Analisis Kedalaman Potensi Akuifer Air Tanah dengan Pemodelan Distribusi Tahanan Jenis secara Inversi 2-D Desa Kompas Raya, Nanga Pinoh, Melawi, Kalimantan Barat

Penyelidikan geofisika dengan metode geolistrik tahanan jenis telah dilakukan di Desa Kompas Raya, Kecamatan Pinoh, Kabupaten Melawi, Propinsi Kalimantan Barat. Desa Kompas Raya merupakan daerah yang selalu kekurangan air pada musim kemarau sehingga masyarakat desa kesulitan untuk mendapatkan air bersih untuk mencukupi kebutuhan sehari-hari. Penelitian ini dimaksudkan untuk melihat penyebaran data tahanan jenis baik lateral maupun vertikal secara dua dimensi. Penyebaran data tahanan jenis ini dapat digunakan sebagai dasar untuk mengetahui informasi potensi keberadaan batuan pembawa air tanah (akuifer) di area penelitian. Metode pengukuran adalah geolistrik sounding yang dilakukan dengan Konfigurasi Schlumberger. Jumlah titik ukur sounding adalah 30 titik yang dibagi menjadi 6 lintasan survei dengan tiap lintasan terdapat 5 titik ukur sounding. Pada penelitian ini, pengolahan data geolistrik dilakukan dengan menggunakan teknik pemodelan inversi 2D berdasarkan data geolistrik sounding. Teknik pemodelan ini akan mengiterpolasi data sounding dalam satu lintasan secara otomatis dan kemudian data kemudian tahanan jenis semu diinversi menjadi tahanan jenis sebenarnya. Hasil yang diperoleh dari penelitian ini adalah terdapatnya dua lapisan batuan dengan nilai tahanan jenis relatif kecil yaitu berturut-turut kurang dari 30 Ohm.m dan 20 Ohm.m. Lapisan pertama diinterpretasi sebagai akuifer dangkal (akuifer-1) dengan kedalaman sekitar 20 m sampai 30 m, sedangkan lapisan kedua diinterpretasi sebagai akuifer dalam (akuifer-2) dengan kedalaman sekitar 90m sampai 100 m. Geophysical investigation by geoelectrical resistivity method have been done at Kompas Raya Village, Pinoh, Melawi, West Kalimantan Province. Kompas Raya Village is an area that is always a lack of water in the dry season, so the villagers are always difficult to get clean water to meet their daily needs. This study aimed to look resistivity distribution both laterally and vertically in two dimensions. The data distribution of resistivity can be used as a basis to determine the potential aquifers in the area of research. The measurement method of sounding resistivity is performed by Schlumberger Configuration. The numbers of measuring points are 30 points soundings which are divided into six survey paths each where each survey path is contained five measuring points. In this study, resistivity data processing is performed using 2D inversion modeling techniques based on data resistivity sounding. The results obtained from this study is the presence of two layers of relatively low resistivity that is each less than 30 Ohm.m and 20 Ohm.m. The first layer is interpreted as a shallow aquifer (aquifer-1) with the depth of about 20 m to 30 m, while the second layer is interpreted as the aquifer (aquifer-2) with the depth of about 90 m to 100 m

Sub-surface Geological Modeling Based on Gravity Residual Data in Adang Volcanic Rock Area, Mamuju, West Sulawesi Province

The Mamuju area of West Sulawesi Province is composed of Adang volcanic rock that is a product of the process of volcanism in a volcanic complex with an eruption center and several lava domes. The geology of the study area is composed of eleven rock units, namely Adang breccia, Adang lava, lava dome, volcanic conglomerate, Ampalas breccia, Malunda breccia, Boteng lava, Tapalang breccia, limestone, reef limestone, and alluvium. The mineralization of uranium, thorium, and rare earth elements formed in Adang lava thorianite veins. Adang lava is intruded by a dioritoid found in the Mamuju river upstream. The gravity modeling technique has produced two 2-D subsurface models based on gravity data on 2-D cross-sections of the residual gravity map. It is known that the rock density range from 2.10 to 2.85 g/cm3 in the study area. Based on the interpretation of two 2-D subsurface models, a batholith, a giant-sized intrusive rock, is found in the southeastern part of the study area with a rock density of about 2.85 g/cm3 and is interpreted to be dioritoids. Furthermore, deep intrusion rocks also occur in the center part of the study area with a rock density of 2.8 g/cm3. It is estimated to be the same as the rock in the southeastern part of the study area. Dioritoid intrudes a volcanic breccia sedimentary rock with a density of about 2.1 g/cm3.The Mamuju area of West Sulawesi Province is composed of Adang volcanic rock that is a product of the process of volcanism in a volcanic complex with an eruption center and several lava domes. The geology of the study area is composed of eleven rock units, namely Adang breccia, Adang lava, lava dome, volcanic conglomerate, Ampalas breccia, Malunda breccia, Boteng lava, Tapalang breccia, limestone, reef limestone, and alluvium. The mineralization of uranium, thorium, and rare earth elements formed in Adang lava thorianite veins. Adang lava is intruded by a dioritoid found in the Mamuju river upstream. The gravity modeling technique has produced two 2-D subsurface models based on gravity data on 2-D cross-sections of the residual gravity map. It is known that the rock density range from 2.10 to 2.85 g/cm3 in the study area. Based on the interpretation of two 2-D subsurface models, a batholith, a giant-sized intrusive rock, is found in the southeastern part of the study area with a rock density of about 2.85 g/cm3 and is interpreted to be dioritoids. Furthermore, deep intrusion rocks also occur in the center part of the study area with a rock density of 2.8 g/cm3. It is estimated to be the same as the rock in the southeastern part of the study area. Dioritoid intrudes a volcanic breccia sedimentary rock with a density of about 2.1 g/cm3

Studi Keterdapatan Torium Pada Endapan Laterit Bauksit di Pulau Singkep Dalam Rangka Pengembangan Eksplorasi Torium di Wilayah Granit Jalur Timah

Eksplorasi torium di wilayah granit jalur timah pada lima tahun terakhir ditargetkan pada keterdapatan torium di cebakan timah primer maupun sekunder. Pulau Singkep adalah bagian dari Granit Jalur Timah, yang potensial terhadap keberadaan torium, sebagai cebakan primer maupun sekunder. Penelitian ini bertujuan untuk mengetahui karakteristik keterdapatan torium pada laterit bauksit menyangkut kadar torium dan kaitannya dengan keterdapatan mineral radioaktif dan kandungan cerium (Ce), lantanum (La), itrium (Y), dan zirkon (Zr) pada laterit bauksit. Data yang diperoleh dari penelitian ini akan digunakan sebagai bahan evaluasi untuk pengembangan eksplorasi torium pada cebakan laterit bauksit di Indonesia. Metode yang digunakan adalah pemetaan geologi, pengukuran kadar torium, dan pengambilan sampel konsentrat dulang untuk analisis mineral butir dan analisis kadar Ce, La, Y, dan Zr. Litologi yang menyusun daerah penelitian terdiri atas granit lapuk yang telah terubah menjadi laterit bauksit dengan kadar torium berkisar antara 25,9 hingga 177,8 ppm eTh. Konsentrat hasil pendulangan adalah konsentrat zirkon-ilmenit dengan kandungan mineral radioaktif terdiri dari zirkon, monasit, dan anatas. Kadar lantanum pada konsentrat zirkon-ilmenit adalah 0–412 ppm, cerium 0–80 ppm, itrium 27–82 ppm, dan zirkon 9.420–100.000 ppm. Keterdapatan torium pada endapan laterit bauksit di Pulau Singkep berhubungan erat dengan keterdapatan mineral zirkon, monasit, dan anatas. Karakterisrik keterdapatan torium pada endapan laterit bauksit mempunyai kemiripan dengan karakteristik keterdapatan torium pada cebakan timah primer dan sekunder. The thorium exploration in the last five years in the granite tin belt region is targeted at thorium availability in primary and secondary tin deposits. Singkep island is the part of granite tin belt which potential for thorium occurences either primer or secondary deposits. The purpose of this study was to determine the characteristics of thorium availability in bauxite laterite deposits concerning thorium content and its relation to the availability of radioactive minerals and cerium (Ce), lanthanum (La), Yttrium (Y), and zircon (Zr) contents on the bauxite laterite deposit. The data obtained from this study will be used as an evaluation material for the development of thorium exploration in bauxite laterite deposits in Indonesia. The methods used are geological mapping, thorium concentration measurements, and sampling of pan concentrate for mineral grain analysis and analysis of Ce, La, Y, and Zr contens. The lithology of the study area was granite that had weathered and turned into bauxite laterite deposit with thorium content ranging from 25.9 to 177.8 ppm eTh. The concentrate of the repeating result is zircon-ilmenite concentrate with radioactive mineral content composed of zircon, monazite, and anatase. La concentration on zircon-ilmenite concentrate is 0–412 ppm, Ce is 0–80 ppm, Y is 27–82 ppm and zircon is 9,420–100,000 ppm. Avaibility of thorium at the bauxite laterite deposit on Singkep Island is closely related to the zircon, monazite, and anatase minerals. Characteristics of thorium availability in the bauxite laterite deposit are similar to the thorium characteristics of the primary and secondary tin deposits

Interpretasi Bawah Permukaan Berdasarkan Distribusi Nilai Tahanan Jenis di Daerah Puspiptek, Serpong

ABSTRAKKawasan Pusat Penelitian Ilmu Pengetahuan dan Teknologi (PUSPIPTEK) Serpong memiliki luas 460 hektar. Sebagian besar kawasan ini merupakan ruang terbuka hijau. Seiring dengan pertumbuhan kegiatan penelitian, kebutuhan sarana infrastruktur dan bangunan juga akan semakin meningkat. Sebagai sarana strategis nasional, diperlukan desin bangunan yang kokoh untuk dan sesuai dengan kondisi bawah permukaan. Survey geolistrik dapat digunakan untuk mengetahui kondisi/informasi di bawah permukaan tanah. Tujuan penelitian ini adalah memperoleh gambaran di bawah permukaan berdasarkan distribusi nilai geolistrik tahanan jenis di area rencana pembangunan Reaktor Daya Eksperimen (RDE). Pengambilan data tahanan jenis menggunakan alat ukur resistivitymeter multichannel tipe MAE X612EM+ secara 2-D menggunakan 48 channel konfigurasi Wenner-Schlumberger. Jumlah elektroda yang digunakan adalah 48 buah dengan interval jarak antar elektroda 5 m. Berdasarkan pemodelan inversi 2-D telah dihasilkan empat model penampang lintasan yaitu line-1, line 2, line-3, dan line-4. Kesalahan data di tiap lintasan relatif kecil, kurang dari 12%. Interpretasi geologi dilakukan pada pada penampang line-2 dan line-3 menggambarkan keberadaan lapisan A, B, dan C. Lapisan A diduga berupa batuan dengan ukuran butir lempung-lanau yang mengandung material organik dengan rentang nilai tahanan jenis 2-20 ohm-m dan variasi ketebalan sekitar 1-7 m. Lapisan B diduga berupa batupasir yang memiliki rentang nilai tahanan jenis 10-90 ohm-m dengan variasi ketebalan 5-20 m. Lapisan C diduga merupakan batulempung yang memiliki rentang nilai tahanan jenis 2-5000 ohm-m dengan variasi kedalaman 10-20 m. ABSTRACTThe area of Center for Research in Science and Technology (PUSPIPTEK) Serpong is 460 hectares wide. Most of the area is a Green Open Spaces (RTH). In the line with the growth of research activities, the need for infrastructure and building facilities also increases. As a national strategic facility, it is necessary to design buildings that are sturdy for and suitable with subsurface conditions. Geolectrical survey can be used to determine of subsurface condition/information. The purpose of this study is to obtain the ilustration of subsurface, based on the distribution of geoelectric resistivity values in the site of Experimental Power Reactor (RDE) construction. The resistivity data acquisition is using a multichannel resistivitymeter MAE X612EM+ type in 2-D by 48 channel of Wenner-Schlumberger configuration. The numbers of elctrodes used are 48 with an electrode interval of 5 m. Based on 2-D inversion model, there are four section models obtained, namely line-1, line 2, line-3, and line-4. The data error for each section is relatively small, less than 12%. Geological interpretation carried out in the section line-2 and line-3 illustrates the existence of layers A, B, and C. Layer A is interpreted as rock with silt to clay grain size containing organic material with resistivity values range 2-20 ohm-m and thickness varries in 1-7 m. Layer B is interpreted as sandstone which has a range of resistivity values from 10-90 ohm-m with thickness variations 5-20 m. Layer C is interpreted as claystone which has a range of resistivity values from 2-5000 ohm-m with depth variation in 10-20 m

Penentuan Anomali Gayaberat Regional dan Residual Menggunakan Filter Gaussian Daerah Mamuju Sulawesi Barat

AbstrakMetode gayaberat merupakan metode geofisika yang sudah sering digunakan dalam prospeksi sumberdaya mineral. Parameter objek pencarian berdasarkan variasi pengukuran percepatan gayaberat di permukaan yang diakibatkan oleh variasi perubahan geologi bawah permukaan. Lokasi penelitian di daerah Mamuju Provinsi Sulawesi Barat yang secara tektonik merupakan wilayah geologi kompleks berada pada pertemuan tiga lempeng besar yaitu Pasifik, Indo-Australia, dan Eurasia serta Lempeng Filipina yang berukuran lebih kecil. Selain itu Mamuju merupakan wilayah dengan laju dosis radioaktivitas tinggi sehingga berpotensi memiliki sumberdaya mineral radioaktif. Tujuan dari penelitian adalah mendapatkan anomali gayaberat dengan cara melakukan pemisahan dan interpretasi secara kualitatif anomali gayaberat regional dan residual. Nilai Anomali Bouguer Lengkap (ABL) daerah penelitian yang didapat dari hasil pengukuran adalah 46,0 – 115,7 mgal. Berdasarkan peta ABL tersebut proses pemisahan anomali gayaberat regional dan residual dilakukan dengan menggunakan teknik Gaussian Filtering. Teknik filtering ini bekerja berdasarkan analisis spektrum perubahan amplitudo gayaberat secara spasial yang hasilnya berupa bilangan gelombang dengan cutoff sebesar 1,1736 x 10-3/ m dan panjang gelombang sebesar 5373,45 m. Anomali gayaberat regional dan residual berturut-turut memiliki rentang nilai 51,8 sampai 102 mGal dan -10,4 sampai 14,8 mGal. Kedalaman wilayah spektrum masing-masing anomali tersebut dapat dihitung berdasarkan panjang gelombangnya yaitu anomali regional sebesar 970,97 m dan anomali residual sebesar 100,21 m. Terdapat lima zona berdasarkan peta anomali residualnya yaitu zona A, B, C, D, dan E. Anomali gayaberat positif paling besar terdapat pada zona A dan B yang diperkirakan dipengaruhi oleh keberadaan lava Adang dengan arah penyebaran relatif utara – selatan. AbstractGravity method is a geophysical method that has been frequently used in prospecting mineral resources. The parameter of searched object is based on variations of gravity acceleration measurements on the surface due to variations in sub-surface geological changes. Research area is located in Mamuju Area of West Sulawesi Province where tectonically a complex geological region, which is at a meeting of three large plates, the Pacific plate, the Indo-Australian plate and the Eurasian plate and the smaller Philippine plate. In addition, Mamuju is an area with a high radioactivity dose rate that has potency to radioactive minerals resources. The purpose of the research is to obtain gravity anomalies by using qualitative separation and interpretation of regional and residual gravity anomalies. Complete Bouguer Anomaly (CBA) value of the research area obtained from the measurements was 46.0 – 115.7 mGal. Based on the CBA map, the separation process of regional gravity anomalies and residual using Gaussian filtering technique conducted. This filtering technique works based on spectral analysis of gravity amplitude changes in spatial where the result is a cutoff wave number of 1.1736 x 10-3/meter and a wavelength of 5373.45 m. The regional and residual gravity anomalies range from 51.8 to 102 mGal and -10.4 to 14.8 mGal respectively. The depth of influence of each anomaly is calculated based on their spectral wavelengths, resulting 970.97 m and 100.21 m for regional and residual anomalies respectively. There are five zones based on the residual anomaly map, which are zones A, B, C, D and E. The heaviest positive gravity anomaly is found in zone A and B, which is predicted to be influenced by Adang lava with relative north – south distribution

Karakterisasi Hidrogeologi Daerah Sekitar Tapak PLTN di Bengkayang, Kalimantan Barat

ABSTRAK. Evaluasi tapak merupakan tahap penting dalam penentuan lokasi calon tapak PLTN skala komersial di Indonesia. Aspek–aspek yang dikaji dalam evaluasi tapak berdasarkan peraturan yang berlaku antara lain aspek geoteknik dan aspek dispersi zat radioaktif. Untuk mendukung kajian aspek tersebut maka perlu adanya kajian karakterisasi hidrogeologi daerah sekitar tapak. Tujuan penelitian ini adalah menentukan karakteristik hidrogeologi daerah sekitar tapak PLTN di Kabupaten Bengkayang, Provinsi Kalimantan Barat berdasarkan aspek geologi dan geofisika. Metode yang dilakukan adalah pemetaan geomorfologi, pemetaan geologi, pemetaan hidrogeologi, pengukuran geolistrik, serta analisis terpadu. Secara morfologi, daerah penyelidikan dibagi menjadi tiga satuan, yaitu dataran aluvial, bukit terisolasi, dan dataran pantai. Secara stratigrafi, satuan batuan yang ditemukan berurutan dari tua ke muda adalah andesit, granodiorit, diorit, endapan pasir kuarsa, endapan pantai, dan endapan aluvial. Pengukuran geofisika menggunakan metode geolistrik dilakukan pada 12 lintasan dengan masing-masing panjang lintasan 470 m dan spasi elektroda 10 m. Pada penampang geolistrik ditemukan beberapa anomali pada kompleks batuan beku yang mengalami frakturasi atau tubuh diorit yang menerobos satuan andesit. Nilai anomali ini berkisar antara 300 Ωm dan >8000 Ωm. Nilai resistivitas yang sangat rendah (8000 Wm. The relatively low resistivity values (<30 Wm) are interpreted as water saturated-alluvial deposits that could have a thickness of ±100 m. There are three hydrogeological units in the study area: aquifers in which flow is intergranular with high permeability, aquifers in which flow is intergranular with moderate permeability, and aquifug of local importance. Generally, the groundwater in the study area flows from SSW to NNE

Interpretasi Deposit Uranium Berdasarkan Data Tahanan Jenis dan Polarisasi Terinduksi di Sektor Rabau Hulu

Rabau Hulu area, Kalan, Kalimantan Barat is a potential area of uranium that has been explored in detail by various methods. Methods of resistivity and induced polarization can be applied in the exploration of uranium deposits in which its mineralization associated with sulphide minerals. Processing, analysis, and interpretation of resistivity and induced polarization data conducted in order to identify the distribution of uranium deposits and lithology of the rocks in the study area. Uranium deposits in the area Rabau Hulu is generally associated with sulphides, tourmaline and contained in favorable rocks. Symptoms of uranium mineralization encountered in other forms of irregular and uneven consists of uraninite, pyrite, chalcopyrite, pyrrhotite, molybdenite, and ilmenite minerals. Data acquisition using dipole-dipole configuration in an area of ​​approximately 36 hectares, 46 lines along + 425 m. Acquisition of induced polarization frequency domain data which the same points and lines with resistivity data. Data processing produces resistivity and metal factor values and subsequently made two-dimensional section. Determination of resistivity and induced polarization are done by correlated boreholes data with the results of data processing. Resistivity of uranium deposits zone worth less than 2,000 Ωm and the value of metal factor greater than 90 mho/m. Uranium deposit zone is expanding along with the depth. Uranium deposits distribution trending Southwestern-Northeast and shaped lens

Penentuan Daerah Prospek Logam Tanah Jarang di Pulau Singkep

ABSTRAK Logam tanah jarang merupakan bahan stategis yang digunakan pada perangkat teknologi tinggi dan energi bersih. Di Indonesia logam tanah jarang terkandung dalam mineral monasit, zirkon, dan xenotim sebagai mineral-mineral ikutan pada penambangan timah di zona granit jalur timah Kepulauan Riau hingga Bangka Belitung. Singkep merupakan salah satu wilayah potensial logam tanah jarang karena terletak pada zona granit jalur timah. Penelitian ini bertujuan untuk menentukan daerah prospek logam tanah jarang di Pulau Singkep. Metoda yang digunakan adalah pengambilan 25 sampel konsentrat dulang pada beberapa tailing bekas tambang timah di Pulau Singkep. Sampel diambil pada setiap formasi batuan yang ada di Pulau Singkep dari batuan berumur tua hingga batuan berumur muda berturut-turut adalah kuarsit Bukit Duabelas berumur Permo-Karbon, komplek malihan Persing berumur Permo-Karbon, granit Muncung berumur Trias, granit Tanjungbuku berumur Yura, endapan rawa dan aluvium berumur Holosen. Setiap sampel konsentrat dulang dibagi menjadi dua bagian untuk analisis kandungan logam tanah jarang dan analisis mineral butir. Dua puluh lima (25) sampel dianalisis kandungan logam tanah jarangnya dan 14 sampel dianalisis kandungan mineral butirnya. Hasil analisis kandungan logam tanah jarang dan mineral butir menunjukkan bahwa daerah prospek logam tanah jarang terletak pada beberapa tailing bekas tambang timah di wilayah formasi batuan granit Muncung. Kadar lanthanum tertinggi mencapai 20100 ppm, cerium 37100 ppm, yttrium 9872 ppm dan neodymium 2840 ppm di mineral monasit, zirkon dan alanit.ABSTRACT Rare earth elements (REE) are strategic material used in high-tech and clean energy devices. In Indonesia, REE contained in monazite, zircon, and xenotime minerals as accessories minerals in tin mining located in the granite tin belt of Riau Islands to Bangka Belitung. Singkep is one of the potential areas of REE because its location is in the granite tin belt. The goal of the study is to determine the REE prospects in Singkep Island. The method used by taking 25 pan concentrated samples on some tailing ex tin mining on the Singkep island. These samples were taken from each rock formation on Singkep Island in sequence from older to younger rocks formation, respectively. They are Permian Carboniferous of Bukit Duabelas quartzites, Permian Carboniferous of Persing Metamorphic Rocks, Triassic Muncung granite, Jurassic Tanjungbuku granite, Holocene swamps deposits and alluvium. Each sample of pan concentrated is divided into two parts for REE content and grain mineral analysis. All 25 samples were analyzed for REE content, while only 14 samples for the grain mineral. The results of REE content and grain mineral analysis indicate that the REE prospect area located in the tailings ex tin mining in the rock formation of the Muncung granite area. The highest concentration of lanthanum reached 20100 ppm, cerium 37100 ppm, yttrium 9872 ppm, and neodymium 2840 ppm in monazite, zircon, and allanite