云南保山金厂河铁铜铅锌多金属矿床Rb-Sr等时线测年及其地质意义

Rb-Sr isochron age of Jinchanghe Fe-Cu-Pb-Zn polymetallic deposit in Yunna Province and its geological significance

金厂河铁铜铅锌多金属矿床位于保山地块北部、NS向保山-施甸复背斜与NNW向澜沧江断裂锐角交汇部位的南部。矿体呈层状、似层状产于寒武系核桃坪组金厂河背斜的层问裂隙中，受NW向、NE向断裂交汇处的控制。选取闪锌矿及其共生的方铅矿、黄铜矿、石英样品，应用Rb-sr同位素测年方法，获得闪锌矿等时线年龄为（118．9±5．9）Ma，闪锌矿＋方铅矿等时线年龄为（119．3±1．7）Ma，闪锌矿＋黄铜矿等时线年龄为（120．3±5．1）Ma，闪锌矿＋石英等时线年龄为（117．0±2．4）Ma，闪锌矿＋方铅矿＋石英等时线年龄为（118．7±1．5）Ma，闪锌矿＋方铅矿＋黄铜矿等时线年龄为（119．6±1．6）Ma，闪锌矿＋方铅矿＋黄铜矿＋石英等时线年龄为（118．9±1．4）Ma。Rb-Sr定年结果表明，金厂河铁铜铅锌多金属矿床的成矿时代为117～120Ma，为早白垩世。热液矿物组合的（^87Sr／^86Sr）i平均值为0．713 885，与保山地块内志本山岩体的（^87Sr／^86Sr）i值接近，指示其成矿物质主要来源于地壳，成矿作用与保山地块内燕山晚期花岗岩岩浆活动有关，结合矿区重力负异常特点，推测矿区内存在隐伏的中-酸性岩体。通过地球动力学背景探讨，认为该矿床的形成可能是对中特提斯洋闭合过程中腾冲地块与保山地块碰撞造山作用的响应，与地块内部受碰撞影响而导致地壳深熔所产生的岩浆作用有关。

The Jinchanghe Fe-Cu-Pb-Zn polymetallic deposit is a concealed mineral deposit located in the northern part of the Baoshan massif and lying at the intersection between the Baoshan-Shidian anticlinorium and the Lancang River fracture. The ore bodies occur in the interlayer fissures of Jinchanghe anticline in Cambrian HetaopingFormation and are controlled by the NW-trending faults and NE-striking faults. The Rb-Sr isotopic dating was carried out for sphalerite and its associated minerals （pyrite, galena, chalcopyrite and quartz） from the Jin- changhe Fe-Cu-Pb-Zn polymetallic deposit. In addition to sphalerite age of （118.9 ± 5.9） Ma and sphalerite ＋ galena assemblage age of （119.3 ± 1.7） Ma, the authors also obtained sphalerite ＋ chalcopyrite assemblage age of （ 120.3 ± 5.1 ） Ma, sphalerite ＋ quartz age of （ 117,0 ± 2.4） Ma, sphalerite ＋ galena ＋ quartz assemblage age of （ 118.7 ± 1.5） Ma, sphalerite ＋ galena ＋ chalcopyrite assemblage age of （ 119.6 ± 1.6） Ma and sphalerite ＋ galena ＋ chalcopyrite ＋ quartz assemblage age of （118.9 ± 1.4） Ma by the same means. The results of Rb-Sr iso- topic dating show that the metallogenic epoch is about 117～120 Ma and the Jinchanghe Fe-Cu-Pb-Zn poly- metallic deposit was formed in Early Cretaceous. The （^87Sr/^86Sr）i of hydrothermal mineral assemblage is equal to 0. 713 885 and closed to the （^87Sr/^86Sr）i of Zhibenshan granite. Based on these data, the authors consider that the ore-forming materials of the ore bodies in the Jinchanghe Fe-Cu-Pb-Zn polymetallic deposit were derived from the crust and the mineralization was related to the local silicic magrnatism in Late-Yanshanian period, h can be inferred that there exist concealed intermediate-acid intrusive rocks, as evidenced by the negative gravita- tional anomaly in the mining area. A study of the geodynarnical setting indicates that the formation of the de- posit was the response to the collision orogenesis of Tengchong block and Baoshan block during the closure of the Meso-Tethys period, and was related to the crustal anatexis in Baoshan block affected by the collision.