The Bajawa Cinder Cone Complex consists of at least 78 cinder cones, which can be grouped into five morphometric ages. The oldest group, Bajawa 01, is dated between 0.53 and 0.73 Ma. The groups Bajawa 02, 03, and 04 have an age range from 0.41 Ma to 0.51 Ma, 0.32 Ma to 0.40 Ma, and 0.22 Ma to 0.31 Ma, respectively; the youngest cinder cone group, Bajawa 05, is aged between 0 and 0.20 Ma.Three batches of magma have contributed to the long eruptive episode of the complex. Magma mixing and fractional crystallization were important processes in differentiation. Magma mixing may have been caused by recharge of a mafic contributor to form a mixed magma in a temperature range of 836 °C 978 °C and at a pressure of less than 1.25 kbar before eruption.

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The Wanagon Gold prospect area located in the Ertsberg District, Papua Province, the eastern part of Indonesia, is predominantly underlain by Upper Mesozoic to Cenozoic sedimentary rocks intruded by the Wanagon Sill monzodiorite-diorite and andesite intrusion (Wanagon Dike). The study by previous researchers at Wanagon Gold prospect was based on pre-2005 exploration data and did not contain extensive additional drillings in 2007-2011. This paper aims to elucidate the genesis of the Wanagon Gold deposits based on the latest exploration data. The mineralogy was determined by using thin section and polish section analyses, a scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), and Near-Infrared spectroscopy (NIR). The chemical composition of the rock was identified using an X-ray fluorescence spectrometer (XRF). Gold mineralization is associated with pyrite, of which there are three types of gold-bearing pyrite: (1) massive pyrite, (2) disseminated pyrite, and (3) fine-grained pyrite associated with clay minerals. Only massive pyrite contains visible gold-bearing minerals such as native gold, electrum, and gold-telluride minerals, while in nonmassive pyrite, gold is only detected by the assay. The deposit is interpreted as structurally controlled distal gold skarn. Instead, its local association of gold with arsenic also indicates a minor component of more-distal sediment-hosted type gold mineralization.

Sari-Batupasir di daerah Bulukuning, Banjarnegara yang dikenal dan bahkan pernah diusulkan sebagai Formasi Bulukuning ini sebelumnya disebut sebagai batupasir greywacke sebagai bagian dari Komplek Mélange Luk Ulo yang berumur Kapur Awal-Paleosen. Keberadaan batupasir ini yang sudah menunjukkan sifat matamorfisme dan hadir pada batulempung bersisik yang umumnya dianggap matriks dari melange menjadi menarik untuk dipelajari lebih lanjut. Penelitian ini mengkaji detail karakteristik litologi, provenannya dan implikasi tektoniknya.Batupasir di dalam satuan batuan ini secara umum, sebelum mengalami deformasi, merupakan perselingan batupasir dan batulempung-batulanau yang berlapis baik, berinterkalasi dengan lempung bersisik. Determinasi paleontologi pada batupasir yang mengandung Paleo-Nummulites dan nanno fosil matriks menunjukkan umur Eosen Tengah-Akhir (NP15-16). Kenampakan struktur yang sering dijumpai selain terlipat dan tersesarkan, batupasir ini menunjukkan karakter blok dalam matrik lempung bersisik (block in matrix) dan pada beberapa bagian berkembang struktur boudin yang merupakan hasil deformasi kenyal-tegar. Analisis pada matriks lempung bersisik menggunakan nilai illite crystallity (IC) menghasilkan interpretasi bahwa deformasi yang mengkontrol pembentukan struktur lempung bersisik dan boudinage berlangsung pada temperatur sekitar 205.916 o -223.014 o C (± 30°).Studi provenan batupasir menunjukkan bahwa batupasir ini sebagian besar merupakan recycled orogen yang berhubungan dengan tatanan tektonik collision orogen. Aktivitas tektonik ini diperkirakan berkaitan dengan dengan tumbukan Mikro Kontinen Jawa Timur dengan bagian timur daratan Sunda pada Eosen akhir-Oligosen Awal, diikuti dengan terangkatnya komplek akresi Karangsambung, batuan vulkanik yang terbentuk sebelumnya serta beberapa blok daratan Sunda. Luk Ulo. Erosi dan pengendapan pada cekungan muka daratan (foreland basin) menghasilkan endapan molasse yang berasal dari sumber hasil percampuran tektonik dalam suatu zona suture.Kata kunci: batupasir, mélange, boudin, deformasi, tektonik. Abstract -Sandstone unit in the Bulukuning area, Banjarnegara known and even once proposed as the BulukuningFormation were formerly referred to as the greywacke sandstones as part of the Luk Ulo Melange Complex which is believed as Early Cretaceous-Paleocene in age. The sandstones are lightly metamorphosed and observed in many places to be inclunded in the exotic blocks within the scaly clay which is generally considered as matrix of melange. This study examines the details of lithological characteristics, their provenances and tectonic implications. (NP15-16). The highly deformed sequence of Bulukuning Sandstones often show block in matrix characters while others develop more boudinage structures as a result of rigid deformation. Analysis of the scaly clay matrix using the illite crystallinity (IC) value suggested that the deformation controlled the formation of scaly clay and boudinage structures occurred at temperatures around 205.916 o -223.014 o C (± 30°). Undefo...

The Una-Una Island is in the Gulf of Tomini, Central Sulawesi Province. This island is a soliter active volcano island with Mount Colo as volcano name. The island is located between the North Arm and East Arm of Sulawesi, which are having complex tectonic regime, situated between two subduction zones. Volcanic rocks from Una-Una Island are basaltic-trachyandesite until trachydasite composition with magma affinity is calk-alkaline, high-K calk-alkaline and shoshonite. Tectonic reconstruction in this area started at Miocene (15 Ma) where the Celebes Sea Plate subducted below the North Arm of Sulawesi with a gentle slope produced adakite-type volcanic rocks. Along with the continuous subduction process and increasingly steep angle of subduction, the magma source then underwent. Intensive movement of the Banggai-Sula microcontinent, resulted in obduction of the ophiolite during collision, whereas volcanic activity in Una-Una Island and surrounding islands are still ongoing. Recent eruption of the Mount Colo in 1983 produced abundant of pyroclastic material with acid silica and still adakite type composition with mineralogical assemblages consist of hornblende-phlogophite-biotite, gives the impression that it originated from the same magma sources. According to composition of magma and eruption history which were produced magmatic explosion followed by pyroclastic surge, flow and fall, the disaster mitigation focus to eruption forecasting through visual and instrumental monitoring provide by Centre for Volcanology and Geological Hazard Mitigation, Geological Agency, Ministry of Energy and Mineral Resources Republic of Indonesia.