Tracing the potential of rare earth element content in the Adian Koting area, Indonesia

Rare earth elements (REE) are substitution elements that form in rock-forming minerals and are considered critical energy elements required by industry as part of the energy transition supply chain.The exploration of REE potential aims to identify prospective areas by examining the megascopic and microscopic characteristics of rocks and their elemental composition as natural resources and for the development of priority commodities.The research was conducted in Adian Koting district, north Tapanuli.Rock samples were collected from outcrop areas.The samples were tested using petrological methods with thin sections and polished sections, and geochemical analysis using xray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS).The samples were prepared in the form of polished sections, which were analyzed using microscopy methods, and ground to a size of 200 mesh for testing using XRF and ICP-MS.The results obtained from the polished sections revealed that the megascopic characteristics of the rocks are coherent igneous rocks, specifically plutonic granite types, with colors ranging from light gray to white with black specks, brownish-white with brick-red to brown patches and black specks, as well as cream to grayish-white with black specks.The rock has an equigranular, hypidiomorphic-granular, and phaneritic texture.The grain shapes are subhedral with a massive structure, composed of minerals such as quartz, plagioclase, biotite, opaque minerals, and hornblende.Microscopically, the rock contains zircon, monazite, and xenotime as REE-bearing minerals.Monazite appears in prismatic, platy, or elongated crystal forms, sometimes large, coarse, and commonly twinned.Monazite and xenotime occur in association, and their presence as inclusions in biotite or quartz indicates early crystallization.Zircon appears as small, bright-colored inclusions.The REE content in the Adiankoting area, based on XRF analysis, shows the presence of Ce and La elements, with Ce concentrations ranging from 74.3 to 97.5 ppm and La concentrations ranging from 90.2 to 141.0 ppm.The ICP-MS test results show the presence of REEs with a dominance of REE elements at concentrations of Sc (3.5-5.5%),La (4.1-5.6%),Y (4-6.1%),Ce (3.5-4.8%),Gd (3.9-5.8%),Tm (5.4-5.6%),Eu (3.1-5.1%).REE and the minimum element include Dy (1.9-3.6%),Yb (0.8-3.5% ) and Er (0.473-84.4%).The presence of REE elements indicates that the Adian Koting area has the potential to be a natural resource for industrial technology materials.