Proses alterasi menyebabkan terjadinya penggantian mineral, pelarutan, dan pengendapan langsung mineral dari larutan yang mengisi rekahan atau pori batuan, tujuan dilakukan penelitian ini untuk mengetahui alterasi dan mineralisasi di daerah penelitian. data awal berupa kondisi litologi pada daerah penelitian di dominasi oleh batuan metamorf berupa sekis muskovit, sekis klorit dan gneiss. Selain itu juga dijumpai batuan beku yang diindikasikan merupakan batuan intrusi. Metode yang digunakan adalah studi literatur dan survei lapangan dilakukan dengan pengambilan sampel batuan pada setiap lokasi yang representatif di daerah penelitian. Data dianalisis dengan menggunaan analisis petrografi dan mineragrafi, dengan analisis petrografi, diharapkan dapat mengetahui jenis-jenis batuan di daerah penelitian, Analisis Mineragrafi dimaksudkan untuk mengetahui jenis mineral bijih, tekstur mineral bijih dan menentukan paragenesis endapan bijih yang terjadi di daerah penelitian.Tipe alterasi yang berkembang di daerah penelitian yaitu tipe alterasi Propilitik dan Argilik.sedangkan mineralisasi di daerah Kolaka Utara terbentuk dalam satu tipe, yaitu tipe tersebar (disseminated), dimana mineral bijih sulfida tersebar dalam pada host rock yang mengalami alterasi, temperatur dan pH fluida hidrothermal ditafsirkan tipe endapan mineral bijih yang dijumpai daerah Kolaka Utara adalah tipe epithermal sulfidasi rendah.Agar hasil penelitian semakin detail maka perlu dilakukan pengambilan data dan analisis sampel yang lebih banyak serta mewakili sebaran kontak batuan beku dan metamorf. Hal ini mengingat analisis tersebut dapat menentukan fasies yaitu umur pembentukan batuan di masa lampau dari partial melting sampai naik ke permukaan dan posisi batuan beku terhadap batuan metamorf di daerah Kolaka Utara Provinsi Sulawesi Tenggara. Kata kunci: alterasi, epitermal sulfidasi rendah, kolaka utara, mineralisasi.
Abstract Bantimala Mélange Complex is about 75 Km to the North of Makassar, the capital city of South Sulawesi Province. The presence of High-pressure Metamorphic Rocks, and Ultrahigh Pressure in the Bantimala Mélange Complex, has been known and studied by a number of geologists. Eclogite and Blue Schist are Ultrahigh, and High-pressure metamorphic rocks in the Bantimala Mélange Complex which have important significance in explaining the Cretaceous tectonics in this area. Furthermore, Bantimala Eclogite is the only Ultrahigh-pressure metamorphic rock known to be exposed in Sulawesi. The results of thin section analysis of Eclogite show the presence of Omphacite Minerals, and Coesite as an index mineral for Ultrahigh pressure metamorphic rocks. While in Blue Schist with Glaucophane Minerals are found which are partially replaced by Chlorite which indicates the presence of Poly-metamorphism as a result of retrogradation from Ultrahigh pressure to High pressure and to Medium pressure metamorphic rocks. Radiometric age dating using the Ar 40 /Ar 39 method shows an age spectrum of 100 Ma-114 Ma (Early Cretaceous). The 114 Ma, age is interpreted as the age of Eclogite’s Ultrahigh pressure metamorphic rocks formation with respect to the peak of subduction tectonics. Whereas the age of 100 Ma before now is interpreted as the age of exhumation or collision as the end of the Cretaceous tectonic subduction in the South Arm of Sulawesi or in the East or Southeast of Sundaland.
W prospekcie Motongkad w regencji East Bolaang Mongondow w prowincji Północne Sulawesi w Indonezji miała miejsce epitermalna mineralizacja złota, zlokalizowana w andezytowo-bazaltowej brekcji, lawy i tufie należących do środkowomioceńskiej skały wulkanicznej (Tmv). Skała wulkaniczna jest intruzją andezytu i zawiera drobne żyły kwarcowe. W żyłach kwarcu znaleziono złoto, srebro i piryt. Badania te składają się z dwóch głównych etapów, prac terenowych i prac laboratoryjnych. Prace terenowe prowadzono na całym obszarze prospektu Motongkad, gdzie losowo, selektywnie i systematycznie pobierano próbki świeżych i zmienionych skał oraz mineralizacji z wychodni oraz z wykopu badawczego. Prace laboratoryjne obejmują petrografię, dyfrakcję rentgenowską (XRD), mikroskopię rudy oraz analizę chemiczną metodą atomowej spektrometrii absorpcyjnej (AAS). Obszar badań uporządkowany jest według trzech jednostek litologicznych. Stratygraficznie jednostkami są andezyt, ryolit i tuf. Zmiany hydrotermalne na badanym obszarze sklasyfikowano w pięciu strefach: kwarcowo-serycytowa, kwarcowo-serycytowo-gliniasta, kwarcowo-kalcytowoserycytowo- chlorynowa, kwarcowo-kalcytowo-serycytowa i kwarcowo-kalcytowo-kaolinitowa. Mineralizacja prospektu Motongkad składa się z dwóch typów, mianowicie typu żylnego i typu rozproszonego. Minerały rudne występujące w prospekcie Motongkad to: złoto, piryt, chalkopiryt, sfaleryt, kowelit, chalkozyn, bornit i tennantyt. Doszliśmy do wniosku, że mineralizacja złota i związane z nią minerały w prospekcie Motongkad są mineralizacją hydrotermalną o właściwościach epitermicznych. Na podstawie wyników analizy mineralogicznej stwierdzono, że istnieją dwa rodzaje minerałów złotonośnych, mianowicie rodzime minerały złota i elektrum, w których zazwyczaj występuje piryt. Na podstawie sporządzonej mapy rozmieszczenia zmian i mineralizacji rekomenduje się, aby spółka prowadziła wydobycie o najwyższej zawartości złota w strefach zmian kwarcowo-serycytowych i kwarcowo-serycytowo-gliniastych, które mieszczą się w granicach 0,83–1,07 g/Mg.
Abstract The research conducted in the Lapaopao area focuses on analyzing the process of serpentinization in ultramafic rocks and its impact on the formation of nickel laterite. Ultrabasic rocks containing olivine and pyroxene minerals undergo hydrothermal metamorphism, resulting in the formation of serpentine minerals. The research purposed to understand effect of serpentinization process to development of nickel laterite. Various samples were taken on location to see the correlation in both the Lapaopao sub-block and Babarina sub-block. There are two (2) types of samples were taken, including fresh rock (bedrock samples) and laterite samples (limonite and saprolite material). All samples were analyzed using methods such as XRF, thin section, and XRD. Bedrock samples were analyzed using the thin section method, while laterite samples (limonite and saprolite) were analyzed using XRF and X-RD analyzing methods. The serpentinization process in the Babarina sub-block is generally medium to high level, while in the Lapaopao sub-block low to moderate level. The enrichment of nickel (Ni) in the supergene zone is dominantly influenced by Ni’s ability to replace magnesium (Mg) in weathered serpentine minerals.
Abstract Incremental accretion of continental fragments from East Gondwana to Eurasia resulted in the growth of Asia and rise of the Tibetan Plateau, yet its detailed evolution remains uncertain. Argoland, a continental fragment that rifted from NW Australia during the Late Jurassic, played a key role in the initial opening of the Indian Ocean and the evolution of eastern Tethys. However, its present identity remains elusive, with East Java-West Sulawesi currently assumed to be the most likely option. To constrain the missing Argoland and its role in India-Asia convergence, we report new detrital zircon data from Sulawesi, Indonesia, and West Burma, Myanmar, and synthesize literature results from relevant regions in Southeast Asia, which (>15,000) reveal age profiles of West Sulawesi, the central Sulawesi metamorphic belt, and southeast Borneo comparable to that of Bird's Head, New Guinea, whereas age patterns of West Burma and East/West Java are similar to those of NW Australia. Notably, the most dominant age populations in NW Australia are rarely detected in Sulawesi and Borneo. These observations, combined with previous geological records and recent paleomagnetic data, suggest that West Burma is the mysterious Argoland, opposing the currently favored East Java-West Sulawesi model, with East Java and West Sulawesi probably having originated from NW Australia and Bird's Head, respectively. We estimate an average northward motion of ∼6–8 cm/yr for West Burma, which split from NW Australia to approach the equator during ca. 155–95 Ma, shedding new light on the reconstruction and breakup of northern East Gondwana, progressive building of Southeast Asia, and India-Asia convergence.
The southern part of Barru is exposed to mineralized tracheal rocks in contact with the limestone of the Tonasa Formation, while in the northern part there is an intrusion of mineralized dacite which penetrates the marl of the Tonasa Formation. The research objective was to determine the chemical characteristics of sulfide alteration and mineralization in trachea and pyrite in limestone. Using petrographic and XRF methods, it is known that sericite, orthoclast alteration and mineralization of galena, chalcopyrite, pyrite in trachea are probably the source of different magma. The calcite carbonate mineral in limestone undergoes sulfide substitution that also results in chemical transformations of Ca, Si and S. Weathering of limestones correlates with hydrothermal solutions, which is supported by a moderate alteration index for the formation of clay minerals, which apparently does not affect limestones. Simultaneously, at moderate alteration conditions Na2O decomposition, K2O replacement pyrite in the cavity filling and occurs in the sulfide phase, hematite oxidation.
Abstract Cenozoic magmatism occurs throughout West Sulawesi, Indonesia, yet its detailed evolution remains enigmatic due mainly to the scarcity of precise dating. Here, we report new whole-rock geochemical and zircon U-Pb-Hf isotopic data of plutonic/volcanic rocks and river sediments from West Sulawesi to constrain the petrogenesis and magmatic tempo. The magmatic rocks are intermediate to felsic (SiO2 = 58.1–68.0 wt%), high-K calc-alkaline to shoshonitic (K2O = 2.2–6.0 wt%), metaluminous to weakly peraluminous, and I-type in composition. Trace element concentrations and ratios (e.g., Nb/U = 1.7–4.3 and Ti/Zr < 28), along with negative zircon εHf(t) values (–17.0 to –0.4) and old crustal model ages (TDMC = 2.1–1.1 Ga), indicate a dominant magma source region from the underlying continental crystalline basement. U-Pb dating on zircons from ten magmatic rocks yielded weighted mean 206Pb/238U ages of 7.2–6.1 Ma, best representing the crystallization ages of host magmas, further consistent with the prominent age peaks (7.3–6.3 Ma) defined by detrital zircons from four sedimentary samples. Our new data, combined with available results, allow the identification of a noticeable climax of magmatism (flare-up) at ca. 7–6 Ma, forming a continuous magmatic belt throughout West Sulawesi. Given the absence of contemporaneous subduction and the coincidence of incipient opening of the South Banda Basin during ca. 7.15–6.5 Ma, the Late Miocene magmatic flare-up in West Sulawesi and coeval regional extension in eastern Indonesia are attributed to a resumed episode of Banda slab rollback.
The Rumbia Mountains, which in this study named Rumbia schist Complex is an east-west oriented, composed by a high-pressure/low-temperature, and a medium-pressure/low-temperature metamorphic rocks. Identified as mica schist, glauchopane schist, and green schist. Rumbia complex known as the location of gold deposits prospects discovered by local communities since 2007. The results of research showed that the metamorphic rocks are as hosts. There are two phase of gold mineralization that occurs in this area, namely: 1) Associated with tectonic deformation and metamorphic rocks exhumation, and 2) gold-related hydrothermal deposits. Radiometric age dating used 40Ar/39Ar geochronology, indicate that the first of gold mineralisation in the Rumbia Complex occurred ∼23 million years ago, and the second gold mineralisation were subsequently overprinting at 7 million years ago.
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