辽北地区块状硫化物矿床的成矿物质来源及成因

SOURCE OF CONSTITUENTS AND GENESIS OF MASSIVE SULFIDE DEPOSITS IN NORTHERN LIAONING PROVINCE

The massive sulfide deposits in northern Liaoning province occur in the felsic volcanic-sedimentary rock series of Qinyuan greenstone belt. Shapes of the deposits are variable and they run from discordant to concordant with surrounding rocks. some are broadly lensoid and have a stratiform appearance while others are irregular-shaped.Geochemical feature of ore stable isotope and the REE of host rocks show that the sources of ore constituents of the deposits closely relate to the volcanism of the greenstone belt, especially to the felsic volcanism. The sulfur isotopic composition implies that the sulfur are mantle-derived, being of magmatic-hydrothermal origin with characters very close to that of the Noranda district in Candian Shield. According to the lead isotopic composition, the source of the metals of deposits are mainly from the host rocks. The forming-time of the deposits are same as the host rock. The REE patterns of the felsicvolcanic rocks related to the deposits are similar to that of the deposits in Canadian Shield. The LREE have a slight enrichement, Eu shows a strong depletion. The extent of the HREE depletion directly represents the mineralized degree.In brief, the massive sulfide deposits are products of the precipitation of volcanic-emanated hydrotbermal solution of the greenstone belt and the enrichement by tectonism.