华北地台东北缘西岔地区金多金属矿成矿地质体年代学、地球化学及成矿动力学

西岔地区金多金属矿位于华北地台东北缘。研究区经历了太古宙结晶基底的形成,元古宙"辽吉洋"的构造演化,中生代早期遭受古亚洲洋最终闭合的影响,中-新生代又有滨太平洋构造域的叠加与改造,造就了复杂的构造格局,同时也记录了丰富的成矿信息。为厘清区内多金属矿成矿时代与成矿动力学背景,本文对研究区不同成矿地质体开展了锆石LA-ICPMS U-Pb测年和全岩地球化学研究。结果表明:(1)具有条带状贱金属矿化的荒岔沟组变粒岩锆石年龄为2157Ma,其形成与辽吉洋洋壳俯冲产生的强烈海底火山喷发密切相关,在火山喷发的间歇期形成了条带状矿化的火山-沉积岩;(2)正岔矽卡岩型铅锌矿的成矿地质体(正岔岩体)由具有埃达克属性的高镁闪长岩和低镁花岗岩组成,形成于晚三叠世(2243～2185Ma),是古亚洲洋闭合和持续碰撞造山导致的加厚下地壳拆沉作用的产物,暗示华北地台北缘岩石圈规模有限的减薄和克拉通破坏的起始时间可能为晚三叠世;(3)西岔金银矿的成矿地质体西岔正长斑岩的锆石U-Pb年龄将西岔金银矿的成矿时代限定在～1211Ma。结合前人研究成果,认为西岔金银矿的形成与古太平洋板块俯冲后伸展作用相关。

Geochronology, geochemistry and metallogenic dynamics of gold-polymetallic deposits in Xicha region, the northeastern margin of the North-China Platform

Xicha region is located in the northeastern margin of the North-China Platform. The study area has undergone the formation of the Archean crystalline basement of the North China Plate, the evolution of the Liaoji Ocean in the Proterozoic, the development and evolution of the Paleo-Asian Ocean tectonic domain in the Paleozoic-Mesozoic, and the overlap and transformation of the Paleo-Pacific tectonic domain in the Mesozoic-Cenozoic, which created a complex tectonic framework and also recorded abundant metallogenic information. In order to clarify the age and dynamics background of polymetallic metallogenesis in the study area, we conducted whole-rock geochemistry and zircon LA-ICP-MS U-Pb dating study on the ore-forming geological bodies of different mineralization. The results show that: (1) the zircon age of the Huanchagou Formation granulite with banded base metal mineralization is 2157Ma, and the Huanchagou Formatio is closely related to the intense submarine volcanic eruption caused by the subduction of the Liaoji oceanic crust. The banded mineralized volcanic-sedimentary rocks are formed during the interval of volcanic . (2) Zhengcha pluton, the ore-forming geological body of Zhengcha skarn-type lead-zinc deposit, was formed in the Late Triassic (224.3~218.5Ma) and composed of high-Mg^# diorite and low-Mg^# granite with adakite properties, which is the product of the thickened lower crust delamination caused by the closure and continuous collision orogeny of the Paleo-Asian Ocean, suggesting that the starting time of lithosphere thinning and destruction of craton in the northern margin of North-China Platform may be in Late Triassic. (3) The Xicha syenite porphyry is the metallogenic geological body of Xicha gold-silver deposit, and the zircon U-Pb age of which limits the metallogenic age to ~121.1Ma. And combined with previous study results, we believe that its formation is related to the extension after subduction of the Paleo-Pacific plate.