GEOLOGY AND CHARACTERISTICS OF LOW SULPHIDATION EPITHERMAL VEIN IN SENEPO AREA, EAST JAVA

Authors

  • Arifudin Idrus Department of Geological Engineering, Gadjah Mada University
  • Esti Handayani Puslitbang tekMIRA - KESDM

DOI:

https://doi.org/10.30556/imj.Vol20.No2.2017.274

Keywords:

geology, alteration, characteristics, quartz vein, ore mineralization, Senepo

Abstract

Senepo area is one of several epithermal mineralization prospects in Southern Mountains of Java Island. This study is aimed to investigate the geological framework and hydrothermal alteration of the prospect as well as to characterize the low sulphidation (LS) epithermal vein including vein textures, ore mineral, ore chemistry and hydrothermal fluid that are responsible for the formation of the quartz vein. Detailed field mapping was completed to understand the geological framework and hydrothermal alteration zones. Petrographic, ore microscopic, XRD and AAS analyses were applied to characterize the quartz vein. The study area is occupied by pebbly sandstone, andesite breccia, andesite units and alluvial deposit. Ore mineralization is mainly hosted by andesite of Oligo-Miocene of Watupatok Formation. The host-rock has been suffered by overprinted hydrothermal alteration and weathering. The epithermal veins are found as N-S-trending quartz veins with a thickness of 1-2 meters. These veins show massive texture, crustiform, cockade, druzy, comb, and disseminated sulphides, which is included in Crystalline Quartz Zonation (X). Optical microscopy and XRD analysis indicate that these veins contain several ore minerals such as chalcopyrite, sphalerite, galena, pyrite, hematite, covellite and malachite, associated with gangue mineral including quartz, felspar, chlorite and clay minerals. AAS analysis displays variable chemical composition of precious and base metals such as Au (17-37 ppb), Ag (8.1-32.6 ppm), Cu (122.1-81,450 ppm), Pb (35.4-883.6 ppm) and Zn (18.3-2,628 ppm). Gold and silver are relatively low compared to the base metals. Fluid inclusion micro thermometric analysis indicates that ore mineralization originated at temperatures of 187-263 oC and salinity of 0.18-0.53 % wt. NaCl eq. This salinity corresponds with a minimum hydrostatic pressure of about 10-55.1 bars. Based on those characteristic data, mineralized quartz veins in the study area are classified into a base metal horizon of LS epithermal system.

References

Buchanan, L. J. (1981) “Precious metal deposits associated with volcanic environments in the southwest,” Arizona Geol. Soc. Digest, 14, pp. 237–261.

Haas, J. L. (1971) “The effect of salinity on the maximum thermal gradient of a hydrothermal system at hydrostatic pressure,” Economic Geology, 66(6), pp. 940–946. doi: 10.2113/gsecongeo.66.6.940.

Hastuti, E. W. D. (2010) “Karakteristik struktur geologi di daerah mineralisasi logam dasar: studi kasus ngrayun dan sekitarnya, Ponorogo, Jawa Timur,” Jurnal Rekayasa Sriwijaya, 19(2), pp. 45–54.

Hedenquist, J. W., Izawa, E., Arribas, A. and White, N. C. (1996) Epithermal gold deposits: styles, characteristics and exploration. No. 1. Resources Geology Special Publication.

Idrus, A., Hakim, F., Kolb, J., Appel, P. and Aziz, M. (2013) “Ore and alteration mineralogy of Paningkaban-Cihonje gold prospect, Gumelar Sub-District, Banyumas Regency, Central Java: A new discovery of carbonate base metal gold epithermal deposit,” in Proceedings of International Conference on Geological Engineering. Yogyakarta: Gadjah Mada University, pp. 80–86. Available at: https://repository.ugm.ac.id/96983.

Isyqi, I., Aziz, M. and Idrus, A. (2016) “Karakteristik tekstur dan zonasi endapan urat epitermal daerah Cihonje, Kecamatan Gumelar, Kabupaten Banyumas, Jawa Tengah,” Jurnal RISET Geologi dan Pertambangan, 26(1), p. 23. doi: 10.14203/risetgeotam2016.v26.258.

Khant, W., Warmada, I., Idrus, A. and Watanabe, K. (2012) “Alteration mineralogy and quartz texture of polymetallic epithermal quartz veins at Soripesa prospect area, Sumbawa Island, Indonesia,” in Proceedings of the 2nd Asia Africa Mineral Resources Conference 2012. Bandung. Available at: https://www.researchgate.net/publication/259990678_Alteration_Mineralogy_and_Quartz_Textures_of_Polymetallic_Epithermal_Quartz_Veins_at_Soripesa_Prospect_Area_Sumbawa_Island_Indonesia.

Kojima, S. (1992) “The nature of chalcopyrite inclusions in sphalerite; exsolution, coprecipitation, or ‘disease’?; discussion,” Economic Geology, 87(4), pp. 1191–1192. doi: 10.2113/gsecongeo.87.4.1191.

Koski, R. A. (2012) Supergene ore and gangue characteristics. Virginia. Available at: https://pubs.usgs.gov/sir/2010/5070/c/Chapter12SIR10-5070-C-3.pdf.

Morrison, G., Guoyi, D. and Jaireth, S. (1990) Textural zoning in epithermal quartz veins. Townsville: Klondike Exploration Services.

Samodra, H., Gafoer, S. and Tjokrosapoetro, S. (1992) Peta geologi lembar Pacitan, Jawa Timur. Bandung. Available at: https://www.dropbox.com/s/46y0hc9ijxssz78/34-1507-4-Pacitan.jpg?dl=0.

Sampurno and Samodra, H. (1997) Peta geologi lembar Ponorogo, Jawa Timur. Bandung.

Setijadji, L. D. (2009) “Gold-related deposits in the southern mountains of East Java, Indonesia,” in International Conference Earth Science and Technology. Yogyakarta.

van Bemmelen, R. W. (1949) The geology of Indonesia vol. II: Economic geology. The Hague.

Visaiphone, S. (2010) Geology and characteristics of ore mineral deposits at Slahung Area, Ponorogo Regency, East Java, Indonesia. Gadjah Mada University. Available at: http://etd.repository.ugm.ac.id/index.php?mod=penelitian_detail&sub=PenelitianDetail&act=view&typ=html&buku_id=47207.

Widodo, W. and Simanjutak, S. (2002) “Hasil kegiatan eksplorasi mineral logam kerjasama teknik asing, daerah Pegunungan Selatan Jawa Timur,” in Kolokium Direktorat Inventarisasi Sumber Daya Mineral (DIM) TA. 2002. Bandung: Pusat Sumber Daya Geologi, pp. 1–8. Available at: http://psdg.bgl.esdm.go.id/kolokium 2002/08_Proseding logam1.pdf.

Wilkinson, J. . (2001) “Fluid inclusions in hydrothermal ore deposits,” Lithos. Elsevier, 55(1–4), pp. 229–272. doi: 10.1016/S0024-4937(00)00047-5.

Downloads

Published

2017-10-29