KARAKTERISTIK MINERAL LEMPUNG HASIL UBAHAN PADA SUMUR LW-1 DAN LW-2 DENGAN MENGGUNAKAN METODE DIFRAKSI SINAR-X PADA SISTEM PANAS BUMI GUNUNG LAWU

THE CHARACTERISTICS OF CLAY MINERAL ALTERATION FROM WELLS LW-1 AND LW-2 USING X-RAY DIFFRACTION METHOD IN THE MOUNT LAWU GEOTHERMAL SYSTEM

  • Lano Adhitya Permana, S.T., M.T Pusat Sumber Daya Mineral, Batubara dan Panas Bumi
  • Candra Widya Sastrawijaya Pusat Sumber Daya Mineral, Batubara dan Panas Bumi
  • Dudi Hermawan Pusat Sumber Daya Mineral, Batubara dan Panas Bumi
Keywords: XRD, clay minerals, degree of crystallinity, temperature, caprock, Mount Lawu

Abstract

The LW-1 and LW-2 geothermal wells are located in the depression zone between Mount Lawu and Mount Jabolorangan contain rocks that are hydrothermally alterated as indicated by the presence of alteration minerals that are classified as argillic to advanced argillic alteration. To determine the character of the altered minerals that were formed, especially the presence of clay minerals in LW-1 and LW-2 wells, a study of clay minerals is required using the X-Ray Diffraction approach. This study aims to determine the presence and characteristics of clay minerals in LW-1 and LW-2 also their correlation to the formation of a geothermal system in the Gunung Lawu area. The analysis and interpretation using XRD method in LW-1 and LW-2 wells shows that within the temperature increases the crystal shape of the clay minerals becomes more perfect which is represented by a smaller degree of crystallinity. Whereas the effect of grain size on the XRD pattern shows that the crystallinity of the clay minerals tend to decrease with increasing grain size. The altered clay minerals in LW-1 and LW-2 wells consist of smectite, illite, kaolinite and halloysite which can be acted as caprock in the Mount Lawu geothermal system.

References

Anonim, 2009. Survei Terpadu Geologi dan Geokimia Daerah Panas Bumi Gunung Lawu, Provinsi Jawa Tengah dan Jawa Timur. Pusat Sumber Daya Geologi - Badan Geologi, Bandung.

Anonim, 2010a. Pengeboran Landaian Suhu Sumur LW-1 Daerah Panas Bumi Gunung Lawu, Kabupaten Karang Anyar, Provinsi Jawa Tengah. Pusat Sumber Daya Geologi - Badan Geologi, Bandung.

Anonim, 2010b. Pengeboran Landaian Suhu Sumur LW-2 Daerah Panas Bumi Gunung Lawu, Kabupaten Magetan, Provinsi Jawa Timur. Pusat Sumber Daya Geologi - Badan Geologi, Bandung.

Anonim, 2010c. Survei Magnetotellurik Daerah Panas Bumi Gunung Lawu, Kabubapten Karang Anyar, Provinsi Jawa Tengah dan Kabupaten Magetan, Provinsi Jawa Timur. Pusat Sumber Daya Geologi - Badan Geologi, Bandung.

Browne, P.R.L., 1999. Hydrothermal alteration, 665.611 Lectures Notes. Geothermal Institute, University of Auckland.

Corbett G. J. dan Leach T.M., 1996. Southwest Pasific Rim Au/Cu System: Structure, Alteration and Mineralization. Workshop Manual, 186 hal.

Eberl, D.D dan Velde, B., 1989. Beyond the Kubler Index. Clay Miner, vol 24,571–577.

Fitriyana,D.F., Sulardjaka, Iskandar,N., dan Dzulfikar,M.,2018. Pengaruh Suhu Hidrotermal Terhadap Karakteristik Zeolit yang Disintesis dari Lembah Geotermal. Majalah Ilmiah Momentum, Vol. 14, No. 1, Hal. 46-50.

Hamilton, W.B.,1979. Tectonics of Indonesian Region, USGS Profesional Paper 1078.

Ji,J dan Browne, P.R.L, 2000. Relationship Between Illite Crystallinity and Temperature in Active Geothermal System of Zealand. Clays and Clay Minerals, Vol. 48, No. 1, 139-144.

Kingston Morrison, 1995. Important Hydrothermal Minerals and Their Significance. Geothermal and mineral services division. Kingston Morrison Ltd, edisi ke 6.

Ma, C., Browne, P.R.L. dan Harvey,CC.,1992. Crystallinity of Sub Surface in The Te Mihi Sector of The Wairakei Geothermal System,New Zealand. Proceeding New Zealand Geothermal Workshop 14 th, 267-272.

Moore, D.M. dan Reynolds, Jr, R.C., 1989 : X-ray diffarction and The Identification and Analysis of Clay Minerals. Oxford University Press, 332 hal.

Permana, L.A., 2011. Studi Karakteristik Mineral Ubahan Pada Sumur LW-1 dan LW-2 di Daerah Panas Bumi Gunung Lawu. Tesis. Departemen Teknik Geologi - Institut Teknologi Bandung. Tidak dipublikasikan.

Prasetyo,I,M., Sardiyanto, Koestono,H., dan Thamrin,M.H., 2015. Clay Alteration Study from Wells of Tompaso Geothermal Field, North Sulawesi, Indonesia. Proceedings World Geothermal Congress, Melbourne, Australia.

Reyes, A.G., 1990. Petrology of Philipine Geothermal Systems and The Application of Alteration Mineralogy to Their Assessment. Journal Vulcanology and Geothermal, vol 43, 279-309.