贵州紫云方解石矿床地球化学特征及成因研究

Study on Geochemical Characteristics and Genesis of Calcite Deposit from Ziyun County,Guizhou Province,China

贵州紫云方解石矿床是在贵州西南部新发现的非金属矿床,方解石矿体呈脉状、透镜状和似层状产出。对紫云火山关、达则等方解石矿床开展同位素地球化学及微量元素、稀土元素研究,结果表明碳、氧同位素显示成矿物质来源于海相碳酸盐岩,成矿流体以富含HCO_3^-为主,大气水参与成矿,与岩浆作用关系不大。其中达则矿段相对于围岩,成矿物质具有较高的Sr、Zn和Ni含量,稀土元素配分曲线明显区别于围岩,δEu显示正异常等特征,暗示可能有深部流体参与成矿。火山关、打劳等其他矿段,矿体和围岩具有相似的稀土配分模式和∑REE变化规律,表明成矿物质来源于碳酸盐岩围岩。通过区域成矿作用比较,认为成矿时代可能属于印支—燕山期。

The Ziyun calcite deposit is a newly discovered non-metallic deposit in southwest of Guizhou Pro-vince. Orebodies are veined, lenticulared or stratoid in form and are hosted in the carbonate rocks and are found to have been developed in the faults. Calcite is the dominant mineral. The ores revealed a variety of hydrother-mal structural characteristics. Ore samples were collected from Huoshanguan, Daze, etc. at Ziyun County and were tested for the isotope geochemistry, trace and rare earth element contents. The carbon and oxygen isotope geochemistry indicate that metallogenetic material came from marine carbonate rocks. Ore-forming fluids are dominated by HC03 , and thus a great amount of precipitation is added in the following mineralization, which has not a close relationship with magma. In contrast to the surrounding rocks, the Daze ore block has obvious characteristics by analysis of different REE distribution patterns, Eu positive anomalies and high content of Sr, Zn and Ni. This indicates that the ore-forming fluid was probably from deep source evolved in the process of mineralization of the Daze ore block. Both the orebodies and the surrounding rocks have similar REE distribu-tion pattern and regularity variation of X REE in the Huoshanguan, Dalao and other ore blocks, which shows that the metallogenetic material may come from carbonate rocks. Compared with the regional mineralization, metallogenetic epoch of the calcite deposit could be Indo-Yanshanian.