莲花山地区成矿作用动力学背景的新认识

莲花山地区位于华北克拉通北缘,在赤峰市西约40km处。该区广泛发育金成矿作用,形成莲花山金矿床。金矿体的赋矿围岩为上太古界建平群变质岩系,属于石英脉型金矿床。我们的研究否定了以往认为本区金成矿作用与燕山期酸性岩浆活动相关的看法,提出金矿化作用发生在印支期,并与该期构造—岩浆活动紧密联系;大量含金石英脉体与大量闪长玢岩脉在空间上伴生,它们的稳定同位素及地球化学等特征均证明金矿化作用与中基性岩浆活动密切相关。此外,首次在本区结晶基底变质岩系中发现韧性滑脱带的存在,提出本区金成矿作用是发生在构造—热隆起的构造环境中,从而对本区金矿形成的动力学背景提出了新的认识。基于上述成果建立了莲花山地区金成矿模式,对金成矿作用的具体动力学过程做了进一步的解释。

A NEW VIEWPOINT ON METALLOGENETIC DYNAMICS OF LIANHUASHAN AREA

The Lianhuashan area is located near the northern boundary of the North China plate, 40 km west to the Chifeng city, where the gold metallogenesis is widely spread and results in the formation of Lihuashan gold deposits. The gold deposit is of quartz vein type, with the wall rocks consisting of metamorphic rocks of the Jianping Group in age of Late Archean. Our study indicates that the gold metallogenesis in the area occurred in Indosinian epoch, related to the tectono-magmatic activities of the Indosinian orogeny. The spatial distribution of a great amount of auriferious quartz veins being closely associated with diorite porphyry dykes, the data of stable isotope and geochemistry indicate that gold metallogenesis is related to the basic-intermediate magmatic activities, instead of the Yan shanian acidic magmatic activity. Based on the first discovery of ductile detachment zone in the crystallined basement, it is thought that the gold metallogenesis occurred in an environment of structural thermal-upheaval. A new metallogenetic dynamics, and based on which a model for the formation of gold deposits in Lianhuashan area are put forward, which can explain the dynamic process and formation of the gold deposit better.