Buletin Sumber Daya Geologi

KARAKTERISASI MINERALISASI TEMBAGA-EMAS BERDASARKAN GEOKIMIA MULTIUNSUR DENGAN METODE K-MEANS DAN ANALISIS KOMPONEN UTAMA, TOGURACI, INDONESIA

Dharma irwanda — 2024-08-20

Multielement geochemical data processing with K-means and principal component analysis was carried out in the Toguraci, part of the Gosowong gold mine contract of work in North Halmahera Regency, North Maluku Province. Previous research has suggested that there is overprinting low sulphidation epithermal Au-Ag mineralization and Cu-Au porphyry. This research focused on 2 selected drill holes with a total of 540 samples that were analyzed for Au and 46 other geochemical elements. The purpose of this research is to determine the characteristics of the copper-gold mineralization, and its host rock with multielement geochemical analysis, in order to provide a guide for exploration activities. Multielement geochemical data processing with K-means produced 3 lithogeochemical clusters based on their immobile element composition, namely basalt and diorite which are the host rocks, and quartz vein. Principal component analysis shows consistent results for the 3 clusters, where the combination of PC1 and PC2 which cumulatively represented 46,32% of the variance, indicates high and low loading scores describing the association of immobile elements that separates basalt, diorite and quartz vein. Data simplification with 7 principal components (P1-PC7) representing 73,62% of the variance has produced 6 geological domains which have their respective geochemical characteristics, namely Quartz vein, Basalt-1, Basalt-2, Diorite-1, Diorite-2, and Diorite-3. Copper mineralization is found in Basalt-1 and Diorite-1 related to porphyry type that has characteristics of Mo-Cu-Re-Ge-Au elemental association. While gold mineralization is found in the Quartz vein domain related to low sulphidation epithermal type which is characterized by Ag-Sb-Te-Au-Tl-Bi-As-Pb-Se-In elemental association.

ESTIMASI SUMBER DAYA BAUKSIT MENGGUNAKAN METODE ORDINARY KRIGING DI KECAMATAN MELIAU, KALIMANTAN BARAT

Westia Alifah Surya Pratiwi — 2024-08-23

The estimation of mineral resources is crucial in mining, particularly in determining production targets, pit design, and investment decisions. Accurate resource estimation results will facilitate optimal mine planning. The objective of this study is the application of estimation techniques that consider geostatistics, namely ordinary kriging, in estimating bauxite deposit resources. The research location is in the laterite arc of West Kalimantan. The data used for estimation are exploration data from 212 test pit locations. The aim of this study is to identify the lithology of the bauxite deposit, distribution of grades, and estimate bauxite resources as well as determine the optimal spacing of test pits as a basis for resource classification in the study area. Petrographic analysis was conducted on four samples to determine the lithology. The study results indicate that the lithology forming the bauxite deposit consists of granodiorite, quartz diorite, and granite. The bauxite deposits in the study area are predominantly derived from granodiorite with high content, thus characterizing the bauxite as kaolinitic bauxite. The bauxite resource estimation results, based on a cut-off grade of >35%, <8%, dan ≤30%, amounted to 722,720 tons of washed bauxite, with an average grade of 39,78% , dan 25,05% , with a concretion factor of 48.44%. The inferred washed bauxite resources are 146,962 tons, the indicated resources are 550,482 tons, and the measured resources are 221,643 tons. Based on the sill variogram calculation, the optimal spacing for test pits for bauxite exploration in the study area with resource classification is 100 m for inferred, 50 m for indicated, and 25 m for measured resources.

EVALUASI KELAYAKAN PROYEK DAN PERANKINGAN AREA PROSPEK PANAS BUMI KANDIDAT LOKASI PROGRAM GOVERNMENT DRILLING

Husin Setia Nugraha — 2024-09-05

Government drilling is a geothermal exploration well drilling program carried out by the government. For planning, it is necessary to rank candidate prospect areas to be included in the program. This study ranked twenty candidate drilling sites using the incremental internal rate of return or incremental IRR method from discounted cash flow (DCF) calculations. The stages for the method are calculating project value and feasibility based on profitability parameters in each prospect area and calculating and ranking based on incremental IRR. As a result, based on the value of the profitability parameter, only two candidate areas for the program are feasible based on the project's IRR and NPV values, namely Nage and Mount Galunggung. Meanwhile, based on the BCR value, in addition to those two locations, two prospect areas are categorized as feasible, namely Bittuang and Mount Papandayan. Thus, Nage and Mount Galunggung are financially viable, and Bittuang and Mount Papandayan are economically viable. Improving the financial viability of Bittuang and Gunung Papandayan requires other fiscal incentives. For ranking, the results based on incremental IRR calculations and IRR result in the same order for the top four or the viable projects. The same results are because of their homogeneous project type, which is a geothermal project. Based on the results of this study, it is recommended to re-evaluate candidate prospect area locations for the program. It is because out of twenty candidate locations, only two are financially viable, and four are economically viable. Choosing the right location is one of the keys to the success of this program.

GEOLOGI, MINERALOGI, DAN GEOKIMIA ENDAPAN BAUKSIT LATERIT DI DESA MUKTI JAYA, KABUPATEN SANGGAU, KALIMANTAN BARAT

Aisha Permatasari — 2024-09-20

The geology of West Kalimantan, especially Sanggau Regency, contains a wide range of acidic to intermediate rocks of Lower Cretaceous age with stable tectonic conditions that meet the requirements for the formation of bauxite on an economical scale. The research area is in Mukti Jaya Village, Sanggau Regency, West Kalimantan Province. This research aims to determine the geology, mineralogical, and geochemical characteristics of bauxite deposits. The research methodology includes geological mapping, test pits, and laboratory analysis using XRF, A total of 390 bauxite samples were analyzed by XRF, 5 bauxite samples were analyzed by XRD, 4 bedrock samples and 2 bauxite samples were analyzed petrographically, and 2 bauxite concretion samples were analyzed mineragraphically. Based on the results of geological mapping, granodirite, quartz diorite and tonalite rocks were found. Bauxite is composed of the minerals quartz, gibbsite, kaolinite, hematite, biotite, boehmite, goethite, diaspor, muscovite, plagioclase, chlorite, and magnetite. From the results of XRF analysis content obtained 16.63% – 52.56% Al₂O₃; 14.5% – 66.69% TSiO₂; 0.47% – 10.2% RSiO₂; and 3.56% – 32.92% Fe₂O₃. The results of the correlation analysis showed a very strong and negatively correlated level of relationship between Al₂O₃ and TSiO₂, as well as a very low level of relationship between Al₂O₃ and RSiO₂. From the results of the regression analysis, it was found that TSiO₂ had an effect on Al₂O₃ and RSiO₂ had no effect on Al₂O₃.

IDENTIFIKASI KANDUNGAN LITIUM PADA BATUAN FILIT KOMPLEKS LUK ULO, JAWA TENGAH

Isyqi — 2024-10-01

Production of lithium-ion batteries in Indonesia will be more feasible if Indonesia has its own lithium resources. Metapelitic rocks have the potential to serve as an alternate raw material for lithium. Phyllite, a type of metapelitic rock, was found in the Luk Ulo Complex, Central Java. The objective of this study is to determine the mineral composition and lithium concentration of the phyllite rocks from the Luk Ulo Complex. This will serve as a representative model for understanding the occurrence of lithium in similar rock types. The techniques employed to accomplish this objective include field surveys, petrographic, XRD, and ICP-AES/MS analysis. Phyllite in the Luk Ulo Complex is found in several locations and exhibits well-developed schistosity, characterized by a predominant mineral composition of quartz, graphite, chlorite, and white mica. The concentration of lithium in the phyllite from the Luk Ulo Complex exceeds the average concentration of lithium in the earth's crust, which typically ranges from 18.2 to 84.7 ppm. The presence of lithium in the phyllite rock is believed to be associated with the white mica minerals in the rock because the principal component analysis reveals a significant correlation between the lithium level in phyllite and the major elements K₂O, CaO, Na₂O, MgO, and Al₂O₃, which are responsible for the formation of the white mica. The phyllite rocks in the Luk Ulo Complex have a lithium enrichment that is five times more than the concentration of lithium in the earth's crust. It is believed that this enrichment is generated from the protoliths of the phyllite rocks, which are pelitic sedimentary rocks of continental origin. The presence of lithium in the phyllite rocks of the Luk Ulo Complex makes them suitable as lithium sources. However, due to their location within the Karangsambung Geological Reserve Area, these rocks are not to be exploited.