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金厂沟梁位于张家口-赤峰-朝阳金矿集区东端,区内发育大量规模不等的脉岩,岩性以闪长岩、闪长玢岩为主.对其进行了锆石U-Pb年龄、主微量元素及Sr-Nd同位素分析.脉岩锆石LA-ICP-MS U-Pb年龄值可分为三组:2458～2524Ma、253±6Ma(MSWD=3.0)及228±1Ma(MSWD=0.26).2.5Ga锆石反映成岩过程中有古老地壳物质参与,253 Ma锆石可能与古亚洲洋闭合时的岩浆事件有关,228 Ma则为脉岩的形成年龄.脉岩Si O2(51.22%～68.48%)、MgO(1.35%～8.13%)含量变化较大,且具有高Na2O+K2O、Al2O3及低的TiO2、P2O5含量等特征.岩石LREE及LILE富集,HFSE亏损.脉岩(87Sr/86Sr)i比值较为一致(0.70495～0.70592),而εNd(t)(-0.2～-9.5)及T2DM(1.02～1.77Ga)值变化范围较大.主微量元素及同位素研究结果表明:部分熔融的岩石圈地幔熔体底侵到壳幔边界,诱发古老地壳物质的部分熔融,随后发生的幔源熔体与壳源熔体的混合是脉岩最可能的源区过程.主微量元素构造判别图解指示岩石形成于陆弧向板内演化的构造环境;结合区域上同时代脉岩群、碱性岩带及A2型花岗岩的侵位,认为晚三叠世华北板块北缘已完成与蒙古弧地体的碰撞并进入造山后伸展阶段.
Located in the east of Zhangjiakou-Chifeng-Chaoyang gold ore district, Jinchang Gully is characterized by a large number of vein rocks ranging in scale from dacite to diorite, and zircon U- Pb ages, major and trace elements and Sr-Nd isotopes.According to LA-ICP-MS U-Pb ages of zircons, the ages can be divided into three groups: 2458-2524Ma, 253 ± 6Ma (MSWD = 3.0) and 228 ± 1Ma MSWD = 0.26) .2.5Ga zircons reflect the involvement of ancient crustal materials during the diagenesis, and the 253 Ma zircons may be related to the magmatic events during the closure of the Paleo-Asian Ocean and 228 Ma is the age of the veins. 51.22% ~ 68.48%), and the contents of MgO (1.35% ~ 8.13%) varied greatly with high contents of Na2O + K2O, Al2O3 and TiO2, P2O5, etc. LREE and LILE were enriched and HFSE was depleted. (87Sr / 86Sr) i is relatively uniform (0.70495 ~ 0.70592), while εNd (t) (-0.2 ~ -9.5) and T2DM (1.02 ~ 1.77Ga) have a wide range of variation.The main and trace elements and isotope studies show that: The melting of the partially melted lithospheric mantle melts to the crust and mantle boundary, inducing the partial melting of the ancient crustal material, and the consequent mantle-derived melt and shell-derived melt are the most likely source zone processes. The trace element tectonic discrimination diagram indicates that the rock was formed in the tectonic environment evolving from the arc to the plate. Combining with the emplacement of the same age group of melanges, alkaline rocks and A2-type granites in the area, it is considered that the northern margin of the North Triassic in the Late Triassic Complete the collision with the Mongolian arc and enter the post-orogenic extension.