Analisis Petrografi, Parameter Fisis, dan Geokimia Untuk Karakterisasi Batuan Karbonat di Kawasan Karst Pacitan Barat

Kawasan karst merupakan bentang alam yang memiliki ciri khas unik baik di bawah permukaan maupun di atas permukaan. Penelitian ini bertujuan untuk mengkarakterisasi batuan karbonat di kawasan karst pacitan bagian barat. Karakterisasi batuan berdasarkan analisis petrografi, parameter fisis, dan geokimia. Lokasi pengambilan sampel batuan meliputi Kecamatan Donorejo, Punung, dan Pringkuku. Hasil Analisis thin section menunjukkan batuan karbonat pada daerah penelitian berjenis wackestone. Hasil pengukuran parameter fisis meliputi nilai kecepatan primer (Vp) sebesar 3104,9, nilai resistivitas sebesar 1062,87 Ohm.m, porositas efektif sebesar 16,51% dan densitas kering sebesar 2,13 gram/cm3. Hasil pengukuran geokimia di bagian barat tersusun atas unsur utama berupa Ca dan unsur minor berupa Fe, Cu, Sr, Mo, di bagian timur tersusun atas unsur utama berupa Ca, Si, Al, Fe dan unsur minor berupa S, Ti, Mn, Cu, Br, Sr, Ba. Berdasarkan rasio Ca/Mg, didapat batuan karbonat pada daerah penelitian berjenis Limestone dengan tingkat kemurnian lebih tinggi di bagian barat daerah penelitian dan pengotor lebih tinggi di bagian timur. Hasil analisis menunjukkan pengaruh ukuran dan kelimpahan pori terhadap pengukuran nilai parameter fisis batuan , serta penurunan nilai resistivitas terhadap peningkatan kandungan unsur Fe. Tingkat karstifikasi lebih tinggi pada bagian barat dan rekristalisasi ditemukan lebih tinggi pada bagian timur daerah penelitian. ===================================================================================================== Karst area is a landscape that has unique characteristics both below the surface and above the surface. This study aims to characterize carbonate rocks in the karst area of western Pacitan. Rock characterization based on petrographic analysis, physical parameters, and geochemistry. Rock sampling locations include the Districts of Donorejo, Punung, and Pringkuku. The results of the thin section analysis show that the carbonate rocks in the study area are wackestone types. The results of the measurement of physical parameters include the value of primary velocity (Vp) is 3104.9, resistivity is 1062.87 Ohm.m, effective porosity is 16.51% and dry density is 2.13 gram/cm3. The results of geochemical measurements in the western part are composed of the main elements in the form of Ca and minor elements in the form of Fe, Cu, Sr, Mo, in the eastern part are composed of the main elements in the form of Ca, Si, Al, Fe and minor elements in the form of S, Ti, Mn, Cu , Br, Sr, B. Based on the Ca/Mg ratio, the carbonate rock in the study area is of the Limestone type with a higher purity level in the western part of the study area and higher impurities in the eastern part. The results of the analysis show the effect of pore size and abundance on the measurement of rock physical parameter values, as well as decreasing resistivity values with increasing Fe content. The karstification rate was higher in the western part and recrystallization was found to be higher in the eastern part of the study area