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Abstrak :
Daerah penelitian “X” merupakan daerah prospek alterasi dan mineralisasi endapan emas yang termasuk dalam Zona Pegunungan Selatan Jawa bagian Timur. Penelitian ini bertujuan untuk mengetahui karakteristik alterasi dan mineralisasi endapan emas meliputi kehadiran himpunan mineral alterasi, mineral bijih, geokimia bijih, tekstur mineralisasi, persebaran zona alterasi hidrotermal, serta paragenesa endapan mineral bijih pada daerah penelitian. Pada penelitian ini, terdapat empat metode yang dilakukan meliputi petrografi, mineragrafi, XRD, dan AAS. Analisis petrografi dilakukan untuk mengamati karakteristik tekstur urat, mengidentifikasi kandungan mineral penyusun batuan dan keterdapatan himpunan mineral penciri zona alterasi hidortermal pada sampel batuan. Analisis XRD dilakukan untuk mengidentifikasi asosiasi mineral-mineral ubahan yang terbentuk pada zona alterasi di daerah penelitian yang sulit teridentifikasi melalui analisis petrografi. Analisis mineragrafi dilakukan untuk mengetahui karakteristik mineral bijih yang hadir, tekstur mineral bijih, keterdapatan mineral bijih yang berasoasiasi dengan endapan emas, serta penentuan paragenesa endapan mineral bijih pada daerah penelitian. Analisis AAS dilakukan untuk mengetahui keterdapatan unsur logam beserta kadar masing-masing unsur logam yang teridentifikasi pada daerah penelitian. Berdasarkan analisis petrografi dan XRD, zona alterasi hidrotermal yang berkembang pada daerah penelitian terdiri dari zona alterasi argilik dan propilitik. Zona alterasi argilik dicirikan oleh kehadiran mineral montmorillonite dan dickite dengan temperatur pembentukan diperkiran pada rentang suhu 200°-250°C. Zona alterasi propilitik dicirikan oleh melimpahnya kehadiran mineral klorit, epidot, dan kalsit dengan temperatur pembentukan diperkiran pada rentang suhu 120°-320°C. Berdasarkan analisis petrografi menunjukkan kehadiran tekstur urat pada daerah penelitian meliputi tekstur comb dan mosaic. Berdasarkan analisis mineragrafi, mineral bijih yang hadir di daerah penelitian meliputi mineral magnetit, pirit, kalkopirit, galena, rutil, ilmenit, hematit, kalkosit, goethite, dan hydrous iron oxide dengan tekstur mineral bijih berupa tekstur open space filling, diseminasi, penggantian, intergrowth, colloform, dan eksolusi. Berdasarkan analisis AAS, kehadiran emas ditunjukkan oleh terdeteksinya kadar unsur logam Au sebesar 0,09 - 2,5 ppm. Terdapat beberapa unsur logam lainnya yang teridentifikasi pada analisis AAS meliputi Cu, Pb, Zn, dan Ag. Mineral bijih yang berasosiasi dengan endapan emas pada daerah penelitian meliputi mineral pirit, kalkopirit, dan galena. Paragenesa endapan mineral bijih daerah penelitian terbagi menjadi dua tahap pembentukan yang diawali oleh terbentuknya mineral primer pada tahap hipogen meliputi mineral magnetit, pirit, kalkopirit, galena, rutil, dan ilmenit serta dilanjutkan oleh terbentuk mineral sekunder pada tahap supergen meliputi mineral hematit, kalkosit, goethite, dan hydrous iron oxide. Berdasarkan karakteristik alterasi dan mineralisasinya daerah penelitian termasuk dalam sistem endapan porfiri dan epitermal sulfidasi rendah. ......Research area "X" is a prospect area for alteration and mineralization of gold deposits which is included in the Southern Mountain Zone of Eastern Java. This research aims to determine the characteristics of alteration and mineralization of gold deposits including the presence of alteration mineral assemblages, ore minerals, ore geochemistry, mineralization texture, distribution of hydrothermal alteration zones, as well as the paragenesis of ore mineral deposits in the research area. In this research, four methods were used including petrography, mineragraphy, XRD, and AAS. Petrographic analysis was carried out to observe the texture characteristics of the veins, identify the mineral content that makes up the rock, and the presence of mineral assemblages that characterize hydrothermal alteration zones in the rock samples. XRD analysis was carried out to identify alteration mineral associations formed in alteration zones in the research area that are difficult to identify through petrographic analysis. Mineragraphic analysis was carried out to determine the characteristics of the ore minerals present, the texture of the ore minerals, the presence of ore minerals associated with gold deposits, as well as determining the paragenesis of ore mineral deposits in the research area. AAS analysis was carried out to determine the presence of metal elements and the levels of each metal element identified in the research area. Based on petrographic and XRD analysis, the hydrothermal alteration zone that develops in the research area consists of argillic and propylitic alteration zones. The argillic alteration zone is characterized by the presence of montmorillonite and dickite minerals with formation temperatures estimated to range from 200°-250°C. The propylitic alteration zone is characterized by the abundant presence of chlorite, epidote, and calcite minerals with formation temperatures estimated to range from 120°-320°C. Based on petrographic analysis, it shows the presence of vein textures in the study area including comb and mosaic textures. Based on mineragraphic analysis, the ore minerals present in the research area include magnetite, pyrite, chalcopyrite, galena, rutile, ilmenite, hematite, chalcocite, goethite, and hydrous iron oxide with the ore mineral textures shown including open space filling, dissemination, replacement, intergrowth, colloform, and exsolution. Based on AAS analysis, the presence of gold was indicated by the detection of Au metal element levels of 0.09 - 2.5 ppm. There are several other metal elements identified in AAS analysis including Cu, Pb, Zn, and Ag. The ore minerals associated with gold deposits in the research area include pyrite, chalcopyrite, and galena. The paragenesis of ore mineral deposits is divided into two stages, starting with the formation of primary minerals at the hypogene stage including magnetite, pyrite, chalcopyrite, galena, rutile and ilmenite and continued by the formation of secondary minerals at the supergene stage including hematite, chalcocite, goethite, and hydrous iron oxide. Based on the characteristics of alteration and mineralization, the research area is classified within the porphyry and low-sulfidation epithermal deposit systems.

Abstrak :
Pada lapangan panas bumi “X” Daerah Gunung Slamet, Kabupaten Tegal Jawa Tengah keterdapatan manifestasi berupa mata air panas yang kemunculan dan persebarannya mengikuti kelurusan struktur geologi berupa sesar normal dan sesar mendatar berorientasi baratlaut-tenggara. Sehingga dari kondisi geologi daerah penelitian yang menunjukkan adanya struktur yang dapat menjadi jalur fluida panas tersebut, batuan teralterasi beserta mineral ubahan sangat mungkin terbentuk didaerah ini. Penelitian ini dilakukan bertujuan untuk mengidentifikasi litologi, zona alterasi berdasarkan mineral alterasi yang terbentuk dan kaitan mineral alterasi dengan temperatur dan sifat fluida pembentukan mineral alterasi tersebut di daerah penelitian. Metode yang digunakan ialah analisis petrografi melalui sayatan tipis dan metode analisis difraksi sinar-X (X-ray Diffraction). Metode petrografi dilakukan guna mengidentifikasi keberadaan mineral teralterasi atau tidak teralterasi pada sampel sayatan tipis. Lalu, Metode XRD bertujuan untuk mengidentifikasi lebih lanjut mengenai mineral alterasi yang terkandung yang sebelumnya tidak dapat teridentifikasi pada analisis petrografi. Berdasarkan hasil analisis petrografi batuan, litologi daerah penelitian tersusun atas batuan beku andesit, dan kristal tuf. Berdasarkan hasil analisa petrografi dan XRD pada sampel daerah penelitian dapat dibagi menjadi dua zona alterasi berdasarkan mineral alterasi yang ditemui, yaitu zona propilitik dan zona argilik. Pada zona argilik rentang temperatur keterbentukan mineral yaitu pada suhu 80-120°C. Sedangkan, zona alterasi propilitik memiliki rentang suhu keterbentukan mineral pada >250°C. Berdasarkan mineral alterasi yang ditemukan temperatur daerah penelitian terbagi menjadi dua kelompok yaitu kelompok tingkat keasaman (pH) netral dan asam yang dicirikan dengan keberadaan mineral kaolinit. ......In the geothermal field "X" Slamet Mountain area, Tegal Regency, Central Java, there are manifestations in the form of hot springs whose appearance and distribution follow the alignment of geological structures in the form of normal faults and stike-slip faults oriented north west-south east. So that from the geological conditions of the research area that shows the existence of structures that can be a hot fluid path, alterated rocks and altered minerals are very likely to form in this area. This study was conducted to identify the lithology, alteration zones based on alteration minerals formed and the relationship of alteration minerals with temperature and fluid properties of the formation of alteration minerals in the study area. The methods used are petrographic analysis through thin section and X-ray diffraction analysis method. The petrographic method was used to identify the presence of altered or unaltered minerals in the thin section samples. Then, the XRD method aims to further identify the alteration minerals contained that could not previously be identified in the petrographic analysis. Based on the results of rock petrographic analysis, the lithology of the study area is composed of andesite igneous rocks, and tuff crystals. Based on the results of petrographic and XRD analysis on the samples of the study area can be divided into two alteration zones based on the alteration minerals found, namely the propylitic zone, and argillic. In the argillic zone, the temperature range for mineral formation is 80-120°C. Meanwhile, the propylitic alteration zone has a mineral formation temperature range of >250°C. Based on the alteration minerals found, the temperature of the research area is divided into two groups, namely neutral and acidic acidity (pH) groups which are characterized by the presence of the mineral kaolinite.