rock,albitite and possible others.

Newly studied samples, collected by GHS and by GEH(MJE02 samples are in the petrology collection of theAmerican Museum of Natural History), include a darkgreen jadeitite (sample No. K068), white jadeitites (sampleNo. D, 8-4, FC-1), black omphacitites (sample No. YX-1,Rma), kosmochlor rocks (sample No. K13, K15A, WM1),jadeitite-amphibolite (sample No. 012), white-gray albi-tites (sample No. D2, WJ-1, WJ-3), albitite-jadeititeboundary (sample No. Ab-Jd-01), jadeitized rodingite(sample No. 22), and white-grayish zeolite-predominantrocks at the pinching out of a jadeitite vein (sample No.MJE02-3-6 and MJE02-3-9).

3. Lithological features

3.1. Lithological variations of jadeitite and relatedrocks

Jadeitite occurs as veins and blocks and is associated withomphacitite, kosmochlor rock, jadeitized rodingite, amphi-bolites (sodic-calcic amphiboles mostly) and albitite,either as enclosed selvages or boundary assemblages.Most jadeitite is white (Fig. 2a), but other colors includegreen (Fig. 2b), purple/lavender, and occasionally gray-to-black. Ochre to brown coloring is due to staining fromsurface exposure. Jadeitite consists primarily of jadeitewith minor accessory minerals such as omphacite, amphi-bole, albite, analcime and zircon, etc. Deformation is acommon feature, sometimes approaching mylonitic tex-ture, with recrystallization and fluid infiltration crystal-lization responsible for rock cohesion (Sorensen et al.,2006). Undeformed jadeitite selvages are occasionallyretained even in highly deformed samples (Shi et al.,2009b). Veining and cavity clusters of jadeite in jadeititeare a common, late-stage feature (Fig. 2a, b).

Omphacitite is dark green to black and typically occurs asboulders (Fig. 2c). It is typically composed of omphaciteand jadeite with minor titanite, phlogopite, albite, ilmenite,amphibole, zircon, and vesuvianite, a Ba-Sr-bearing mineraland zeolite (e.g., Yi et al., 2006). Most omphacitite is fine-grained and may show a replacement texture of omphaciteby jadeite and may even be cut by jadeite veins.Unfortunately, a direct contact between jadeitite andomphacitite has not been observed. Kosmochlor rock isdark green and occurs together with jadeitite (Fig. 2b, d).It is composed of kosmochlor, jadeite, and Cr-bearingjadeite, with minor chromite, albite, sodic amphibole �uvarovite � clinochlore � natrolite (Mevel & Kienast,1986; Harlow & Olds, 1987; Colombo et al., 2000;Hughes et al., 2000). Jadeitized rodingite consists of ompha-cite, garnet and jadeite, with minor allanite-(La), phlogopite,

zeolite, chlorite, and barian mineral (Li, 2003; Wang et al.,2012). Its fresh surfaces have green to dark green (pyroxene)color with areas of light yellow-gray (garnet). This rock israre and only one piece has been found as a small weatheredblock from eluvium near Hpakan city. Amphibolite appearsgreen to black (Fig. 2b, e, f), consisting principally of sodicto sodic-calcic amphiboles identified as eckermannite, mag-nesiokatophorite, nyboite, glaucophane, richterite andwinchite (Shi et al., 2003). Albitite is transparent and color-less to opaque and white (Fig. 2f), consisting primarily ofalbite with possible thomsonite-Ca, pectolite, vesuvianite,hyalophane, cymrite, and celsian.

3.2. Metasomatic reaction zones and zonations

Primary jadeitite veins occur in serpentinite with albititeand/or amphibolite boundaries, as illustrated by Bleeck(1907) and in fig. 2 of Shi et al. (2008). Additionally,some jadeitite blocks are made up of broken jadeitite frag-ments in a matrix of amphibole/amphibolite (Fig. 2e),whereas others consist of foliated jadeite aggregates (Fig.2b, f) due to deformation events, both syn- and post-

Fig. 2. (a) A cluster of euhedral jadeite crystals (Jd-II) formed onfine-grained jadeite aggregate (Jd-I, assuming Jd-I precedes Jd-II)from Myanmar (sample R2, height�10 cm). (b) Comb-like structureof jadeite aggregates (Jd-II) on deformed jadeitite base (Jd-I) fromMyanmar (Sample 012, width �15 cm). (c) Omphacitite boulder(sample Rma, width �10 cm). (d) Kosmochlor rock and jadeitite(width�16 cm). (e) Crushed jadeitite fragments filled by amphibolematrix (width �20 cm each). (f) Later stage albitite vein cuttingthrough jadeitite, omphacitite, amphibole rock and/or kosmochlorrock (sample Ab-Jd01, width �30 cm).


crystallization of the jadeitite. Textural observations sug-gest that amphibole forms during fluid infiltration into thecontact zone between the jadeitite bodies and the surround-ing ultramafics at high-pressure conditions by means ofmetasomatic reaction (see Shi et al., 2003). Kosmochloraggregates occasionally occur as broad bands outside thejadeitite vein (Fig. 2d), or mostly as small isolated augen orzones between amphibolite bands and jadeitite veins (Fig.2b). They also often occur as a string of small roundedspherules or elongated aggregates wrapped within jadeititeand amphibolite. Between kosmochlor and jadeite zonesthere usually exists a sharp compositional boundary. Thepreservation of relict chromite in the core of kosmochlorand chromian jadeite indicates a metasomatic origin from aperidotite protolith, which was infiltrated by an aqueoussolution rich in Na, Al, and Si (Mevel & Kienast, 1986;Harlow & Olds, 1987; Shi et al., 2005b).

3.3. Mineralogical diversity

More than thirty mineral species have been identified in theMyanmar jadeitite and closely related rocks. A few arerelict minerals from protoliths (e.g., chromite, ilmenite,and possibly zircon), but most are either vein crystalliza-tion or metasomatic reaction products. The latter includepyroxenes (jadeite-omphacite series pyroxenes and Cr-bearing pyroxenes), amphiboles (sodic, sodic-calcic, andcalcic amphiboles), phlogopite, vesuvianite, garnet, feld-spars, zeolites, sulfide minerals and a few other minerals.

Most minerals are Na-dominant to Na-bearing species,even those that are nominally Na-free, such as vesuvianiteand uvarovite, in which small amounts of Na have beenmeasured (e.g., Nyunt et al., 2009). The Na-dominant sili-cate minerals can be divided into five subgroups which areeither Al-, Mg-, Cr-, Ca- or (Ba, Sr)-dominant (Table 2).Jadeite and albite are the two main and abundant minerals inthe Al-dominated subgroup. Albite, together with analcimeand natrolite in the same subgroup, formed later at lowerpressure. Six species of amphibole, typically mixed in com-plexly zoned samples, constitute most of the Mg-dominantsubgroup; they are considered metasomatic reaction pro-ducts between a fluid rich in Na, Al and serpentinizedultramafic rocks (e.g., Shi et al., 2003) at HP conditions.Kosmochlor and Cr-bearing jadeite-omphacite are theminerals in the Cr-dominant series, which have been inter-preted as metasomatic reaction products of chromite withjadeitic fluids under HP conditions (e.g., Harlow & Olds,1987; Ouyang, 2001; Shi et al., 2005a); chromian amphi-boles are also a part of the group; although they are Mg-rich,the relevant crystallographic site for Cr is dominantly occu-pied by it. The chromian amphiboles are also the result ofreactions between fluid and ultramafic (Mevel & Kienast,1986; Harlow & Olds, 1987). In the Ca- and (Ba, Sr)-dominant series, the minerals formed at low P conditions,generally after jadeite (omphacite, which may be consideredto belong to several groups, may have formed before or afterjadeite). The abundance of Na-dominant silicate mineralsclearly reflects the influence of the fluid composition and its

capacity to crystallize and/or react with minerals of thesubduction channel and overlying ultramafic rocks.

The Na-poor or Na-absent silicate group can be dividedinto four subgroups: Ca-, K-, (Ba, Sr)-dominant and alkali-or alkali-earth-free (Table 2). In the Ca-dominant sub-group, uvarovite, grossular and allanite possibly formedbefore jadeite and may be related to mantle metasomatismor oceanic hydration prior to subduction. Titanite formed atthe expense of ilmenite (or possibly rutile, although it hasnot been reported in Myanmar jadeitite) and is texturallypost-jadeite in Myanmar. Vesuvianite occurs in late-stagevein fillings. Thus there are at least two stages of Ca-dominant mineral formation in the Myanmar jadeitite. Inthe (Ba, Sr)-dominant series, celsian in chromian jadeitereplaces a precursor Ba mineral (Shi et al., 2005a), sominerals of this subgroup may have formed before, during,or after the main formation of jadeite, although the mostcommonly observed textures suggest late-stage formation.Among the silicates without alkalis or alkaline earths,the only generalizations are for the clay and clay-likespecies that formed during weathering. Ilmenite is clearlyinherited; quartz is very rare but potentially inherited,primary or secondary, and zircon can be both inheritedand primary.

Finally, there are the non-silicates which have individualcharacteristics. Sulfides can form at any time but appear tobe late. Chromite derives from the overlying ultramaficsand the�100 mm iron spherules sheathed in wustite appearto be inherited from sea-floor sediment (Shi et al., 2011).Small black carbonaceous inclusions have not been studiedsufficiently to know whether it is inherited organic matteror primary graphite crystallized from a fluid.

The mineralogical diversity in Myanmar jadeitite-related lithologies reflects the complexity of subductionchannel – melange constituents and the fluid-rock interac-tions during the complex dynamic evolution of the rocks,

Table 2. A simplified grouping of minerals in the Myanmar jadei-tites and related rocks according to chemical composition.

Group Subgroup Minerals

Na-rich Al-dominant Jadeite, albite, analcime, natrolite,omphacite

Mg-dominant Nyboite, eckermannite, glaucophane,magnesiokatophorite, richterite,winchite, omphacite

Cr-dominant Kosmochlor, Cr-bearing jadeite-omphacite, Cr-rich eckermannite,glaucophane, nyboite, andkatophorite

Ca-dominant Thomsonite-Ca, pectolite(Ba, Sr)-dominant Banalsite, thomsonite-Sr

Na-poor orabsent

Ca-dominant Vesuvianite, titanite, grossular,uvarovite, allanite

K-dominant Phlogopite, hyalophane(Ba, Sr)-dominant Hyalophane, cymrite, celsianOthers Zircon, quartz, diaspore, kaolinite,

ilmeniteNon-

silicatesPyrite, galena, chromite, graphite,

iron spherule


from sea floor through subduction and exhumation toweathering.

3.4. Bulk-rock compositions

Unfortunately whole-rock chemical analysis has only beencarried out on samples of white jadeitite from Myanmar (Shiet al., 2008). Trace elements display U-shaped REE patternswith pronounced positive Eu anomalies, very low total REEabundances, moderate enrichment of high field strengthelements Ti, Zr, and Hf and large ion lithophile elementsPb, Ba, Sr, as well as Li. These features indicate a metaso-matic origin (see Shi et al., 2008) or crystallization fromsuch a metasomatic fluid with a contribution from continen-tally derived sediments (e.g., Sorensen et al., 2006; Simonset al., 2010). In addition, Lu-Hf isotope analyses on zirconsin the jadeitite show positive eHf(t) values (eHf(t) ¼15.5–20.0). Such highly positive eHf(t) values for the jadei-tite zircons indicate their derivation from prompt reworkingof very juvenile crust and support the assumption of thepresence of Mesozoic intra-oceanic subduction within theIndo-Burman Range (see Qiu et al., 2009; Shi et al., 2009a).

4. Textures and mineral parageneses ofdifferent stages of mineralization

4.1. Formation and recrystallization of jadeitite

Jadeitites manifest both original crystallization and pro-nounced deformation textures. Undeformed jadeitite canbe granoblastic to feathery in microtexture and is found inprimary veins or as preserved zones in deformed jadeitite.Jadeite crystals are typically euhedral to subhedral and canbe very large in size, even reaching more than �5 cm longand �2 cm wide. Jadeite rims display growth zoning,commonly rhythmic in polarized light, back-scatteredelectron (BSE) or cathodomuminescence (CL) images(Fig. 3a, b; also see Shi et al., 2005b, 2009b). The zoningpatterns are similar to those described from other jadeititelocalities (Harlow, 1994; Sorensen et al., 2006; Garcia-Casco et al., 2009; Schertl et al., 2012).

Two-phase, gas/liquid fluid inclusions are common inundeformed jadeite grains, but rare in the deformed jadei-tite. They are interpreted as being primary because they areelongated parallel to the c-axis of the host jadeite crystalsand randomly distributed throughout the whole grains,rather than aligned along healed fractures. The inclusionscan be classified into two groups, either methane rich orpoor (Fig. 3c), reflecting the hydrothermal growth medium(see Shi et al., 2000m 2005b for details).

Deformed jadeitite from Myanmar contains crystalswith undulatory extinction in polarized light and hasclearly experienced shear stress. Microstructures of thejadeitites from Myanmar suggest that deformation andrecrystallization occurred heterogeneously at the expenseof the primary texture (Shi et al., 2009b). Deformed jadeitecrystals are smaller than the granoblastic grains, generally

showing variable preferred orientation of crystals,mechanical twinning, shear zones, development of sub-grains, serrated high-angle sutured grain boundaries, or a‘‘foam’’ pattern. The microstructure of the Myanmar jadei-tite has twofold significance both in gemology and inrheology. The most precious jadeite jades with high

Fig. 3. (a) Cathodoluminescence image showing oscillatory zoningof a coarse-grained jadeite from Myanmar (sample D). (b) Back-scattered electron (BSE) image showing that the rhythmic zonationof the jadeite crystals is an oscillatory variation in chemical compo-sition. (c) Photomicrograph of fluid inclusions in a jadeite crystalin a coarse-grained jadeitite (plane-polarized light; sample D).(d) Photomicrograph of curved mechanical twinning of a jadeitecrystal (crossed polarizers; sample No. 8-4).


translucency, termed as ‘‘icy’’ or ‘‘glassy’’ jades, havevery fine grain size and show pronounced microstructuralalignment, suggesting a close correlation between thedeformed microstructure and the appearance of the jadeitejade. Shi et al. (2009b) proposed a ‘‘uniform aggregatemodel’’ for the transparent jadeite jade: individual jadeitecrystals are small in size (so that the inherent cleavage willnot propagate), all grains have preferred orientation (sothat there is no or only infinitesimal variation in refractiveindex across the neighboring grains), and grain boundariesare very tight and narrower than the wavelength of visiblelight (letting light transmit through without scattering atgrain boundaries; see fig. 16 in Shi et al. (2009b)).

On the other hand, diverse microstructural characteris-tics of the Myanmar jadeitite prove themselves to be idealsamples for understanding HP/LT rheology in subductionzones. For example, natural mechanical jadeite twinninghas been found in UHP rocks and is regarded as the resultof syn-seismic loading below brittle-ductile transition con-ditions (Trepmann & Stockhert, 2001; Orzol et al., 2003).In Myanmar, mechanical twinning has occurred in bothpure jadeitite and in surrounding amphibolite, and sometwinned crystals have even been bent (Fig. 3d, also see fig.8 from Shi et al. (2009b)). Although macro- to microtex-tures appear to be ductile, all our P-T estimates argue forbrittle-dominant deformation, thus the twinning is possiblystrain induced as is evident from macrotextures and themelange source environment.

4.2. Multi-phase pseudomorphs

Multi-phase pseudomorphs (see fig. 3a of Shi et al. (2010))occur in chromian clinopyroxene rock composed predomi-nantly of chromian omphacite with minor sodic and sodic-calcic amphiboles and small disseminated multi-phase pseu-domorphs. Most multi-phase pseudomorphs with unde-formed hexagonal shapes 100–400 mm across formed notlater than the pyroxenes. According to Shi et al. (2010),multi-phase pseudomorphs can be classified into two typesin terms of celsian content: celsian-rich, and celsian-poor.The celsian-rich multi-phase pseudomorphs are composedof celsian and kaolinite with or without minor graphite anddiaspore. Textural relationships indicate that kaolinite andgraphite were formed subsequent to celsian crystallization.Diaspore crosscuts kaolinite, and formed as a later stage ofalteration. The celsian-poor multi-phase pseudomorphs aremade up of kaolinite, with minor celsian, graphite, diasporeand quartz. Celsian is surrounded by kaolinite. Diasporeoccurs as fibrous, silky or sheet-like grains crosscuttingkaolinite. Graphite is xenomorphic and occurs mainly inassociation with kaolinite. Quartz is 5–10 mm in size andfound surrounded by kaolinite in one multi-phase pseudo-morph. A reasonable explanation for the formation of themulti-phase pseudomorphs is the decomposition of a pre-cursor cymrite. Another possible model is that they representalteration products derived directly from fragments of barite-bearing oceanic sediment, but this explanation is not favored(Shi et al., 2010). Quartz and diaspore are more likely to be

formed by decomposition of the surrounding kaolinite (Shiet al., 2010) and after formation of the jadeitite.

4.3. Formation of later stage veins and hydrothermalalteration of HP minerals

There are at least two textural settings in the jadeitites;jadeitite-II occurs either as a cluster of prismatic crystals(Fig. 2a) or as comb-like aggregates (Fig. 2b) on jadeitite-I,which forms massive aggregates. Commonly jadeitite-IIcrystals appear as later-stage veins cutting jadeitite-I,reflecting at least two formation stages of the jadeitite.Albitite veins occur either as fine veins of less than 1 cmor as broad veins of more than 10 cm (Fig. 2f). The latervein cuts through surrounding rocks of jadeitite, amphibo-lite and kosmochlor rock, and often includes fragments ofthese surrounding rocks, suggesting an even later forma-tion relative to these surrounding rocks.

Hydrous minerals such as natrolite, analcime, thomso-nite-Ca, thomsonite-Sr, pectolite, vesuvianite and cymriteoften occur as late phases along jadeite grain boundaries,or as later-stage veins adjacent to or cutting the jadeitite.They represent hydrothermal alteration of previous HPminerals, and are inferred to have formed from residualor reworking fluids related to jadeite-forming fluids alongcracks of the jadeitite and related rocks.

5. Compositions of primary and metasomaticminerals

5.1. Analytical techniques

Optical and SEM/BSE petrographic and microprobe ana-lysis of thin sections and X-ray diffraction of mineralgrains were performed in this study. Minerals were ana-lyzed by electron microprobe in thin sections. As variousinstruments in different labs were utilized, the specifics ofeach are given in the Appendix, freely available online onthe GSW website of the journal, http://eurjmin.geoscien-ceworld.org/. Mineral formulae were normalized either toa number of oxygen or silicon atoms. Estimates of Fe2þ

and Fe3þ were made for some species (e.g., pyroxene andamphibole) using an algorithm similar in concept to that ofFinger (1972); details are given in Harlow et al. (2011).

5.2. Relict minerals

There are three minerals found in jadeitite and relatedrocks that are interpreted as the relics of a protolith fromthe subduction channel–mantle wedge: zircon, ilmenite,and chromite. Zircons from Myanmar jadeitite and ompha-citite (Fig. 4a; see also fig. 6 in Shi et al. (2008)) provideimportant age and origin constraints (Shi et al., 2008,2009a). At least two growth periods have been distin-guished, as discussed above. Zircon-I grains (163.2 � 3.3Ma average age) were interpreted as being inherited from aprotolith, whereas zircon-II (146.5 � 3.4 Ma average age)


formed contemporaneously with jadeitite crystallization.This interpretation is consistent with the suggestion byMitchell et al. (2004) that high-pressure rocks in the JadeMines Tract uplift were possibly generated in the earlyJurassic collision event and finally exhumed within ser-pentinite diapirs in the Tertiary.

Ilmenite occurs as rounded inclusions in the cores oftitanite grains (Fig. 4b) in omphacitite. Ilmenite is likely arelict igneous mineral from a mafic protolith such as basaltor gabbro rather than eclogite, which would probably con-tain rutile. The grain size was too small to obtain anaccurate analysis, although dominant Fe and Ti viaEPMA support the phase identification.

Chromite occurs in kosmochlor and kosmochlor-amphi-bole rocks (e.g., Ou Yang, 1984; Mevel & Kienast, 1986;Harlow & Olds, 1987; Shi et al., 2005a) and is surrounded bykosmochlor (Fig. 4c). The EPMA data show that the relictchromite replaced by kosmochlor is a little higher in Al andlower in Fe3þ than that in the adjacent serpentinized perido-tite, and that relict chromite grains rimmed by kosmochlor

display a chemical trend such that Mg contents decrease andFe contents increase from the core to the rim, suggesting acompositional trend towards magnetite (Shi et al., 2005a).On the other hand, Harlow & Olds (1987) noted low Al andMg as well as high Cr, Mn, and Zn in chromite, suggestingpreferential reaction of the former during metasomatism andan increase in the latter elements in residual chromite.

5.2. Pyroxenes

5.2.1. Jadeite-omphacite series pyroxenes

Jadeite is the main constituent in jadeitite, and a commonmineral in other related rocks such as omphacitite, kosmo-chlor rocks and amphibole rocks, and even in albitite fromthe Jade Mine Tract. Jadeite in jadeitite veins is generallyvery pure, with jadeite content (XJd) greater than 98 mol%(Table 3). Undeformed crystals with rhythmic chemicalzoning patterns increase in diopside content (XDi) to �8mol% (Shi et al., 2005b). Omphacite and aegirine mainlyoccur in omphacitite, jadeitized rodingite or as a minorphase in albitite and amphibole-kosmochlor rocks. Inomphacitite, replacement of omphacite (Jd26–43Ae29–22

Di22–37) by jadeite or an addition of new jadeite is obvious(Fig. 4a; also see Yi et al., 2006). This texture of omphaciteis also obvious in the jadeitized rodingite (Wang et al.,2012). However, Harlow & Olds (1987) described a singlecobble containing Cr-bearing omphacite, which appears tobe a chromite-bearing omphacitite cut by veins of jadeitewith reaction growth of kosmochlor (sample AMNH-98642). The compositional range of omphacite isJd30–72Di25–49Kos0–29 Aeg0–34 (for detailed data seeHarlow & Olds (1987); Shi et al. (2003, 2005a, 2010); Yiet al. (2006); Nyunt et al. (2009)). Some pyroxenes in theomphacitite contain more Fe3þ than Al and are interpretedas aegirine-augite, e.g., Jd26Di28Aeg42Other4 in Yi et al.(2006), according to the pyroxene nomenclature ofMorimoto et al. (1988); a metasomatic origin is indicated.

5.2.2. Cr-bearing pyroxenes

Kosmochlor occurs as an accessory mineral in iron meteor-ites (Laspeyres, 1897; Frondel & Klein, 1965; Couperet al., 1981) and in carbonaceous chondrites (Greshake &Bischoff, 1996). Occurrences from UHP metamorphicrocks (Liu et al., 1998), peridotite xenoliths (Sobolevet al., 1997), kimberlites (Sobolev et al., 1975), and meta-sediments (Reznitskii et al., 1999) were reported to containCr-bearing jadeite and omphacite, but no kosmochlor. Bycontrast, kosmochlor and other Cr-bearing pyroxenes arecommon in rocks from the Myanmar jadeite area (OuYang, 1984, 2001; Mevel & Kienast, 1986; Harlow &Olds, 1987; Shi et al., 2005a). Compositions along theJd-Kos binary are most abundant and offer an opportunityto study their paragenesis as well as the binary itself.

The rocks that contain the Cr-bearing jadeite and ompha-cite are mostly jadeitite, but also omphacitite (Harlow &Olds, 1987). Maw-Sit-Sit, a green rock from the mine ofthat name consists of Cr-bearing jadeite–kosmochlor þ

Fig. 4. BSE images of (a) replacement of omphacite by jadeite, newjadeite filling fractures, with zircon and titanite (Sample YX-1). (b)Titanite with residual ilmenite core in omphacite-bearing jadeitite andomphacitite (YX-1). (c) Photomicrograph of kosmochlor aggregateswith a corona texture surrounding relict chromite (sample WM1).


Tab

le3

.R

epre

sen

tati

ve

chem

ical

com

po

siti

on

so

fp

yro

xen

esfr

om

the

Jad

eM

ine

Tra

ct,

My

anm

ar.

Sam

ple

K0

68

22

WJ-

3W

J-1

Ab

-Jd

-01

Ph

ase

Ko

sK

os

Ko

sK

o-A

ug

?C

r-O

mp

JdJd

JdJd

JdO

mp

Om

pO

mp

JdJd

Om

pO

mp

JdJd

Jd

No

.5

69

10

16

15

38

–3

53

8–

38

38

–3

93

8–

45

38

–4

03

8–

41

38

–4

22

0–

12

1–

14

0–

14

1–

21

–D

ec1

8–

12

0–

1S

iO2

51

.26

52

.55

53

.84

52

.54

56

.73

57

.36

58

.58

58

.50

57

.96

57

.81

56

.98

56

.35

57

.64

59

.87

59

.91

57

.40

57

.15

59

.80

59

.57

58

.85

TiO

2b

dl

bd

lb

dl

bd

l0

.02

0.0

30

.02

0.0

90

.17

0.0

70

.01

0.0

40

.07

bd

l0

.01

0.1

5b

dl

bd

l0

.02

0.0

2A

l 2O

35

.49

1.5

16

.83

2.6

71

6.8

12

1.4

12

2.5

92

1.4

92

1.9

82

0.6

01

4.3

81

1.7

51

8.2

12

5.1

32

5.0

51

2.8

61

2.9

22

4.3

32

4.9

32

0.7

0C

r 2O

31

9.4

71

8.4

51

9.4

21

6.0

43

.66

1.7

50

.29

0.4

20

.64

0.1

20

.89

1.0

30

.75

bd

lb

dl

bd

l0

.01

bd

lb

dl

0.0

5F

e 2O

37

.64

12

.86

0.0

31

6.1

40

.00

0.0

01

.00

1.7

51

.63

3.2

13

.04

4.4

71

.66

bd

lb

dl

3.0

53

.01

0.0

0b

dl

1.5

1M

gO

0.9

90

.18

1.6

30

.24

3.9

41

.52

0.9

81

.62

1.1

11

.44

5.6

66

.61

2.6

00

.10

0.1

27

.68

7.2

90

.41

0.7

71

.85

Mn

Ob

dl

bd

lb

dl

bd

lb

dl

bd

lb

dl

bd

lb

dl

bd

l0

.06

0.0

70

.03

bd

l0

.05

0.0

70

.09

0.0

20

.02

bd

lF

eO0

.00

0.1

31

.62

0.0

00

.75

0.7

30

.29

0.1

40

.00

0.0

00

.80

0.7

62

.06

bd

lb

dl

0.5

50

.40

0.2

8b

dl

0.9

8C

aO3

.91

0.5

02

.43

0.2

25

.62

1.9

71

.33

2.4

11

.86

2.3

08

.82

10

.47

4.3

50

.15

0.0

81

0.4

51

0.3

70

.66

0.3

22

.39

Na 2

O1

2.1

41

3.3

21

2.2

41

3.6

91

1.3

01

3.4

21

4.3

01

3.7

81

4.1

51

3.9

09

.90

8.9

31

2.2

21

5.7

51

5.5

58

.86

8.9

61

4.8

41

4.5

51

3.6

0K

2O

bd

lb

dl

bd

lb

dl

bd

lb

dl

0.0

10

.01

bd

lb

dl

bd

lb

dl

0.0

10

.01

0.0

1b

dl

0.0

10

.01

0.0

2b

dl

To

tal

10

0.9

09

9.5

09

8.0

41

01

.54

98

.83

98

.19

99

.39

10

0.2

09

9.5

09

9.4

51

00

.54

10

0.4

99

9.6

01

01

.01

10

0.7

81

01

.07

10

0.2

11

00

.35

10

0.2

09

9.9

5S

i1

.90

61

.99

62

.00

61

.95

91

.99

01

.99

32

.00

21

.99

31

.98

71

.99

31

.98

71

.98

62

.00

51

.99

82

.00

21

.99

11

.99

82

.00

91

.99

82

.01

3T

in

.c.

n.c

.n

.c.

n.c

.0

.00

10

.00

10

.00

10

.00

20

.00

40

.00

20

.00

00

.00

10

.00

2n

.c.

0.0

00

0.0

04

n.c

.n

.c.

0.0

01

0.0

01

Al

0.2

41

0.0

68

0.3

00

0.1

17

0.6

95

0.8

77

0.9

10

0.8

63

0.8

88

0.8

37

0.5

91

0.4

88

0.7

47

0.9

89

0.9

87

0.5

26

0.5

32

0.9

63

0.9

86

0.8

34

Cr

0.5

72

0.5

54

0.5

72

0.4

73

0.1

02

0.0

48

0.0

08

0.0

11

0.0

17

0.0

03

0.0

25

0.0

29

0.0

21

n.c

.n

.c.

n.c

.0

.00

0n

.c.

n.c

.0

.00

1F

e3þ

0.2

14

0.3

72

0.0

01

0.4

53

0.0

00

0.0

00

0.0

26

0.0

45

0.0

42

0.0

83

0.0

80

0.1

18

0.0

43

n.c

.n

.c.

0.0

80

0.0

79

0.0

00

0.0

00

0.0

39

Mg

0.0

55

0.0

10

0.0

91

0.0

13

0.2

06

0.0

79

0.0

50

0.0

82

0.0

57

0.0

74

0.2

94

0.3

47

0.1

35

0.0

05

0.0

06

0.3

97

0.3

80

0.0

21

0.0

39

0.0

94

Mn

n.c

.n

.c.

n.c

.n

.c.

n.c

.n

.c.

n.c

.n

.c.

n.c

.n

.c.

0.0

02

0.0

02

0.0

01

n.c

.0

.00

10

.00

20

.00

30

.00

10

.00

1n

.c.

Fe2þ

0.0

00

0.0

04

0.0

50

0.0

00

0.0

22

0.0

21

0.0

08

0.0

08

0.0

00

0.0

00

0.0

23

0.0

22

0.0

60

n.c

.n

.c.

0.0

16

0.0

12

0.0

08

n.c

.0

.02

8C

a0

.15

60

.02

00

.09

70

.00

90

.21

10

.07

30

.04

90

.08

80

.06

80

.08

50

.32

90

.39

50

.16

20

.00

5n

.c.

0.3

88

0.3

88

0.0

24

0.0

12

0.0

88

Na

0.8

75

0.9

81

0.8

84

0.9

90

0.7

69

0.9

04

0.9

47

0.9

10

0.9

41

0.9

29

0.6

69

0.6

10

0.8

24

1.0

19

1.0

08

0.5

96

0.6

07

0.9

67

0.9

46

0.9

02

Kn

.c.

n.c

.n

.c.

n.c

.n

.c.

n.c

.0

.00

00

.00

0n

.c.

n.c

.n

.c.

n.c

.0

.00

00

.00

00

.00

0n

.c.

0.0

00

0.0

00

0.0

01

n.c

.

Su

m4

.01

84

.00

04

.00

04

.01

43

.99

53

.99

64

.00

13

.99

84

.00

44

.00

74

.00

03

.99

94

.00

04

.01

74

.00

84

.00

04

.00

03

.99

33

.98

24

.00

0Jd

0.0

50

.06

0.3

00

.04

0.6

80

.86

0.9

10

.85

0.8

60

.82

0.5

70

.46

0.7

50

.99

0.9

90

.51

0.5

30

.96

0.9

50

.84

Ko

s0

.57

0.5

50

.57

0.4

70

.09

0.0

40

.01

0.0

10

.02

0.0

00

.03

0.0

30

.02

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

0A

e0

.21

0.3

70

.00

0.4

50

.00

0.0

00

.03

0.0

40

.04

0.0

80

.08

0.1

20

.04

0.0

00

.00

0.0

80

.08

0.0

00

.00

0.0

4

No

te:

bd

l,b

elo

wd

etec

tli

mit

;n

.d.,

no

td

etec

ted

;n

.c.,

no

tca

lcu

late

d.


albite þ sodic amphibole � clinochlore � natrolite �chromite (Mevel & Kienast, 1986; Harlow & Olds, 1987;Colombo et al., 2000; Hughes et al., 2000). There are fivedistinct textures and related compositions of kosmochlorand Cr-bearing jadeite in rocks from Myanmar: (1) kosmo-chlor corona aggregates with a corona texture (radiatingprisms) surrounding relict chromite in amphibole matrix(Fig. 4c; e.g., Harlow & Olds, 1987; Shi et al., 2005a); (2)kosmochlor corona aggregates with a core of low-Cr jadeitecontaining approximately 10 mol% Kos (Fig. 5a, e.g., Shiet al., 2005a); (3) the commonly observed replacementtexture of kosmochlor penetrating fractured chromite (Fig.5b; also see Ou Yang, 1984; Harlow & Olds, 1987; Shiet al., 2005a); (4) granoblastic textures of undeformedcoarse-grained crystals; and (5) recrystallized fine-grainedaggregates in deformed low-Cr jadeitite. The purest kosmo-chlor reported from a terrestrial rock (97 mol% NaCrSi2O6)was found in a coronal growth around chromite (Shi et al.,2005a). Chemical compositions of kosmochlor and otherCr-bearing pyroxenes vary greatly (Table 3; also see OuYang, 1984; Harlow & Olds, 1987; Tsujimori & Liou,2004; Shi et al., 2005a).

5.3. Amphiboles

Of all the jadeitite localities worldwide, extensive amphi-bole boundaries between jadeitite and serpentinite are onlydocumented in the Jade Mine Tract. In addition to theobservations of Mevel & Kienast (1986) and Harlow &

Olds (1987); Shi et al. (2003) identified a complex amphi-bole association representing solid solutions involvingcompositional variations crossing six distinct amphibolespecies in the amphibolite border zone, according to thenomenclature of Leake et al. (1997) and Hawthorne &Oberti (2006): nyboite, richterite and winchite, magnesio-katophorite, eckermannite and glaucophane (Table 4). Theamphiboles are present as fine-grained (,10 mm maximumdimension) matrix and also as coarse-grained porphyro-blasts (up to 6 mm max. dimension) interspersed within thefine-grained matrix. Three amphibole growth episodeswere identified: in stage 1, magnesiokatophorite and rich-terite coexist during the earliest stage of amphibolegrowth; nyboite subsequently formed, rimming magnesio-katophorite and also coexisting with eckermannite duringstage 2 (Fig. 6; also see Shi et al., 2003). In stage 3,eckermannite rims nyboite and richterite and coexistswith glaucophane and winchite in the fine groundmass.Jadeite coexists during all of the stages of amphibolegrowth. Mevel & Kienast (1986) found a similar evolutionin chromian amphiboles from kosmochlor-rich samples,with the zoning evolution starting with katophorite throughglaucophane and eckermannite to richterite. This last trendfrom eckermannite to richterite is not consistent with Shiet al. (2003) but might demonstrate a local difference latein the chemical evolution from more sodic (and aluminous)to one more calcic (and less aluminous).

In addition to the compositions being controlled byreactions involving components such as jadeite þ serpen-tine þ fluid � chromite (Mevel & Kienast, 1986; Harlow& Olds, 1987; Shi et al., 2003), crystallochemically thetypical low and decreasing contents of tetrahedral Al buthigh Na in both A and B sites (using amphibole site label-ing of Hawthorne & Oberti (2006)) are consistent with HP-LT conditions in the presence of a highly sodic fluid, asinterpreted for jadeitite formation. In terms of specifictrends, Mevel & Kienast (1986) point out that the ecker-mannite evolution from glaucophane represents theexchange CMgANaCAl –1

A& –1 (A& is a vacancy on theA-site) and from katophorite to eckermannite byTSiBNaTAl–1

BCa–1, which is the most commonly observedzoning among studied samples (also noted by Shi et al.(2003)). Late richterite would evolve from eckermannitethrough the exchange (or compositional change)CMgBCaCAl–1

BNa–1, not unlike the late trend in zonedjadeite compositions toward higher diopside content.However, making quantitative interpretations is impededby the likely non-equilibrium conditions during transientprocesses as well as inadequate data on the phase equilibriainvolved, particularly for amphiboles and fluids. A presen-tation of the amphibole compositions follows.

5.3.1. Sodic amphiboles

Glaucophane in Myanmar is generally rare and transitionalto eckermannite in individual grains, with some misassign-ments in the literature (including Shi et al. (2003)). Itdiffers distinctly in composition from that of blueschistsin HP or UHP metamorphic belts, as Mg contents in the C

Fig. 5. Photomicrographs (plane-polarized light) of (a) coronal kos-mochlor aggregates with a core of low-Cr jadeite (Sample K15A).(b) Replacement texture of chromite by kosmochlor (K13).


sites are high, reaching a maximum of �3.0 apfu beforecrossing into eckermannite composition space. The valuesof Mg/(Mg þ Fe2þ þ Mn) are also high, .0.8 (Mevel &Kienast, 1986; Shi et al., 2003). The high Mg is most likelyrelated to the reaction with serpentinized peridotite ratherthan metabasite metamorphism. Of all the coexisting sodicand sodic-calcic amphiboles of stage 3, glaucophaneshows the lowest Na contents on the A-site with0.00–0.35 apfu Na (Mevel & Kienast, 1986; Shi et al.,2003).

Nyboite is known from HP to UHP metamorphic envir-onments and has been described so far from only threelocalities (Ungaretti et al., 1981; Hirajima et al., 1992;

Hirajima & Compagnoni, 1993) and from the Myanmarjadeitite area (Mevel & Kienast, 1986; Harlow & Olds,1987; Htein & Naing, 1994; Shi et al., 2003). Nyboite fromMyanmar shows Si contents of 7.31–7.49 apfu, BNa con-tent ranging from 1.64 to 1.84 apfu, CMg ranging from 3.16to 3.42 apfu, and ANa from 0.54 to 0.94 Na apfu. In theclassification diagram of Leake et al. (1997), the chemicalcompositions of nyboite from the inner rims are very closeto end-member nyboite (Shi et al., 2003).

Eckermannite associated with HP metamorphism hasbeen described only from jadeitites so far (Bauer, 1895;Lacroix, 1930; Chhibber, 1934; Mevel & Kienast, 1986;Harlow & Olds, 1987; Htein & Naing, 1994; Colombo

Table 4. Chemical compositions of amphiboles from the Jade Mine Tract, Myanmar.

Sample 118Sa Cb 012b 012b 012b 012b 012b 18401c 118Sa 012b 012b 29965c 016b Cb Cb

SiO2 58.75 55.89 53.77 53.90 55.70 58.20 58.31 58.47 57.63 52.17 52.15 52.71 56.18 58.16 57.89TiO2 0.14 0.07 0.02 bdl bdl bdl bdl 0.04 0.05 bdl bdl bdl bdl 0.04 0.11Al2O3 10.51 11.04 10.98 9.69 7.03 6.15 7.08 3.55 0.18 10.82 11.18 5.96 4.14 7.99 8.76Cr2O3 3.56 1.30 bdl bdl bdl 0.08 bdl bdl 10.16 bdl 0.13 0.01 bdl 1.22 0.96Fe2O3 0.19 0.00 1.89 0.00 4.08 2.07 0.00 2.27 0.00 0.00 0.00 0.00 0.36 0.00 0.00MgO 13.87 14.05 15.66 15.90 17.81 19.09 18.50 19.77 18.01 15.83 15.82 19.62 19.20 16.14 16.06FeO 2.47 4.41 3.68 6.82 2.46 1.41 2.76 2.27 1.65 5.52 5.63 3.66 5.53 4.54 5.19MnO 0.03 0.17 bdl bdl bdl 0.24 0.14 0.06 0.00 bdl bdl 0.10 bdl 0.18 0.12NiO 0.09 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.CaO 1.04 2.61 1.60 2.45 1.59 0.64 0.22 1.94 0.09 4.11 4.23 9.61 3.56 2.41 2.61Na2O 7.26 7.24 10.17 8.47 9.79 10.59 9.78 9.24 10.08 8.61 7.66 5.42 8.44 5.70 5.56K2O 0.06 0.81 bdl 0.21 0.18 0.25 0.32 0.37 0.78 0.17 0.21 n.d. 0.25 1.16 0.93H2Od 2.24 2.19 2.18 2.16 2.19 2.22 2.20 2.20 2.17 2.15 2.15 2.14 2.16 2.20 2.21

Total 100.21 99.78 99.95 99.60 100.84 100.94 99.32 100.17 100.80 99.38 99.15 99.23 99.82 99.74 100.41T-site

Si 7.870 7.649 7.401 7.499 7.610 7.844 7.933 7.980 7.971 7.292 7.287 7.395 7.808 7.924 7.844Al 0.130 0.351 0.599 0.501 0.390 0.156 0.067 0.020 0.029 0.708 0.713 0.605 0.192 0.076 0.156Sum 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000

C-siteTi 0.014 0.007 0.002 n.c n.c n.c. n.c. 0.004 0.005 n.c n.c n.c n.c 0.004 0.011Cr 0.377 0.141 n.c n.c n.c 0.009 n.c. n.c. 1.111 n.c 0.014 0.001 n.c 0.131 0.103Al 1.530 1.430 1.182 1.088 0.741 0.821 1.068 0.551 0.000 1.075 1.128 0.381 0.486 1.207 1.243Fe3þ 0.019 0.000 0.196 0.000 0.420 0.209 0.000 0.233 0.000 n.c. 0.000 0.000 0.038 0.000 0.000Mg 2.770 2.867 3.213 3.298 3.627 3.836 3.752 4.022 3.713 3.299 3.295 4.104 3.978 3.278 3.244Fe2þ 0.276 0.505 0.408 0.614 0.212 0.122 0.180 0.189 0.171 0.637 0.562 0.430 0.643 0.517 0.398Mn 0.003 0.020 n.c n.c n.c 0.000 0.000 0.000 0.000 n.c. n.c 0.012 n.c 0.000 0.000Ni 0.010 n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.c n.cSum 4.999 4.969 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 4.929 5.000 5.000 5.000

B-siteCa 0.149 0.383 0.236 0.365 0.233 0.092 0.032 0.284 0.013 0.616 0.633 1.445 0.530 0.352 0.379Na 1.851 1.617 1.748 1.455 1.698 1.847 1.818 1.641 1.966 1.365 1.271 0.555 1.325 1.489 1.417Fe2þ 0.000 n.c 0.016 0.180 0.070 0.034 0.134 0.070 0.020 0.019 0.096 0.000 0.145 0.138 0.190Mn 0.000 n.c n.c n.c n.c 0.027 0.016 0.006 0.000 n.c n.c 0.000 n.c. 0.021 0.014Sum 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000

A-siteNa 0.034 0.304 0.966 0.830 0.896 0.921 0.762 0.804 0.737 0.968 0.804 0.919 0.949 0.016 0.044K 0.010 0.141 bdl 0.037 0.031 0.043 0.056 0.064 0.138 0.030 0.037 n.c. 0.044 0.202 0.161Sum 0.054 0.445 0.966 0.867 0.927 0.964 0.817 0.868 0.874 0.998 0.842 0.919 0.993 0.218 0.204

Totalcations

15.043 15.414 15.966 15.867 15.927 15.964 15.817 15.868 15.874 15.998 15.842 15.848 15.993 15.218 15.204

OHd 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2Name Gln Gln Nyb Nyb Eck 1 Eck 2 Eck 2 Eck Cr-Eck Mg-Kat Mg-Kat Rich Rich Win-Gl Win

Notes: aanalyses 12 & 7 from table 4 of Mevel & Kienast (1986).bData from Shi et al. (2003)c18401 and 29965 are jadeitite specimens from AMNH mineral collection (see Appendix)dH2O and OH calculated from amphibole stoichiometry assuming only OH in nominally monovalent anion site


et al., 2000; Shi et al., 2003; Schumacher, 2007; Nyuntet al., 2009). Three parageneses of the eckermannite aredistinguished by Si content and texture (Shi et al., 2003).The texturally earliest eckermannite-I (rim of nyboite, Fig.6) from stage 2 coexisting with nyboite has lower Si content(,7.6 apfu). Texturally later eckermannite-II rimmingnyboite and richterite has higher Si content (.7.6 apfu).Matrix eckermannite-III shows even higher Si content(7.9–8.0 Si apfu). These data suggest that there is significantTschermak’s substitution (TSiCMg TAl–1

CAl–1) from ecker-mannite-I, to -II and then to -III (Shi et al., 2003).Kosmochlor-bearing jadeitite (Mevel & Kienast, 1986;Harlow & Olds, 1987) and maw-sit-sit (our work) alsocontains eckermannite with comparably elevated Si, Cr to.1 apfu, and typically has slightly lower BNa (,1.95 apfu).

5.3.2. Sodic-calcic amphiboles

Magnesiokatophorite is very rare in high-P and UHProcks, known from two localities in the Western Alps(Reynard & Ballevre, 1988) and the Dabie Shan area(Dong et al., 1996). However, it is abundant in the reactionboundaries of jadeitite from the Jade Mine Tract (Mevel &Kienast, 1986; Shi et al., 2003). Chemical compositions ofmagnesiokatophorite show Si contents of 7.16–7.36 apfu,high Mg content on the C sites ranging from 3.15 to 3.50apfu, and BNa content from 1.29 to 1.46 apfu and a largevariation in the ANa from 0.64 to 0.93 apfu. The composi-tional change from magnesiokatophorite cores to outernyboite zones can be attributed to a coupled substitution

such as the Gln-exchange BNaAlCa–1 Mg–1 (Shi et al.,2003).

Richterite has been described in UHP metapelites fromGreece (Mposkos & Kostopoulos, 2001) and a blueschistfrom the Klamath Mountains in California (Helper, 1986).This amphibole in Myanmar jadeitite has high Si values of7.72–7.88 apfu, BNa content from 0.50 to 1.48 apfu, Mgcontents on C from 3.62 to 4.30 apfu, and lower Al on thetetrahedral sites (TAl ¼ 0.12–0.28 apfu). The composi-tional change from richterite to magnesiokatophorite canbe explained by a Tschermak’s substitution.

Winchite has been discovered in the manganese ore mineat Kajlidongri, India (where it is violet in color; Leake et al.,1986) and as Mg- and Al-rich winchite from Venezuela(Maresch et al., 1982). However, there is a lack of informa-tion on this species (Sokolova & Hawthorne, 2001). It wasreported in the Myanmar jadeitite as a fine-grained amphi-bole matrix or aggregate, and the composition showsslightly elevated Mg contents of 3.26–3.28 apfu and Cacontents ranging from 0.35 to 0.38 apfu (Shi et al., 2003).

5.3.3. Suspected calcic amphiboles

Tremolite-actinolite had been mentioned by several authors(Chhibber, 1934; Deer et al., 1963; Soe Win, 1968;OuYang, 1993; Hughes et al., (2000) from the Myanmarjadeitite. It is described as secondary fibrous tremolitewhich partly replaced some jadeite in the course of late-stage metasomatism, and as part of the blackwall (darkgreen) boundary between the jadeitite vein and serpentinite.However, no chemical compositions were reported, and ithas not yet been detected in our mineralogical investiga-tions, ostensibly for lack of access to blackwall samples.

5.4. Phlogopite

Whereas phlogopite has been reported from many otherjadeitite occurrences (e.g., Guatemala, Harlow (1994,1995); Harlow et al. (2011); the Monviso meta-ophiolite,Piemonte Zone, Italian western Alps, Compagnoni et al.(2007); the Sierra del Convento, Cuba, Garcia-Casco et al.(2009); and the Nishisonogi metamorphic rocks, Kyushu,Japan, Shigeno et al. (2005)), phlogopite has not beenpreviously reported from Myanmar jadeitite. Phlogopiteis also rare in Guatemala where phengite and paragoniteare common, and even preiswerkite is more common thanphlogopite. However, phlogopite was found in a late-stagevein adjacent to jadeitite and as a microcrystalline inter-growth with cymrite and vesuvianite (Fig. 7a, b), and showsvariable composition (Tables 5 and 6). Some of this varia-tion may be due to submicrometer scale interlayers ofanother K-poor phyllosilicate with higher water content, asmanifested in the analysis 9-11 in Tables 5 and 6.

5.5. Allanite

Allanite occurs in a jadeitized rodingite as irregularlyshaped grains in association with garnet (Fig. 8a).

Fig. 6. Photomicrographs of an amphibole grain with magnesioka-tophorite core, nyboite mantle and eckermannite rim: (a) plane-polarized light and (b) crossed polarizers (sample 012).


Allanite has high Ce2O3 and La2O3 (5.3–11 wt% La2O3,7.0–9.2 wt% Ce2O3, 13–20 wt% (Ce2O3 þ La2O3) andappears to vary between allanite-(La) and allanite-(Ce)(Table 6). We report the analyses of Li (2003) with ourcalculation of cations normalized to 6 Si atoms. There areinexplicable deficiencies in total M cations and, withoutaccounting for other REEs, deficiencies in A site cations,as well. Nevertheless, compositions resemble those ofallanite from Buca Della Vena mine, Apuan Alps(Orlandi & Pasero, 2006).

5.6. Garnets

Garnet group minerals identified from the Myanmar jadei-tite sources are grossular and uvarovite. Grossular has beenidentified in a jadeitized rodingite consisting primarily ofjadeite, omphacite, and grossular in Myanmar (Wanget al., 2012), and in related rocks from other jadeititelocalities (e.g., Kobayashi et al., 1987; Harlow, 1994;Tsujimori et al., 2005). An example of the microtexture(Fig. 8a) shows a late formational stage of jadeite andomphacite with grossular. Compositionally, grossularsamples (Table 7) contain over 80 mol% Grs end-member,with less than 4.7 wt% Fe2O3 (corresponding to 11.1–13.6mol% andradite), and a small amount of TiO2 (0.16–1.2wt%), MnO (,0.4 wt%), and MgO (,0.1 wt%).

Uvarovite is rare and has only been reported in onejadeitite sample from Myanmar (Qi et al., 1999). Usingbackscattered electron imaging on this sample (K068), we

found that the residual chromite core was directly sur-rounded by radial uvarovite aggregates, which were subse-quently wrapped by radial kosmochlor aggregates and thenby Cr-bearing jadeite aggregates (Fig. 8b). This successionof uvarovite, kosmochlor, and Cr-bearing jadeite aroundchromite adds an extra compositional complexity in com-parison with the kosmochlor coronas around chromite (Fig.4c). The uvarovite varies greatly in composition, rangingfrom 61 to 85 mol% Uv although some analyses are not ofhigh quality (Qi et al., 1999); only a single analysis is shownin Table 7. The texture and composition of uvarovite sug-gest that Ca-rich metasomatism is more likely to haveoccurred before the growth of kosmochlor without thenecessary presence of jadeite, at least for this sample.

5.7. Feldspars

Minerals of the feldspar group identified in the Myanmarjadeitite include albite, celsian, hyalophane and banalsite.

Table 5. Representative chemical compositions of phlogopites inrocks from the Jade Mine Tract, Myanmar.

SampleMJE02-3-6

Anal. 8-2 8-3 9–11

SiO2 41.15 40.42 39.85TiO2 0.03 0.00 0.06Al2O3 19.57 17.73 15.61Cr2O3 0.06 0.09 0.11Fe2O3 3.62 0.00 6.36FeO 0.00 4.51 0.00MnO 0.06 0.14 0.03MgO 18.26 20.21 19.63CaO 0.08 0.10 1.54SrO 0.05 0.00 0.03BaO 2.14 0.35 0.09Na2O 0.04 0.09 0.09K2O 10.04 10.45 9.44H2Oa 4.25 4.18 4.14

Total 99.35 98.26 96.98Oxygens 22 22 22Si 5.812 5.801 5.776Aliv 2.188 2.199 2.224SUM T 8.000 8.000 8.000Ti 0.003 0.000 0.007Al 1.070 0.799 0.442Cr 0.007 0.011 0.013Fe3þ 0.385 0.385 0.693Fe2þ 0.000 0.541 0.000Mn 0.007 0.017 0.004Zn 0.000 0.000 0.000Mg 3.844 4.323 4.240Ca 0.012 0.015 0.239Ba 0.119 0.020 0.005Na 0.011 0.024 0.025K 1.809 1.914 1.746Sum C 15.266 15.663 15.415OHa 4 4 4

Note: aH2O and OH calculated from mica stoichiometry assumingonly OH in nominally monovalent anion site.

Fig. 7. BSE images of (a) later-stage pectolite surrounding cymrite,which includes phlogopite (sample MJE02-3-6). (b) Vesuvianitewith phlogopite and cymrite (sample MJE02-3-6).


Albite has been reported frequently from the Myanmarjadeitite area (Chhibber, 1934; Mevel & Kienast, 1986;Harlow & Olds, 1987; Shi et al., 2003). Albite commonlyoccurs in albitite, a mono-mineralic rock comprised mainlyof albite that formed in late-stage veins cutting throughjadeitite, omphacitite, amphibole rock and/or kosmochlorrock (Fig. 2f). In addition, albite also occurs as a cavity orintergranular filling phase within jadeitite and omphacitite.Chemically the albite is very pure and homogeneous(Table 8). Similar to the jadeitite, albitite from Myanmarcan be classified into two types: undeformed albitite anddeformed albitite, and some deformed albitite shows simi-lar ‘‘icy and glassy’’ appearances as the jadeitite.

Celsian was first reported from the Jade Mine Tract byShi et al. (2010) as being in jadeitite, chromian omphacititeand in late-stage veins adjacent to the jadeitite. In multi-phase pseudomorphs within chromian clinopyroxene rock,celsian occurs with kaolinite, sometimes quartz, graphite,and diaspore, and is probably replacing cymrite by decom-position caused by decreasing pressure during exhumation

(see details in Shi et al. 2010). In jadeitite, celsian crystals(3–15 mm across) are surrounded by jadeite grains (Shiet al., 2010); however, it is unclear whether the celsian isin equilibrium with the jadeite. In late-stage assemblagesadjacent to jadeitite, celsian occurs in veins cutting banal-site (Fig. 9), indicating it formed after banalsite. Therefore,celsian may have formed both as a precursor and subse-quent phase relative to jadeite crystallization. All celsiangrains are compositionally homogeneous with 92–97mol% Cls and less than 10 mol% of Ab þ Or þ An (Shiet al., 2010). Late celsian in the multi-phase intergrowthsadjacent to jadeitite contain �95 mol% Cls (Table 8).

Hyalophane was first reported in a Myanmar jadeitite byShi et al. (2010) as an interstitial phase within cracks oralong grain boundaries of jadeite or amphibole. Hyalophanecontains 10.7–16.7 wt% BaO and 9.5–12 wt% K2O, corre-sponding to 21–33 mol% Cls and 62–77 mol% Or (Shiet al., 2010). This lies in the range between the Ba-rich(Cls56–59Or40–42Ab2An0–1) and Ba-poor(Cls7–15Or83–92Ab1–3An0–1) feldspars from a jadeitite fromJapan (Morishita, 2005) and is comparable to a hyalophanewith 22 mol% Cls from Guatemala (Harlow, 1994).

Banalsite (Na2BaAl4Si4O16) was reported first in ajadeitite by Harlow & Olds (1987), and then Htein &Naing (1994). It is also reported in Guatemala jadeitite(Harlow, 1994; Harlow et al., 2011). In this study, banal-site occurs as cavity- or vein-filling material in or adjacentto jadeite grains (Fig. 9). It is very pure, containing less

Table 6. Representative chemical compositions of allanites in rocksfrom the Jade Mine Tract, Myanmar.

22

Anal. No. aln14a aln15a aln2a

SiO2 38.70 38.85 35.62TiO2 0.37 0.03 0.39Al2O3 23.49 24.15 20.96Ce2O3 6.98 8.18 9.16La2O3 6.85 5.31 11.04Cr2O3 0.00 0.00 0.00FeOT 9.81 8.73 9.05MnOT 0.00 0.18 0.08NiO 0.00 0.38 0.00MgO 0.15 0.00 0.15CaO 11.31 11.70 10.40Na2O 0.00 0.00 0.00K2O 0.02 0.10 0.00H2Oa 1.93 1.94 1.78

Total 99.61 99.55 98.63Mineral Aln Aln AlnNormalize to 6 SiSi 6 6 6Ti 0.043 0.004 0.050Al 4.292 4.397 4.161Fe 1.272 1.127 1.275Mn 0.000 0.024 0.011Ni 0.000 0.048 0.000Mg 0.035 0.000 0.037Sum M 5.642 5.599 5.534Ce 0.397 0.462 0.565La 0.392 0.302 0.686Ca 1.879 1.936 1.877Na 0.000 0.000 0.000K 0.004 0.020 0.000Sum A 2.671 2.721 3.128Sum All 14.313 14.320 14.662OHa 2 2 2

Note: aH2O and OH calculated from allanite stoichiometry assumingonly OH in nominally monovalent anion site.

Fig. 8. BSE images of (a) grossular including allanite in a jadeitizedrodingite consisting of the major minerals grossular, omphacite andjadeite in the Myanmar sample 22. (b) Uvarovite together withkosmochlor and chromian jadeite (Cr-Jd) forming a symplectiterim around a relict chromite core (sample K068).


than 3 mol% OrþAn (Table 8), and a small amount of SrO(0.30–0.40 wt%).

5.8. Zeolites

Minerals of the zeolite group commonly occur in jadeititeand related rocks worldwide (e.g., Morkovkina, 1960;Coleman, 1961; Yudin, 1965; Kobayashi et al., 1987;Harlow, 1994; Miyajima et al., 1999; Hughes et al.,2000; Morishita, 2005; Harlow et al., 2011). In this study,we report analcime, natrolite and thomsonite-Ca identifiedin Myanmar jadeitite and related rocks. All these mineralshave been confirmed using powder X-ray diffraction.

Analcime has been reported in Myanmar (Hughes et al.,2000), Guatemala and Japan jadeitite localities (Harlow,1994; Morishita, 2005). In Myanmar jadeitite it occurs as alate-stage phase with natrolite along jadeite grain boundary,or as veins through jadeitite (Fig. 10). Compositionally, itlooks intermingled with other zeolites, so only rough com-positions of this phase are given in Table 9.

Natrolite occurs in ultramafics of the Borus Ridge, WestSayan (Yudin, 1965) and in jadeitite from the same locality(Dobretsov, 1963), in addition to the Itoigawa area

(Miyajima et al., 1999), Oeyama belt (Kobayashi et al.,1987), California – Clear Creek, New Idria, California(Coleman, 1961), Ketchpel, Polar Urals, Russia(Morkovkina, 1960), and Itmurundy, Kazakhstan(Dobretsov & Ponomareva, 1965). However, it has notbeen previously reported in the Myanmar jadeitite; itoccurs along jadeite grain boundaries or in veins cuttingjadeitite (Fig. 10), obviously a late-stage phase.Compositionally, it is mixed with other zeolites, so com-positions given in Table 9 are slightly non-stoichiometric.

Thomsonite-Ca has been reported in the Osayama jadei-tite, SW Japan (Kobayashi et al., 1987) and has beenconfirmed by X-ray diffraction in late-stage veins cuttingjadeitite in this study. In MJE02-3-9, a vein termination ofa jadeitite body, we have found both thomsonite-Ca andthomsonite-Sr; the latter appears to be the second occur-rence of this mineral. In Table 9 are presented representa-tive analyses of the two thomsonites, which show solidsolutions between the two types.

5.9. Vesuvianite

Nyunt et al. (2009) describe an occurrence of vesuvianitein a Myanmar jadeitite, the first report from HP/LT condi-tions. They report compositions with up to 1.5 wt% Na2Oand 3.2 wt% TiO2 and suggest that the formation of thisvesuvianite is explained by an interaction with a hydrousfluid phase with high chemical potentials of Ti and Ca. Acomparable occurrence of vesuvianite with relatively highNa and Ti has been recorded in a Guatemalan jadeitite(Harlow et al., 2011). In this study, vesuvianite has beenobserved in a late-stage vein at the contact between jadei-tite and altered serpentinite (MJE02-3-6) and is intergrownwith phlogopite and cymrite (Fig. 7b). The vesuvianitecontains less than 1 wt% Na2O and �0–3 wt% TiO2

(Table 10). It may not have formed at comparable P-Tconditions as those reported from other jadeititeoccurrences.

5.10. Other minerals

Cymrite is the hydrous analog of celsian and was reportedin Guatemala jadeitite (Harlow, 1994). As cymrite is theHP phase via the reaction BaAl2Si2O8 (Cls) þ H2O ¼BaAl2Si2O8�H2O (Cym) and defines a thermobarometer(Graham et al., 1992), it is petrogenetically as well ascompositionally significant. It has been interpreted as theprecursor phase for celsian in Myanmar (Shi et al., 2010).Cymrite has now been found along a jadeite grain bound-ary in a Myanmar jadeitite as euhedral hexagonal prismsand formed after jadeite as well as banalsite (Fig. 7a, b, 9and 10). Compositionally it is close to end-member Cym(Table 9).

Titanite has been reported from all jadeitite localities,except perhaps those in the New Idria serpentinite body,Myanmar, California and the Yenisey River, Khakassia(see Harlow et al., 2007). In the present investigation it

Table 7. Representative chemical compositions of garnet mineralsin rocks from the Jade Mine Tract, Myanmar.

SampleK068 22

Phase Uvr Grs

No. 2 3 G-54a G-56a 38-9 38-12

SiO2 37.76 35.96 39.34 39.58 39.23 39.25TiO2 0.62 0.29 0.12 0.16 0.22 0.34Al2O3 6.96 3.73 18.87 18.61 20.12 20.39Cr2O3 18.95 24.03 1.19 1.3 0.67 0.92Fe2O3 0.61 1.03 4.35 4.57 2.22 1.42FeO 1.37 0.00 0.50 0.29 0.80 2.16MnO 0.27 0.23 0.42 0.39 0.41 0.42MgO 0.10 0.06 0.01 0.01 0.04 0.05CaO 31.72 34.08 36.02 36.41 35.58 34.43SrO n.d. n.d. n.d. n.d. 0.00 0.01Na2O 0.79 0.07 0.06 0.03 0.01 0.05K2O 0.01 0.00 0.00 0.00 0.00 0.00

Total 99.16 99.48 100.88 101.36 99.3 99.46Oxygens 24 24 24 24 24 24Si 6.115 5.932 5.977 5.988 6.002 6.002Ti 0.076 0.036 0.014 0.018 0.025 0.040Al 1.328 0.726 3.378 3.318 3.628 3.675Cr 2.426 3.134 0.143 0.155 0.081 0.111Fe3þ 0.075 0.128 0.497 0.521 0.256 0.163Fe2þ 0.185 0.000 0.063 0.037 0.102 0.276Mn 0.037 0.032 0.054 0.050 0.053 0.055Mg 0.024 0.015 0.002 0.002 0.009 0.012Ca 5.504 6.024 5.863 5.902 5.832 5.640Sr n.d. n.d. n.d. n.d. 0.000 0.001Na 0.248 0.022 0.018 0.009 0.004 0.016K 0.002 0.000 0.000 0.000 0.000 0.001

Total 16.020 16.049 16.009 16.001 15.992 15.991

Notes: a From Wang et al. (2011).


has been found in an omphacite-bearing jadeitite and anomphacitite from Myanmar along jadeite grain boundaries.Some titanite grains contain ilmenite cores (Fig. 4b), show-ing replacement of ilmenite by titanite. Compositionally,Myanmar titanites have low Al (0.90–1.1 wt% Al2O3, XAl

, 0.05 where XAl¼ [Al /(Alþ Fe3þþ Ti)]; see Table 10),even lower than those low-Al titanites (XAl ¼ 0.050 –0.115; 1.3 – 3.0 wt% Al2O3) from carbonate-bearing

rocks in the Dabieshan-Sulu UHP terrane, eastern China(e.g., Ye et al., 2002).

Pectolite is a sodium calcium silicate mineral of thewollastonite group and is reported in jadeitite from Japan,California, Guatemala (e.g., Coleman, 1961; Morishita,2005; Tsujimori et al., 2005; Harlow et al., 2011) andalso Myanmar (Nyunt et al., 2009). In this study it isfound in late-stage veins in jadeitite (Fig. 7a, 10, Table 10).

Fig. 9. BSE image of celsian formed later than banalsite, and euhe-dral cymrite occurring at the boundary between jadeite and banalsite(sample MJE02-3-9).

Table 8. Representative chemical compositions of feldspars from the Jade Mine Tract, Myanmar.

SampleMJE02-3-6 MJE02-3-9 Ab-Jd01 WJ-01

Phase Bnl Bnl Bnl Bnl Cls Cls Hyl Hyl Ab Ab Ab Ab

No. 7-6 7-8 11-1 11-11 11-4 11-8 12-4 12-7 22 79 53 60SiO2 37.17 36.49 35.69 35.63 32.96 34.31 55.21 56.93 68.67 68.95 68.86 68.57TiO2 0.03 0.09 0.00 0.00 0.07 0.06 0.02 0.00 0.02 0.00 0.00 0.00Al2O3 31.48 30.74 30.50 30.35 26.09 29.69 20.34 20.01 19.03 19.65 18.94 19.10Cr2O3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.04 0.04 0.01MgO 0.00 0.00 0.00 0.00 0.00 0.02 0.01 0.00 0.01 0.00 0.00 0.02CaO 0.33 0.19 0.03 0.08 0.02 1.64 0.00 0.02 0.00 0.01 0.01 0.00MnO 0.00 0.00 0.00 0.00 0.00 0.00 0.03 0.00 0.03 0.00 0.05 0.00FeO 0.00 0.06 0.00 0.00 0.02 0.04 0.03 0.00 0.01 0.02 0.04 0.00SrO 4.15 3.71 0.35 0.14 0.08 0.10 0.00 0.00 0.04 0.00 0.03 n.d.BaO 17.31 18.48 23.35 23.44 39.22 33.68 10.97 8.89 0.00 0.00 0.01 n.d.Na2O 9.56 9.80 9.29 9.25 0.11 0.74 0.07 0.10 11.96 12.03 11.94 11.94K2O 0.00 0.00 0.00 0.01 0.75 0.65 12.38 13.19 0.01 0.01 0.02 0.03

Total 100.03 99.56 99.22 98.90 99.32 100.93 99.06 99.14 99.80 100.71 99.93 99.65Oxygens 8 8 8 8 8 8 8 8 8 8 8 8Si 1.998 1.991 1.987 1.990 2.057 1.998 2.783 2.824 3.007 2.992 3.011 3.005Ti 0.001 0.004 0.000 0.000 0.004 0.003 0.001 0.000 0.001 0.000 0.000 0.000Al 1.994 1.977 2.001 1.998 1.919 2.037 1.208 1.170 0.982 1.005 0.976 0.987Cr 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.000Mg 0.000 0.000 0.000 0.000 0.000 0.002 0.001 0.000 0.001 0.000 0.000 0.001Ca 0.019 0.011 0.002 0.005 0.001 0.102 0.000 0.001 0.000 0.000 0.001 0.000Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.001 0.000 0.002 0.000Fe 0.000 0.003 0.000 0.000 0.001 0.002 0.001 0.000 0.000 0.001 0.001 0.000Sr 0.129 0.117 0.011 0.005 0.003 0.003 0.000 0.000 0.001 0.000 0.001 0.000Ba 0.365 0.395 0.509 0.513 0.959 0.768 0.217 0.173 0.000 0.000 0.000 0.000Na 0.997 1.036 1.003 1.002 0.013 0.084 0.007 0.010 1.016 1.012 1.012 1.015K 0.000 0.000 0.000 0.001 0.060 0.049 0.796 0.835 0.001 0.001 0.001 0.002

Total 5.502 5.535 5.514 5.512 5.017 5.048 5.014 5.013 5.009 5.012 5.007 5.010

Fig. 10. BSE image showing that analcime and natrolite with pecto-lite occur as later vein surrounding earlier cymrite and banalsite; theyall are adjacent to jadeitite (sample MJE02-3-9).


Other rare minerals in the Myanmar jadeitite and relatedrocks include graphite, quartz, diaspore and kaolinite in themulti-phase pseudomorphs surrounded by kosmochlor andCr-bearing jadeite aggregate (see details in Shi et al. 2010),and the sulfide minerals pyrite and galena in jadeitite (Shiet al., 2008).

6. Discussion and conclusions

6.1. Origin of minerals in jadeitite and related rocks inMyanmar

Growing numbers of observations support an origin ofjadeite in pure jadeitite blocks by direct precipitationfrom Na-Al-Si rich hydrous fluids. Trace-element compo-sitions of jadeitites (Sorensen et al., 2006; Morishita et al.,2007; Shi et al., 2008; Simons et al., 2010), together withoscillatory zoned jadeite, indicate the presence of a Jd-saturated vein fluid. Fluid inclusions and stable isotopestudies of the Guatemala and Myanmar jadeitite unam-biguously indicate that jadeite grains formed from hydrousfluids (Johnson & Harlow, 1999; Shi et al., 2000, 2005b;Simons et al., 2010). However, there are still debates about

the origins of the fluids. The depleted Hf isotope feature inall zircons from the Myanmar jadeitite suggests their deri-vation from reworking of juvenile crust during theMyanmar jadeitite crystallization from the Jd-saturatedvein fluids (Qiu et al., 2009; Shi et al., 2009b).Alternatively, such fluids could also have been producedby interaction between seawater, the subducted oceaniccrust and its sedimentary cover (Sorensen et al., 2006;Simons et al., 2010) and possibly from rodingitization ofoceanic mafic rock (Wang et al., 2012). Correlationsbetween the jadeite-forming fluids and seawater or sea-floor sediments are revealed by the isotope features of fluidinclusions in jadeitite, Ba-bearing minerals in jadeitites,and their bulk geochemical features (e.g., Mevel &Kienast, 1986; Harlow, 1995; Johnson & Harlow, 1999;Morishita, 2005; Shi et al., 2005b, 2008, 2010; Sorensenet al., 2006; Simons et al., 2010). Thus, the fluids are likelyderived from a subducted slab that has reacted with sea-water, possibly with minor addition from the dehydrationof serpentine minerals at greater depths (e.g., Hyndman &Peacock, 2003).

The origin of omphacite in omphacitite is less well under-stood. Yi et al. (2006) have argued that it is a product ofreaction between jadeitic fluid and mantle pyroxenite athigh P-T. Other possibilities include fluid interaction with

Table 9. Representative chemical compositions of zeolite minerals in rocks from the Jade Mine Tract, Myanmar.

SampleMJE02-3-6 MJE02-3-9

No. M7-20 M7-17 M14-10 M14-17 M10-9 M10-11 M13-9 M13-1Phase Ntr Ntr Ntr Ntr Anl Anl Thm-Ca Thm-Sr

SiO2 49.81 48.99 49.57 49.62 56.50 55.85 39.36 36.45TiO2 0.02 0.03 0.00 0.01 0.00 0.00 0.00 0.00Al2O3 26.92 26.10 27.74 26.83 22.85 23.20 30.15 27.63Cr2O3 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.01MgO 0.00 0.03 0.03 0.00 0.00 0.03 0.02 0.00CaO 0.05 0.25 1.25 1.29 0.03 0.19 11.46 4.08MnO 0.02 0.00 0.00 0.00 0.02 0.01 0.00 0.01FeO 0.00 0.00 0.01 0.03 0.00 0.01 0.02 0.00SrO 0.04 0.53 0.00 0.00 0.04 0.07 1.91 13.65BaO 0.03 1.24 0.12 0.01 0.03 0.00 0.22 0.93Na2O 14.43 14.45 13.23 13.71 13.04 14.42 4.04 3.43K2O 0.01 0.01 0.02 0.01 0.04 0.05 0.00 0.02H2Oa 9.68 9.55 9.74 9.68 8.30 8.35 13.43 12.41

Total 101.04 101.19 101.72 101.19 100.85 102.18 100.60 98.62Oxygens 10 10 10 10 96 96 20 20Si 3.086 3.076 3.051 3.075 32.645 32.100 5.267 5.292Ti 0.001 0.001 0.000 0.001 0.000 0.000 0.000 0.000Al 1.966 1.931 2.012 1.959 15.562 15.714 4.756 4.727Cr 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.001Mg 0.000 0.003 0.003 0.000 0.000 0.026 0.004 0.001Ca 0.003 0.017 0.083 0.086 0.020 0.115 1.642 0.634Mn 0.001 0.000 0.000 0.000 0.011 0.004 0.000 0.001Fe 0.000 0.000 0.001 0.001 0.000 0.004 0.002 0.000Sr 0.002 0.019 0.000 0.000 0.013 0.024 0.148 1.149Ba 0.001 0.031 0.003 0.000 0.006 0.000 0.011 0.053Na 1.734 1.759 1.579 1.647 14.608 16.074 1.048 0.965K 0.001 0.001 0.001 0.000 0.027 0.036 0.000 0.005Sum 6.796 6.838 6.733 6.769 62.891 64.098 12.879 12.828H2Oa 2 2 2 2 16 16 6 6

Note: aH2O calculated from zeolite stoichiometry assuming full water occupancy of appropriate site.


channel metabasites or sediment. The precipitation ofjadeite along cracks or cleavages in omphacite and theformation of less pure jadeite reflect a replacement or infil-tration of omphacite by jadeite. Since omphacite is inter-mediate between jadeite and diopside, the omphacite couldbe the result of a chemical admixture between diopsidecomponent from mantle pyroxenite and jadeite from jadei-tization. The formation of fine jadeite veins crosscuttingboth omphacite and replaced jadeite, and the absence of anobvious compositional gap between omphacite and jadeite(Fig. 11a), as shown for another jadeitite-omphacitite(AMNH 107991), supports a model of fine-scale dilutionof more diopsidic compositions by jadeite (or kosmochlor)component, probably as micro-scale intergrowths below thespatial resolution of the microprobe, given the low tempera-ture interpretation for these rocks (see below).

Before the formation of the jadeitite, Ca-rich metaso-matism may have occurred. This is supported by the uvaro-vite-bearing rock, which formed by replacement of

chromite. Subsequently, Na-dominant formation of kos-mochlor and Cr-bearing jadeite/omphacite took place(Fig. 8). A tendency of Cr-decrease from chromite touvarovite, kosmochlor and to Cr-bearing jadeite (Fig.11b) is interpreted to be related to the progressive changeof the composition of the crystallizing fluid infiltrating thereplaced chromite.

The six amphibole species from the amphibole rocks arethe result of metamorphic and metasomatic reactionsbetween jadeitites and peridotites at HP/LT conditions(Mevel & Kienast, 1986; Harlow & Olds, 1987; Shi et al.,2003). As the Myanmar jadeitite formed by direct precipita-tion from Na-Al-Si rich fluids, the amphibolite, being boththe spatial and chemical intermediate between jadeitite andserpentinite, is therefore considered to be the product ofwater-rock interaction between the two (e.g., Shi et al.,2003). The zoned amphibole porphyroblasts with magne-siokatophorite in the cores and nyboite and eckermannite inthe rims (Fig. 5) formed in the presence of jadeite, and the

Table 10. Representative chemical compositions of cymrite, vesuvianite, pectolite and titanite in rocks from the Jade Mine Tract, Myanmar.

SampleMJE02-3-6 D2 YX-1

RmaPhase Cym Cym Cym Ves Ves Ves Pct Pct Pct Pct Pct Ttn Ttn Ttn Ttn

No. 8-4 8-11 8-16 9-4 9-6 9-8 8-19 7-3 73 74 75 26 30 31 32

SiO2 30.87 31.89 31.36 36.87 36.86 36.77 53.07 53.41 53.70 54.90 54.98 30.31 30.32 30.37 30.31TiO2 0.11 0.06 0.03 1.90 2.73 2.29 0.00 0.03 0.00 0.00 0.02 39.37 39.05 39.02 39.88Al2O3 25.75 25.78 25.79 18.53 21.77 17.88 0.23 0.12 0.04 0.15 0.39 1.03 1.06 1.15 1.21Cr2O3 bdl bdl bdl 0.11 0.00 0.02 0.00 0.06 0.00 0.08 0.03 0.05 0.02 0.02 0.00Fe2O3 nc nc nc 2.01 1.86 1.67 nc nc nc nc nc nc nc nc ncFeO 0.04 0.06 0.03 0.00 1.60 0.53 0.08 0.07 0.07 0.20 0.10 0.31 0.40 0.62 0.71Mn2O3 nc nc nc 0.00 0.05 0.00 nc nc nc nc nc nc nc nc ncMnO bdl bdl bdl 0.03 0.00 0.01 0.03 0.33 0.18 0.16 0.16 0.02 0.00 0.02 0.04MgO bdl bdl bdl 1.48 1.37 1.45 0.16 0.01 0.01 0.05 0.08 0.01 0.00 0.00 0.03CaO 0.01 0.02 0.12 34.58 34.32 34.75 33.21 33.36 32.63 31.38 31.57 28.37 28.29 27.88 27.27SrO bdl 0.03 0.02 bdl 0.05 bdl 0.02 0.07 n.d. n.d. n.d. n.d. n.d. 0.04 0.05BaO 38.3 38.43 38.10 bdl bdl bdl 0.10 0.07 0.00 0.00 0.00 n.d. n.d. 0.00 0.00Na2O 0.07 0.26 0.10 0.71 0.87 0.68 8.86 9.27 9.15 9.09 9.74 0.05 0.00 0.09 0.08K2O 0.12 0.09 0.25 bdl bdl bdl 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00H2Oa 4.60 4.68 4.64 3.07 2.98 2.69 2.67 2.69 2.67 2.70 2.72 – – – –

Total 99.67 101.31 100.44 99.37 99.20 98.73 98.44 99.50 98.46 98.71 99.79 99.51 99.14 99.20 99.58Normalization 8 O 8 O 8 O 18 Si 18 Si 18 Si 17 O 17 O 17 O 17 O 17 O 10 O 10 O 10 O 10 OSi 2.014 2.042 2.028 18.000 18.00 18.00 5.969 5.963 6.024 6.101 6.057 1.988 1.996 1.998 1.985Ti 0.005 0.003 0.002 0.697 1.00 0.84 0.000 0.003 0.000 0.000 0.002 1.942 1.933 1.930 1.963Al 1.980 1.946 1.965 10.662 10.447 10.316 0.030 0.015 0.005 0.020 0.051 0.080 0.082 0.089 0.094Cr 0.000 0 0 0.044 0.026 0.006 0.000 0.005 0.000 0.007 0.003 0.003 0.001 0.001 0.000Fe3þ nc nc nc 0.738 0.686 0.613 nc nc nc nc nc nc nc nc ncMn3þ nc nc nc 0.000 0.019 0.000 nc nc nc nc nc nc nc nc ncFe 0.002 0.003 0.002 0.013 0.000 0.003 0.007 0.007 0.007 0.019 0.009 0.017 0.022 0.034 0.039Mn 0.000 0 0 0.031 0.000 0.218 0.003 0.031 0.017 0.015 0.015 0.001 0.000 0.001 0.002Mg 0.000 0 0 1.076 0.996 1.057 0.026 0.002 0.002 0.008 0.013 0.001 0.000 0.000 0.003Ca 0.001 0.001 0.008 18.088 17.994 18.227 4.002 3.991 3.922 3.736 3.726 1.994 1.995 1.966 1.913Sr 0.000 0.001 0.001 0.000 0.012 0.000 0.005 0.001 0.000 0.000 0.000 – – 0.001 0.002Ba 0.979 0.965 0.965 0.000 0.000 0.000 0.005 0.003 0.000 0.000 0.000 – – 0.000 0.000Na 0.009 0.033 0.012 0.673 0.823 0.648 1.933 2.006 1.990 1.959 2.080 0.006 0.000 0.011 0.010K 0.010 0.007 0.021 0.001 0.000 0.000 0.001 0.001 0.001 0.000 0.000 0.000 0.000 0.000 0.000

Total 5.000 5.002 5.004 50.024 50.007 49.933 11.983 12.028 11.969 11.865 11.955 6.032 6.029 6.032 6.010OHa 10.000 9.742 10.000 2 2 2 2 2H2Oa 1 1 1

Note: aH2O and OH determined by stoichiometry assuming ideal full occupancy of the appropriate site.


metasomatic fluid infiltration led to the formation of diverseamphibole compositions spanning six species resulting fromcompositional changes during the infiltration event.Because of extensive reactions, the variation of amphibolecomposition (Fig. 11c) at the jadeitite-serpentinite contactobviously reflects non-equilibrium and transient states.

The presence of Ba- and (Ba, Sr)-bearing minerals andtheir textures indicate that Ba and Sr enrichments arecoupled with the development of jadeite-forming fluids.Crystallization of Ba and Sr silicates (celsian, cymrite,hyalophane, thomsonite-Sr, barium mica–kinoshitalite(Harlow, 1995), banalsite, etc.), either from jadeite-

forming fluids or from later fluids after jadeite crystalliza-tion, is an important indication of Ba abundance and mobi-lity in subduction zones at HP conditions. Such high Baconcentrations could result from deep-sea sediments wherebarite is deposited in regions of high biological productiv-ity (e.g., Schmitz, 1987; Dymond et al., 1992; Gingele &Dahmke, 1994; van Beek et al., 2003), as is obvious fromcompilations of deep-sea sediment compositions (Plank &Langmuir, 1998) and hydrothermally infiltrated sediments,particularly near the source of hydrothermal fluids (e.g.,Greinert et al., 2002; Plank, 2005). When these sedimentswere subducted with the down-going oceanic slab, they

Fig. 11. Compositional plots for pyroxenes and amphiboles from rocks in the Jade Mine Tract (a) Pyroxenes, from Table 3 (not includingK068-5, 6, 9, 10 due to high Cr contents), from Yi et al. (2006), and jadeitite-omphacitite AMNH 107991. (b) Pyroxenes (recalculated), fromfig. 12 in Shi et al. (2005a); Ou Yang (1984); Mevel & Kienast (1986) and Harlow & Olds (1987). (c) Amphiboles, from fig. 13c in Shi et al.(2003). Plot of BNa vs. Si. The closed symbols in these plots indicate amphibole compositions with tetrahedral Si of 7.5–8 apfu, open symbolsamphiboles with Si , 7.5 apfu. The amphibole species associated with the symbols are open squares Mkt, open diamonds Nyb, closeddiamonds Eck, upright closed triangles Gln, reversed closed triangles Wnc, closed squares Rct. The chemical analyses are all from tables 4–7in Shi et al. (2003).


became the source for barium released into jadeite-formingfluids (e.g., Shi et al., 2010) and subsequently crystallizedin the barian minerals. This interpretation is supported bythe common occurrence of Ba-bearing minerals in otherwell-documented jadeitite localities (e.g., Harlow, 1995;Morishita, 2005; Shi et al., 2010), and it is possibly thesame source of the Sr-enrichments (Kobayashi et al., 1987;Harlow, 1994; Miyajima et al., 1999, 2001, 2002).

The zeolites and other related hydrous minerals in theMyanmar jadeitite area occur spatially in close associationwith the jadeitite veins. All the zeolites are Na-rich. However,little attention has been paid to these minerals, and theirparageneses are not well explained, although they may havesignificant implications for the fluid evolution (and jadequality). This is clearly a topic for future investigation.

6.2. Pressure and temperature of formation

Jadeitites are clearly the result of HP/LT conditions pro-duced only in subduction zone environments. However,the nearly monomineralic high variance assemblages donot provide ready P-T constraints, as has been pointed outpreviously (e.g., Sorensen et al., 2006; Harlow et al.,2007). Primary crystallization of jadeite from a fluid with-out quartz or albite only indicates pressure above the reac-tion Anl¼ Jdþ H2O. Four estimates of P-T conditions areavailable (Fig. 12): Mevel & Kienast (1986) give a roughestimate based on the presence of jadeite and analogy withrocks from the western Alps – a broad band of 1 GPa , P, 1.5 GPa and 300 �C , T ,500 �C; Goffe et al. (2000)used textural constraints and a phase assemblage in ablueschist overprint in an eclogite recovered from allu-vium in the Jade Tract area (1.4 GPa , P , 1.6 GPa and400 �C , T , 450 �C); Shi et al. (2003) included phaseequilibria with amphiboles, and Oberhansli et al. (2007)recalculated jadeite-omphacite-amphibole equilibria usinga pseudo-section approach. These broad PT estimates areshown in Fig. 12. Other jadeitite, notably that from Sierradel Convento in eastern Cuba (Garcia-Casco et al., 2009;Cardenas-Parraga et al., 2010), is interpreted to form athigher T, 550–560 �C based on intimate Jd – Omp inter-growths and their compositions. Whereas we cannot as yetrule out such an interpretation, as with Harlow et al. (2011)the preponderance of nearly pure Jd with Ab and lateintergrown omphacite, in most cases, would suggest thesomewhat lower temperature maximum we present above.Clearly from our discussion above, the applicability ofthese approaches assuming equilibria among the phasesused have serious limitations. Subsequent formation ofalbite and analcime requires lower pressure which likelyresulted from continued fluid infiltration during exhuma-tion. An estimate of P-T evolution is given in Fig. 12,showing the requisite decrease of pressure with time.

6.3. Final comments

Although jadeitites can be cryptic rocks with few otherphases than jadeite, particularly in gem quality material,

mineral diversity is considerable at all jadeitite localities ifsampling is sufficient. Apart from the Myanmar jadeititeoccurrences, all the well-documented jadeitite localitieshave a generally similar and diverse suite of minerals(Table 11). Minerals identified from all localities representmore than 50 species. Even in recently reported localities,such as Iran, Italy, Cuba, and the Dominican Republic(e.g., Oberhansli et al., 2007; Compagnoni et al., 2007,2012; Garcia-Casco et al., 2009; Schertl et al., 2012),similar mineral associations among relatively rare rock-forming phases have been reported, with some significantvariations with respect to the presence of thermobarometri-cally important phases like lawsonite versus clinozoisite,particularly micas, and quartz. Similarities with respect toenrichments in Ba or Sr phases have not been reported in thenewer finds, but this may change with further sampling andresearch. Nevertheless, the commonalities lead to twopoints. One is that the similar mineral suites in jadeitite andrelated rocks result from similar combinations of enrich-ments in several alkaline metals and alkaline earths, water,and a broadly similar conditions and perhaps P-T-t evolu-tion. The other is that mineralogical distinctions, a functionof bulk composition, conditions, and evolution, among thenow 19 sources typically do exist among them – they are notidentical. This can be used for interpreting sources of thejadeite jade, particularly in archaeology.

Mineralogy of jadeitites worldwide, combined with stu-dies of tectonics, age dating and trace-element signatures

Fig. 12. An approximate P-T path (broad dashed arrow) for jadeititeand related rocks in Myanmar based on available petrogenetic gridsand phase equilibria (P-T condition diagram from Shi et al. (2010)).


Tab

le1

1.

Ph

ases

pre

sen

tin

jad

eiti

tes

and

thei

rre

tro

gra

de

asse

mb

lag

esfr

om

mo

sto

fth

elo

cali

ties

wo

rld

wid

e.

Min

eral

gro

up

Spec

ies

Jade

Min

e

Tra

ct,

Myan

mar

Nan

sibon,

Myan

mar

N.

of

Mota

gua

Fau

lt,

Guat

emal

a

S.

of

Mota

gua

Fau

lt,

Guat

emal

a

New

Idri

a

Ser

p.,

Cal

iforn

ia

Sie

rra

del

Conven

to,

Cuba

Dom

inic

an

Rep

ubli

c

Itoig

awa

area

,

Japan

Osa

yam

a-

Wak

asa-

Oya,

Japan

Nis

his

onogi

Bel

t,

Japan

Iran

Pola

r

Ura

ls,

Russ

ia

Boru

s

Bel

t,

Khak

assi

aK

azak

hst

an

Syro

s-

Tin

os,

Gre

ece

Ital

ian

Alp

s

Pyro

xen

eJa

dei

teP

PP

PP

PP

PP

PP

PP

PP

P

Om

phac

ite

PP

P,

IP

,I

PP

PP

PP

,I

PS

PP

SP

Augit

eU

P?

R

Kom

osc

hlo

rP

Dio

psi

de

SS

Chro

mia

npyro

xen

eP

PP

PP

IP

Fel

dsp

arA

lbit

eS

SI,

SS

SS

PS

SS

SS

SS

K-f

eldsp

arS

SU

Hyal

ophan

eI

II

I

Cel

sian

IS

SI

I

Ban

alsi

teI

SU

Str

onal

site

SS

Am

phib

ole

Eck

erm

annit

eP

?

Nyboit

eP

‘‘H

orn

ble

nde’

’P

Mag

nes

io-

kat

ophori

teP

Kat

ophori

te

Ric

hte

rite

P

Gla

uco

phan

eP

PU

PU

Win

chit

eP

Tar

amit

e-fe

rrota

ram

ite

I,S

Tre

moli

te

-act

inoli

te

?S

SS

SS

S

Mic

aP

hlo

gopit

eU

II?

UU

SP

PP

Bio

tite

SS

P

Par

agonit

eP

PP

Musc

ovit

e-phen

git

eP

PP

PW

hit

emic

a

Pre

isw

erkit

eS

Tal

cS

Chlo

rite

SS

SU

US

Zeo

lite

Anal

cim

eS

SI,

SS

SS

SS

SS

S

Nat

roli

teS

US

Thom

sonit

e-C

aU

US

Thom

sonit

e-S

rU

U

Pec

toli

teU

SU

US

Pum

pel

lyit

eS

PU

Ves

uvia

nit

eS

SS

S

Gar

net

Gro

ssula

rP

II,

SU

P

Uvar

ovit

eP

Alm

andin

eR

R�

P?

Tit

anit

eU

P,I

,SP

,I,S

UP

US

PP

Pre

hnit

eS

Zir

con

R,

PP

PP

PP

R,

PR

,P

PP


Tab

le1

1.

Co

nti

nu

ed

Min

eral

gro

up

Spec

ies

Jade

Min

e

Tra

ct,

Myan

mar

Nan

sibon,

Myan

mar

N.

of

Mota

gua

Fau

lt,

Guat

emal

a

S.

of

Mota

gua

Fau

lt,

Guat

emal

a

New

Idri

a

Ser

p.,

Cal

iforn

ia

Sie

rra

del

Conven

to,

Cuba

Dom

inic

an

Rep

ubli

c

Itoig

awa

area

,

Japan

Osa

yam

a-

Wak

asa-

Oya,

Japan

Nis

his

onogi

Bel

t,

Japan

Iran

Pola

r

Ura

ls,

Russ

ia

Boru

s

Bel

t,

Khak

assi

aK

azak

hst

an

Syro

s-

Tin

os,

Gre

ece

Ital

ian

Alp

s

Epid

ote

gro

up

Zois

ite,

clin

ozo

isit

eS

PI

PP

Epid

ote

UP

PS

P,

S

All

anit

eU

PP

UR

?or

PP

P

Cli

niz

ois

ite-

(Sr)

I

Ruti

leR

?R

or

PU

PR

??

Ilm

enit

eU

U

Law

sonit

e

Gro

up

Law

sonit

eP

,S

U�

PU

U

Itoig

awai

teU

Cym

rite

SI

SU

Nep

hel

ine

S

Phosp

hat

esA

pat

ite

PP

PP

?R

?

Monaz

ite

PP

Spin

elG

roup

Chro

mit

eR

RR

R

Mag

net

ite

Quar

tzS

�P

,I,

S�

PS

P

Sulf

ides

Gal

ena

SS

Pyri

teU

I

Chal

copyri

teI

Cal

cite

SS

SP

S

Dia

spore

S

Kao

linit

eS

SS

Per

rier

ite

gro

up

Ren

gei

teS

Mat

subar

aite

S

Nat

ive

elem

ents

Gra

phit

eP

I,S

IR

Iron

R

Copper

U

Note

s:S

ym

bols

refe

rto

stag

ein

asse

mbla

ges

:�

indic

ates

dis

tinct

types

wit

han

dw

ithout

this

phas

e,R

,R

elic

t(i

nher

ited

);P

,P

rim

ary;

I,In

term

edia

te;

S,

Sec

ondar

y;

U,

unsp

ecif

ied;?

,su

spec

ted

but

unco

nfi

rmed

.

Min

eral

occ

urr

ence

sar

eco

mpil

edac

cord

ing

toal

lav

aila

ble

rela

ted

lite

ratu

res

of

jadei

tite

s,in

cludin

gB

auer

(1895);

Noet

ling

(1893,1896);

Ble

eck

(1907,1908);

Chhib

ber

(1934);

Mork

ovkin

a(1

960);

Cole

man

(1961);

Dobre

tsov

(1963);

Yudin

(1965);

Ess

ene

(1967);

Chih

ara

(1971);

Ben

der

(1983);

Ou

Yan

g(1

984);

Thin

(1985);

Mev

el&

Kie

nas

t(1

986);

Har

low

&O

lds

(1987);

Kobay

ashi

etal.

(1987);

Har

low

(1994,1995);

Hte

in&

Nai

ng

(1994);

Miy

ajim

aet

al.

(1999,2001,2002);

Qi

etal.

(1999);

Hughes

etal.

(2000);

Tsu

jim

ori

(2002);

Har

low

etal.

(2003,2007,2011);

Har

low

&S

ore

nse

n(2

005);

Shi

etal.

(2003,2005a,

2010,2011);

Mori

shit

a

(2005);

Shig

eno

etal.

(2005,2012);

Tsu

jim

ori

etal.

(2005);

Tsu

jim

ori

&H

arlo

w(2

012);

Yi

etal.

(2006);

Com

pag

noni

etal.

(2007,2012);

Ober

han

sli

etal.

(2007);

Gar

cia-

Cas

coet

al.

(2009);

Nyunt

etal.

(2009);

Wan

g

etal.

(2012),

Sch

ertl

etal.

(2012);

and

dat

afr

om

this

inves

tigat

ion.


of depleted mantle from zircon, plus chemical and isotopicsignatures (Morishita et al., 2007; Shi et al., 2008, 2009; Fuet al., 2010; Simons et al., 2010; Yui et al., 2010, 2012)suggest that jadeitites world-wide share similarities in ori-gin, despite differences of formation ages, mineral assem-blages and quality of the jadeite jade. Although there arestill some controversies about the exact source of the jadei-tic fluids (Sorensen et al., 2006; Morishita et al., 2007; Shiet al., 2008; Garcia-Casco et al., 2009; Fu et al., 2010;Simons et al., 2010; Yui et al., 2010; Harlow et al., 2011),further research on the mineralogy, petrology and geo-chemistry of jadeitites and related rocks world-wide willenhance our understanding of the origin of the fluids andthe nature of the water-rock interactions involved.

Acknowledgements: We are indebted to R.X. Zhu andL.C. Chen for their kind support during the fieldwork andsubsequent research. We extend thanks to Q. Mao and Y.G.Ma for their help with EPMA. Constructive comments byT. Tsujimori (Guest Editor), W.V. Maresch (Special IssueEditor), R. Miyawaki and an anonymous referee were veryhelpful and are highly appreciated. The research was sup-ported by the National Basic Research Program of China(2009CB421008), the Program for the New CenturyExcellent Talents in China (NCET-07-0771), theFundamental Research Funds for the Central Universities(2001YXL048), and Collection Study Grant Program(40.0699) of the American Museum of Natural History.

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Received 26 January 2011

Modified version received 28 November 2011

Accepted 4 January 2012


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Mineralogy of Jadeitite and Related Rocks From Myanmar