Intermediate-sulfidation epithermal mineralization at Monterado goldfield in Western Borneo (Indonesia): Geological, mineralogical, and fluid inclusion microthermometric perspectives

Ilmawan, Ilham and Idrus, Arifudin and Lai, Chun-Kit and Dana, Cendi Diar Permata and Nugroho, Andhika Patria Adi (2023) Intermediate-sulfidation epithermal mineralization at Monterado goldfield in Western Borneo (Indonesia): Geological, mineralogical, and fluid inclusion microthermometric perspectives. Geological Journal, 58 (1). 315 – 332. ISSN 00721050

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Abstract

Gold mining in Western Borneo can be traced back over a century in the Dutch era. Many of these gold deposits are hosted in auriferous quartz veins, yet their geology and alteration/mineralization features have never been well documented. In this study, we present the first detailed account on gold mineralization in Western Borneo, using the Monterado goldfield as an example. Our results reveal that the auriferous quartz veining occurred in both intrusions (Mensibau granodiorite and Sintang Suite diorite porphyry) and volcanic-sedimentary sequences (Raya Volcanics and Hamisan Formation), and wallrock alterations are well developed. Distributions of the veins are controlled largely by N-S-trending (tensional veins, e.g., Nek Rimban and Muisan) and NW-SE (en-échelon tensional gash veins, e.g., Mertua, Lipan, and Sekar) structures. Vein textures include mainly massive, breccia, comb, drusy, and stockwork. Advanced Mineral Identification and Characterization System mineral mapping on the ore veins and mineralized wallrocks show the presence of electrum, acanthite, pyrite, chalcopyrite, bornite, sphalerite, galena, and supergene products such as malachite, covellite, cuprite, chalcocite and rosasite. Polymetallic sulfide mineralization is spatially associated with adularia within auriferous quartz veins and silicic alteration. Ore chemistry on 285 vein ore samples yielded on average 1.46 g/t Au and 6.58 g/t Ag. Fluid inclusion microthermometry indicates that the homogenization temperature ranges from 273 to 362°C (avg. 338°C), with salinities of 1.1–8.7 wt NaCl eq. (avg. 4.4 wt NaCl eq.). Accordingly, the Monterado Au–Ag quartz vein-type mineralization is best classified as intermediate-sulfidation epithermal style. © 2022 John Wiley & Sons Ltd.

Item Type: Article
Additional Information: Cited by: 0
Uncontrolled Keywords: Borneo; Indonesia; epithermal deposit; fluid inclusion; gold; mineralization; mineralogy; quartz vein; scanning electron microscopy; thermometry; X-ray fluorescence
Subjects: Q Science > QE Geology
Divisions: Faculty of Engineering > Geological Engineering Department
Depositing User: Sri JUNANDI
Date Deposited: 05 Nov 2024 08:51
Last Modified: 05 Nov 2024 08:51
URI: https://ir.lib.ugm.ac.id/id/eprint/10850

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