Study of Groundwater Types Using the Vertical Electrical Sounding (VES) Method in the ‘Martani Field’ Ngemplak District of Yogyakarta

Study of groundwater types using the Vertical Electrical Sounding (VES) method in 'Martani Field’ Ngemplak District of Yogyakarta was done by carrying out eight measurement points to look for groundwater potential. This area is an area on the southern slopes of Mount Merapi which is included in the Yogyakarta Groundwater Basin. The type of lithology is identified based on the measurement of its resistivity value so that there are several types of lithology, namely Breccia (110-670 Ωm), Clay (1.99-10.12 Ωm), Sandstones (17.06-56.82 Ωm) and andesite lava (688-1657 Ωm). The bottom of the aquifer in this basin is composed of rock formations that are impermeable or semi impermeable which are non-aquifer, namely by Breccias, Clay and Andesite Lava. The existence of sandstones that act as aquifers is found near the surface at a depth of <25 m and at a depth of about 60-100 m below the surface so that it is divided into two categories, namely shallow groundwater and deep groundwater.

Identifikasi Struktur Geologi dan Petrografi di sekitar Observatorium Astronomi Lampung Gunung Betung

Lampung Astronomical Observatory (LAO) is located on Betung Mountain which is quite close to the Semangko active fault zone. Betung Mountain is part of the Bukit Barisan which is located west of the city of Bandar Lampung. This mountain has an altitude of about 1200 meters above sea level. There are 6 interesting stations. Most of the stations are located on the upper slopes of Betung Mountain. In the Talang Aji area, there are 2 springs. The other 4 stations consist of waterfalls with varying heights: Talang Teluk waterfall (30 m), Talang Rabun waterfall (20 m), Betung waterfall consists of two minor terraced waterfalls with a height of 5 and 10 m respectively, and Kubu Jambu waterfall (12 m). In general, the orientation of the faults of Mt. Betung was northeast-southwest. The faults are also associated with several waterfalls found in the field. From the joint data processing, it can be interpreted that the fault formed on Betung Mountain is normal. The lithology of Betung Mountain is dominated by volcanic deposits in the form of tuffs. In certain rivers, there are outcrops of lava igneous rock in the form of Andesites. Andesite lava in the northern and southern parts of Betung Mountain has different characteristics.

Identifikasi Bidang Gelincir Zona Rawan Longsor Menggunakan Metode Geolistrik Di Ruas Jalan Toraja – Mamasa

Abstrak. Metode geolistrik tahanan jenis merupakan salah satu dari metode geofisika yang dapat mendeteksi aliran listrik di bawah permukaan bumi. Salah satu aplikasi metode geolistrik tahanan jenis adalah dapat mengidentifikasi bidang gelincir pada daerah rawan longsor. Penelitian ini bertujuan untuk mengetahui bidang gelincir pada daerah rawan lonsor di ruas jalan Toraja – Mamasa. Hasil dari pengukuran geolistrik tahanan jenis dipadukan dengan hasil pengeboran di beberapa titik agar tidak terjadi kesalahan dalam proses interpretasi batuan yang diduga sebagai penyebab terjadinya tanah longsor. Informasi tentang perlapisan tanah tersebut digunakan untuk mengetahui batas-batas ketidakstabilan pada lapisan tanah yang dapat menjadi acuan dalam pengembangan wilayah, khususnya ruas jalan Toraja - Mamasa. Dalam penelitian ini diperoleh nilai resistivitas yang berbeda-beda untuk setiap batuan. Variasi resistivitas yang diperoleh dimulai dari 0 – 978 Ωm. Nilai resistivitas batuan pada bidang gelincir di lokasi penelitian berada pada bidang batas 50-300 Ωm. Batuan penyusunnya berupa batupasir lempung, lava andesit dan basalt. Abstract The resistivity geoelectric method is one of the geophysical methods that can detect the flow of electricity below the earth's surface. One application of the resistivity geoelectric method is to identify the slip field in landslide prone areas. The research aimed to discover slip area of landslide prone zone at the segment road of Toraja-Mamasa. The results of the geoelectric resistivity measurements are combined with the results of drilling at several points so that there are no errors in the process of rock interpretation which are thought to be the cause of landslides. Information about the soil layers is used to determine the boundaries of instability in the soil layer which can be used as a reference in regional development, especially the Toraja - Mamasa road segment. In this research, it was obtained different resistivity values for each rock. The resistivity variation obtained started from 0 - 978 Ωm. The rock resistivity value in the slip plane at the research location is in the 50-300 Ωm boundary fields. The rocks lithologies are clay sandstones, andesite lava and basalt.

INTERPRETASI SISTEM PANAS BUMI SUWAWA BERDASARKAN DATA GAYA BERAT

The research of gravity on Suwawa Sub-District geothermal is done for the purposes to determine fault structure using Second Vertical Derivative (SVD) technique, create a 2D subsurface model and 3D tentative model using regional anomaly data, and interpreting Suwawa geothermal system. Data processing is done in the research include: drift correction, terrain correction, free air correction, complete Bouguer anomaly, spectral analysis, SVD analysis, 2D modeling and 3D inversion modeling and tentative model. The research results showed that the research area has low Bouguer anomaly with a range of 75.8 to 79.5 mGal values in the West and Southeast, while high anomaly with a range of 90.9 to 111.2 mGal values in the Northern and Southern, there is correlation of fault based on SVD analysis with geological fault that indicate the presence of Libungo hot springs, the inversion results indicate the presence of low density (ρ = 1.8 g/cc) which is an alluvial rocks and high density (ρ = 2.9 g/cc) which is Andesite Lava rocks, 3D tentative modeling indicate the presence of reservoir is at a depth of 2 km from the ground surface. Based on the model created, Cap Rock is located on Andesite Lava rocks with ρ = 2.9 g/cc at a depth of 1200 m and Heat Source located at a depth of 2000 m.

Development of Andesite Utilization in Gunung Ragas, Clering, Jepara, in the Industrial Sector Based on Petrological and Geochemical Data Analysis

The research area was the exposed extruded igneous lava rock in Clering which became the mining location of PT Semarang Mineral Pembangunan in Clering, Donorejo, Jepara with an area of ± 11 ha. This study aims to identify and determine the composition of andesite minerals by macroscopic and microscopic, the main oxide compound data, the use of andesite in industrial sector. The lithology consisted of andesite lava textured, plagioclase, leucite, clinopyroxene, sanidine as phenocryst and ground mass in the form of microlithic andesite lava as a trachytic texture. The hardness of lithology tends to be more moderate, it is considered unsuitable for building foundations. Andesite and tuff in the study area are currently being mined to be used as raw material for glass because of high silica content. In the industrial sector, the feldspar minerals for flux glass, and ceramic raw materials with standard of PT Semarang Mineral Pembangunan and SNI ISO 14703: 2011, 1147-1984 and SNI ISO 12543: 2011. The lithology tuff can be utilized in the manufacturing of ceramics due to high silica and felspar content. The lithology andesite can be utilized as rocks flour in the manufacturing of fertilizer due to high natrium, potassium, and magnesium content.

Geology and Petrogenesis of Igneous Rocks from Batur Paleovolcano, Gunungkidul, Yogyakarta: Evidence from their Textures, Mineralogy, and Major Elements Geochemistry

Batur paleovolcano is located in Wediombo Beach area, Gunungkidul Regency, Yogyakarta and is being part of Wuni Formation. Several volcanic products including lava flow, autoclastic breccia and volcanic breccia can be found associated with diorite intrusions. This research is aimed to characterize geological, mineralogical andgeochemical variations of igneous rocks from Batur paleovolcano to understand its petrogenesis. Detailed geological mapping with scale of 1:12,500 is conducted to identify geological aspects and delineate igneous rocks distributions. Igneous rocks and selected wall rocks samples were prepared for laboratory analysis including 8 samples for petrography and 5 samples for ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Several geochemical data from previous study are also added to investigate the geochemical variations. Geological condition of the research area consists of four rock units including colluvial deposit, limestone, andesite lava and diorite intrusion. Geological structures found are normal fault and shear joint where the main stress direction is north–south. Petrography analysis showed that igneous rocks in this research area consist of diorite intrusion and andesite lava with phorphyritic texture. Plagioclase become the most abundant minerals found both as phenocryst phase and groundmass. Hornblende only occur as phenocryst phase in minor amounts as accesory mineral. Major elementsgeochemistry analysis showed the rocks are characterized by intermediate silica with low alkali content. They are can be categorized as calc-alkaline series. However, some samples are fall into tholeiitic series. Major elements variation and textural study also indicate the magma is experienced differentiation process by fractional crystallization mechanism. This study suggests that igneous rocks from Batur paleovolcano is formed by two phases of formation. Earlier phase is the formation of andesite lava in island arc tholeiitic tectonic setting then at the later phase is formation of diorite intrusion in the calc-alkaline basalts tectonic setting.

Gold mineralization in the Neo-Tectonic Region of Honje Formation and Cipacar Formation

The gold ore mineralization region is a zone of mineralization which is inseparable from the role of geological structures, one of which is fracture. The Cibaliung and surrounding areas are epithermal gold mineralization zones, in this region there are two main mineralized zones, namely Cibitung Zone and Cikoneng Zone. It has almost the same characteristics where the fractures formed are quite large so that it influences the class of rock mass, but the other side is the presence of many fractures which make it easier for scattered mineralization to fill the fracture so that the formed vein is thick enough. This study aims to analyze the relationship of Rock Mass Rating (RMR) and Rocks Quality Design (RQD) to tectonic movements in the region to prove the neo-tectonic phenomena in the Honje Formation and Cipacar Formation using surface mapping methods. The methods used are rock type mapping, rock structure mapping, mapping and RQD measurements, rock descriptions and rock sample collection. All the data obtained are then verified and validated before processing and statistical tests. Statistical tests are carried out to ensure an analysis with a basis that is recognized by all parties. Both formations above have different ages, which is for the Honje Formation (Andesite Lava) with the final Miocene age and Cipacar Formation (tuff) at the age of Pleistocene. The findings of this study are the two formations measured by RQD and RMR on rock cracks and surrounding conditions; the RMR observation station made around 125 points in the Honje Formation and 117 points in the Cipacar Formation. The R2 value of the RMR value of the Honje Formation and the Cipacar Formation shows a positive relationship of 67%; The biggest RMR value is in Tuff rock. In addition, the relation between RMR Andesite Lava Value and RMR Tuff Value is done with T-Test between Andesite Lava and Tuff where the result shows no difference of mean between RMR Andesite Lava and RMR Tuff Value. Therefore, the tectonic processes that occur in the Honor Andesite Lava Unit of Honje Formation with the preceding position are formed, and the older age at the end of the Miocene age that is blocked by the field of unconformity experienced Continuity on Cipacar Formation Tuff Unit with the upper position that is formed after Honje Formation and younger age in Pleistocene. The continuation of the tectonic process proves the existence of active tectonic activity better known as Neo-tectonic.

FASIES KUARTER VULKANIK DAERAH PAGAR JATI DAN SEKITARNYA, KAB.BENGKULU TENGAH, BENGKULU

The Jati Fence Area, Bengkulu is the fore arc basin area whose deposition is influenced by the volcanic event. The deposition event took place on a quaternary volcano that has been active in having sedimentation activities that continue. This study aims to carry out mineralogical analysis in the proximal facies deposit area with petrographic data at observation locations (LP) 14, 59, 81,108, and (ST) 14,70 which are sourced from the results of local geological mapping. In LP 81 and 14 with proximal facies have volcanic breccia lithology with compilation components which are dominated by andesitic rocks, pyroclastic matrix composition, packed packing, hard hardness, and mineralogicalcomposition which tend to have many crystals. In LP 59 and 108 proximal facies found andesite lava.