ZHOU Xin, FENG De-xin, FAN Bing-liang*, YU Jia-shu, GASANG Dun-zhu,YI Jin-ling

(Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, China)

Abstract: On the basis of field investigation, many Ni-bearing carbonatites , which are exposed as stocks in sizes ranging from tens to hundreds of meters, have been discovered in the Leiwuqi area, Tibet, China. They are intruded into ultrabasic rocks with obviously embayed and dendritic intrusive contacts between them. They have xenoliths of ultrabasic rocks, with fine crystallized equigranular texture but no bedding, indicating that they are igneous carbonatites. They belong to magnesian carbonatite with main mineral component of magnesite and MgO contents of 27.16%－31.75%. They have gently right-declined REE distribution patterns with the obvious fractionation of LREE and HREE, obvious positive Eu anomalies, weak negative Ce anomalies, Relatively enriched Rb, Th, Nb, and Hf, but relatively depleted K, U, and Ti. The Ni-bearing carbonatite could be the product of metasomatism of ultrabasic rocks by deep-seated CO2-rich fluid in the middle and lower crusts. It has favorable potential for searching nickel sulfide deposits.

Keywords: carbonatite; elemental geochemistry; petrogenesis; Leiwuqi

ACTA MINERALOGICA SINICA Vol. 40, No.2, 2020, page 109-115