岩脉在热液矿床成因研究中的意义——以胶东西北部金矿床为例

THE SIGNIFICANCE ABOUT THE VEIN IN STUDYING THE GENESIS OF HYDROTHERMAL ORE DEPOSITS

我国热液型金矿床所占的储量比例很大,由于热液来源和矿质来源的多样性,致使许多金矿床存在岩浆热液、变生热液和混合岩化热液成因之争,笔者认为:研究脉岩与金矿的时间、空间和成因关系是判别不同成因类型金矿床的重要标志。 本文通过论证岩脉—金矿床—滦家河花岗岩之间的时间、空间和成因关系,阐明岩脉在热液矿床成因研究中的意义。

This paper discusses the relationship of time, space and genesis between some veins, gold ore deposits and Luanjiahe granite in the north-western Shandong Peninsula, one of the most important metallogenetic province in China, and states the new ideal about the vein in studying the genesis of hydrothermal ore deposits.The Zhaoye gold metallogenetic belt in this region is controlled by the north contact-zone of Luanjiahe granite,and both of the ore deposits and granite are coincident in strike, that is, the east-western direction.The main ore deposits in the belt are located within the range of 0.6-6 km in the north-part of the contact zone, where the veins are concentrated. It is known from the statistics of the Linglong ore area that 82.3 percent of veins and 68.7 percent of gold orebodies are controlled by the fissure structures which are 20°-60° in strike, and most of them are overlapping each other. The veins associated closely with ore bodies in not only space but time as well.The gold ore deposits in the area are formed in the processes for veins to intrude frequently. According to the intersected relationship of vein rocks with ore bodies the veins can be divided into three sorts;pre-mineral-vein,during-mineral-vein. and post mineral-vein. In the former two sorts the interfacise between veins and wall rocks and their fissures (or joints) limit the distribution of ore bodies, which are sumed up as six forms in this paper.The trace elements of Luanjiahe granite and veins are similar to those of ore bodies, and their petrochemical constitution shows that all of them are a cognate series, and it has been obtained from K-Rb and Rb-Sr studies that there is an identical tendency of evolution for the tripartition above. In(Sm/ Eu)sample/(Sm/Eu)chondrite-Sm diagram the projected points of the granite, veins and ores are located near the ordinate I and the stright line parallel to the abscissa.To sum up, it is concluded that the granite, veins and ores come from the same source. In chondrite-normalized REE plot they are characterized by the middle-f ractionation and the form of cuvres inclining harmoniously to right. Their δEu and δCe values are positive anomaly and near positive anomaly respectively and similar to that of metamorphic rocks in the Jiaodong group, so that we futher conclude that all of them are the products of the regenerated magma resulting from the remelt of deeper rocks in the Shandong Penisula group.The conclusions from studying veins are coincident with those from other methods (including stable isotope), that is,the gold ore deposits in this region are the regenerated magmatic hydrothermal ore deposits. In the process of studying hydrothermal ore deposits,the veins should be considered to be an important evidence determining magmatic hydrothermal ore deposits, which is absent for metamorphic migmatitic and supergenetic hydrothermal ore deposits.According to the geochemical mark mentioned in the paper which is that the granite, veins and ores have cognate feature, the writers consider that the gold ore deposits in other metallogenic provinces in China-the gold metallogen-ic provinces in the south Liaodong Peninsula, Jilin and Xiaoqinling-are magmatic hydrothermal gold ore deposits.The premise and guides for seeking other gold ore deposits in those regions are very similar to those in this region. In a word, our enough attention should be drawn to the magmatic hydrothermal gold ore deposits.