ofiolit adalah batuan yang terbentuk di dasar laut

1. The Petrology, Geochemistry,
Metamorphism and Paleogeographic
reconstruction of the East Sulawesi
Ophiolite
Dr. Ir. Ade Kadarusman
Pusat Penelitian Geoteknologi
LIPI-Bandung
Maret 2003

2. 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) Tectonophysics
special issue of ophiolite, eds: Y. Dilek &
E.M. Moores (in press)

4. 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 subduction
zone). The oceanic lithosphere thrusted onto
continentals or island arcs margin due to
particular geotectonic circumstance.

12. Objective
The 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

13. 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),

28. Major, Trace, Rare Earth
Elements Geochemistry
• Whole rock geochemistry (XRF, ICP-MS)
• Mineral chemistry (EPMA, SIMS IMS-3F)

29. Whole rock geochemistry of basalt and diorite

30. Major and trace elements variation of peridotite (whole rock)

32. N-MORB normalized REE pattern for clinopyroxenes from Lamasi
and Poh Head basalts.

33. Composition of mafic cumulate
and various gabbro in the
Pagimana-Bunta area.
(a) Coexisting plagioclase and
clinopyroxene,
(b) Coexisting plagioclase and
olivine

34. 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).

35. Spinel composition

36. Chondrite-normalized REE
patterns for clinopyroxenes from
six peridotites, from three
different localities (i.e. Ampana,
Soroako and Kabaena).

37. Summary of geochemistry

38. Ocean Floor Metamorphism

40. Pressure and
temperature
estimation for
amphibolite of
cumulate gabbro:
T=270-350 deg C
P=4-5 kb (10-12 km
depth)

42. Paleogeographic Reconstruction
1.ages of eruption and accreted time
2. Paleoposition (paleomagnetic data)
3. Plate trajectory method

45. SE Asia Continental Fragments