贵州滥木厂金汞铊矿床地质地球化学特征及其地质意义北大核心CSCD

黔西南滥木厂矿床是世界上罕见的汞(大型)-铊(大型)-金(小型)多金属矿床,具有独特的成矿元素分带现象。本文通过系统研究滥木厂矿床金、汞-铊、汞、铊矿石及围岩样品的主量、微量及稀土元素地球化学特征,对比分析不同类型矿化的成矿环境,以探讨成矿元素共生分离机制。研究表明,相对于滥木厂矿床的围岩样品,同岩性的各类矿化岩石的SiO_(2)含量显著增加,CaO和MgO含量之和明显降低,表明成矿过程中伴随广泛的硅化和去碳酸盐化作用,K_(2)O-Al_(2)O_(3)投图表明区内存在显著的高岭石化作用。各类矿石与围岩均显示Au、As、Sb、Hg、T1和轻稀土富集特征,且具有相似的稀土配分模式;但成矿元素分布于不同的特征因子中,并表现出富集程度的差异,表明成矿物质继承了原岩的部分地球化学特征,在成矿过程中发生了分离。Y/Ho比值在金矿石中普遍高于28,在其它矿化类型岩石中均低于28,反映金成矿热液富含氟络合物,汞和铊成矿热液以碳酸氢根的络合物为主。各类矿石通常具有Ce正异常,铊、汞-铊和金矿石普遍显示Eu正异常,汞矿石呈现轻微的Eu负异常,表明成矿环境处于相对氧化的状态,并具氧化还原波动性。综合元素地球化学特征与收集的碳、氢、氧、硫、铅同位素成果,认为滥木厂矿床金、汞、铊矿化的成矿物质及成矿流体具有多源性,各类矿化在温度、氧逸度、酸碱性及配合物类型等方面的差异可能是成矿元素产生分异的重要原因。

Geological and geochemical characteristics of the Lanmuchang gold-mercury-thallium deposit in southwestern Guizhou Province and their geological implications

The Lanmuchang deposit in southwestern Guizhou Province is a rare mercury (large scale) - thallium (large scale) - gold (small scale) polymetallic deposit in the world, with unique ore-forming element zoning. This study analyzed the geochemical characteristics of major, trace and rare earth elements of gold ores, mercury ores, thallium ores, mercury ores, thallium ores, and country rock samples from this deposit, and compared the metallogenic environments of various types of mineralization, in an attempt to discuss the paragenesis-separation mechanism of metallogenic elements. Compared with the country rocks from the same lithology, the SiO2 content of various ores increases significantly, and the sum of CaO and MgO is relatively reduced, indicating that the mineralization process was accompanied by extensive silicification and decarbonization. The projection of K2O and Al2O3 shows that significant kaolinization was involved in the mineralization process. All kinds of ores and country rocks display the enrichment of Au, As, Sb, Hg, Tl, and LREE, and have similar rare earth distribution patterns. However, the ore-forming elements are distributed in different rotation factors, and exhibit varying degrees of enrichment. It is indicated that the ore-forming materials inherited geochemical characteristics of the original rock and were separated in the process of mineralization. The Y/Ho ratio is generally greater than 28 in gold ores and smaller than 28 in other mineralized rocks. Gold metallogenic hydrothermal fluid is thus inferred to be rich in fluorine complexes, and the mercury and thallium metallogenic hydrothermal fluid is mainly composed of bicarbonate complexes. Various ores generally have positive Ce anomalies. Mercury-thallium ores show slightly negative Eu anomaly, while other ores generally show positive Eu anomalies. The metallogenic environment tended to be in a state of relative oxidation, with no exclusion of reducing environment. A synthesis of element geochemistry with previous carbon, hydrogen, oxygen, sulfur and lead isotopes suggests that, the gold, mercury and thallium mineralization in the Lanmuchang deposit may share the same source of ore-forming materials and ore-forming fluids. The differentiation of ore-forming elements was possibly contributed to the varying temperature, oxygen fugacity, acidity and alkalinity and the types of complex.