Introduction Central part Indonesianugroho.setiawan.blog.ugm.ac.id/files/2014/02/130117-Nugroho-Setiawan.pdf• Bantimala Complex is located approximately 40 km northeast of Makassar,

Introduction

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•  C e n t r a l p a r t I n d o n e s i a geographical ly is including Kalimantan, Sulawesi and Java islands.

•  Accretionary and metamorphic complexes expose in the Central Java, South Kalimantan and South–Central Sulawesi.

•  N o r t h w e s t e r l y - d i r e c t e d Cretaceous subduction was suggested responsible to build these formations (Sukamto, 1 9 8 2 ; v a n L e e u w e n a n d Muhardjo, 2005).

•  M e t a t o n a l i t e s e x p o s e i n Nangapinoh area of West Kalimantan, which associated as later granitods event. The granitoids were generated by the intrusion related of subduction during earlier Jurassic to Early Cretaceous (Williams et al., 1988).

•  The protolith and emplacement-timing of the metamorphic rocks in central part of Indonesia have remained obscure.

•  This presentation will discuss about geochemical character of the high-P metamorphic rocks and other related rocks from South Sulawesi, Central Java, South Kalimantan and the results of LA-ICP-MS U-Pb zircon dating from metapelites of Bantimala and Barru Complexes.

•  The geochemical character of metatonalites from Schwaner Mountains of West Kalimantan also will be discussed and the first report of LA-ICP-MS U-Pb zircon dating.

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Introduction

Regional geology of study areas 3 •  Bantimala Complex is located

approximately 40 km northeast of Makassar, South Sulawesi.

•  Metamorphic rocks are intercalated with melange deposits.

•  Mainly consist of high-P metabasites and pelitic rocks (eclogite, Grt-Gln rock, Grt-Jd-Qz rock)

•  Peak metamorphic have been reported 1.8–2.4 GPa at 580–650 ºC from eclogite and Grt-Gln rock (Miyazaki et al., 1996; Setiawan et al. 2012) and VHP metamorphic rock from Coe bg Grt-Jd-Qz rock reported >2.7 GPa at 720–760 ºC (Parkinson, 1998).

•  K-Ar ages from phengite on Grt-Gln rock and ec log i te y ie ld Ear ly Cretaceous (137 to 113Ma) (Wakita et al., 1994, 1996; Parkinson et al., 1998).

•  B a r r u C o m p l e x i s l o c a t e d approximately 30 km north of the Bantimala area.

•  Mainly consist of garnetiferous mica schist.

•  K-Ar ages from phengite yield Early Cretaceous (106 ± 5 Ma ) from quartz-mica schist (Wakita et al., 1994).

Bantimala and Barru Complexes

Modified from Sukamto (1982)

Modes of occurences 4

Photomicrographs 5

Eclogite Grt-Gln rock

Grt-Gln-Ph-Qz schist Grt-Bt-Ms-Qz schist

Scale bar indicates 1 mm

Regional geology of study areas 6

Luk Ulo Complex

Modified from Asikin et al. (2007)

•  Luk Ulo Complex is located in Karangsambung area of Central Java.

•  Metamorphic rocks are intercalated with melange deposits. •  Mainly consist of high-P metabasites and pelitic rocks (eclogite,

Grt-Gln schist, blueschist). •  Peak metamorphism have been reported to 1.8–2.2 GPa at

359–570 ºC from eclogite and Jd-Qz-Gln rock (Miyazaki et al., 1998; Kadarusman et al. 2007).

•  K-Ar ages from phengite on Grt-Gln rock and eclogite yield Early Cretaceous (124 to 110 Ma) (Miyazaki et al., 1998; Parkinson et al., 1998).

Mode of occurences & photomicrographs 7


Grt-Ms-Qz schist

Eclogite

Grt amphibolite


Meratus Complex

Modified from Sikumbang and Heryanto (2009)

•  Meratus Complex i s l oca ted in southwestern part of Meratus Mountains, South Kalimantan with the shape of NE-SW.

•  Metamorphic rocks are tectonic blocks in fau l t contact wi th u l t ramaf ic and sedimentary rocks (Sikumbang and Heryanto, 2009).

•  Mainly consist of serpentinite and various low-grade schists (Parkinson, 1998).

•  Tentative pressure estimation from Mg-rich Cld is ~1.8 GPa (Parkinson, 1998).

•  K-Ar dating from various mica schists yielded Early Cretaceous (119–10 Ma) (Wakita, 1998; Sikumbang and Heryanto (2009).

Mode of occurences & photomicrographs 9



Nangapinoh

Modified from Amiruddin and Trail (1993)

•  Metatonalites expose in Nangapinoh area, which associated as later granitoids event.

•  Strike of foliation metatonalites ranges from E–W to NE–SE (Amiruddin and Trail, 1993).

•  The granitoids formed a belt of 200 km wide and 500 km long with E–W directions.

•  The g ran i t o i ds i n t r uded l ow-g rade metamorphic rocks and formed local contact metamorphism.

•  K-Ar of granitoids from Schwaner Mts ranging from 157 to 77 Ma (Late Jurassic–Cretaceous), while NW block are from 320 to 204 Ma (Carboniferous–Triassic) (Haile et al., 1977; William et al., 1988; Amiruddin and Trail, 1993).

Mode of Occurences & photomicrographs 11

Metatonalite Metatonalite


Summary of petrography and occurences 12

Pressure (GPa) Temp. (ºC)Bantimala, South Sulawesi Eclogite Grt, Omp, Gln, Ph, Ep 1.8–2.4 580–640 Miyazaki et al. (1996)

2.2–2.4 580–650 Setiawan et al. (2012)Grt-Gln rock Grt, Gln, Ph, Ep 1.8–2.4 580–640 Miyazaki et al. (1996)Grt-Jd-Qz rock Grt, Jd, Qz, Ep >2.7 720–760 Parkinson et al. (1998)Glaucophanite Gln, Ph, EpGrt-Gln-Ph-Qz schist Grt, Gln, Ph, Qz, EpGln-Ph-Qz schist Gln, Ph, Qz, Ep

Barru, South Sulawesi Grt-Bt-Ms-Qz schist Grt, Bt, Ms, QzLuk-Ulo, Central Java Eclogite Grt, Omp, Gln, Ph, Ep 1.8–2.2 359–442 Kadarusman et al. (2007)

Jd-Gln-Qz rock Jd, Gln, Qz ~2.2 ~530 Miyazaki et al. (1998)Grt-Gln schist Grt, Gln, Ph, EpGln-Ep schist Gln, Ph, EpGrt amphibolite Grt, Hbl, ZoGrt-Ms-Qz schist Grt, Ms, QzGln-Ep-Qz schist Gln, Ep, Qz, Ph

Meratus, Grt-Ep-Act-Qz schist Grt, Ep, Act, Ms, Ep, QzSouth Kalimantan Grt-Cld schist Grt, Cld, Ms, Qz ~1.8 Parkinson et al. (1998)

Act-Tlc schist Act, Tlc, QzSerpentinite Srp, Spl

Nangapinoh, Metatonalite Pl, Bt, Ms, Hbl, CpxWest Kalimantan Amphibolite Hbl, Pl, Bt

Crd-And-Bt hornfels Crd, And, Bt, QzAnd-Bt hornfels And, Bt, Qz

ReferencesLocation Rock TypePeak MetamorphismMajor Mineral

Assemblages

Geochemical analyzes U-Pb zircon age determination

Major element consentration 13

Winkler (1979) Irvine and Baragar (1971)

Winchester and Floyd (1977)

High-P metamorphic and associated rocks

Trace and rare-earth elements 14

McDonough and Sun (1995) C1 Chondrite Norm.

Pearce and Cann (1973)

Meschede (1986)


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Summary of the protolith metamorphic rocks from South Sulawesi, Central Java and South Kalimantan

•  The geochemical signatures on the metamorphosed sedimentary rocks indicate protolith of pelite to greywacke.

•  Based on the trace and rare-earth elements analyses, the protolith of the basic metamorphic rocks from South Sulawesi and Central Java derived from MORB and within-plate basalt with tholeiite nature.

•  From South Sulawesi, all analyzed samples contain both MORB and within-plate basalt signature. It might indicate that several hot spots were existed and formed ocean islands that subducted together oceanic floor composed of MORB.

•  From Central Java, eclogite and blueschist mostly show within-plate basalt signatures, whereas protolith of relatively low-P/T metamorphic rocks (amphibolites and Grt amphibolites) are characterized by MORB. The results suggest several possibilities;

1.  Different component between upper and lower oceanic crusts 2.  Difference of the metamorphic age between eclogite- and amphibolite-facies metamorphism 3.  Change of the subduction angle between two metamorphic events


Locality Rock Type OIB N-MORB E-MORB Amount

South Sulawesi Eclogite ! ! ! 13Grt-Gln rock/schist – – ! 9Glaucophanite ! ! ! 5

Central Java Eclogite ! – – 1Grt-Gln schist ! – – 6Gln schist ! – ! 3Grt amphibolite – ! ! 4Amphibolite – ! – 2

! : present, – : absent

LA-ICP-MS U-Pb detrital zircon Bantimala Complex

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•  Age data concentrate at ca. 430–390 Ma (S i lu r ian–Devon ian ) , 309 ± 9 Ma (Carboniferous) and 199 ± 6 Ma (Jurassic) from 6 analyses of 6 grains.

Scale bar indicates 10 µm


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•  Age data ranging at ca. 280–550 Ma (Permian–Cambrian) and 1400–1600 Ma (Proterozoic) from 42 analyses of 42 grains.

Scale bar indicates 10 µm LA-ICP-MS U-Pb detrital zircon Barru Complex


LA-ICP-MS U-Pb detrital zircon from Bantimala and Barru Complexes

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•  Detrital zircons were recognized on the pelitic rocks from Bantimala and Barru Complexes. Both areas give similar clustering ages of Silurian to Permian (ca. 436–280 Ma) that have possibility derived from the similar provenance. The youngest ages from Bantimala Complex is show (199 ± 6 Ma) Early Jurassic, therefore the metamorphic age still has possibility o f C re taceous ages and the subduction has possibility generate during Jurassic.

•  Detailed age determinations of both protoliths (MORB and within-plate basalt) and both metamorphisms (blueschist-eclogite and amphibolite) from Central Java are needed and also be compared with South Sulawesi.


LA-ICP-MS U-Pb detrital zircon from Bantimala and Barru Complexes

19 High-P metamorphic and associated rocks

Compared with detrital zircon from Central Sulawesi, have similar clustering age at ~400 Ma (Devonian) and ~1550 (Proterozoic).

Leeuwen et al. (2006)

Bantimala and Barru Complexes

1550 Ma (Proterozoic) might indicates source provenance from Indochina craton

20 Schwaner Mountains, Metatonalite

Trace and rare-earth elements 21

Sun and McDonough (1989) MORB Norm. Pearce et al. (1984)

Defant and Drummond (1990)

Irvine and Baragar (1971) Barker and Arth (1979)

Schwaner Mountains, Metatonalite

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Sun and McDonough (1989) MORB Norm. Defant and Drummond (1990)


2013)

2013)

LA-ICP-MS U-Pb magmatic zircon

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•  Concordant age at 233 ± 3 Ma (Triassic) from 23 analyses of 11 grains ! Magmatic zircon

Scale bar indicates 10 µm


Summary of metatonalite in Schwaner Mountains •  The trace element normalized pattern,

discrimination diagrams, and the calc-alkaline rock signature indicate that the protolith of metatonalites were derived from volcanic-arc tectonic environments.

•  The magmatic age of one sample adakitic metatonalite yield Triassic age (233 ± 3 Ma). The age are older than the reported K-Ar granitoids age from Schwaner Mountains (77–157 Ma) (Haile et al., 1977; Williams et al., 1988; Amiruddin and Trail, 1993) but still in a range of the K-Ar granitoids ages from northwest Kalimantan (204–320 Ma; Williams et al. 1988).

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Implication for subduction-related felsic magmatism during Mesozoic •  The chemical characteristics and the determined age strongly

suggest that the subduction mechanism and felsic magma genesis changed between the Early Triassic and Cretaceous or magmatism of granitoids of several parts in Schwaner Mountains was contemporaneous with the northwest Kalimantan domain and Triassic eastern-range granite of Indochina craton.

•  Some metatonalites, excepting adakite rock, show similar signature to Cretaceous granite, indicating the subsequent metamorphism occurred during Cretaceous in this area.

•  It is proposed that the Schwaner Mountains, composed of metamorphic and granitic complexes, were not formed by a consecutive subduction system and much more geochemical data for metatonalites and each protolith age with the P-T evolution and the age of metamorphism are highly significant to realize the Mesozoic tectonic evolution in this region.

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Conclusion High-pressure metamorphic rocks 1.  Protolith of metabasic rocks derived from

MORB and within-plate basalt with tholeiite nature.

2.  Detrital zircons were recognized on the pelitic rocks from Bantimala and Barru Complexes. Both areas give similar clustering ages of Silurian to Permian (ca. 436–280 Ma) that have possibility derived from the similar provenance. The youngest ages from Bantimala Complex is show (199 ± 6 Ma) Triassic–Jurassic, therefore the metamorphic age still has possibility of Cretaceous ages.

Metatonalites in Schwaner Mountains 1.  Protolith of metatonalites were derived from

volcanic-arc tectonic environments with two samples indicate adakite nature.

2.  The magmatic age of one sample adakitic metatonalite yield Triassic age (233 ± 3 Ma). The age are older than the reported K-Ar granitoids age from Schwaner Mountains (77–157 Ma) (Haile et al., 1977; Williams et al., 1988; Amiruddin and Trail, 1993) but still in a range of the K-Ar granitoids ages from northwest Kalimantan (204–320 Ma; Williams et al. 1988) and Triassic eastern range granite of Indochina craton.

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THANK YOU FOR YOUR ATTENTION

P-T estimation compiled 28

Rock Type

Prograde Peak Retrograde

Bantimala Complex Eclogite - 1.8–2.4 GPa

580–640 ºC ~1.0 GPa 350 ºC

Grt-Gln rock

- 1.8–2.4 GPa 580–640 ºC

~0.5 GPa 350 ºC

(Miyazaki et al., 1996) Grt-Jd-Qz rock

- >2.7 GPa 720–760 ºC

~1.0 GPa 500ºC

(Parkinson et al., 1998)

Eclogite Gln stability field

2.2–2.4 GPa 580–650 ºC

Act stability field

(Setiawan et al., 2012) Luk Ulo Complex Jd-Qz-Gln rock

- 2.2±0.2 GPa 530±40 ºC

-

(Miyazaki et al., 1998)

Eclogite 1.5–2.1 GPa 283–415 ºC

1.8–2.2 GPa 359–442 ºC

0.8–1.0 GPa 350–400 ºC

(Kadarusman et al., 2007)

Major element consentration 29

Harker Diagram

•  The SiO2 contents of metabasic rocks are ranging from 37.38–53.10 w t % . H o w e v e r , c o n d i d e r i n g t h e p e t r o g r a p h i c a l observations and the o t h e r e l e m e n t concentrations (e.g., MgO = 1.63–18.04 wt%, Mg# = 0.22–0.58, Ni = 48.34–943.32 ppm, and Cr = 41.73–1222.37 ppm), the SiO2 value <45 wt% are not likely ultramafic rocks.

•  The wide range and scattered values for major elements should suggest the elemental migration from protolith due to the later metamorphism and fluid-assisted alteration.

Whole Rock Chemistry

•  Major, trace and rare-earth element contents of metamorphic rock samples were analyzed by X-ray fluorescence spectrometry (XRF) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) at Division of Earth Sciences, Faculty of Social and Cultural Studies, Kyushu University

•  Totally 84 metamorphic rocks samples as follows; 34 samples from South Sulawesi (13 eclogites, 9 Grt-Gln rocks, 5 glaucophanites, 5 Grt-Gln-Ph-Qz schists, and 2 Grt-Bt-Ms-Qz schists), 21 samples from Central Java (1 eclogites, 6 Grt-Gln schists, 3 Gln schists, 4 Grt amphibolites, 2 amphibolites, and 5 Grt-Ms-Qz schists), 3 samples of Grt-Ep-Act-Qz schists from South Kalimantan, and 4 samples of metatonalites from West Kalimantan.

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Documents

Introduction Central part Indonesianugroho.setiawan.blog.ugm.ac.id/files/2014/02/130117-Nugroho-Setiawan.pdf• Bantimala Complex is located approximately 40 km northeast of Makassar,