Kawah Ratu yang terletak di Gunung Salak, Bogor, Jawa Barat ini memiliki mineral lempung hasil alterasi (Stimac et al, 2006). Penelitian ini bertujuan untuk mengetahui litologi, struktur, persebaran mineral lempung alterasi hidrotermal, intensitas alterasi, dan keterkaitan antara pembentukan mineral alterasi dengan tipe fluida di Kawah Ratu dan sekitarnya. Metode yang digunakan dalam penelitian ini meliputi pemetaan, petrografi, dan Powder X-Ray Diffraction (XRD). Berdasarkan hasil analisis, didapat litologi daerah penelitian berupa andesit, breksi andesit, dan batuan hidrotermal. Intensitas alterasi di daerah penelitian umumnya sangat kuat dengan mineral berupa kaolinit, dickite, montmorillonite, klorit, pyrophyllite, dan serisit. Keberadaan mineral tersebut dipengaruhi oleh suhu 100-350°C dengan tipe fluida asam-netral.

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Kawah Ratu which is located on Mount Salak, Bogor, West Java has clay minerals as a result of alteration (Stimac et al, 2006). This study aims to determine the lithology, structure, distribution of hydrothermal alteration clay minerals, intensity of alteration, and the relationship between the formation of alteration minerals and the type of fluid in Kawah Ratu and its surroundings. The methods used in this research include mapping, petrography, and Powder X-Ray Diffraction (XRD). Based on the analysis results, the research area lithology is obtained in the form of andesite, andesite breccia, and hydrothermal rocks. The intensity of alteration in the study area generally very strong with minerals in the form of kaolinite, dickite, montmorillonite, chlorite, pyrophyllite, and sericite. The presence of these minerals is influenced by a temperature of 100-350°C with an acid-neutral fluid type.