A STUDY OF THE GEOLOGY AND GEOCHEMISTRY OF ALTERED ROCKS FROM LIBA GOLD DEPOSIT IN GANSU
SUN Xing li 1, LIU Xing de 1, GAO Zhao kui 2, QIAN Wen guang 3, RAN De fu 3 (1.Chengdu University of Technology, China; 2.Guansu Geological Prospecting Buearu for Non Ferrous Metals; 3.Gansu Institute of Geology for Non Ferrous Metals)
The Liba gold deposit located in the northern zone of west Qinling is situated in the Middle Devonian turbidite formation of the Liba Group. The gold mineralization is strickly controlled by fault and intrusive mass.Alteration from orebodies to unaltered rocks can be grouped into four zones, that is, pyritization silicification sericitization, sericitization, chloritization and biotitization. All gold orebodies lie in the zone of sericitization overlapped pyritization, weak silicification and carbonatitization.K metasomatism belonging to alkaline metasomatism caused significant chemical changes to silt phyllite, which now contains up 4.71% K 2O, 57.83% ~61.66% SiO 2 and 3.12%~3.99% Fe 2O 3. The separation of K, Na which are a pair of incompatible elements took place in the course of biotitization and sericitization. Ti, Al, and HREE remained immobile during the formation of potassic and chlorite alteration, whereas LREE, P, Mg and Au were mobilized. The potassic alteration could provide some ore forming elements leaching from altered rocks.K metasomatism can make the density of altered rocks lower and the porosity increase, and meanwhile provides sufficient room for ore forming fluid which took place pervasive acid alteration to form gold deposits.
【CateGory Index】： P618.51