A PETROGRAPHICAL REVIEW OF METAMORPHIC ROCKS … MPB-06 A... · the Bantimala, Luk Ulo, and Meratus Complexes, which have protolith of MORB, OIB, and arc signatures more than sedimentary

PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-9 PERAN PENELITIAN ILMU KEBUMIAN DALAM PEMBERDAYAAN MASYARAKAT

6 - 7 OKTOBER 2016; GRHA SABHA PRAMANA

624

A PETROGRAPHICAL REVIEW OF METAMORPHIC ROCKS FROM CILETUH

COMPLEX, IN WEST JAVA AND THEIR RELATED METAMORPHISM IN

CENTRAL INDONESIA REGION

Anton Prasetyo1*, Jordan Romora S.1, Yeftamikha1, Fransiskus L. B.1,

Nugroho Imam S.1

1Departemen Teknik Geologi, Fakultas Teknik, Universitas Gadjah Mada, Jl. Grafika No.2, Bulaksumur,

Yogyakarta,

Indonesia, Telp. 0274-513688

*Email : [email protected]

ABSTRACT Ciletuh Complex is considered to be one among other localities (Luk Ulo, Bantimala, Meratus

Complexes) in Indonesia in which Cretaceous subduction fossil was occurred. The objective of this study

is determining the variation of metamorphic rocks in Ciletuh Complex by petrographical analysis

through their texture and mineral assemblages.

Metamorphic rocks in Ciletuh Complex were collected in Gunung Badak and Tegal Pamidangan areas.

Based on petrographical analysis, metamorphic rocks in Gunung Badak area consist of Grt-Ms-Qz

schist, Ms phyllite, quartzite and serpentinite. Meanwhile in Tegal Pamidangan area, consist of Ms-Qz

phyllite and slate. The metamorphic rocks indicate low-grade metamorphism in the greenschist-facies.

The protolith of metamorphic rocks are suggested from pelitic, ultramafic, and quartz-rich rocks.

Present study did not recognize the blueschist or eclogites-facies rocks which indicates high-pressure

and low-temperature metamorphism in the subduction system. The present of serpentinite among the

low-grade metamorphic rocks indicates that metamorphic environment still correlate with oceanic crust

environment or mantle. Low-grade metamorphic rocks might be developed on the near surface of the

subduction system.

Keywords : petrography analysis, mineral assemblages, metamorphic facies, protolith

I. INTRODUCTION

Ciletuh is one of three regions in Java Island

that consists of Pre-Tertiary rock. The other

two is Jiwo Hills/Bayat and Luk Ulo, Central

Java. The rock was formed by a subduction

of oceanic plate during Jurassic to Late

Cretaceous (Satyana, 2014).

Ciletuh Complex itself is a mélange that

consists of ophiolite, sedimentary, and

metamorphic rocks. The ophiolite is consists

of peridotite, gabro, and basalts; the

sedimentary rocks consists of chert, black

shale, graywacke, and limestone; and

metamorphic rocks consists of serpentinite,

schist, and phyllite (Rosana et al., 2006;

Satyana, 2014). This paper explains the

occurence of metamorphic rocks in Gunung

Badak and Cikepuh Complex, Ciletuh, West

Java, with a detailed petrographical

observation. Furthermore, those results are

combined with previous research to know the

relationship between Ciletuh Complex with

other complexes: Jiwo Hills and Luk-Ulo

Complex, Central Java.

II. REGIONAL GEOLOGY

There are three complexes of Pre-Tertiary

rocks in Ciletuh: Gunung Badak, Cikepuh-

Citisuk, and Citireum. As mentioned before,

this paper only focused on Gunung Badak

and Cikepuh Complex. Gunung Badak

consists of peridotite, pillowed basalt, gabbro,

phyllite, schist, amphibolite, serpentinite,

graywacke, limestone, and shale (Rosana et

al., 2006; Satyana, 2014). The subduction

from the southern part has made the

basement rock revealed, became a mélange,

and formed an amphitheatre. Gunung Badak

complex also has been influenced by strike

slip fault that happened after the deposition of

mélange.



625

Cikepuh-Citisuk Complex consist of Recent

to Pre-Tertiary rocks. Pre-Tertiary consist of

metamorphic, ultrabasic, and basic rocks

such as basaltic lava, gabbro, peridotite, and

schist outcropped in Gunung Beas, Pasir

Luhur and along the flow of Citisuk, Cikopo,

and Cikepuh River. Quartz sandstone unit in

this complex is part of Ciletuh Formation

aged Eocene. Limestone boulders

considerably can be found in this unit, that

consist fossil from the group of Discocyclina

sp., Nummulites sp., and Asterocyclina sp..

Geological structure in Cikepuh-Citisuk

Complex can be seen from the contact of

ophiolite and melange also sedimentary rock

of Ciletuh Formation. Generally, geological

structures that can be found are strike-slip

fault with NW-SE orientation, reverse fault

with NE-SW orientation, and anticline and

syncline that has almost the same orientation

with reverse fault (Rosana et al., 2006).

III. METHODS

The works include field sampling in Ciletuh

Complex, thin section petrography

observation, and integration with many

published paper in central Indonesia region

which is related with Ciletuh metamorphism.

Petrographical works include determining the

variation of metamorphic rock through their

texture and mineral assemblages. Field

studies were conducted by authors of this

paper in several field session to Ciletuh, Luk

Ulo, and Bayat for comparised their

metamorphism.

The result of this work and field studies are

synthesized to result in new metamorphism

concept: metamorphism for subduction

system concept and metamorphism

environment for Ciletuh Complex in central

Indonesia region and their related field such

as Bayat and Luk Ulo.

IV. RESULTS

In this paper, authors just make observation

in Gunung Badak and its surrounding area in

the north, Tegal Pamidangan-Gunung Beas

area. Suhaeli et al. (1977) explained the

metamorphic rocks consist of serpentinite,

phyllite, and blue/glaucophane schist in

Ciletuh Complex.

Based on this research, in Gunung Badak area

the metamorphic rocks consist of Grt-Ms-Qz

schist, Ms phyllite, quartzite, and serpentinite.

Dark grey well foliated phyllites are noticed

on Gunung Badak.

IV.1 Grt-Ms-Qz schist

Grt-Ms-Qz schist petrographically consists of

quartz (40-45%), phengite (30-35%), garnet

(10-15%), hematite (5-10%), minor opaque

minerals, and tourmaline. Based on this

mineral assemblage, Grt-Ms-Qz Schist in

Ciletuh are derived from the pelitic rocks

within greenschist facies.

IV.2 Ms phyllite

Ms phyllite petrographically consist of quartz

(40-45%), muscovite (40-45%), and minor

opaque minerals.

IV.3 Serpentinite

Serpentinite consists of serpentine (65-70%),

clinopyroxene (25-30%), and minor spinel

mineral. Based on this mineral assemblage,

serpentinite are derived from mafic-

ultramafic rocks.

Presence of Grt-Ms-Qz schist in this area is a

new discovery, whereas previous publication

simply explained that metamorphic facies

only up to phyllitic. Hand specimen of this

schist is like glaucophane schist which is

have dark blue colour mineral with clear

foliation, but from thin section observation

glaucophane does not appear. Present study

of Gunung Badak area recognized that this

area was developed on the near surface of the

subduction system by greenschist facies. This

hypothesis supported by present of

serpentinite that metamorphic environment

still correlates with oceanic crust

environment from Xeno Tethys (Satyana,

2014).

Approximately 3.5 kilometers to the

Southwest (central area of Ciletuh Complex),

in the Tegal Pamidangan area, metamorphic

outcrops area composed of Ms-Qz phyllite

and slate.

IV.4. Ms-Qz phyllite

Ms-Qz phyllite petrographically consists of

quartz (50-60%) and muscovite (40-50%).



626

IV. 5 Slate

Slate are consists of microcrystalline quartz

and microcrystalline muscovite in fine grain

size. Both of them, are derived from pelitic or

quartz rich sedimentary rocks.

Suhaeli et al. (1977) recognized that Citisuk-

Pasir Luhur area consist of blue/ glaucophane.

They are seen to be well foliated and

greenish-grey in color. Under the microscope

it can be seen that almost all of the minerals

are dominated by mica, plagioclase, and also

glaucophane. But, authors cannot find

blue/glaucophane schist in this area.

Parkinson et al. (1998) reported that quartzite

contain glaucophane, also the existence of

epidote amphibolite and crossite-epidote

metamafic rock. Eclogite has not been

reported from Ciletuh Complex.

The metamorphic rocks indicates low-grade

metamorphism in the greenschist-facies. The

protolith of metamorphic rocks are suggested

from pelitic, ultramafic, and quartz-rich rocks.

Present study did not recognize the blueschist

or eclogites-facies rocks which indicates

high-pressure and low-temperature

metamorphism in the subduction system. The

present of serpentinite among the low-grade

metamorphic rocks indicates that

metamorphic environment still correlate with

oceanic crust environment or mantle. Low-

grade metamorphic rocks might be developed

on the near surface of the subduction system.

In the area of Gunung Badak and around the

Citisuk area (central of Ciletuh Complex),

ophiolite rocks are mixed with metamorphic

rocks and sedimentary rocks of different

environments. The stratigraphy of the areas

was very difficult to ascertain. These

difficulties are mainly the result of the

disruption of lateral continuity. No continual

distribution of these rocks were visible. These

strongly suggest that the complex of the rocks

in Ciletuh area is a mélange complex.

V. DISCUSSION

Jiwo Hills, Bayat District is located over 530

km to the east of Ciletuh Complex and 80 km

of Luk Ulo Complex. The first geological

publication in Jiwo Hill was conducted by

Bothé (1929). Latest geological

investigations and studies for the Jiwo Hill

were conducted by Setiawan et al. (2013).

Pre-Tertiary rock complex of the Jiwo Hill,

Bayat area is mainly composed of similar

metamorphic rocks with Ciletuh Complex:

phyllite, schist, serpentinite, and glaucophane

schist. Recent absolute dating was conducted

on this pre-Tertiary basement, on two mica

schist samples and resulted in 98.05±2.10 Ma

and 98.54±1.45 Ma (mid-Cretaceous/

Cenomanian - Prasetyadi, 2007).

Setiawan et al. (2013) explain that phyllite so

dominantly in Jiwo Hills metamorphic area

with quartz and calcite veins fill the phyllitic

foliations. Microscopically, quartz mineral

predominates the rock (60-70%), followed by

chlorite and sericite (20-25%), opaque

mineral and epidote (5%). This composition

indicates the protolith may be derived from

pelitic rocks. Jiwo Hills phyllite’s has

similiarity with phyllite in Ciletuh Complex,

that had protolith from pelitic rocks. But

difference with Jiwo Hills, phyllitic foliations

in Ciletuh Complex is not truncated with

quartz and calcite veins.

Schists petrographically consists of quartz

(40-50%), calcite (15-20 %), orthoclase (10-

15%), muscovite (10-15%), minor opaque

minerals, and epidote (Setiawan et al. 2013).

Slightly different with Jiwo Hills, Ciletuh

Complex consist of dominantly quartz and

muscovite with minor tourmaline mineral.

Based on this mineral assemblage, Grt-Ms-

Qz Schist in Ciletuh are derived from the

pelitic rocks within greenschist facies.

Different from Ciletuh Complex, Setiawan et

al. (2013) show that Jiwo Hills contain of

blueschist-facies. It suggests that Jiwo Hills

is one of the high-pressure metamorphic

terranes in Indonesia region together with

Luk-Ulo Complex of Central Java, Bantimala

Complex of South Sulawesi, and Meratus

Complex of South Kalimantan. That

glaucophane schist was exhume with

serpentinite from deeply subducted levels to

the base of the crust by serpentinite’s extreme

buoyancy. However, highest metamorphic

facies in Ciletuh Complex based on this

research is only up to greenschist facies.

Other differences with Luk Ulo and Jiwo

Hills Complex, mélange deposit, ophiolite,



627

and oceanic plate stratigraphy (e.g. chert,

pillow lava), which found in the Luk Ulo

Complex and Ciletuh Complex, were not

observed in the Jiwo Hills.

Ciletuh Complex does not have detailed

chemistry analysis eg. ACF diagram.

Warmada (2008;unpublished data in

Setiawan et al. 2013) explained that bulk

chemistry analyzed of several metamorphic

rocks in the Jiwo Hills by ACF diagram,

shows that the protolith were derived from

sedimentary rocks without any basic igneous

rock signature. This is different from those in

the Bantimala, Luk Ulo, and Meratus

Complexes, which have protolith of MORB,

OIB, and arc signatures more than

sedimentary rocks.

Sedimentary rocks are much more developed

in the continental crust. Recent hypothesis, it

might have possibility that Jiwo Hills was a

part of Southeast Java Microcontinent

(Satyana, 2014) and had subducted beneath

the Sundaland during Cretaceous (Setiawan

et al. 2013).

VI. CONCLUSIONS

1. The metamorphic rocks in Ciletuh

Complex is from low-grade

metamorphism in the greenschist-facies,

with the protolith from pelitic, ultramafic,

and quartz-rich rocks. This study did not

recognize the blueschist or eclogite facies.

2. All metamorphic complexes in Java

Island (Ciletuh, Luk Ulo, and Bayat) are

believed from the same subduction

process.

VII. ACKNOWLEDGEMENT

We would like to thank to Optical Geology

Laboratory of Geological Engineering

Department, Universitas Gadjah Mada for

providing us facilities for doing petrography

analysis.

REFERENCES

Bothe, A.Ch.D., 1929. Djiwo Hills and Southern Range, Excursion Guide IVth Pac. Sci. Congr.

Miyazaki, K., Sopaheluwakan, J., Zulkarnain, I., and Wakita, K. 1998. “Jadeite-quartz glaucophane

rock from Karangsambung, Central java, Indonesia and its tectonic implications”, The Island

Arc, Vol. 7, pp. 223–230.

Parkinson, C. D., Miyazaki, K., Wakita, K., Barber, A. J., and Carswell, A. 1998. “An overview and

tectonic synthesis of the pre-Tertiary very-high-pressure metamorphic and associated rocks of

Java, Sulawesi and Kalimantan, Indonesia”, The Island Arc, Vol. 7, pp. 184–200.

Prasetyadi, C. 2007. “Evolusi tektonik Paleogen Jawa bagian Timur”, Doctoral thesis, Bandung Institute

of Technology, Bandung, Indonesia.

Rosana, M.F., Mardiana, U., Syafri, I. 2006. Geologi kawasan Ciletuh, Sukabumi: karakteristik,

keunikan dan implikasinya. Lokakarya Penelitian Unggulan dan Pengembangan Program

Pascasarjana FMIPA UNPAD 3 April 2006.

Satyana, A.H. 2012. Accretion and dispersion of Southeastern Sundaland: the growing and silvering of

continent and petroleum implications. AAPG International Convention and Exhibition,

Singapore 16-19 September 2012.

Satyana, A. H. 2014. New consideration on the Cretaceous subduction zone of Ciletuh-Luk Ulo-Bayat-

Meratus: implication for Southeast Sundaland petroleum geology. Proceedings Indonesian

Petroleum Association Thirty Eighth Annual Convention & Exhibition, May 2014.

Setiawan, N.I., Osanai, Y., Nakano, N., Adachi, T., Yonemura, K., Yoshimoto, A., Wahyudiono, J.,

Mamma, K. 2013. An overview of metamorphic geology from Central Indonesia: importance of

South Sulawesi, Central Java and South-West Kalimantan metamorphic terranes. Bulletin of

the Graduate School of Social and Cultural Studies, Kyushu University, Vol. 19 (2013), pp.39-

55.



628

Sikumbang, N. and Heryanto, R. 2009. Geological map of the Banjarmasin Quadrangle, Kalimantan,

Scale 1: 250.000, Geological Research and Development Centre, Indonesia.

Suhaeli, E.T., Said, E.L., Siswoyo, and Priyomarsono, S., 1977. The status of the melange complex in

the Ciletuh area, South West Java, Proceedings Indonesian Petroleum Association, 6th Annual

Convention, Jakarta, 241-254.

Wakita, K. 2000. Cretaceous accretionary-collision complexes in Central Indonesia. Journal of Asian

Earth Sciences 18 (2000), pp. 739-749.

Wakita K., Miyazaki, K., Zulkarnain, I., Sopaheluwakan, J., and Sanyoto, P. 1998. “Tectonic

implications of new age data for the Meratus Complex of south Kalimantan, Indonesia”, The

Island Arc, Vol. 7, 202–222.

Wakita, K., Munasri, Sopaheluwakan, J., Zulkarnain, I., and Miyazaki, K. 1994. “Early Cretaceous

tectonic events implied in the time-lag between the age of radiolarian chert and its metamorphic

basement in the Bantimala area, South Sulawesi, Indonesia”, The Island Arc, Vol. 3, pp. 90–

102

Wakita, K., Sopaheluwakan, J., Miyazaki, K., Zulkarnain, I., and Munasri. 1996. “Tectonic evolution

of the Bantimala Complex, South Sulawesi, Indonesia”, in: R. Hall and D.J. Blundell, eds.:

Tectonic Evolution of Southeast Asia, Geological Society of London Special Publication, Vol.

106, pp. 353-364.



629

TABLE

Table 1. Summary of metamorphic rock types in high-pressure metamorphic terranes in central

Indonesia region.

Complexes and metamorphic

grades

Rock Types

Age (Ma) Pelitic / Felsic rocks

Mafic /

Intermediate

rocks

Ultramafic /

Calc-silicate

rock

Ciletuh Complex

Greenschist, serpentinite

Grt-Ms-Qtz schist Serpentinite

Ms phyllite ?

Ms-Qtz phyllite

Luk Ulo Complex

Eclogite, blueschist,

amphibolite, serpentinite

(Miyazaki et al. 1998;

Setiawan, 2013)

Ep-Gln schist Eclogite Serpentinite 110-124

(Miyazaki et al.,

1998; Parkinson

et al., 1998).

Grt-Ms schist Grt-Gln schist

Ms schist Grt amphibolite

Amphibolite

Jiwo Hill

Blueschist, greenschist,

serpentinite

(Setiawan, 2013)

Phyllite Ep-Gln schist Serpentinite

98 (Prasetyadi,

2007) Calc-silicate

schist

Meratus Complex

Blueschist-amphibolite (high-

P), greenschist, serpentinite

(Setiawan, 2013)

Grt-bg-Ep-Brs

schist

Serpentinite 110-119

(Wakita, 1998;

Sikumbang and

Heryanto (2009)

Ep-Brs schist

Ep-Gln-Qtz schist

Ms schist

Bantimala Complex

Eclogite, blueschist,

greenschist, serpentinite

(Miyazaki et al. 1996;

Setiawan, 2013)

Grt-Gln-Qtz schist Eclogite Serpentinite 113-137

(Wakita et al.,

1994, 1996;

Parkinson et al.,

1998)

Ep-Gln-Qtz schist Grt-Gln schist

Grt-Jd-Qtz rock Ep-Gln schist

Barru Complex

Amphibolite, greenschist

(Setiawan, 2013)

Grt-Bt-Ms schist Serpentinite 106 ± 5

(Wakita et al.,

1994).



630

Table 2. Collected Metamorphic rock samples from Ciletuh Complex, West Java and their mineral assemblages.

No Sample ID Rock types Metamorphic

grade

Major Mineral Minor Mineral Remark

Grt Qtz Ph Ms Act Cpx Srp Hem Tur Spl

1 CLT/12/15/5 Serpentinite Serpentinite - - - - -

- - ±

2 CLT/12/15/6 Ms schist Greenschist -

- - - - - ± - weathered

3 CLT/12/15/8 Grt-Ms-Qtz

schist Greenschist

-

- - - ± - -

4 CLT/1/16/D1 Ms-Qtz phyllite Greenschist -

- - - - - - -

5 CLT/1/16/E Grt-Ph-Qtz schist Greenschist

- - - - - ± -

6 CLT/1/16/F Serpentinite Serpentinite - - - - -

- - -

8 CLT/1/16/L1 Slate Zeolite -

- - - - - - -

9 CLT/1/16/L3 Ms phyllite Greenschist -

- - - - - - -

11 CLT/1/16/M Qtz phyllite Greenschist -

- - - - - - - weathered

Abundant (81-100%), Rich (51-80%), Moderate (11-50%), Poor – absent (≤10%), ± Occur only in some samples



631

FIGURE

Figure 1. Geographical and situated map of Java, Indonesia with the distribution of high-pressure

metamorphic rocks.

Figure 2. Explanation on the next page

a



632

Figure 2. Simplified geological map with sampling points at Ciletuh Complex. (a) Gunung Badak area

and (b) Tegal Pamedangan-Citisuk-Cikepuh area (after Suhaeli et al. 1977).

Figure 3. Outcrops and boulder of metamorphic rocks from Ciletuh Complex. (a) Serpentinite indicates

that the metamorphic environment still correlates with oceanic crust environment or mantle.

(b) Grt-Ms-Qtz schist hand specimen looks like glaucophane schist but from thin section

observation glaucophane does not appear (c) Quartzite in Gunung Badak area.

b



633

Figure 4. The scale bar without expression indicates 0.5 mm. Photomicrographs of metamorphic rocks

from Ciletuh Complex. (a) Garnet-Muscovite-Quartz schist has main compositions of

muscovite, quartz, and garnet with minor hematite-tourmaline. (b) Ms-Qtz phyllite with

quartz and muscovite grains. (c) Serpentinite with mainly consist serpentine, clinopyroxene,

and minor spinel grains. (d) Slate has main composition of microcrystalline quartz and

muscovite in fine grain texture. (e) Phyllite with dominantly muscovite composition. (f)

Garnet-Muscovite-Quartz schist has main composition of muscovite, quartz and actinolite

with minor garnet grains.

Documents

A PETROGRAPHICAL REVIEW OF METAMORPHIC ROCKS … MPB-06 A... · the Bantimala, Luk Ulo, and Meratus Complexes, which have protolith of MORB, OIB, and arc signatures more than sedimentary