D. F. Yudiantoro
Geological Engineering, UPN “Veteran” Yogyakarta

Published : 2 Documents

Found 2 Documents

Interstratified Illite/Montmorillonite in Kamojang Geothermal Field, Indonesia Yudiantoro, D. F.; suparka, E.; Yuwono, S.; Takashima, I.; Ishiyama, D.; Kamah, Y.; Hutabarat, J.
Indonesian Journal on Geoscience Vol 8, No 4 (2013)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1141.816 KB) | DOI: 10.17014/ijog.v8i4.167


DOI: 10.17014/ijog.v8i4.167Kamojang geothermal field located in West Java Province, falls under the Pangkalan Subregency, Bandung Regency. The researched area is a geothermal field located in the Quaternary volcanic caldera system of about 0.452 to 1.2 Ma. The volcanic activity generated hydrothermal fluids, interacting with rocks producing mineral alteration. The minerals formed in the areas of research are interstratified illite/montmorillonite (I/M). Analyses to identify interstratified I/M have been performed by X-ray diffraction using ethylene glycol, while the determination of the type and percentage of interstratified I/M was based on the calculation method of Watanabe. The methodology was applied on core and cutting samples from Wells KMJ-8, 9, 11, 13, 16, 23, 49, 51, and 54. The result of analysis of the samples shows that the type of clay is interstratified illite/montmorillonite and the minerals are formed at temperatures ranging from 180 to 220° C. The type of interstratified I/M in the studied area is S = 0 and S = 1. The percentage of illite type S = 0 is between 20 - 35% illite, whereas type S = 1 has about 45 - 72% illite. Along with the increasing depth, the percentage of illite is getting greater. This is consistent with the vertical distribution of temperature which increases according to the depth. This correlation results in an interpretation that the upflow zone of the geothermal reservoir is located in the centre of the Kamojang geothermal field.
Fluid-Rock Interaction During Hydrothermal Alteration at Parangtritis Geothermal Area, Yogyakarta, Indonesia Yudiantoro, D. F.; Haty, I. Permata; Sayudi, D. S.; Aji, A. Bayu; C., S. Umiyatun; Adrian, M. Nuky
Indonesian Journal on Geoscience Vol 6, No 1 (2019)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (6952.341 KB) | DOI: 10.17014/ijog.6.1.29-40


DOI: 10.17014/ijog.6.1.29-40Parangtritis Volcano is part of the Tertiary magmatic belt in Java, which was tectonically formed by collisions between the Eurasian Continental Plate and Indo-Australian Oceanic Plate. The collisions have taken place since Late Cretaceous and still continue until today. In that period, the magmatic belt in Java Island was formed and produced mineralization and geothermal. The characterization of geothermal in Tertiary volcanoes differs from the geothermal system that is on Quaternary volcano alignment in the middle of Java, such as: Awibengkok, Wayang Windu, Darajat, and Kamojang which have a high temperature. The purpose of this research is to study the mobilization elements due to interaction of hydrothermal fluids with wall rocks in low enthalpy geothermal regions of the Tertiary magmatic arc in Parangtritis. Identification of minerals and chemical element changes is approached by methods of petrographic and scanning electron microscope (SEM) analyses. As for knowing the composition and the origin of hydrothermal fluids, it used analyses of cations, anions, and isotope δ18O and δD of hot water manifestation. The occurrence of geothermal manifestations in Parangtritis, such as hot water and rock alteration, reflects the interaction of hydrothermal fluids with wall rocks which generates an argillic zone with mineral alteration such as quartz, calcite, montmorillonite, and hematite. The presence of alteration mineral montmorillonite replacing pyroxene provides an evidence that there have been interactions between the fluids and rocks. This interaction is as a process of element mobilization. Decrease in elements Si, Ca, Mg, and Fe is accompanied by an increase of Al during the replacement of pyroxene into montmorillonite. The mobility of this element occurs due to acid fluids. However, the hydrothermal fluid composition of the current hot water manifestation is neutral chloride water type composition, and the origin of the fluids is meteoric water (δ18O: -4.20 ‰ and δD: 23.43 ‰).