Penambangan timah hasil intrusi granit tipe-S di Pulau Bangka yang dimulai sejak periode kolonial Belanda menghasilkan produk samping. Presisi, akurasi, dan reproduktivitas dibutuhkan untuk memverifikasi hasil pengukuran perangkat analisis yang memang diperlukan dalam perkembangan ilmu kebumian. Perangkat X-ray fluorescence pada umumnya diaplikasikan untuk mengukur kandungan oksida utama dan beberapa unsur jejak yang memiliki kelimpahan tinggi. Presisi pengukuran oksida utama, unsur jejak, berikut logam tanah jarang pada percontoh produk samping penambangan timah milik PT Timah di Nudur, Pulau Bangka, menggunakan XRF adalah tujuan penelitian ini. Informasi mengenai manfaat ekonomis material sisa penambangan tersebut juga dapat diketahui melalui studi ini sehingga dapat menjadi landasan kebijakan bagi pemerintah maupun PT Timah. Seluruh analit terbukti presisi berdasarkan prinsip RSD <2/3 kali RSDHorwitz, kecuali MgO, CaO, Mo, Cr, dan Zn. Bahan sisa penambangan ini masih cukup ekonomis. Terdapat indikasi awal bahwa titanit dan malayait hadir bersama pada granit pembawa timah di Nudur berdasarkan komposisi geokimia percontoh yang dipelajari. Kata kunci: presisi, produk samping, tambang timah, geokimia.
The geophysical surveys are needed to obtain information on subsurface geology for infrastructure development, mitigation of landslide and geothermal. Cilaki drainage basin is an area Garut Regency at southern part of West Java. The area has complex geological and the main target in development plan of Southern part of West Java. The electrical resistivity method of the Schlumberger configuration was used to identify the geological subsurface and the active fault of the study area. The measurement of the electrical resistivity was made on 7 lanes (GL 1 until GL 7). The location has a height of 195 to 925 meters above sea level with depth reaching more than 120 meters and electrical resistivity value of 6-450 Ω meters. Generally, the electrical resistivity value of Quaternary rock units have value between 80 and 450 Ω meters and Tertiary rock unit have value of 6-40 Ω meters. Based on the results of data analysis can be interpreted that the area has been deformed. This is reflected also in the geomorphology as an indication of tectonic phenomenon in the form of active faults. Quantitatively, this is reflected in the value of the mountain-front sinuosity (Smf) index which ranges 1.036 to 2.173. This phenomenon occurs in geomorphology which is composed of Tertiary and Quaternary rocks.
Internal reference materials are generated by laboratories to overcome the high cost and limited matrix of certified reference materials (CRM). Rare earth elements (REE) are strategic metals which is used in modern technology and explored within different matrices. Rare earth elements exploration surely needs appropriate reference materials for accurate interpretation. The current study aims to explain internal standard reference materials generation of marine sediment matrices from nearby the tin Bangka Island, especially the rare earth elements character, to overcome the CRM dependency. The first sample was taken with a dredger while the second one using a suction vessel. Repeated samples measurements were done by applying inductively coupled plasma - mass spectrometry (ICP-MS) from the Center for Geological Survey Indonesia for repeatability tests. The samples were analyzed in another certified laboratory in Indonesia using the same device for reproducibility assessment. The two candidates should be deposited in different environments with different influx material due to their distinct rare earth elements characters. Most of the analytes’ contents are suitable to be set as internal reference material values according to acceptable repeatability and reproducibility evaluations. The internal reference materials are ready for studying suitable matrices in the future.
The Acid-Base Accounting (ABA) and TCLP methods from overburden samples collected from the coal mine in Kasai were undertaken to predict pre-mining acid mine water quality. Maximum potential acidity (MPA), acid neutralization capacity (ANC), net acid generation (NAG), net acid producing potential (NAPP) and ANC/MPA ratios were determined on the Acid-Base Accounting (ABA) protocol. Most of the samples from KS-10, KS-11 and KS-12 show the pH of NAG of overburden ranges from 5.53–7.86 negatively net acid neutralization potential (NAPP). The ANC/MPA ratio varied from 1.09–26.60 and is classified as non-acid-forming except at an interval depth of 7.00–9.00 m in KS-12, where it is classified as uncertainty. The potentially acid mine water detected in KS-39 at an interval depth of 16.00–36.00 m was classified as potential acid forming (PAF), indicated by a positive NAPP, a low ratio of ANC/MPA (below 1.0) and high dissolved metal iron.
The objective of this paper is to investigate how electrical resistivity changes as electromagnetic waves penetrate deep into the subsurface of Lili-Sepporaki geothermal prospect, using Magnetotelluric data. Lili Sepporaki is an andesitic-trachytic volcanic-rich area located in western Sulawesi-Indonesia. Magnetotelluric data was processed using SSMT2000 and MTEditor software programmes. Results show that resistivity of rocks generally increases with decreasing frequency, that is; less than 100 Ohm-m for frequencies greater than 100 Hertz; and fluctuates between 100-1000 Ohm-m for frequency range 1-0.1 Hertz. Resistivity also increases with depth of penetration of electromagnetic waves. Weathering, hydrothermal alteration, and many times fluids increase the conductivity of rocks. A low resistivity anomaly is seen around the hot spring, northwards. Presence of fluids in an intensively fractured volcanic rock lowers its resistivity. In the future, another Magnetotelluric sounding should be carried with much more measurement stations followed by a three-dimensions interpretation.
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