AbstrakDaerah Sangon, Kokap, Kulon Progo, Daerah Istimewa Yogyakarta tersusun dari Formasi Andesit Tua. Vulkanisme Pegunungan Kulon Progo telah mengendapkan mineral logam, salah satunya di daerah Sangon. Penelitian bertujuan untuk mengetahui tipe alterasi, tipe mineralisasi, serta hubungan pola sebaran urat kuarsa dengan tipe alterasi dan tipe mineralisasi. Penelitian dilakukan pada kavling seluas 2 x 2 km 2 dengan melakukan pemetaan geologi dan analisis laboratorium. Observasi lapangan mencakup pengambilan data struktur dan batuan. Analisis laboratorium yang dilakukan antara lain analisis petrografi, mineragrafi, dan XRD untuk mengetahui mineral primer, sekunder, dan logam. Hasil analisis menunjukkan bahwa stratigrafi daerah penelitian termasuk ke dalam Formasi Andesit Tua berupa batuan lava andesit dan andesit porfir. Struktur geologi yang berkembang berupa sesar geser yang mempengaruhi mineralisasi logam. Pada bagian utara daerah penelitian mempunyai dimensi urat relatif kecil, tipe alterasi lanjut argilik dan inner propilitik, mineral logam emas, pirit, kalkopirit, arsenopirit, sfalerit dengan suhu yang rendah 50 o C -120 o C. Di bagian tengah daerah penelitian mempunyai dimensi urat relatif besar, tipe alterasi propilitik, mineral logam pirit, kalkopirit dengan suhu yang rendah 200 o C -340 o C. Kavling bagian selatan mempunyai dimensi urat relatif kecil, tipe alterasi filik, mineral logam pirit, kalkopirit dengan suhu yang rendah 280 o C -400 o C. Dengan demikian, dapat disimpulkan bahwa Daerah Sangon adalah lokasi endapan epitermal sulfida rendah.Kata Kunci : Sangon, Formasi Andesit Tua, epitermal sulfida rendah. Abstract Sangon area, Kokap, Kulon Progo, Special Region Yogyakarta consist of the Old Andesite Formation. Kulon Progo Tertiary Volcanic deposited metal minerals, one of them is in the Sangon area. The aim of this research is to know the type of alteration, mineralization, and the relation of the pattern of quartz vein distribution with the type of alteration and the type of mineralization.The study was conducted on a 2 x 2 km 2 area by conducting field observation and laboratory analysis. Field observation includes data collection of structures and rocks. Laboratory analysis included petrography analysis, mineragraphy, and XRD to know primary, secondary, and metal minerals. The results of the analysis indicate that the stratigraphy of the study area consist of lava rocks and porous andesite as part of the Old Andesite Formation. The geological structure that developed within the area is a branch shear fault that affects metal mineralization. The northern plots have relatively small urate dimensions, advanced argillic alteration and inner propylitic type, gold metal minerals, pyrite, chalcopyrite, arsenopyrite, sphalerite with low temperature 50oC -120oC. The middle plot has a relatively large urate dimension, type of propylitic alteration, pyrite metal minerals, chalcopyrite with a low temperature of 200oC -340oC. The southern portion has relatively small urate dimensions, type of phyllic alterat...
The research was conducted in Madang and Serakaman Tengah area, Sebuku Island Subdistrict, Kotabaru Regency, South Kalimantan Province which is one of the nickel potential areas in Indonesia. The aim of this research is to know the characteristic and distribution of laterite nickel mineralization. The rocks present in the study area are serpentinized dunite, serpentinized harzburgite, gabbro, silicified gabbro, tuff, and basalt. Methods used in this research were surface geological mapping, rock observation and sampling from outcrop and drill core representing each laterite horizon from limonite horizon to bedrock. Laboratory analysis consist of X-Ray Fluorescene (XRF) analysis is used to determine the abundance of certain chemical elements and compound which characterized the mineralization stage zonation in the laterite profile. The laterite deposite in the study area can be divided based on physical and chemical properties into four zones; red limonite, yellow limonite, saprolite, and bedrock. Saprolite is dominated by a group of hydrocylicic minerals (serpentine) so it can be predicted that the laterite types are developing laterite oxide and laterite silicate types.
The increasing population up to 1.67% per year in the urban coastal city such as Semarang affects enormous stress on the natural resources – groundwater, in particular. To assess groundwater vulnerability to contamination the DRASTIC method was applied. DRASTIC was one method in compiling a zone of groundwater vulnerability to contamination. This method required seven parameters, namely D (water table depth), R (recharge zone), A (media aquifer), S (soil media), T (topography), I (vadose zone), and C (hydraulic conductivity). Processing of each parameter to calculate the Drastic Index (DI) was developed by using spatial analysis in ArcGIS. The results conduct there is three-level of groundwater vulnerability to contamination namely low, medium, and high. The low vulnerability has the number of DI of 61 to 100, while the DI of moderate is around 101-140. The high level is represented by 141-180 of DI. The low level is distributed in some areas in the south of Semarang, while the medium is dominated in the Ngaliyan area, Gajahmungkur, Semarang Selatan, also found in Tugu, Semarang Barat, Candisari, and some areas in the Semarang Tengah. Indeed, the high level is found in the plains areas in the northern, in the western, and eastern part of Semarang.
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