JPSE (Journal of Physical Science and Engineering), Vol. 4, No. 2, 2019, Page 37–44 DOI: 10.17977/um024v4i22019p037 37 http://journal2.um.ac.id/index.php/jpse EISSN: 2541-2485 JPSE (Journal of Physical Science and Engineering) Type of Mineral Deposits on Alteration Rocks using Petrography, X-Ray Fluorescence (XRF), and X-Ray Diffraction (XRD) Method in Geothermal Prospect in Tiouw Village, Maluku Received 21 February 2020 Revised 13 March 2020 Accepted for Publication 01 April 2020 Published 17 July 2020 R R Lokollo 1* and J R Kelibulin 1 1. Physics, Faculty of Mathematics and Natural Science, Universitas Pattimura, Ir. M. Putuhena Street, Ambon, 97126, Indonesia. *Email: rlokollo@gmail.com This work is licensed under a Creative Commons Attribution- ShareAlike 4.0 International License Abstract Indonesia is a country with abundant geothermal energy potential. One of the locations that have potential geothermal energy sources is Tiouw Village, Saparua, Central Maluku. This study was conducted on the types of mineral deposits using the petrographic method, X-Ray Diffraction (XRD), and X-Ray Fluorescence (XRF). Based on the results of petrographic analysis and XRD, rock samples 1, 2, and 3 of Tiouw include andesite igneous rocks with propylitic alteration type. While sample 4 is dacite igneous rock with argillic alteration type. Each rock sample has a mineral set of kaolinite, chlorite, quartz, cristobalite, epidote, and plagioclase. The XRF results showed the highest chemical composition of SiO2, followed by Al2O3 and K2O. This mineral content can indicate the subsurface temperature of the geothermal field in the range of 200–300 ºC with varying salinity, pH close to neutral, and low permeability. This interpreted that the type of mineral deposits in Tiouw Village was high sulfidation epithermal deposits. Keywords: Hydrothermal alteration, petrography, XRF, XRD, rock minerals. 1. Introduction Indonesia has abundant geothermal energy, such as gold, copper, platinum, nickel, lead, coal, crude oil, natural gas, and geothermal [1], [2]. Indonesia contains the largest geothermal across the world [3]. According to Geological Resource Center’s (PSDG) data in 2009, there are at least 265 geothermal points in Indonesia that can be optimized as renewable energy with a potential of 28.1 GW [4]. Geothermal is heat energy stored in subsurface rocks and fluid reserved in it as natural mineral sources found in the area of volcanic path [1]. The high temperature geothermal system associated with the volcano is divided into two, single phase geothermal system (warm water, hot water, and hot steam) and double phase geothermal system (steam domination and water domination) [5–8]. The geothermal potential of a particular area can be identified through subsurface hydrothermal alteration. Hydrothermal alteration is the texture, mineralogy, and chemical composition changes of rocks caused by hydrothermal fluid activity [9], [10]. The hydrothermal fluid is a hot liquid or fluid that raises and brings metal mineral components. This fluid is a residual solution formulated by the magma freezing process [11], [12]. Besides discovering the geothermal potential, hydrothermal alteration also identifies altered minerals and estimates fluid acidity levels [13]. The factors that affect hydrothermal alteration are temperature, pressure, permeability, chemical composition, hydrothermal composition, and side rock composition [14], [15]. A hydrothermal process on a particular balance produces groups of minerals that form mineral assemblage [16]. This study was conducted in Tiouw Village, administratively included in Central Maluku Regency, Maluku. Tiouw Village is one of the prospective geothermal areas in Maluku with geothermal manifestation, such as hot water springs and hot pool that is not yet fully developed. This research aims to identify types of hydrothermal alteration mineral deposits based on the petrological analysis of CORE Metadata, citation and similar papers at core.ac.uk Provided by Portal Jurnal Elektronik Universitas Negeri Malang