Phenomenon of schistic breccia, autoclastic breccia and radiolarian chert, a Mesozoic tectonic trace in Bantimala Tectonic Complex Area, Pangkep Regency South Sulawesi Province

Abstract

The presence of the schistic breccia and the autoclastic breccias and the radiolarian chert on the Bantimala tectonic complex is one of the interesting geological phenomena to study. In addition to knowing the position and stratigraphic relationships between radiolarian chert with autoclastic breccia as basement rock, the secular breccia may reveal Bantimala's tectonic environment in the Mesozoic time. This research uses secondary data assessment method from previous researcher and field investigation in the form of observation and rock sampling for petrographic and chemical analysis (X-Ray Fluorescence) to the chemical elements of rock. The appearance of a field indicating the presence of an alternating of the radiolarian chert with a schistic breccias and a sandstone insertion at the bottom of which is in the same composition as the schistic breccia and the autoclastic breccia as the source of some of its components, indicating the stratigraphy relation between radiolarian chert with schistic breccias are conformably, while the radiolarian chert with an autoclastic breccia is unconformably. The metamorphic rock components present in the schistic breccia and the autoclastic breccia are varied in the schistic breccias of about 42.94 - 91.44% SiO2, while the autoclastic breccia 33 - 92.02% SiO2 showing of protolith a mixing of sedimentary rocks, ultramafic, basalt and intermediates rocks. The result of plotting on the spider diagram of trace elements and rare earth elements indicates that the autoclastic breccias originate from the Mid-oceanic ridge basalt (MORB), while the schistic breccias are derived from MORB, OIB and active continental margin.

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