Characteristics of Rare Earth Metals Rock Content in the Parmonangan Area of North Tapanuli Using Petrographic Methods

Abstract Rare Earth Element (REE) are a commodity that continues in increase due to technological advancements. Rare earth metals are not widely know for their resources. The scarcity of rare earth metals identifies the need to search for their geological existence by characterizing the megascopic and microscopic characteristics of rocks. The research was conducted in the Parmonangan subdistrict, North Sumatera. Sampling was carried out in the outcrop area. The rock samples were prepared by making slabs 2-3 cm thick, then cutting them into chips to fit the slides for a polarizing microscope, and subsequently characterized megascopically dan microscopically. Megascropical petrology results show that the rock type is plutonic with reddish brown and yellowish brown, with a massive structure with granite, tonalite, syienite and biotite granite. The results of the microscopic characteristics obtained a rock texture with phaneritic and porphyritic granularity with fine-medium crystal sizes (<1-5 mm). The average primary mineral composition is 20-50% quartz, 20-40 % feldspar, 12-20% biotite, and 5-10% secondary minerals cassiterite, 5-10% monazite and 3-10% zircon.