Geochemistry of trace elements during ore-forming processes in Yinshan deposit

Detailed studies have been conducted of the trace elements in ores, wallrocks of intrusion and orebodies in the Yinshan deposit. It is shown that ΣREE increased in all samples but those close to the intrusion and orebodies decreased. Altered wallrocks are characterized by lower w(LREE)/w(HREE) ratios and depleted in Eu compared with their fresh counterpart. It is suggested by calculation that less than 31% of the increment of REE is caused by mass transfer and the other is responsible for the addition of REE into the rock from hydrothermal fluid that caused rock alteration. The acting hydrothermal fluid was characterized by low w(LREE)/w(HREE) ratio with strong positive anomaly. The reductive state of the hydrothermal fluid resulted in the loss of Eu by returning Eu3+ into more mobile Eu2+. In other trace elements, Hf, Th, U, V, Cr, Co, Nb, Mo, Ta, Zr and Rb showed immobility, Y, Sc and Sr were carried off while Cu, Pb, Zn, Ag, Sn and Ba were introduced into altered wallrocks by hydrothermal fluid during hydrothermal alteration.