<![CDATA[ABSTRACTThe deposit type in Ertsberg District, consist of porphyry and skarn type. Ertsberg skarn associated with Ertsberg diorite intrusion developed in DOM and East Ertsberg Skarn System (EESS). Deep Mill Level Zone (DMLZ) is the lowest mining zone and the part of EESS. Megascopis and microscopic analysis, such as petrography analysis method on core sampel from DMLZ were carried out to determine the characteristics of host rock and mineralization occurred in study area. Based on mineral association and alteration mineral, metallic minerals formed on limestone, calcareous shales, and igneous rock as its host rock. Those host rock was altered on weak to strong intensity. According to characteristic of litology, lithological unit were divided into units, namely : Hornfels Unit, Marble Unit, Altered Limestone Unit, and Intrusion Igneous Rock Unit. Mineralization can be identified as pyrite, chalcopyrite, sphalerite, bornite, magnetite, hematite, and malachite. It formed as disseminated, scattered, patches, and as a veinlet. Ertsberg intrusion intrude carbonates and siliciclastic sediment wall rock in study area and metamorphism occurred. Metamorphic rock appeared in recent sample from study area. Magmatic fluid from magma differentiation interacted with wall rock caused metasomatism and hydrothermal alteration process. Furthermore, metallic minerals that carried away by magmatic fluid precipitated as temperature dropped.Keywords : Deep Mill Level Zone (DMLZ), host rock, mineralization, skarn ABSTRAKTipe endapan yang terdapat di Distrik Ertsberg, meliputi tipe porfiri dan skarn. Skarn Ertsberg berasosiasi dengan intrusi diorit Ertsberg pada endapan skarn DOM dan East Ertsberg Skarn System (EESS). Deep Mill Level Zone (DMLZ) merupakan tambang terbawah dan bagian dari EESS. Metode analisis megaskopis dan mikroskopis, berupa analisis petrografi pada sampel inti dari DMLZ digunakan untuk tujuan mengetahui karakteristik batuan induk dan mineralisasi. Ditinjau dari dari mineral penyusun dan mineral ubahannya, mineral bijih terbentuk pada batuan induk, berupa batugamping, batuserpih karbonatan, dan batuan beku. Batuan induk tersebut secara umum sudah mengalami ubahan dengan intensitas lemah hingga kuat jika dilihat dari banyaknya kehadiran mineral ubahan. Berdasarkan karakteristik litologinya, batuan dibagi menjadi satuan litologi, yaitu Satuan Hornfels, Satuan Marmer, Satuan Batugamping Terubah, dan Satuan Batuan Beku Intrusi. Mineralisasi yang hadir meliputi pirit, kalkopirit, sfalerit, bornit, magnetit, hematit, dan malakit. Kehadirannya dapat tersebar merata, tersebar tidak merata, patches, maupun sebagai urat. Intrusi Ertsberg menerobos batuan samping berupa batuan karbonat dan batuan sedimen silisiklastik di daerah penelitian, sehingga batuan samping mengalami metamorfisme. Batuan metamorf tampak pada sampel batuan saat ini. Fluida magmatik hasil diferensiasi magma yang kemudian berinteraksi dengan batuan samping menyebabkan metasomatisme dan proses alterasi hidrotermal terjadi. Selanjutnya, mineral bijih yang terbawa oleh fluida magmatik terpresipitasi seiring menurunnya suhu.Kata Kunci : Deep Mill Level Zone (DMLZ), batuan induk, mineralisasi, skarn]]>
