鄂东南大箕山铜矿床成因:来自流体包裹体及H-O-S同位素的证据

大箕山铜矿床地处湖北省鄂东南地区,位于阳新岩体西北段岩体内。铜矿体受NW向构造破碎带控制。通过对其矿床地质特征、流体包裹体以及H-O-S稳定同位素研究,探讨大箕山铜矿床的成矿流体性质、成矿流体来源及硫的来源,基于上述研究结果讨论其矿床成因类型。大箕山铜矿床的形成过程符合典型的矽卡岩矿床成矿过程的"二期五阶段",即矽卡岩期,包括干矽卡岩阶段、湿矽卡岩阶段以及氧化物阶段;石英-硫化物期,包括铜(铅锌)硫化物阶段和银(金)阶段,其中铜(铅锌)硫化物阶段为主成矿阶段。流体包裹体研究表明,主成矿阶段流体具有中低温(140~300℃)、中低盐度(6%~12%NaCleq)特征。石英中流体包裹体的δ18OH2O值为3.51‰~5.92‰,δDV-SMOW值为-75.4‰~-60.5‰,表明其成矿流体主要以岩浆水为主,可能有地层组分的加入;硫化物(黄铜矿、黄铁矿)的δ34S值为-0.6‰~2.7‰,且集中于0~2‰,表明矿石的硫具有幔源硫特征。以上表明,大箕山地区铜成矿作用与岩浆作用密切相关。综合上述矿床地质特征、流体包裹体以及H-O-S同位素研究结果,认为大箕山铜矿床成因类型应为典型的矽卡岩型矿床,为内矽卡岩带的产物。

Genesis of the copper deposit in Dajishan, southeastern Hubei Province: Evidences from fluid inclusions and H-O-S isotopes

The Dajishan copper deposit is located in the northwest section of the Yangxin granite pluton,the southeast area of Hubei Province. Copper ore body is strictly controlled by NW structrural fracture zone. By studying the geological characteristics of the deposit,fluid inclusions and H-O-S stable isotopes,the characteristics of ore-forming fluid,the source of ore-forming fluid and the source of sulfur of dajishan copper deposit are discussed,and the genetic type of the deposit is determined based on the above research results. The formation process of Dajishan copper deposit accords with the"two periods and five stages"of the mineralization process of typical skarn deposit,namely skarn period,including dry skarn stage,wet skarn stage and oxide stage,and the quartz-sulfide period including the copper( lead and zinc) sulfide stage and the silver( gold) stage,among which the copper( lead and zinc) sulfide stage is the main metallogenic stage. The fluid inclusions showed that the fluids in the main mineralization stage had the characteristics of medium and low temperature( 140 ~ 300℃) and medium and low salinity( 6%-12%NaCleq). Fluid inclusions in quartz with δ18 OH2 Ovalues between 3.51‰ ~ 5.92‰ and δDV-SMOWvalues between 75. 4‰ ~ 60. 5‰,suggests that the ore-forming fluid mainly comes from magmatic water. The value of δ34 S of the sulfide( chalcopherite and pyrite) is-0.6‰ ~ 2.7‰ with the concentration of 0 ~ 2‰,indicating that the sulfur of the ore is mainly derived from mantle. The results indicate that copper mineralization is closely related to magmatism in Dajishan area. Based on the above geological characteristics,fluid inclusion and H-O-S isotope research results,it is concluded that the genetic type of Dajishan copper deposit should be a typical skarn deposit,which is the product of inner skarn zone.