SPECULATIVE MODELS OF EXHUMATION ON HIGH-PRESSURE LOW-TEMPERATURE METAMORPHIC ROCKS FROM CENTRAL PART OF INDONESIA: AN IMPLEMENTATION OF CONCEPTS AND PROCESSES

• Main Authors: Nugroho Imam Setiawan, Nugroho Imam Setiawan, Salahuddin Husein, Salahuddin Husein, Muhammad Faqih Alfyan, Muhammad Faqih Alfyan
• Format: Article PeerReviewed
• Language: English
• Published: Jurusan Teknik Geologi 2014
• Subjects: Geology
• Online Access: https://repository.ugm.ac.id/135153/1/16-24%20P1O-02.pdf; https://repository.ugm.ac.id/135153/
• Institution: Universitas Gadjah Mada

High-pressure low-temperature metamorphic rocks are considered as fossil subduction zones from the interpretation of progressive and retrogressive metamorphism, metamorphic facies series, protolith, role of fluid, geochronology of the various stages of metamorphism, P-T-t path, and exhumation model during regional metamorphism. Worldwide discovery of these rock types (e.g., Kokchetav, Dabie Shan, Indonesia, Franciscan, and Sanbagawa) have received much attention from earth scientists to demonstrate the exhumation of the rocks that have been metamorphosed at great depths in subduction zones that are exhumed at the surface.High-pressure metamorphic rocks expose in the South Sulawesi, Central Java, and South Kalimantan, which considered as central part of Indonesia. Northwesterly-directed Cretaceous subduction was suggested responsible to build these formations. Most of the metamorphic rocks occur in limited areas and are bounded by thrust fault with other units such as dismembered ophiolites, cherts, mélanges, and serpentinites. This contribution is implementation of published-exhumation concepts and processes, which are focus on the high-pressure metamorphic rocks in central part of Indonesia. The publishedexhumation models on the high-pressure low-temperature metamorphic rocks in subduction zones suggest that buoyancy is the only effective force to exhume rocks from the deeply subducted levels to the base of the crust. Serpentinites are extremely buoyant with respect to the oceanic crust that has been transformed to eclogites during subduction and increasing their density, which are denser than average mantle rocks. Indeed, serpentinites have restricted P-T limit in the subduction zone. However the general P-T metamorphism of eclogites are within the range of serpentinites stability field. Thus, serpentinites might be counter-balancing the negative buoyancy, decouple, and facilitate exhumation of the high-pressure metamorphic rocks. Only rapid uplift accompanied by relatively low temperature rapid cooling maintains the high-pressure minerals in rocks. Furthermore, the presence of mélange units intercalated with high-pressure metamorphic rocks and chaotic occurrence of different metamorphic facies (e.g., eclogite, blueschist, greenschist) are typically formed in the subduction channel environment. Keywords: Exhumation, Model, High-pressure metamorphic rocks, Subduction, Indonesia