Characteristics of subvolcanic intrusion: a case study at Tempel Hill, Kalisonggo, Girimulyo, Kulonprogo, Yogyakarta

Abstract

The genesis of Mount Tempel which is part of Mount Mujil is still being debated by some geologists discussing the Kulon Progo Mountains. The surface and subsurface measurements must be done to know a geological aspect that building the area around Mt. Mujil, precisely in Tempel Hill on the northeast side of Mt. Mujil, Girimulyo, Kulonprogo, Yogyakarta. The geology of this location is still a mystery and has always been a hot topic regarding origins, geotourism, and disasters. The general problem in this study is related to the occurrence of the northeast side of Mt. Mujil which is still not final and much debated, so it is necessary to approach the concept of volcanic geology to help answer these problems. The purpose of this study was to identify the physical characteristics of igneous rocks in Tempel Hill based on surface and subsurface data. The approach method is carried out through geological mapping, geophysical resistivity measurements, and petrological, petrographic and geochemical analysis. The results of the petrological analysis show that the igneous rock has a porphyroafanite – microcrystalline texture without a flow texture, some scoria – massive structures, geochemically it shows that calc – alkali refers to subduction products. On the other hand, resistivity analysis shows the presence of volcanic rocks with density values and resistivity values of intrusive rocks and volcanic breccia in the vicinity. Indications of the presence of volcanic rocks with an area the size of Tempel Hill are defined as magma fossils or subvolcanic intrusion rock bodies. Tempel Hill has potentially for tourist attractions that can improve the welfare of local residents.