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

Danny Zulkifli Herman

Abstract


http://dx.doi.org/10.17014/ijog.vol3no3.20086

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.

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.

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 - 200oC. 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.

 


Keywords


bioclastic limestone; mineralization; metallic sulphide ore

References


Browne, P.R.L., 1993. Hydrothermal alteration and geothermal systems, unpublished 86.102 Geology course outline, Dept. Geology, University of Auckland, 68h.

Chen, C.H., 1970. Geology and geothermal power potential of the Tatun volcanic region. Dalam: Barnes, H.L. (ed.) 1979, Geochemistry of hydrothermal deposits, 2nd edition, John Willey and Sons, New York, h.632-683.

Folk, R.L., 1959. Practical petrographical classification of limestone. American Association of Petroleum Geologists, Bulletin. 43 (1), h.1-38, 41 Figs., Tulsa. Dalam: Flűgel, E.E. (ed.) 1982, Microfacies Analysis of Limestones, Springer-Verslag, Berlin-Heidelberg-New York, 588h.

________1962. Spectral subdivision of limestone types, American Association of Petroleum Geologists, Memoir, 1, h.62-84, Pl.1., 7 Figs., Tulsa. Dalam: Flűgel, E.E. (ed.) 1982, Microfacies Analysis of Limestones, Springer-Verlag, Berlin-Heidelberg-New York, 588h.

Haas, J.L., 1971. The effects of salinity on the maximum thermal gradient of a hydrothermal system at hydrostatic pressure. Economic Geology, 66, h.940-946.

Hamilton, W., 1979. Tectonics of the Indonesian Region, USGS Professional Paper, 1078, 355h.

Hayashi, M., 1973. Hydrothermal in the Otake geothermal area, Kyushu. Dalam: Barnes, H.L. (ed.), 1979, Geochemistry of hydrothermal deposits, 2nd edition, John Wiley and Sons, New York, h.632-683.

Koesoemadinata, S., Noya, Y., dan Kadarisman, D., 1994. Peta Geologi Lembar Ruteng, Nusatenggara, skala 1:250.000. Pusat Penelitian dan Pengembangan Geologi, Bandung.

Kutina, J. dan Sedlackova, J., 1961. The role of replacement in the origin of some cockade textures. Economic Geology, 56, h.149-176.

Potter R.W.III., Clyde, D.M., dan Brown, D.L., 1978. Freezing point depression of aqueous sodium chloride solutions. Economic Geology, 73, h.284-285.

P.T. Prakarsa Arimbi Sejahtera., 2007a. Laporan Kegiatan Eksplorasi Endapan Bijih Mangan dan Permintaan Perpanjangan KP.Eksplorasi Daerah Lepadi dan Sekitarnya Kecamatan Pajo dan Huu, Kabupaten Dompu, Propinsi Nusa Tenggara Barat (KP.Eksplorasi No. 43/2006)

________ , 2007b. Laporan Kegiatan Eksplorasi Bahan Galian Timah Hitam DMP dan Permintaan Perpanjangan KP.Eksplorasi Daerah Lepadi, Kabupaten Dompu, Propinsi Nusa Tenggara Barat (KP.Eksplorasi No. 44/2006)

Pusat Penelitian Geoteknologi LIPI, 2007. Laporan pengukuran mikrotermometri inklusi fluida, tidak dipublikasikan, 10h.

Ratman, N. dan Yasin, A., 1978. Peta Geologi Lembar Komodo, Nusatenggara, skala 1: 250.000. Pusat Penelitian dan Pengembangan Geologi, Bandung.

Sudradjat, A., Andi Mangga, S., dan Suwarna, N., 1998. Peta Geologi Lembar Sumbawa, Nusatenggara, skala 1:250.000. Pusat Penelitian dan Pengembangan Geologi, Bandung.


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