摘要
广东英德周屋铜多金属矿床位于南岭多金属成矿带,其矿床成因存在矽卡岩型和热液改造型的争议,并且研究程度较低,缺乏较为可靠的证据,尤其成矿流体研究是空白。通过对周屋铜多金属矿床系统的流体包裹体岩相学、显微测温和拉曼分析研究表明:在矽卡岩阶段发育富液相包裹体、富气相包裹体和含子矿物多相包裹体。矽卡岩阶段的石榴石和白钨矿中包裹体均一温度为290~≥490℃,高盐度(35.26%~40.10%NaCl_(eqv))和低盐度富气相包裹体(4.18%~4.96%NaCl_(eqv)),表现出流体不混溶现象,或以富气相和富液相包裹体共存为特征,温度范围为320~490℃,盐度变化范围较大(4.18%~17.08%NaCl_(eqv)),表现为沸腾现象。金属硫化物阶段,在硫化物早期石英中包裹体均一温度为290~360℃,高盐度(30.92%~37.40%NaCl_(eqv))和低盐度富气相包裹体(10.48%~11.70%NaCl_(eqv)),表现出流体不混溶现象;硫化物晚期以富气相和富液相包裹体共存为特征,温度范围为202~320℃,盐度变化范围较大(4.18%~24.04%NaCl_(eqv)),显示流体的沸腾现象,硫化物阶段是铜矿主要成矿阶段。褐铁矿-碳酸盐化阶段的石英和方解石中全部发育富液相包裹体,演化为相对较低的温度(Th=120~220℃)和较低的盐度(2.57%~7.59%NaCl_(eqv)),没有沸腾现象,属于NaCl-H_2O成矿体系。拉曼分析结果表明:早期石榴石、白钨矿和石英中包裹体气相成分以CO_2为主,其次是(或含)CH_4或H_2;液相成分主要为H_2O,晚期石英和方解石中包裹体液相和气相成分主要为H_2O和N_2。从早期的石榴石、白钨矿到晚期的石英和方解石,包裹体中H_2O的含量增多,说明在矽卡岩后期阶段,有较多的天水加入。铜矿床的成矿流体在200~490℃区间内至少发生了2次强烈的沸腾作用,改变了体系内的物理化学条件,导致大量铜的金属硫化物沉淀,沸腾作用对铜矿的形成和富集起着重要作用,为探讨矿床成因提供了新的依据。
Zhouwu Cu-polymetal deposit in Yingde, Guangdong Province is tectonically located in the Nan- ling metallogenic belt. The Zhouwu deposit is poorly studied, resulting in disagreement on ore formation including skarn-type or hydrothermal metamorphism deposit, and lacking detailed evidence furthermore hampers the understanding of the nature of Cu-polymetal deposit. We conducted systematic petrography, microthermometry and Roman analysis on fluid inclusions of the skarn stage and sulfide stage from the Zhouwu Cu-polymetal deposit in this contribution. Petrography and microthermometry studies suggest that aqueous inclusions, gas-rich CO2-bearing inclusions and daughter mineral-bearing inclusions are domi- nant in the skarn stage. Fluid inclusions hosted in garnet and scheelite of skarn stage yield homogenization temperature （T h） at 290-≥490℃, aqueous inclusions of high salinity （35.26 %-40.10% NaCleqv） and gas-rich CO2-bearing inclusions of high salinity （4.18%-4.96% NaCleqv）, indicating a fluid immiscibility process. The coexisting aqueous inclusions and gas-rich COz-bearing inclusions yield Th at 320-≥490℃, and salinity of a wide range （4.18%-17.08% NaCleqv）, indicating a boiling during their being entrapped. At the early sulfide stage, fluid inclusions hosted in quartz yield Th at 290-360℃, and aqueous inclusions of high salinity （30.92%-37.40% NaCleqv） and gas-rich CO2-bearing inclusions of high salinity （10.48% -11.70% NaCleqv）, indicating a fluid immiscibility process. Whereas the coexisting aqueous inclusions and gas-rich CO2-bearing inclusions of the late sulfide stage display fluid inclusions with Th at 202-320℃, and salinity of a wide range （4.18%-24.04% NaCleqv）, suggesting a boiling during Cu-sulfide precipitation. Fluid inclusions entrapped in quartz and calcite from limonite-earbonatization stage are aqueous-rich, and evolved to be a NaCl-H2O system yielding relatively low Th （120-220℃） and salinity （2. 57%- 7.59% NaCleqv） without boiling. Roman analyses suggest that CO2 is dominant in gas composition of fluid inclusions entrapped in early garnet, scheelite and quartz, with minor CH4 and/or H2, and H2O compris- ingpredominantly the aqueous inclusions. Whereas H2O and N2 dominates the composition of late quartz and calcite. The amount of H2O in inclusions of late quartz and calcite increases compared to that of pre- cursor garnet and scheelite, indicating the injection of meteoric water during post-skarn stage. The physi- cochemieal conditions change during intense fluid boiling at temperature of 200-490℃, resulting in the precipitation and enrichment of abundant Cu-sulfide minerals. The understanding in this study provides constraints on ore formation as well as exploration regionally in the Nanling metallogenic belt.
出处
《地质科技情报》
CSCD
北大核心
2017年第6期122-135,共14页
Geological Science and Technology Information
基金
中国地质调查局地质矿产调查评价专项项目"南岭成矿带中西段地质矿产调查"(1212010090000150002)
关键词
流体包裹体
显微测温
拉曼
铜多金属矿床
周屋
南岭成矿带
fluid inclusion
microthermometry
laser Raman spectroscopy
Cu-polymetal deposit
Zhou-＇wu, Nanling metallogenic belt
