KARAKTERISTIK, PROVENANCE DAN TINGKAT PELAPUKAN BERDASARKAN ANALISIS GEOKIMIA ENDAPAN LUMPUR SIDOARJO ZONA KENDENG PROVINSI JAWA TIMUR

Sidoarjo mud (LUSI) is an active mud volcano that has occurred since 2006 to the present (2021). The mudflow material that comes out shows chemical anomalies and shows certain morphology and characteristics. This study aims to determine the characteristics of the sediment and its element abundance as well as to determine the type of provenance, tectonic setting and weathering rate of the source rock which produces Sidoarjo Mud sediment. The method used is direct field observations and geochemical analysis to determine the concentration of Sidoarjo mud constituent elements in the form of X-ray Fluorescence (XRF) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) using 8 samples of hand boring results with a depth of 5 meters, and at 5 drilling points. Based on the characteristics of the sediment, LUSI has an average fluid temperature of 100 oC with a pH of 8-9. The LUSI deposit has a gray-black color with varying grain sizes, dominated by clay to sandy clay grains and there are andesite, scoria, pumice and mollusk shells. This study used geochemical analysis methods on 8 mud core samples with 5 drilling points using X-ray fluorescence (XRF) analysis, and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to determine the concentration of the constituent elements of LUSI. From the results of the discriminant diagram geochemical analysis using a Log (Fe2O3 / K2O) compound with Log (SiO2 / Al2O3), it can be seen that the sedimentary rock type of LUSI is Fe-Shale. Meanwhile, based on the diagram using trace elements in the form of Zr / Ti elements with Nb / Y, it can be interpreted that the LUSI material comes from Andesite rocks with an Arc-Related tectonic arrangement. Based on the calculations of the CIA, CIW, Rb / Sr (mean values of each = 64.3, 69.62, 0.18) and the A-CN-K diagram, it can be interpreted that the level of weathering in the source rock or during the transportation process before deposition experiences chemical weathering. which is with intense weathering and is a smectite-type clay mineral.
Keywords : Geochemical analysis, mud volcano, Lumpur Sidoarjo (LUSI), provenance, tectonic setting, weathering rate