Preliminary Study of Accretion Complexes of Mangilu Area, Pangkep Ragency South Sulawesi

Abstract

The exposure of Mesozoic rocks in the Mangilu area, both as a result of tectonic deformation in the form of mélange, low-high degree metamorphism and deep-sea sediments (flysch, radiolarian cherts, and sediment flow in the form of olistostrome), which formed in the subduction zone indicates complex accretionary rocks. The purpose of this study is to identify and study the accretionary complex trace rocks of the Mesozoic era. The method used in this study was field observation, including collection of geological data, tectonic deformation, rock groups and laboratory analysis (petrography). In general, the accretion complex is divided into 2 categories, namely a). oceanic volcanic groups and sediments of the oceanic crust; b). terigenous sediments from continents with sialic beds. The oceanic volcanic group consists of gabbro, diabase, dolerite, pillow and hyaloclastic lava, and oceanic sediments consist of radiolarian chert and mali limestone. The terigen sedimentary group consists of flysch type sandstones and olistostrome flow sediments with components in the form of granite, granodiorite, dacite and diabase. Other components found in autoclastic breccia rocks in the Mangilu area consist of metaperidotite, serpentinite, quartzite and metachert. Based on the Oceanic Plate Stratigraphy (OPS) arrangement, the autoclastic breccia rocks in the Mangilu area consist of bottom up, namely ultramafic/serpentinite, gabbro, diabase, pillow basaltic lava, hyaloclastic, radiolarian chert, mali limestone and flysch sediments. The mixing of rocks originating from oceanic plates with continental plates in autoclastic breccias indicates that the Mesozoic accretion complex in the Mangilu area has experienced strong deformation in the form of thurst in the Tertiary era.