反映矿质沉淀环境的造岩元素地球化学异常——地球化学勘查盲矿预测的重要标志

围岩蚀变有一部分是成矿作用的结果。与成矿作用关系密切的围岩蚀变是矿质沉淀之前的早期围岩蚀变,它的矿物组合在化学上能够接受矿石的沉淀。实际上这样的围岩蚀变是矿石沉淀的条件准备,是早期的热水溶液与有利的围岩介质环境相互作用的结果,所以它是有利于矿质沉淀的地球化学环境的综合体现。后期蚀变围岩新的矿物组合是造岩元素重新分配的结果,因此造岩元素的地球化学异常无疑反映了有利于矿质沉淀的地球化学循环和成矿作用。斑岩铜矿和黑矿型矿床分别具有典型的造岩元素地球化学异常模式,其空间分布形态和量的变化与矿化范围及赋矿部位具有密切的对应关系。包体成分的研究、矿质的络合物迁移理论、矿液与围岩间的物质交换以及黄铁矿矿床成矿初期所成的“交代岩柱”等均表明造岩元素控制了成矿组分的迁移、聚集和沉淀。因此造岩元素地球化学异常不仅是矿床地球化学研究的重要内容,且是地球化学找矿评价尤其是找盲矿的重要标志。

GEOCHEMICAL ANOMALIES OF ROCK-FORMINGELEMENTS REFLECTING PRECIPITATION ENVIRONMENTOF ORE SUBSTANCES-AN IMPORTANT INDICATORFOR PROGNOSIS OF BLIND ORE DEPOSITS INGEOCHEMICAL EXPRORATION

A certain proportion of wall rock alteration is the reflection of ore-forming process. Part of wall rock alteration related intimately to mineralization is early wall rock alteration which took place before the precipitation of ore substances, and its mineral association could chemically accept the precipita tion of ore substances. In fact, such wall rock alteration was the preparation for ore substance precipitation and resulted from the interaction between earlyhydrothermal solutions and favorable wall rock media. It therefore embodies integratedly geochemical environments favorable for ore substance precipita tion. The mineral association of the late altered wall rock resulted from redi stribution of rock-forming elements, and hence geochemical anomalies of rock-forming elements undoubtedly reflect geochemical environments favorable for the precipitation of ore substances.Porphyry copper deposits and kuroko type ore deposits have their respe ctive typical geochemical anomaly models of rock-forming elements, whose distribution forms and quantitative variations are spatially closely related to areas of mineralization and ore-hosting positions. The study of inclusion compo sition, the theory that ore substances migrated in the form of complexes, the material exchange between ore fluid and wall rock and the "metasomatic rock pillar"formed at the beginning of the ore-forming process for the pyrite deposit all indicate that rock-forming elements controlled the migration, accu mulation and precipitation of metallogenic components. Geochemical anomalies of rock-forming elements are not only an important subject in geochemical researches but also an useful indicator in geochemical ore prospecting and evaluation and especially in search for blind ore deposits.