胶东台上金矿床矿物中包裹体研究

A STUDY ON INCLUSIONS IN MINERALS OF TAISHANG GOLD DEPOSIT, EASTERN SHANDONG PROVINCE

胶东台上金矿床是近年来刚探明的一个超大型金矿床。矿体产于滦家河花岗岩体内部,成矿热液主要来自滦家河花岗岩体中的含矿粒间溶液。成矿热液的盐度为5.5～9.0wt%NaCl,密度为0.76～0.92g/cm^3,富含K^+、Na^+、Ca^(2+)、Mg^(2+)、SO_4^(2-)、Cl^-、F^-、HCO_3^-以及挥发分(H_1O、CO_2、CO),并由于这些挥发分的存在,使金易与[(HS)^-]形成稳定的络合物存于溶液中及迁移过程中。当断裂形成时,成矿地球化学系统经历了瞬时减压沸腾作用,导致p、T、pHfo_1等物理化学条件明显改变,含矿粒间溶液迁移和富集,在适宜地点沉淀成矿。台上金矿床形成于弱碱、弱还原的化学环境中,220～300℃,(300～600)×10~5Pa的温压条件下,是一个典型的破碎带蚀变岩型金矿床。

The Taishang gold deposit in eastern Shandong Province is a superlarge gold deposit which has been prospected recently. Studies of inclusions in minerals revealed that the orebody occurred in the Luanjiahe granite, and ore-formlng hydrothermal solutions were originated mainly from ore-bearing intergranular solution in the granite. Salinity of the hydrothermal solu tion ranges from 5.5 to 9.0 wt. % NaCl, and the density from 0.76 to 0.92 g/cm^3. Also, the solution is rich in K^+, Na^+, Ca^(2+), Mg^(2+), SO_4^(2-), HCO_3^-, F^-, and Cl^-, as well as H_2O, CO_2, CO, etc. Due to the existence of gas components such as H_2O, CO_2 and CO, gold can easily complex with [HS^-], which can exist stably or be transported in the solution. When fractures formed, the ore-forming geochemical system would experience a sudden drop of pressure and boiling process, leadlng to obvious changes in physicochemistry, such as p, T, pH, f_(o_2), etc. So, ore-bearing intergranular solutions migrated were concentrated and deposited, finally forming a gold deposit. Moreover, the study also shows that the deposit formed in weak alkalic and reducing conditions, and the forming temperature ranges from 220 to 300℃ and the pressure from 300 to 600 (×10~5 Pa). It is a typical gold deposit of alteration rock type in the fracture zone.