International Journal on Advanced Science, Engineering and Information Technology, Vol. 9 (2019) No. 6, pages: 1798-1806, DOI:10.18517/ijaseit.9.6.8735

Petrological Characteristic and Whole Rock Geochemistry of Metamorphic Rocks in Melangè Complex of Ciletuh Area, West Java, Indonesia

Rinaldi Ikhram, Ildrem Syafri, Mega Fatimah Rosana

Abstract

Melangè Complex of Ciletuh Area, West Java, Indonesia is located at 106 ° 23 '38.9 "- 106 ° 25' 27.6" E  and 7 ° 14 '27.6 "- 7 ° 12' 46.2" S. This area has unique geological features where the Early Cenozoic uplifted subduction rocks such as ophiolites and metamorphic rocks are exposed. This study aimed to determine the condition of the stratigraphic position and geological structure of metamorphic rock unit in the field, to find out the metamorphic facies and their evolution, to know the parental rocks (protoliths) of metamorphic rocks, and to interpret tectonic environments for the formation of metamorphic rocks based on stratigraphy, geological structure, petrography, and geochemistry. Study of literatures, geological mapping, petrology and geochemical analyses were used as methods of this research. The entire analysis is combined as a guidance in interpretation of petro-tectonic environment. Distribution of metamorphic rock outcrops found in several places, such as, Citisuk River, Cikopo River and Cikarikil River. Based on petrography analysis, metamorphic rocks types consist of schistose amphibolite, various type of greenschist, phyllite and quartzite. The protolith of metamorphic rocks in Ciletuh is quite diverse, namely metasediments such as pelitic, psammitic, calc-silicate sediment, and meta-igneous such as gabbro and basalt. The presence of epidote, chlorite, and calcite in schistose amphibolite show retrograde metamorphism process in lower temperature-pressures condition. The occurance of quartz and calcite vein in several samples was shown as an indication of hydrothermal alteration. Based on geochemical characteristics, the result showed that sedimentary source of metasedimentary rocks were derived from the volcanic arc environment. While, metabasalt rocks were originated from the Island Arc tectonic environment. According to the association, these metamorphic rocks were formed by regional metamorphism, as the result of subduction process and orogenic event. Thus, retrograde metamorphism indicates the lifting or accretion process that caused by subsecuent tectonic activity.

Keywords:

Ciletuh; metamorphic rocks; petrography; geochemsitry.

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