川、滇、黔接壤地区铅锌矿床产出的大地构造演化背景及成矿作用

川、滇、黔接壤地区铅锌矿床的分布受大地构造演化背景的控制。天宝山矿床与成矿有关的构造变形的应力、应变场的分析显示与区域变形相对应的区域性应力场有印支晚期和燕山期两期,其主压应力方向分别为NWW向和SSW向,印支晚期区域性近东西向的挤压是形成NWW向容矿的张性断裂的主要动力,该期为主构造期;燕山期NNE-SSW向的区域性挤压应力,具有引发区域性NEE向张性容矿构造的条件。结合区域岩浆活动和矿床同位素年龄资料的分析,认为印支晚期和燕山期发生的两次区域性小规模的岩浆活动与铅锌成矿有较密切的联系,岩浆活动可能为成矿提供了部分成矿物质和热能。构造应力、应变场所反映的构造期次、区域性的构造岩浆热事件与铅锌矿床的成矿在时间上是同步的。该地区铅锌矿两期主要的成矿作用分别和晚三叠世扬子板块与兰坪-思茅地块碰撞、义敦弧与扬子板块碰撞,以及早侏罗世西南部的雅鲁藏布江洋打开、扩张的时间一致。该地区两期主要的成矿作用发生在三叠纪晚期和早侏罗世。

GEOTECTONIC EVOLUTION BACKGROUND AND ORE-FORMING PROCESS OF Pb-Zn DEPOSITS IN CHUAN-DIAN-QIAN AREA OF SOUTHWEST CHINA

The Pb-Zn deposits in the Chuan-Dian-Qian border area in Southwest China, are constrained by geotectonic evolution background, which indicates that the mineralization of the Pb-Zn deposits are related to the two episodes of regional compression that occurred in late Indosinian and Yanshanian epochs, based on analytical results concerning the stress and strain fields associated with Pb-Zn mineralization in Tianbaoshan ore field. The compression in nearly NWW-SEE direction is the main force that led to formation of the regional, NWW-trending extensional faults, and hosting of ore bodies in the end of late Triassic. The regional compression of nearly SSW-NNE direction is also the main cause for the formation of regional, NEE-trending extensional faults, and hosting of ore bodies in Jurassic. So, the late Indosinian and Yanshanian tectonic movements are the main tectonogenetic forces in the study area. Based on regional magmatism and isotopic data concerning diagenesis and mineralization, it is realized that two small-scale magmatism events, occurring in the same time with tectonic stress and strain fields, are concurrent with the Pb-Zn mineralization, so it is possible that these two magmatism events may have provided partial metallogenic materials and geothermal energy for the mineralization. The Pb-Zn mineralization in this area is the results of collision between Yangtze plate and LanpingSimao block and between Yidun island arc belt and Yangtze plate at the end of late Triassic, and the opening and expansion of Yaluzangbu Paleo-ocean in early Jurassic. These two main tectonic-active episodes, and the regional tectono-magmatism geothermal events are synchronic with the mineralization. Based on some isotopic ore-forming age results published recently, it is found that the age data for these actions are concentrated in 226～225Ma and 176.5±2.5Ma. So, this area underwent two main Pb-Zn mineralizing periods, i.e., late Triassic and early Jurassic.