摘要
黄家湾矿床是近几年在贵州遵义地区寒武系底部黑色页岩中新发现的以Ni-Mo为主的多元素矿床,本文首次对该矿床成矿阶段方解石的流体包裹体、REE和C、O同位素组成特征进行了系统研究。研究结果显示:(1)该矿床成矿阶段方解石中含有3种类型的流体包裹体:富液相气液两相水溶液包裹体;富气相气液两相水溶液包裹体;纯液相包裹体。它们的气相分数变化较大,显示成矿过程中可能发生过沸腾作用。流体包裹体的显微测温结果显示,成矿流体的冰点温度为-11.6～-5.5℃,流体盐度变化范围为8.55%～15.57%NaCleqv,均一温度为109.0～181.8℃,对应流体密度为0.97～1.44g·cm-3;(2)遵义黄家湾钼-镍多金属矿床中与成矿期有关的方解石的稀土总量高且变化范围宽(39.9×10-6～275×10-6),配分曲线为轻稀土富集((La/Yb)N=29.6～63.3)的右倾型,且铕正异常明显(Eu/Eu*为2.14～14.8),与现代海底热液矿床中方解石的稀土特征类似;(3)同位素测定显示成矿流体的碳氧同位素组成分别为δ13CV-PDB=-6.3‰～-5.7‰,δ18OV-SMOW=15.6‰～16.0‰,计算得到流体水的δ18OV-SMOW-H2O‰平均值变化于-0.97‰～+5.16‰之间。上述综合研究表明:黄家湾Ni-Mo多金属矿床成矿流体主要为海水和地层中的建造水(盆地热卤水),同时由海水演化来的海底热液也参与了成矿过程。成矿流体中的碳可能由深源碳与海相碳酸盐岩共同提供。
The Huangjiawan Ni-Mo polymetallic ore deposit occurred in the basal black shale sequence of the Cambrian strata in the Zunyi area, Guizhou Province, China. In order to investigate the sources of ore-forming fluids and the mechanism of mineralization, fluid inclusion, REE, carbon and oxygen isotopes studies have been performed on calcite of the main mineralization stage from the studied area. Three types of fluids inclusions, i.e., liquid-rich two-phase fluid inclusions, gas-rich two-phase inclusions, and pure liquid aqueous inclusions, have been recognized in this study. In addition, different types of inclusions with remarkably varied vapor-liquid ratios exist together, implying that boiling might have occurred during mineralization. Meanwhile, microthermometric measurement of the fluid inclusions show that the ice melting temperatures range from -11.6℃ to -5.5℃ and the corresponding salinities vary from 8.55% to 15.57% NaCleqv. The homogenization temperatures range from 109.0℃ to 181.1℃, with densities from 0.97g·cm-3 to 1.44g·cm-3. Rare earth element （REE） analyses show that the calcites are characterized by high ∑REE content （39.9×10-6~275×10-6）, enrichment in LREE, （（La/Yb）N=29.6~63.3）, right-inclining chondrite-normalized patterns, and positive Eu anomalies （Eu/Eu＊=2.14~14.8）, which are coincident with those of sea-floor exhalative-hydrothermal deposits. Carbon and oxygen isotopic results of the calcites are characterized by δ13CV-PDB=-6.3‰^-5.7‰, δ18OV-SMOW=15.6‰~16.0‰, and the calculated oxygen isotopic compositions （δ18OV-SMOW-H2O） of the hydrothermal fluids are from -0.97‰ to ＋5.16‰, which suggested that the carbon in ore-forming fluids was mainly derived from seawater-derived hydrothermal fluids. Based on the above discussion, we conclude that the ore-forming fluids of Huangjiawan Mo-Ni-polymetallic deposits are mainly composed of sea water and formation water （basin hot brine）, and the seafloor hydrothermal fluid evolved from sea water participated ore-forming fluid process.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2011年第12期3763-3776,共14页
Acta Petrologica Sinica
基金
国家自然科学基金项目(40972071)
贵州省科学技术基金项目(黔科合J字[2008]号)联合资助
