Geochronology of high-pressure and amphibolite-facies rocks from the Bantimala Complex, SW Sulawesi, Indonesia

Basic data for this project

Description

This proposal seeks funding for field-based research activities that aim at establishing a solid geochronologic foundation for in-depth understanding of subduction- and collision-related metamorphic processes in the Bantimala Complex, SW Sulawesi, Indonesia. Previous research activities have mainly focused on petrological and geochemical characteristics of the high-pressure/low-temperature rocks that occur in mélange sequences. Available isotopic ages for such rocks that are based on the K-Ar dating method are insufficient under both quantitative and qualitative aspects and do not provide unambiguous data for assessing the temporal evolution of the Bantimala complex and similar occurrences in the larger region. This study aims at closing this gap by dating of well-preserved eclogites and blueschists using a multimethod geochronological approach. Depending on sample characteristics different methods of age determination (Rb-Sr, U-Pb, Sm-Nd) will be utilized. Emphasis will be placed on the following questions: What is the geological significance of the previously published K-Ar dates? What are the exact ages recorded by the HP/LT rocks? Is there any evidence for contamination with excess Argon? What are the timescales for subduction and exhumation? Is it possible to date distinct P-T stages of the metamorphic evolution? Are the metamorphic processes related to a single short-lived event or to discontinuous episodes that occurred over a protracted time span? What is the age of the amphibolite-facies metamorphism in the Barru block? The new age data will help developing a deeper understanding of the metamorphic history of the Bantimala complex and will provide a solid and robust foundation for the interpretation of large-scale geodynamic processes. The newly gained knowledge will terminate existing ambiguities about the age of subduction-related metamorphism in the study area. At a later stage it will be necessary to expand the geochronological data base by including other HP/LT-occurrences of the Central Indonesia Accretionary Collision Complex. Such data are a prerequisite for an improved understanding of the geodynamic processes that have led to the formation of the pre-Tertiary accretionary complexes of Indonesia. The overall objective goes beyond a purely regional importance, but aims at establishing a solid basis for plate tectonic reconstructions in the complex region between Eurasian, Indian-Australian and Pacific plate.