Mineralisasi pada batuan induk batugamping di daerah Lepadi, Dompu, Nusa Tenggara Barat

• Main Author: Danny Zulkifli Herman
• Format: Article
• Language: English
• Published: Geological Agency 2014-06-01
• Series: Indonesian Journal on Geoscience
• Subjects: bioclastic limestone; mineralization; metallic sulphide ore
• Online Access: https://ijog.geologi.esdm.go.id/index.php/IJOG/article/view/58

<p><a href="http://dx.doi.org/10.17014/ijog.vol3no3.20086" target="_blank">http://dx.doi.org/10.17014/ijog.vol3no3.20086</a></p><p><em>Lepadi area situated in the Regency of Dompu, West Nusa Tenggara, is occupied by limestone unit comprising limestone and sandy limestones; and sandstones which are occasionally found as lenses within units of tuffaceous sand and tuff breccia.</em></p> <p><em>Indication of metallic mineralization is shown by the occurrence of the base metal-bearing quartz veins penetrating a host rock of limestone. A pervasive hydrothermal alteration was formed as chlorite-calcite- muskovite/sericite-quartz and kaolinite/haloysite series with veins consisting of massive quartz veinlets (millimeter to 2.0 cm maximum width) and very thick vuggy quartz veins (± 3.2 m width). The first quartz type contains ore minerals such as galena, sphalerite, chalcopyrite, pyrite and iron oxide; whilst the second type has a predominant galena content with an association of, chalcopyrite, covelite, pyrite and iron oxide which occurred as tiny vugs filling and distributed sporadically within the quartz body.</em></p> <p><em>The result of studies by using microscope (petrography and mineragraphy), infra-red analysis (PIMA), chemical analysis and fluid inclusion on entirely altered rock/ore mineral/quartz vein samples reveals that the alteration and mineralization processes might occur in a mineralization system involving hydrothermal fluid of near neutral at the temperature ranging from 275º - 200</em><em>o</em><em>C. It brings to a suggestion that deposition of quartz veins and associated ore minerals has taken place in a depth ranging from 620 – 150 m beneath paleosurface. It is based on hydrothermal fluid’s salinity ranging from 1.2 – 2.2 equivalent wt.% NaCl de- tected from fluid inclusion within quartz crystal samples.</em></p> <p> </p>