GEOTHERMOMETER DAN HEAT LOSS DALAM EKSPLORASI GEOKIMIA LAPANGAN PANASBUMI DAERAH CISOLOK-CISUKARAME KABUPATEN SUKABUMI, PROPINSI JAWA BARAT

Posisi Indonesia yang berada di pertemuan tiga lempeng mengakibatkan terjadinya tumbukan yang memunculkan banyak gunungapi. Di daerah sekitar gunungapi banyak terdapat cebakan panasbumi sebagai salah satu sumber energi terbarukan. Salah satu daerah prospek panasbumi berada di Cisolok – Cisukarame yang terletak di Kabupaten Sukabumi Propinsi Jawa Barat. Stratigrafi daerah penelitian terdiri dari tua ke muda tersusun oleh batugamping Formasi Citarete, intrusi dasit, intrusi andesit, Formasi Citorek, Breksi Tapos, Lava Halimun, dan Endapan Alluvial. Struktur yang berkembang didaerah telitian berupa sesar berarah baratlaut – tenggara dan Timurlaut - Baratdaya, “Collapse Structure” dan sesar Utara Selatan yang membentuk struktur Graben. Manifestasi permukaan yang mengidentifikasi potensi panasbumi di daerah penelitian yaitu mata air panas, steaming geound, batuan alterasi, serta uap dan mata air panas. Keberadaan dan jenis manifestasi panasbumi mata air panas berperan penting dalam menentukan besarnya s uhu reservoar dan dapat digunakan untuk menghitung besarnya hilang panas alamiah panasbumi ( heat loss ) . Berdasarkan pengolahan data lapangan, diperoleh nilai geothermometer panasbumi Cisolok berkisar antara 154°C-169°C, sedangkan untuk daerah Cisukarame geothermometernya berkisar 188°C-213°C. Diperoleh pula nilai heat loss daerah Cisolok sebesar 5.137,44 KJ/s, dan didaerah Cisukarame sebesar 19.372,5 KJ/s. Kata kunci : manifestasi, panasbumi, geothermometer, heat loss Indonesia’s position is in the middle of the three plate, that cause so many vulcanoes. In aroud of the vulcanoes there are so many geothermal prospect as a one of renewable resources. One of them is Cisolok – Cisukarame geothermal field that located in Sukabumi district, West Java province. Cisolok and Cisukarame geothermal field consist of eight rock units, from oldest to youngest are limestone of Citarete Formation, dasit intrusion, andesit intrusion, Citorek Formation, Breksi Tapos, Lava Halimun, and Alluvial deposit. Geological structure in the research area are NW – SE fault, NE – SW fault, collapse structure, and N – S fault that made graben structure. Manifestations in Cisolok – Cisukarame geothermal field that shown geothermal potention are hot spring, fumarole, and altered rock. The existense of geothermal manifestation especially hot spring required to determine geothermometer dan heat loss. Based on the processing of data, geothermometer in Cisolok field between 154°C-169°C (Fournier, 1979), 163°C-174°C (Giggenbach, 1988). And Cisukarame’s geothermometer between 188°C-213°C.. Cisolok’s heatloss around 5.137,44 KJ/s, and Cisukarame’s heatloss around 19.372,5 KJ/s. Key words : manifestation, geothermal, geothermometer, heat los

GEOTHERMOMETER DAN HEAT LOSS DALAM EKSPLORASI GEOKIMIA LAPANGAN PANASBUMI DAERAH CISUKARAME, KABUPATEN SUKABUMI, PROPINSI JAWA BARAT

Keberadaan dan jenis manifestasi panasbumi mata air panas berperan penting dalam menentukan besarnya suhu reservoar dan dapat digunakan untuk menghitung besarnya hilang panas alamiah panasbumi (heat loss). Berdasarkan pengolahan data lapangan, diperoleh nilai geothermometer panasbumi Cisukarame berkisar 188°C-212°C. Diperoleh pula nilai heat loss daerah Cisukarame sebesar 19.367 kj/kg. Nilai hilang panas alamiah ini dapat digunakan untuk menentukan potensi yang dapat dimanfaatkan sebagai pembangkit listrik tenaga panasbum

Dampak Konversi Tata Guna Lahan di Daerah Resapan Terhadap Penurunan Cadangan Airtanah di Kabupaten Sleman, Daerah Istimewa Yogyakarta

Utilization of land use in the Daerah Istimewa Yogyakarta Province resulted in an increase insubsidence and reduced groundwater recharge area of rainwater in catchment areas. The aim of thisstudy was to determine the area of agricultural land were converted to housing, other infrastructure,and the mining area during the last 5 years, as well as to analyze changes in the hydrological systemdue to land conversion, especially the water supply to the area of the aquifer. This study is asummary based on secondary data collection, observation and description in the field, measurementsof rock permeability and infiltration, as well as laboratory and studio work. Employment in the field isalso observed for conversion of land use that occurred and compare the physical properties of rocksbefore and after conversion. Evaluation is emphasized on the water balance equilibrium calculationhas been calculated on the amount of percentage changes in land use and analysis of the impact ofthe conversion of land use in the catchment area to change the content of groundwater. Based onthe results of the calculation of the projected reserves of groundwater due to land conversion, waterreserves and infiltrasiakan volume continued to decline from year to year. This study is expected bythe general public is expected to use the existing land well and wisely with regard to groundwaterreserves so that it can minimize the reduction in water reserves and infiltration from year to year

Peramalan Kinerja Reservoir Lapangan Panas Bumi Gunung Iyang-Argopuro, Jawa Timur, Indonesia Menggunakan Simulasi Numerik TOUGH2

The Mount Iyang-Argopuro geothermal field is a prospect field located in East Java, Indonesia. This field has a water-dominated reservoir and still in the exploration stage. Therefore, this study was conducted to find out how the production capacity of the Mount Iyang-Argopuro reservoir. The scenario of field development is done by simulating a reservoir model that has reached a natural state. The model was created and simulated with a TOUGH2 simulator, assuming the field will be produced for 30 years with a production capacity of Iyang-Argopuro geothermal field is 55 MW. Several production scenarios are tested on the model to obtain an appropriate production target. Based on the simulation results, a production capacity of 55 MW for 30 years was achieved with 9 production wells. Fluid from the wells flow to a 9 bar pressurized separator and an 8.5 bar turbine pressure. Despite the decline in production, the scenario is still able to maintain generating capacity above 55 MW

Perubahan Sistem Kelestarian Air Tanah di Cekungan Air Tanah Wates Akibat Pembangunan Bandara Internasional Temon Kabupaten Kulonprogo DIY

Underground water is a component in the hydrological cycle, formed by rainwater that seeped into thesoil and flows through the media layer of rock (aquifer) in groundwater basin. Wates basin’sgrounwater includes the Wates District, Temon, Panjatan, Lendah, Brosot, a little part of the DistrictSentolo and Pengasih located in Unit Plateau of volcanics fluvio, beach units and sand dunes with thealluvial material consisting of sand, gravel, silt, and clay, flat morphology, relatively lithology andgroundwater characteristics. This lithology is potential with the occurrence of groundwaterconservation system changes, if there is excessive ground water extraction in the region which can becharacterized by the increase in salinity in ground water. The main objective of this study is to assessthe full qualitative and quantitative groundwater in the Basin Groundwater Wates International Airportdue to Temon airport construction in relation to maintaining the sustainability of groundwater systems.The methods in this study consists of several steps, starting from observation and rock’s/soildiscribtion include: measurement of rock bedding, measurement of geological structural elements,observation of morphological conditions, and sampling soil / rock to be tested in laboratory about thecontent of the mineralogy, texture and structure. Observation of surface water and groundwater isdone by testing the physical properties of the surface water include: smell, taste, turbidity, temperature(T), acidity (pH), electrolit conductivity (EC), and taking water samples to be tested in the laboratory todetermine the elements it contains a chemical that results will be used to created Diagrams Stiff andTrilinier. Estimation of resistivity (geoelectric) was conducted to determine the condition of the soil/rockbelow the surface to a depth of more than 75 m, with the aim to determine the configuration of theaquifer both laterally and vertically, the results of which will provide an overview/three-dimensionalcross-section of the local groundwater system deposits carefully situations and recharge area. Thecross-sectionwill shown information quantity/amount of groundwater and the identification of the coasttowards the potential intrusion of sea water. The results of mineralogical analysis of rocks andhydrochemical groundwater will provide information on the distribution of groundwater quality. Thisquality conditions will certainly change with the start of construction of the airport and afterconstruction of the airport. Information about the mineralogical content of rocks, hydrochemicalcontent of water and aquifer configuration will be able to contribute to efforts in the area ofgroundwater International Airport Temon, DIY

Studi Hidrogeokimia Air Tanah di Daerah Kebumen Bagian Barat, Indonesia

Abstrak - Studi penilaian hidrogeokimia air tanah telah dilakukan di Kebumen bagian barat yang dicirikan dengan fitur karstnya berdasarkan parameter fisikokimia (pH, konduktivitas elektrik, zat padat terlarut, kesadahan, Ca2+, Mg2+, Fe3+, Mn2+, K+, Na+, Li+, and NH4+, HCO3-, Cl-, SO42-, NO2-, and NO3-). Data sampel air diambil dari 25 sumber air tanah dangkal berupa mata air, goa basah dan sumur. Data fisikokimianya mengindikasikan hanya ada kontaminasi alami maupun dari manusia yang sangat rendah. Dari diagram Piper ditunjukkan bahwa fasies air tanah yang berada di daerah ini adalah kalsium-magnesium bikarbonat yang mengindikasikan efek litologi karbonatan yang sangat kuat ke air tanah. Diagram Durov menunjukkan bahwa air tanah di daerah studi hanya mengalami pertukaran ion yang sangat rendah yang mengindikasikan kemurnian air tanah ini dari dampak kontaminasi alami maupun dampak antropogenik.Kata kunci: hidrogeokimia, air tanah, karst, Kebumen Abstract - A groundwater hydrogeochemistry assessment study has been conducted in western Kebumen, characterized by its karstic features based on physicochemical parameters (pH, electric conductivity, total dissolved solids, hardness, Ca2+, Mg2+, Fe3+, Mn2+, K+, Na+, Li+, and NH4+, HCO3-, Cl-, SO42-, NO2-, and NO3-). Water samples were taken from 25 shallow groundwater sources such as springs, wet caves, and wells. The physicochemical data indicates very low natural and/or human contamination. The Piper diagram shows that the groundwater facies in this area is calcium-magnesium bicarbonate, indicating a very strong effect of carbonate lithology on groundwater. The Durov diagram shows that the groundwater in the study area only undergoes very low ion exchange, indicating the purity of this groundwater from natural contamination or anthropogenic impacts.Keywords: hydrogeochemistry, groundwater, karst, Kebume

STUDI DEFORMASI PERMUKAAN PUNCAK GUNUNG MERAPI PADA TAHUN 1993 – 1995, DI PERBATASAN PROVINSI DAERAH ISTIMEWA YOGYAKARTA DAN JAWA TENGAH

Secara geografis, lokasi penelitian terletak pada koordinat X1: 438120mE; Y1: 9167090mN; X2: 439750mE; Y2: 9167090mN; X3: 439750mE; Y3: 9165680mN; dan X4: 438120mE; Y4: 9165680mN. Penelitian menggunakan data sekunder, data deformasi telah diperoleh melalui pengukuran GPS pada periode 1993-1995(Beauducel, 1998) berupa koordinat dan vektor perpindahan titik GPS puncak pada periode 1993-1995, data tersebut menunjukkan pola deformasi yang tidak simetris. Bersumber pada penelitian oleh Aisyah dan kawankawan (2018),menerangkan deformasi tidak simetris tahun 2006 dan 2010 yakni dengan penggunaan metode kombinasi block movement serta inflasi sumber tekanan, maka pada periode 1994-1995 dapat dijelaskan menggunakan metode yang sama, sementara itu pada periode 1993-1994 hanya diterapkan inflasi sumber tekanan. Geomorfologi yang terdapat di puncak Gunung Merapi adalah bentuk asal vulkanik, dengan bentuk lahan berupa lereng aliran lava (V1), lereng endapan aliran piroklastik (V2), kawah (V3) serta kubah lava (V4). Pola pengaliran yang berkembang yakni radial sentrifugal. Diskontinuitas struktural pada puncak Gunung Merapi berupa rekahan dan batas antara bekas aliran lava. Vulkanostratigrafi (sumber erupsi) pada puncak Gunung Merapi dapat dibagi menjadi Merapi Tua (Satuan Aliran Lava Andesit Piroksen Merapi 2) dan Merapi Muda (Satuan Aliran Lava Andesit Piroksen Merapi 3, Satuan Endapan Aliran Piroklastik Muda dan Guguran Merapi, serta Satuan Aliran Lava Andesit Piroksen Merapi 4). Terdapat dua blok yang bergerak secara signifikan, masing-masing diperkirakan bergerak ke arah barat laut dan selatan-barat daya. Perkiraan lokasi sumber tekanan pada periode 1993-1994 yakni 600 m di bawah puncak Gunung Merapi, sementara itu pada periode 1994-1995 sekitar 740 m dibawah puncak. Pada periode 1993-1994 diestimasikan total nilai perubahan volume injeksi magma yakni sebesar 80.8 x, sedangkan periode 1994-1995 total perubahan volume injeksi magma diperkirakan sebesar 90.8 x. Pergerakan blok ke arah barat laut dan selatan-barat daya disebabkan perubahan volume serta tekanan pada sumber, yang dikontrol oleh diskontinuitas struktural di sekitar puncak berupa rekahan maupun batas antara bekas aliran lava, di bagian barat laut berupa batas antara aliran lava 1957 dan 1888, selanjutnya di bagian selatan yakni batas antara lava 1911-1913 dan lava 1888-1909.Kata kunci: Gunung Merapi, Deformasi, GPS, Block movement, Sumber Tekanan

Evolution Magmatism of Nagasari Volcano Dieng, Central Java, Indonesia

Nagasari Volcano, part of the Dieng volcanic complex, is one of the unique volcanoes in Central Java. Around this volcano grow eruption craters, volcanic cones, and pyroclastic flow ridges. There were several 14 eruption centers around Mount Nagasari, so it is necessary to know the development of magmatism evolution. The aims of the research to determine the evolutionary development of magmatism. The methodology used is geological mapping and petrographic analysis. The observations of rocks found in the study area include andesite lava, lapilli-tuff, fallen pyroclastic breccias, and flow pyroclastic breccias. Meanwhile, geological mapping and petrographic observations of volcanic rock samples show that the evolution of magmatism in the study area from the oldest to the youngest is basaltic magma that formed Prau Volcano in the pre-caldera period. On the other hand, magmatism in the post-caldera I period was of the type of pyroxene andesite forming the Gembol to Jimat Volcano group. In contrast, in the post-caldera II period, the hornblende-biotite andesite group formed the Dieng Kulon to Kendil group

PENYELIDIKAN PENDAHULUAN MANIFESTASI PANASBUMI NGEBEL PONOROGO, JAWA TIMUR

Penyelidikan pendahuluan panasbumi yang dilakukan di Daerah Ngebel, Propinsi Jawa Timur menemukan indikasi keberadaan potensi panasbumi dengan pemunculan manifestasi panasbumi berupa mataair panas yang muncul di batuan breksi.Berdasarkan pengamatan lapangan diketahui suhu mataair panas di Kali Padosan sebesar 62°C, suhu udara sekitar 22°C, debit mataair panas <1L/s pada ketinggian 662m. Berdasarkan analisis senyawa kimia, ditunjukkan bahwa konsentrasi SiO2 hanya 262,44 mg/L, sedangkan konsentrasi Cl dan Na relatif lebih tinggi, Cl = 529,25 mg/L; Na = 461,60 mg/L, dengan pH 7,22 dan DHL 3810(umhos/cm). dan termasuk tipe air klorida (Cl-SO4- HCO3), terletak pada zona partial equilibrium (Na-K-Mg).Data hasil analisa geokimia dapat digunakan untuk menentukan jenis fluida manifestasi dan menghitung geothermometer