The Petrology, Geochemistry, The Petrology, Geochemistry, Metamorphism and Metamorphism and PaleogeographicPaleogeographicreconstruction of the East reconstruction of the East SulawesiSulawesi

OphioliteOphiolite

Dr. Ir. Dr. Ir. AdeAde KadarusmanKadarusmanPusatPusat PenelitianPenelitian Geoteknologi Geoteknologi

LIPILIPI--BandungBandungMaretMaret 20032003

Study of the East Sulawesi Ophiolite(ESO)

• A part of the PhD Thesis (2001) funded by the Superplume project (1999-2001) of Dept. of Earth and Planetary science, Tokyo Institute of Technology, Tokyo, Japan

• Publication:Kadarusman et al. (2004) Tectonophysicsspecial issue of ophiolite, eds: Y. Dilek & E.M. Moores (in press)

Ophiolites• Ophiolites are fragment of fossil oceanic

lithosphere, which are found in most mountain ranges of the Earth, either in continents or in island arcs.

• Ophiolite is present because the oceanic lithosphere escape from the normal fate (to return to the deep of mantle, through subductionzone). The oceanic lithosphere thrusted onto continentals or island arcs margin due to particular geotectonic circumstance.

ObjectiveThe East Sulawesi Ophiolite

• One of the three largest ophiolites in the world along with the Oman Ophiolite and the Papua New Guinea Ophiolite

• The origin and age(s) of the ESO are still matters of debate due to incomplete geochemical and geochronological data sets.

• Large areas of the peridotite component of the ESO (especially the northwestern region in the East Arm and SE Arm) have never been studied in detail. It is vital to establish the basic structure and petrology of these rocks in many different localities.

• It is possible that the ESO is not a single coherent ophiolite body, but composed of collages ophiolite fragments with different ages and origins

Previous Study

• The current study is part of a program which aims to describe petrological and geochemical features of the ESO in many different localities

• Two major tectonic settings have been proposed for the origin of the ESO:

• A suprasubduction zone (SSZ) setting (Monnier et al., 1995; Bergman et al., 1996; Parkinson, 1998).

• A mid-oceanic ridge (Soeria-Atmadja et al., 1974; Simandjuntak 1987),

Major, Trace, Rare Earth Elements Geochemistry

• Whole rock geochemistry (XRF, ICP-MS)• Mineral chemistry (EPMA, SIMS IMS-3F)

Whole rock geochemistry of basalt and diorite

Major and trace elements variation of peridotite (whole rock)

N-MORB normalized REE pattern for clinopyroxenes from Lamasiand Poh Head basalts.

Composition of mafic cumulate and various gabbro in the Pagimana-Bunta area.

(a) Coexisting plagioclase and clinopyroxene,

(b) Coexisting plagioclase and

olivine

Relationships between (a) Cr# of spinel and Fo content of coexisting olivine and (b) Cr# and Mg# of spinels. OSMA (olivine spinel mantle array) are from

Arai (1994).

Spinel composition

Chondrite-normalized REE patterns for clinopyroxenes from

six peridotites, from three different localities (i.e. Ampana,

Soroako and Kabaena).

Summary of geochemistry

Ocean Floor Metamorphism

Pressure and temperature

estimation for amphibolite of

cumulate gabbro:T=270-350 deg C

P=4-5 kb (10-12 km depth)

Paleogeographic Reconstruction1.ages of eruption and accreted time

2. Paleoposition (paleomagnetic data)3. Plate trajectory method

SE Asia Continental Fragments