DOI: 10.5176/2251-3353_GEOS13.38
Authors: Rahmad Dwi PUTRA, Nurcahyo Indro BASUKI, Rifki ADRIANDA, Patra EMBARA and Afy SYAHIDAN1
Abstract: Granite in Sibolga Granite Complex contain large number of rare earth elements and has been undergone supergene enrichment in soil. The overlapping between the rare earth elements in rocks and soil on the spider diagram (chondrite normalized) shows the value of the content of rare earth elements between rock and soil are similar but slightly larger in the local soil as it has been undergone supergene enrichment. pH and Eh were the controller in the enrichment of rare earth elements in soil. The presence of microcline that has the highest value is 45{6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} and the highest clay minerals is 15{6e6090cdd558c53a8bc18225ef4499fead9160abd3419ad4f137e902b483c465} in granite, both of them have a positive correlation to the number of rare earth elements. These minerals are inferred to be carrier of the rare earth elements in granite which has been altered. During the weathering of rocks into soil seen that lanthanide group has fractionated, it seen well from the data that the ratio of Tb and Tm elements are differents at each depth interval. The enrichment of rare earth elements in soil was also controlled by the structure (fracture or fault). Value of rare earth elements tend have positive corellation with lineament that seen in the SRTM and topographic maps. These structures were serves as the entrance of ground water that dissolved and precipitated rare earth elements. Suggested for further exploration in the areas surrounding geological structure being the main target.
Keywords: Sibolga Granite Complex, rare earth elements, pH, Eh, SRTM, fractionation and geological structure
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