摘要
本文对锡铁山铅锌矿床的矿石矿物包裹体进行了系统研究,查明早期火山喷发沉积或矿热液和火山作用期后主要成矿热液的温度、压力、含盐度、密度、化学成分以及它们的差异,还探讨了主要成矿热液在成矿过程中的不混溶作用以及物理化学条件的演变。火山喷发沉积成矿热液温度110-140℃,含盐度0.85％-5.1％;火山作用期后热液成矿流体温度137-360℃,含盐度33-34.7％,压力260-470b,相当于2000-3000m深处,形成具火山喷气沉积,热液叠加改造型块状硫化物多金属矿床。
The formation of Xitieshan Pb-Zn deposit is closely related to Xitie- shan-Luliangshan-Sachitenshan Lower Palaeozoic ophiolitic volcanic rocks and volcanism. There are two stages during the formation of the deposit, i. e, volcanic erupto-sedimentary formarion and hydrothermal ore-forming of late stage volcanism. Hydrothermal temperature: 110-140℃and salinity: 0. 85-5. 1%(NaCl wt%)for the volcanic erupto-sedimentary stage. Tempera- ture: 137-360℃ and salinity: 0. 85-34. 7% for the hydrothermal ore-form- ing process of late stage volcanic action. They are marked by the evolution of the initial stage temperature: 320-360℃ and salinity:33. O^34. 7%(Pyri- te--forming stage), to temperature: 200-254℃ and salinity: 5. 1-23. 3%, chiefly 14. 3-23. 3% (galena, sphalerite and quartz-forming stage), and up to late stage temperature: 137-148℃ and salinity: 0. 85-1. 7%(calcite etc. carbonate minerals-forming stage). Components of the ore-fluid are: H_2O, CO_2, H_2S, SO_2, SO_3, CO, CH_4, N_2, and H_2 etc. which carry rich Fe, Pb, Zn, Mn, Cu, Cd, Au, Ag…etc. metal elements and Si, S, Ca, Na…etc. nonmetal elements, PH=5. 83 for the ore-fluid, belonging to neutral or weak alkalic liquid. The ore-fluid possess the character of non-consolution pro- cess, becoming ore-fluid rich in Pb, Zn, and ore-fluid rich in Si after fractionization. The sphaleritic pearly drops are the drops of ore-fluid rich in Pb, Zn trapped in the course of crystallization of quartz. The ore-forming process was completed in the reductive condition. The ore-forming pressure is calculated to be 260-470b, corresponding to a depth of about 2000-3000 m, in which the seawater is suppored under such a depth of about 500-1000 m. The ore-forming model is proposed that initial metal suphide ore bed was formed during primitive volcanic erupto-sedimentation, and afterward the ore-forming fluid, generated by seawater penetrated into the lavas through fracture and was heated by it (being mixed with the hot residu- al bittern of volcanism). The action is something like pumping and recyc- ling by circulation. As a result the ore-forming elements were extracted from the rocks in the course to form ore fluid and then migrated to favor- able sites to form hydrothermal ore deposits. At the same time, the hydro- thermal activity reactivated and reformed the initial volcanic eruption- sedimentation ore bed. This is how the volcanic exhalation-sedimentation and hydrothermal superpositional-reformed massive sulfide deposit were formed.
