湖北省京山县香山寺铅锌矿床地质特征及成因探讨

Geological characteristics and ore genesis of the Xiangshansi Pb-Zn deposit, Jinshan County, Hubei Province

湖北京山香山寺铅锌矿床赋存于震旦系上统灯影组和寒武系下统下部庄子沟组，矿石类型为碳酸盐岩型和含碳页岩型两种。铅锌矿体受北西向构造控制，襄樊一广济深大断裂为导矿构造，控制着成矿流体的形成和运移，次级的北西向断裂及其破碎带、裂隙为容矿构造。流体包裹体研究显示，成矿流体属于NaCl-MgClrH2O体系，盐度为9．47％～9．98wt．％NaCleq．，温度为90～128℃，压力为（375．52～400.31）×10^5Pa（最小捕获压力），对应的形成深度为1．25～1．33km（最小捕获深度），表明其属于低温浅成热液矿床。矿石硫同位素组成δ34SCDT值变化介于-0．47‰～10．16‰之间，极差为10．63‰，平均值为6．99‰。矿石铅同位素组成206Pb／204pb值在17．842～17．976之间，平均17．923；207/pb／204pb值在15．577～15．599之间，平均15．586；208pb／204pb值在37．786～37．867之间，平均37．834。μ值=9．47～9．51，平均值为9．49。Th／U值=3．69～3．78，平均值为3．72。这些结果表明成矿物质主要是与造山作用有关的深部来源，属于热液成因的充填型铅锌矿床。

The Xiangshansi Pb- Zn deposit, located in Jinshan County, Hubei Province, is hosted in the upper Sinian Dengying formation and the lower Cambrian Zhuanggouzi formation. The mineralization can be divided into two types, carbonate- type and carbon- bearing shale- type. Pb- Zn mineralization is controlled by the northwestward structures. The nearby Xiangfan- Guangji deep fault controls the formation and transportation of the ore- forming fluid and is a conducting structure. The subordinate northwestward faults and fractures are host structure. Results of fluid inclusion show that the ore- forming fluid belongs to Na Cl- Mg Cl2- H2 O system with the salinity between 9.47 ~ 9.98 wt%Na Cleq and homogenized temperature 90 ~ 128 ℃, which indicates a minima trapping pressure and depth between(375.52 ~ 400.31) ×105Pa and 1.25 ~ 1.33 km, respectively, and a low- temperature epithermal deposit. The δ34SCDTcomposition of galena spans- 0.47 ‰~10.16 ‰ with a range of10.63 ‰ and an average of 6.99 ‰. The composition of lead isotopes206Pb/204 Pb ranges from 17.842 ~ 17.976(average 17.923);207Pb/204 Pb 15.577 ~ 15.59(average 15.586);208Pb/204 Pb 37.786 ~ 37.867(average 37.834). Theμ values are between 9.47 ~ 9.51, averaging 9.49 and Th/U 3.69 ~ 3.7, averaging 3.72. Those combined evidence indicate ore- forming materials are mainly from deep source associated with orogenesis, and Pb- Zn deposit is subjected to structurally controlled filling type.