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320 R.T. Orozbaev, K. Yoshida, A.B. Bakirov, T. Hirajima, A. Takasu, K.S. Sakiev and M. TagiriJournal of Mineralogical and Petrological Sciences, Volume 106, page 320─325, 2011
doi:10.2465/jmps.110621cR.T. Orozbaev, [email protected] Corresponding author
LETTER
Preiswerkite and högbomite within garnets of Aktyuz eclogite, Northern Tien Shan, Kyrgyzstan
Rustam T. OrOzbaev*,**, Kenta YOshida*, Apas B. bakirOv**, Takao hirajima*, Akira Takasu***, Kadyrbek S. sakiev** and Michio Tagiri****
*Department of Geology and Mineralogy, Kyoto University, Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
**Institute of Geology, Kyrgyz National Academy of Science, 30 Erkindik Avenue, Bishkek 720481, Kyrgyzstan
***Department of Geosciences, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
****Hitachi City Museum, Miyatacho 5-2-22, Hitachi 317-0055, Japan
We report the occurrence of preiswerkite and högbomite as inclusion phases within the garnets of eclogite from the Aktyuz area of Northern Tien Shan, Kyrgyzstan. Preiswerkite and högbomite occur both as a constituent of multiphase solid inclusions (MSI) and as single discrete grains in the mantle and rim of the garnets. However, they do not occur in the core of the garnet and in the matrix of the eclogite. Preiswerkite is associated with the minerals paragonite ± staurolite ± Mg-taramite ± Na-biotite ± hematite ± högbomite ± chlorite ± titanite ± phengite ± magnetite, and högbomite is associated with paragonite ± preiswerkite ± staurolite ± hematite ± chlorite ± Na-biotite ± magnetite in MSI. The average compositions of preiswerkite and högbomite are (Na0.96K0.02Ca0.01)0.99(Mg1.52Fe2+
0.54VIAl0.93)2.99(IVAl1.93Si2.07)4.00O10(OH)2 and (Mg1.47Fe2+
3.02Zn0.04Fe3+1.45)5.98(Fe3+
0.31Al15.13Ti0.56)16O30
(OH)2, respectively. Na-biotite, with an average composition of (Na0.89K0.07Ca0.01)0.97(Mg1.66Fe2+0.69
VIAl0.63)2.98(IVAl1.57
Si2.43)4.00O10(OH)2, corresponding to the intermediate composition between preiswerkite and aspidolite (i.e., Na-phlogopite), is also observed. The compositions of the newly found preiswerkite and Na-biotite with similar XMg values (0.66-0.78) are arrayed along preiswerkite-aspidolite solid solution series. The mode of occurrence of inclusion phases in garnets may suggest that the activity of Na-Al-rich and Si-undersaturated aqueous fluids played a major role in the formation of preiswerkite during the prograde stage of high-pressure eclogitic meta-morphism.
Keywords: Preiswerkite, Högbomite, Na-biotite, Aktyuz area, Eclogite, Tien Shan, Kyrgyzstan
INTRODUCTION
The trioctahedral Al-rich sodium mica preiswerkite (Prw) is a rare naturally occurring mineral with the ideal formu-la Na(Mg2Al)(Al2Si2O10)(OH)2. Ever since it was first de-scribed in a metarodingite in the Geisspfad ultramafic complex, the Penninic Alps, Switzerland (Keusen and Pe-ters, 1980), preiswerkite has been reported from several localities in the world. A summary of the host rock type, mode of occurrence, and mineral assemblage associated with preiswerkite from each locality is compiled in sup-plementary Table S1 (available online http://joi.jlc.jst.go.jp/JST.JSTAGE/jmps/110621c). These data suggest
that preiswerkite mostly occurs as symplectitic or coroni-tic aggregates, thus as constituent of retrograde mineral assemblages.
In this paper, we report on the first occurrence of preiswerkite as an inclusion phase within the garnets of eclogite from the Aktyuz area, Northern Tien Shan, Kyr-gyzstan. It occurs as discrete grains and as a constituent of multiphase solid inclusions (MSI) along with other minerals such as paragonite (Pg), staurolite (St), hematite (Hem), Na-biotite (Na-Bt), chlorite (Chl), högbomite (Hgb), magnetite (Mag), Mg-taramite (Mtm), phengite (Ph), and titanite (Ttn). We further report that högbomite, a rare mineral with the general formula (Mg,Fe,Mn,Zn)6
(Fe,Al,Ti)16O30(OH)2 related to the spinel group, is newly found in the Aktyuz eclogite.
321Preiswerkite and högbomite in garnets, Aktyuz eclogite
The petrography and mineral chemistry of the main constituent minerals in the studied sample have been de-scribed by Orozbaev et al. (2007, 2010). Herein, our pri-mary focus is on the mode of occurrence of preiswerkite and högbomite inclusions within garnets. We describe their chemical composition, Raman spectroscopy data and discuss their significance in MSI.
GEOLOGICAL SETTING AND PETROGRAPHY
The Aktyuz Formation is located in the Zaili Range in Northern Tien Shan, Kyrgyzstan, and it consists of pelitic gneisses, gneissose-granites and migmatites, accompa-nied by eclogites, garnet amphibolites and amphibolites that occur as layers or lenticular bodies (Bakirov, 1978; Tagiri et al., 1995; Bakirov et al., 2003; Orozbaev et al., 2007, 2010). A detailed description of the geology in the area and the location of studied sample (KG-426) were previously reported by Orozbaev et al. (2007, 2010). Eclogites in the Aktyuz area experienced three distinct metamorphic events (M1-M3), namely a precursor medi-um-pressure and high-temperature (MP-HT) metamor-phic event (M1), a high-pressure and low-temperature (HP-LT) eclogitic event (M2), and a high-pressure and high-temperature (HP-HT) metamorphic event (M3), whereas the surrounding country-rock gneisses experi-enced a single metamorphism of the HP-HT event (M3) (Orozbaev et al., 2007, 2010).
Orozbaev et al. (2007) divided garnets of eclogites according to their chemical composition into core [Mg = 0.17-0.73, Ca = 1.07-0.78, Fe < 2.16, and Mn < 0.16 per formula unit (p.f.u.)] and rim (Mg = 0.73, Ca = 0.56, Fe =
1.74, and Mn = 0.01 p.f.u.), and proposed that mineral in-clusions in garnets formed at two distinct metamorphic events i.e., M1 and M2. For instance, a relic mineral as-semblage of staurolite + Mg-taramite + paragonite ± he-matite ± oligoclase (An<16) in garnet cores is referred to be formed under the precursor amphibolite or epidote-amphibolite facies metamorphism (M1; 560-650 °C, 4-10 kbar). Another group of mineral inclusions that are repre-sentative of the epidote-blueschist facies conditions (330-
570 °C, 8-16 kbar) during the prograde stage of the eclog-itic metamorphic event (M2) are composed of glaucophane, barroisite, Mg-katophorite, epidote, paragonite, phengite, aegirine-rich omphacite, albite, quartz, rutile, and hema-tite. This group of mineral inclusions also occurs in the garnet core and only rarely at garnet rims. Discrete miner-al inclusions of omphacite, phengite, paragonite and rutile occurring in garnet rims are suggested to have been formed under the peak conditions of M2 (550-660 °C, 21-23 kbar; Orozbaev et al., 2010).
The sample (KG-426) is medium- to coarse-grained, and consists mainly of garnet, omphacite, phengite and paragonite, along with minor rutile and quartz.
Garnets in the eclogite are subhedral, up to 2 mm in diameter, and contain various types of inclusions (Fig. 1). Garnets show zoning from core to rim with decreasing Ca, Fe, and Mn contents and with increasing Mg content (see supplementary material Fig. S2, available online http://joi.jlc.jst.go.jp/JST.JSTAGE/jmps/110621c), and on the basis of their chemical compositional zoning they can be divided into core (Mg = 0.17-0.38, Ca = 1.07-0.81, Fe = 2.16-1.86, and Mn = 0.16-0.07 p.f.u.), mantle (Mg = 0.38-0.73, Ca = 0.81-0.66, Fe = 1.86-1.74, and Mn =
Figure 1. Backscattered electron images showing the mode of occurrences of preiswerkite, Na-biotite, and hög-bomite within garnet of Aktyuz eclog-ite (KG-426). (a) Subhedral crystal of zoned garnet containing discrete and multiphase solid inclusions (MSI). (b) Epidote, Mg-katophorite, rutile, apa-tite, and ilmenite occurrences with MSI of St + Na-Bt in the garnet core. (c) MSI of Prw + St + Pg + Hem + Na-Bt + Chl and St + Hem + Na-Bt in the garnet mantle. Preiswerkite occurs as discrete grains. (d) MSI consisting of Prw + Pg + Hgb + Mag and Prw + Pg. Zircon grains occur nearby. (e) Paragonite occurs next to the MSI of St + Hgb + Hem + Na-Bt in the rim of the garnet.
322 R.T. Orozbaev, K. Yoshida, A.B. Bakirov, T. Hirajima, A. Takasu, K.S. Sakiev and M. Tagiri
0.07-0.02 p.f.u.), rim (Mg = 0.73-0.81, Ca = 0.66-0.53, Fe = 1.74-1.65, and Mn = 0.02-0.01 p.f.u.), and outer-most rim (Mg = 0.56, Ca = 0.55, Fe = 1.81 and Mn = 0.03 p.f.u.). These differing zones are illustrated in Figure 1a, in which it is shown that the garnet has a bright core sur-rounded by a grey mantle and a dark rim. The outermost rim can be seen as bright, very thin layers that lie at the margins of the garnet rim. These four zones correlate well with the compositional zoning of Mg, Ca, and Fe shown in the color element map (Fig. S2). Moreover, they corre-spond to the core (core and mantle in this study) and rim (rim and outermost rim) reported by Orozbaev et al. (2007).
Preiswerkite occurs both as a member of MSI and as discrete grains in the mantle and rim of garnets (Figs. 1a, 1c, and 1d). Preiswerkite is either colorless or pale yellow to pale green in color, and it occurs as small-sized plates up to 80 µm in length, with a typical mica habit. The MSI associated with preiswerkite are mainly composed of par-agonite, staurolite, hematite, Na-biotite, chlorite, hög-bomite, magnetite, Mg-taramite, phengite and titanite. The following assemblages are observed (Figs. 1c and 1d): Prw + Pg + Hgb ± Mag ± Chl, Prw + Pg + St + Hem + Chl ± Na-Bt, Prw + St + Mtm + Na-Bt + Hem, Prw + Pg + Hem ± Chl, Prw + St + Na-Bt + Chl, Prw + Pg + Mtm + Chl + Ttn + Ph, Prw + St ± Hem, Prw + Pg, and Prw + Hgb.
Other sodium micas observed in the MSI are parago-nite and Na-mica referred to as “Na-biotite”. Paragonite is colorless and occurs as plates of up to 300 µm in length, mainly in the mantle and rim zones of garnets (Figs. 1a, 1c, 1d, and 1e) but rarely in the core part. It can also be found as discrete grains. On the other hand, Na-biotite always occurs as a constituent mineral of MSI (Figs. 1b, 1c, and 1e). It is pale green to green in color and occurs as platy grains that are up to 100 µm in length.
Högbomite is brown in color and forms fine-grained subhedral grains (up to 60 µm in length). It occurs both as a member of MSI and as discrete grains in the mantle and rim of garnets. Högbomite-bearing MSI are mainly com-posed of the following assemblages: Hgb + Pg + Prw ± Mag ± Chl, Hgb + St + Hem + Na-Bt ± Pg, and Hgb + Prw.
Staurolite is colorless to pale brown in color and forms prismatic (sometimes idiomorphic) crystals that can reach 300 µm in length. It also occurs as a member of MSI or as discrete grains, mainly in the mantle and rim of garnets but rarely in the core. Staurolite-bearing MSI oc-curring in the core of garnets are preiswerkite-free and are mainly composed of St + Na-Bt (Fig. 1b) and St + Mtm + Pg ± Hem ± Pl (Orozbaev et al., 2007).
Other inclusion phases such as epidote, sodic and so-
dic-calcic amphiboles (glaucophane, Mg-katophorite, Mg-taramite, taramite, and barroisite), aegirine-rich om-phacite, rutile, ilmenite, hematite, pyrite, plagioclase, and rare quartz occur mainly in the core and rarely in the mantle of garnets. In the rim of the garnets, mineral inclu-sions of omphacite (with less aegirine component), para-gonite, rutile, apatite, and rare epidote are present. The constituent minerals of MSI, such as preiswerkite, hög-bomite, staurolite, Na-biotite, and magnetite are not ob-served in the matrix of eclogite and they present only as inclusions within garnets.
MINERAL CHEMISTRY AND RAMAN SPECTROSCOPY DATA
Mineral compositions were determined using electron probe micro analyzers at Shimane University (JEOL JXA-8800M) and Kyoto University (JEOL JXA-8105). Backscattered electron images were obtained using a Hi-tachi S3500H scanning electron microprobe equipped with an EDAX energy-dispersive X-ray analytical system at Kyoto University. The representative microprobe anal-yses of the minerals (preiswerkite, Na-biotite, and hög-bomite) are listed in Table 1.
The average composition of twelve microprobe anal-yses of preiswerkite gives a structural formula of (Na0.96
K0.02Ca0.01)0.99(Mg1.52Fe2+0.54
VIAl0.93)2.99(IVAl1.93Si2.07)4.00O10
(OH)2, based on 11 oxygen, which is close to the theoreti-cal end-member formula Na(Mg2Al)(Al2Si2O10)(OH)2 (Fig. 2). The obtained formula of preiswerkite exhibits the interlayer cation >0.85 and octahedral cation >2.5 (Table 1), suggesting that it is a trioctahedral sodium-rich true mica (Reider et al., 1998). The preiswerkite composition shows trend toward the aspidolite (i.e., Na-phlogopite) and preiswerkite solid-solution series (Fig. 2). XMg = Mg/(Mg + Fe + Mn) varies from 0.68 to 0.78, which is the lowest value comparing to those reported in the literature (XMg = 0.74-0.96, see Table S1). XNa = Na/(Na + K + Ca) ranges from 0.92 to 0.99. The Cr2O3, Cl, and F contents are negligible (<0.03 wt%).
The composition of Na-biotite lies between those of the preiswerkite and aspidolite solid-solution series, and plots near the “aspidolite” composition (XMg = 90-91) re-ported by Banno et al. (2005) (Fig. 2). The average com-position of eleven microprobe analyses of Na-biotite cor-responds to the structural formula (Na0.89K0.07Ca0.01)0.97
(Mg1.66Fe2+0.69
VIAl0.63)2.98(IVAl1.57Si2.43)4.00O10(OH)2. Na-bio-tite differs from preiswerkite in terms of the (Mg + Fe) and IVAl values (Fig. 2); however, the XMg ratios of Na-Bt and Prw are relatively similar, 0.66-0.73 and 0.68-0.78, respectively. The Cr2O3, Cl, and F contents are negligible (<0.04 wt%).
323Preiswerkite and högbomite in garnets, Aktyuz eclogite
Högbomite is relatively homogeneous in composi-tion, with the average structural formula (Mg1.47Fe2+
3.02Zn0.04
Fe3+1.45)5.98(Fe3+
0.31Al15.13Ti0.56)16O30(OH)2 (Table 1). It can be classified as ferrohögbomite (Armbruster, 2002). The XMg values range between 0.22 and 0.25, whereas the ZnO content is less than 0.31 wt%. Högbomite contains ferric iron (up to 1.86 p.f.u.), as calculated assuming the stoichi-ometry (Droop, 1987).
Paragonite has Si = 2.55-2.98 p.f.u. and XNa = 0.72-
0.91, with a high margarite component of up to Ca = 0.27 p.f.u. XMg of staurolite ranges between 0.16 and 0.29, and the ZnO content is as much as 0.32 wt%.
Raman spectroscopy analysis of preiswerkite and högbomite was performed with a laser Raman spectro-photometer (JASCO NRS-3100) at Kyoto University, us-ing the 514.5 nm line of an Ar+ laser. Calibration of the instrument was verified using the 520 cm−1 Si band and a Ne spectrum. In the case of preiswerkite, the observed peaks at 212, 280, 643, and 911 cm−1 and the OH stretch-ing peak at 3625 cm−1 were identical to those in the refer-ence preiswerkite spectra (peaks at 216, 292, 648, and 916 cm−1 and the OH stretching peak at 3628 cm−1) re-
Figure 2. IVAl vs. Mg + Fe composition plot of preiswerkite, Na-biotite, and paragonite in Aktyuz eclogite. The reported composi-tions of preiswerkite (all combined in Table S1) and aspidolite from other localities are also shown.
Table 1. Representative microprobe analyses of preiswerkite, Na-biotite, paragonite, and högbomite in the Aktyuz eclogite
* Average composition of 12 and 11 analyses, respectively. ** Standard deviation. *** Total Fe as FeO.
324 R.T. Orozbaev, K. Yoshida, A.B. Bakirov, T. Hirajima, A. Takasu, K.S. Sakiev and M. Tagiri
ported by Tlili et al. (1989). The Raman spectra of hög-bomite, with peaks at 257, 412, 525, 711, 776, and 830 cm−1, was similar to the högbomite spectra (peaks at 261, 421, 529, 723, 782, and 846 cm−1) reported by Tsunogae and Santosh (2005). The slight differences in the wave-numbers (within <16 cm−1) may reflect the compositional variations between variety of preiswerkite and högbomite considered in this study and those reported in the litera-ture.
DISCUSSION
Preiswerkite and högbomite occur as constituents of MSI and as single discrete grains within garnets, while neither is observed in the matrix of the Aktyuz eclogite. Pre-iswerkite is associated with St ± Pg ± Mtm ± Na-Bt ± Hem ± Hgb ± Chl ± Ttn ± Ph ± Mag, and högbomite is associated with Pg ± Prw ± St ± Hem ± Chl ± Na-Bt ± Mag in MSI.
The possible stability field of preiswerkite is sug-gested to be within the range P = 0.5-5.0 kbar and T = 500-850 °C, according to the experimental study on K-
Na-Al-Fe-Mg micas (Hewitt and Wones, 1975; Franz and Althaus, 1976). The natural occurrences of pre-iswerkite are reported within the conditions P < 15 kbar and T < 700 °C (Table S1). These previous studies illus-trate that preiswerkite appears in H2O-saturated, unusual Na-Al-rich, and Si-poor systems (e.g., Godard and Smith, 1999; Visser et al., 1999), and the rarity of this mica is not related to extreme or unusual P-T conditions.
Högbomite has been described from greenschist/am-phibolite facies to ultra-high temperature (UHT) granulite facies metamorphic rocks (T = 400-800 °C; P = 3-15 kbar). It is considered as a product of retrogressive meta-morphism after spinel, mainly caused by the introduction of hydrous and oxidized fluids (Rammlmair et al., 1988; Liati and Seidel, 1996; Tsunogae and Santosh, 2005; Ra-kotonandrasana et al., 2010). Some prograde högbomite experiencing UHT metamorphism with T > 1000 °C has also been reported from the granulite facies Mg-Al rock (Nishimiya et al., 2009).
Rammlmair et al. (1988) found preiswerkite and chlorite symplectite at the contact between högbomite and spinel in a Mg-Fe-Al-rich layer within the serpentinite schist in Botswana (Table S1). They suggested that hög-bomite is a retrograde product after spinel, still at the granulite facies, whereas preiswerkite is developed after högbomite during amphibolite/greenschist facies meta-morphism.
On the basis of the discussion above, we conclude that preiswerkite and högbomite can be stable over a wide range of P-T conditions and that their formation is mainly
controlled by the unusual bulk chemistry of the rock. In Aktyuz eclogite, preiswerkite always exists as a
constituent of MSI and as discrete grains in the mantle and rim of prograde zoned garnets, where the Ca and Mg contents are lower and higher than those in the core, re-spectively (Fig. S2). Furthermore, Ca-bearing phases (ep-idote and sodic-calcic amphiboles, Figs. 1a and 1b) are abundant in the core of the garnet but less in the mantle/rim, where the amounts of Na-micas and Al-rich phases are increases (Figs. 1c, 1d, and 1e). These facts may sug-gest that the preiswerkite was formed during prograde metamorphism, prior to or close to the peak eclogite fa-cies stage, possibly caused by the infiltration of hydrous Na-Al-rich and Si-undersaturated fluids at the garnet mantle/rim forming stage. On the other hand, Ferrando et al. (2005) proposed that the MSI in peak minerals can represent the remnants of silicate-rich aqueous fluids that were dominant under prograde or peak metamorphic con-ditions. Further detailed studies on the formation mecha-nism of MSI in garnets will open a new window in the study of deep fluid activity below plate convergent re-gions.
ACKNOWLEDGMENTS
Constructive reviews by Toshiaki Tsunogae and an anony-mous referee and editorial handling by Norimasa Shimo-bayashi are greatly acknowledged. We thank Tetsuo Kawakami for his valuable discussion and help with the EPMA analyses. We also thank Atsushi Goto for his com-ments on the early version of the manuscript. This study was partly supported by a JSPS Grant-in-Aid for Scien-tific Research to T.H. (Nos. 21109004 and 22244067) and A.T. (No. 17340149).
SUPPLEMENTARY MATERIAL
Table S1 and Figure S2 showing the color element (Mg, Ca, Fe, and Mn) maps of garnet are available online from http://joi.jlc.jst.go.jp/JST.JSTAGE/jmps/110621c.
REFERENCES
Armbruster, T. (2002) Revised nomenclature of högbomite, niger-ite, and taaffeite minerals. European Journal of Mineralogy, 14, 389-395.
Bakirov, A.B. (1978) Tectonic positions of metamorphic complex-es in Tien-Shan. pp. 261, Ilim, Frunze.
Bakirov, A.B., Tagiri, M., Sakiev, K.S. and Ivleva, E. (2003) The Lower Precambrian rocks in the Tien-Shan and their geody-namic settings. Geotectonics, 37, 368-380.
Banno, Y., Miyawaki, R., Kogure, T., Matsubara, S., Kamiya, T. and Yamada, S. (2005) Aspidolite, the Na analogue of phlog-opite, from Kasuga-mura, Gifu Prefecture, central Japan: de-
325Preiswerkite and högbomite in garnets, Aktyuz eclogite
scription and structural data. Mineralogical Magazine, 69, 1047-1057.
Bucher, K. and Grapes, R. (2009) The eclogite-facies Allalin gab-bro of the Zermatt-Saas ophiolite, Western Alps: a record of subduction zone hydration. Journal of Petrology, 50, 1405-
1442.Droop, G.T.R. (1987) A general equation for estimating Fe3+ con-
centrations in ferromagnesian silicates and oxides from mi-croprobe analyses, using stoichiometric criteria. Mineralogi-cal Magazine, 51, 431-435.
Ferrando, S., Frezzotti, M.L., Dallai, L. and Compagnoni, R. (2005) Multiphase solid inclusions in UHP rocks (Su-Lu, China): Remnants of supercritical silicate-rich aqueous fluids released during continental subduction. Chemical Geology, 223, 68-81.
Franz, G. and Althaus, E. (1976) Experimental investigation on the formation of solid solutions in sodium-aluminium-mag-nesium micas. Neues Jahrbuch für Mineralogie, Abhandlun-gen, 126, 233-253.
Godard, G. and Smith, D. (1999) Preiswerkite and Na-(Mg,Fe)-margarite in eclogites. Contributions to Mineralogy and Pe-trology, 136, 20-32.
Harlow, G.E. (1994) Jadeitites, albitites and related rocks from the Motagua Fault Zone, Guatemala. Journal of Metamorphic Geology, 12, 49-68.
Hewitt, D.A. and Wones, D.R. (1975) Physical properties of some synthetic Fe-Mg-Al trioctahedral biotites. American Miner-alogist, 60, 854-862.
Keusen, H.R. and Peters, T. (1980) Preiswerkite, an Al-rich trioc-tahedral sodium mica from the Geisspfad ultramafic complex (Penninic Alps). American Mineralogist, 65, 1134-1137.
Liati, A. and Seidel, E. (1996) Metamorphic evolution and geo-chemistry of kyanite eclogites in central Rhodope, northern Greece. Contributions to Mineralogy and Petrology, 123, 293-307.
Meyer, J. (1983) The development of the high-pressure metamor-phism in the Allalin metagabbro (Switzerland). High-pres-sure metamorphism: indicator of subduction and crustal thickening (abstract). Terra Cognita, 3, 187.
Miller, C. (1990) Petrology of the type locality eclogites from the Koralpe and Saualpe (Eastern Alps), Austria. Schweizerische mineralogische und petrographische Mitteilungen, 70, 287-
300.Nishimiya, Y., Tsunogae, T., Santosh, M., Dubessy, J. and Chetty,
T.R.K. (2009) Prograde and retrograde högbomites in sapphi-rine + quartz bearing Mg-Al rock from the Palghat-Cauvery Suture zone, southern India. Journal of Mineralogical and Petrological Sciences, 104, 319-323.
Orozbaev, R.T., Takasu, A., Tagiri, M., Bakirov, A.B. and Sakiev, K.S. (2007) Polymetamorphism of Aktyuz eclogites (northern Kyrgyz Tien-Shan) deduced from inclusions in garnets. Jour-nal of Mineralogical and Petrological Sciences, 102, 150-
156.Orozbaev, R.T., Takasu, A., Bakirov, A.B., Tagiri, M. and Sakiev,
K.S. (2010) Metamorphic history of eclogites and country rock gneisses in the Aktyuz area, Northern Tien-Shan, Kyr-
gyzstan: a record from initiation of subduction through to oceanic closure by continent-continent collision. Journal of Metamorphic Geology, 28, 317-339.
Peng, G., Lewis, J., Lipin, B., McGee, J., Bao, P. and Wang, X. (1995) Inclusions of phlogopite and phlogopite hydrates in chromite from the Hongguleleng ophiolite in Xinjiang, north-west China. American Mineralogist, 80, 1307-1316.
Rammlmair, D., Mogessie, A., Purtscheller, F. and Tessadri, R. (1988) Högbomite from the Vumba schist belt, Botswana. American Mineralogist, 73, 651-656.
Reider, M., Cavazzini, G., D’yakonov, Y.S., Frank-Kamenetskii, V.A., Gottardi, G., Guggenheim, S., Koval’, P.V., Müller, G., Neiva, A.M.R., Radoslovich, E.W., Robert, J-L., Sassi, F.P., Takeda, H., Weiss, Z. and Wones, D.R. (1998) Nomenclature of the micas. The Canadian Mineralogist, 36, 905-912.
Rakotonandrasana, N.O.T., Arima, M., Miyawaki, R. and Rambe-loson, R.A. (2010) Widespread occurrences of högbomite-2N2S in UHT metapelites from the Betroka Belt, Southern Madagascar: implications on melt or fluid activity during re-gional metamorphism. Journal of Petrology, 51, 869-895.
Schreyer, P., Abraham, K. and Kulke, H. (1980) Natural sodium phlogopite coexisting with potassium phlogopite and sodian aluminian talc in a metamorphic evaporate sequence from Derrag, Tell Atlas, Algeria. Contributions to Mineralogy and Petrology, 74, 223-233.
Smith, D.C. and Kechid, S.A. (1983) Three rare Al- and Na-rich micas in the Liset eclogite pod, Norway: Mg-Fe-margarite, preiswerkite and Na-eastonite (abstract). Terra Cognita, 3, 191.
Tagiri, M., Yano, T., Bakirov, A.B., Nakajima, T. and Uchiumi, S. (1995) Mineral parageneses and metamorphic P-T path of ultrahigh-pressure eclogites from Kyrgyzstan, Tien-Shan. Is-land Arc, 4, 280-292.
Tlili, A., Smith, D.C., Beny, J.M. and Boyer, H. (1989) A Raman microprobe study of natural micas. Mineralogical Magazine, 53, 165-179.
Tsunogae, T. and Santosh, M. (2005) Ti-free högbomite in spinel- and sapphirine-bearing Mg-Al rock from the Palghat-Cauv-ery shear zone system, southern India. Mineralogical Maga-zine, 69, 937-949.
Visser, D., Nijland, T.G., Lieftink, D.J. and Maijer, C. (1999) The occurrence of preiswerkite in a tourmaline-biotite-scapolite rock from Blengsvatn, Norway. American Mineralogist, 84, 977-982.
Wang, R., Xu, S. and Xu, S. (2000) First occurrence of pre-iswerkite in the Dabie UHP metamorphic belt. Chinese Sci-ence Bulletin, 45, 748-750.
Whitney, D.L. and Evans, B.W. (2010) Abbreviations for names of rock-forming minerals. American Mineralogist, 95, 185-
187.
Manuscript received June 21, 2011Manuscript accepted September 26, 2011
Manuscript handled by Norimasa Shimobayashi
