GEOLOGICAL STUDY AND THE DISCHARGE CONTROLLER OF TUBBE WARM SPRING, PANTAR ISLAND, ALOR DISTRICT, EAST NUSA TENGGARA

• Main Author: Gumelar, Panji
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69694
• Institution: Institut Teknologi Bandung

Tubbe Warm Spring appears in Tubbe Village and is the only source of water used by people in Pantar Island. Tubbe Warm Spring has a temperature of 40°C and is a fresh water indication that there is a groundwater flow pattern below the surface. This research was conducted in Tubbe village and its surroundings. The purpose of this study is to map geological conditions and determine the geological control of Tubbe Warm Spring emergence. Research objectives include analyzing geomorphological conditions based on satellite imagery and field observations, investigate stratigraphy and geological structure, and identifying geological conditions controlling Tubbe Warm Spring discharge. Research methods used are literature studies, geological mapping, geomorphological analysis, vulcanostratigraphy, petrography and mineral spectral, which are then integrated to compile geological history and define the discharge controller of Tubbe Warm Springs. Geomorphology of research area is delineated based on image analysis and field observations resulting in twenty-one geomorphological units which are dominated by volcanic mountain landscapes. The boundaries of these geomorphological unit become a reference for boundaries of rock unit in study area. Division of rock units is based on principles of lithostratigraphy and vulcanostratigraphy. Volcanostratigraphic analysis resulted in a volcanism sequence starting from Lalafang Tertiary Volcanic Complex, Wasbila, Ishabbang and Sirung Brigades. There are seventeen rock units with six faults present in the study area. Petrographic and spectral analysis of minerals carried out for altered rocks in Lalafang Tertiary Volcanic Complex resulted in two groups of altered minerals, the first being neutral pH markers; chlorite, illite, quartz, sericite, calcite and the second being acidic pH; quartz, kaolinite, alunite, and pyrophyllite. The alteration is controlled by the Raubanang and Tonte Fault. The discharge of warm springs in Tubbe Village is controlled by Tubbe Reverse Right Strike Slip Fault which was formed in Post-Caldera Period. Meteoric water recharges through the walls of Uki Baha Galu Caldera, then were heated by heat flow and emerged to the surface as a Tubbe warm spring with a discharge >1 L/s. The Uki Baha Galu Caldera ring fault acts as a barrier for geothermal system in Tubbe Village, so that seawater flow does not mix with fluid circulation in the subsurface.