LITHOSPHERIC STRUCTURE AND DEEP-SEATED MINERALIZATION IN JIAODONG GOLD DEPOSIT CONCENTRATION REGION, SHANDONG, CHINA
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摘要: 利用胶东及其邻区1∶2 0万重力异常和1∶10万航磁异常探测资料, 结合地震各向异性研究成果, 解析其三维岩石圈结构.在此基础上, 综合深部结构和矿床地质特征, 探讨深部作用与成矿动力学, 深化矿床成因认识, 为科学找矿提供决策依据.研究表明, 壳幔结构的不均一性制约着成矿系统物质和能量的交换, 反映在其结构、构造和演化等多个方面.矿集区为地幔隆起带的坳陷区, 幔坳与幔隆接触部位成矿强度大, 幔隆区的局部隆起部位成矿强度小; 金矿床主要分布于花岗岩变薄部位与变质岩的接触带上; 印支中晚期郯庐断裂带深切上地幔, 通过壳-幔相互作用, 将含矿流体系统输运到更高的层位, 发生蚀变、矿化作用.艾山岩体所处构造部位的特殊性, 反映了它可能是壳幔岩浆对流侵位中心.Abstract: The information of geophysical field was, based on the results of 1∶1 000 00 aeromagnetic anomaly and 1∶2 000 00 Bouguer gravity anomaly in Jiaodong and its neighboring regions, Shandong, China, divided into two parts: deep-and shallow focus-field. The information of the two different fields was then combined with these of wave velocity anisotropy and deep-seated geology. The integrated result was adapted to the analysis of the three-dimension structure, the probe into deep seated mineralization and the dynamics of ore-forming system. This research indicated that the interaction and conversion of materials and energy in the ore-forming system were restricted by the heterogeneity of lithospheric structure, resulting in effects in different aspects, such as texture, tectonics and evolution. The occurrences and processes of deposit concentration region in Jiaodong were basically controlled by the transformation of tectonic regimes. The deposit concentration region is located in the down-warping area of the mantle upwelling zone, but gold deposits are located in gradient-variation and deformation places of Mohole. The major mineralization intensity is located at the junction between down-warping and upward region, while the minor one is located in the upward district of the upward region. The down-warping area of the mantle is related to the tectonic regime of compression, but the local deformation following the down-warping is connected with the tectonic regime of extension. The gold deposits, controlled by large deep seated faults and shear belts, are mainly distributed near the gradient belts of gravity anomaly and the brink of sub aeromagnetic anomaly regions, the junction between thinning positions of granites and metamorphic rocks. The Tancheng-Lujiang fault is a mature lithosphere fault of deep mantle cut, and also a fluid bearing mantle shear zone. Because of long term reduction of lithospheric thickness, the asthenosphere enriched with fluid components and metallogenic elements, occurred under the Tancheng-Lujiang fault where occurred the coupling of fluid-heat-chemistry-physics. The shear anatexis of the fault was responsible for the lithogenesis and mineralization, and also for the ore forming reactivation and migration. The mantle ore-fluid system was migrated to the upper horizon through this solution divergence and migration along the Tancheng-Lujiang fault in the middle-late Indo-Chinese epoch when the alteration and mineralization took place. The uniqueness of the tectonic position of the Aishan pluton shows that the Aishan pluton might be the center of the convection and intrusion displacement of the crustal mantle magma.
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图 1 胶东地区构造分区与变质岩相分布
据1∶20万山东省变质图和地质图及本次资料编制.Ⅰ.胶北地块; Ⅰ1.胶西北隆起; Ⅰ2.胶莱坳陷; Ⅱ.胶南地块; Ⅲ.牟平-即墨构造混杂带; 1.中生界; 2.蓬莱群; 3.粉子山群; 4.荆山群; 5.胶东群; 6.花岗质杂岩; 7.榴辉岩相; 8.角闪麻粒岩相; 9.高角闪岩相; 10.低角闪岩相; 11.低角闪岩相及高绿片岩相; 12.低绿片岩相; 13.剪切带; 14.构造单元界线
Fig. 1. Distribution of lithofacies and structural regions in Jiaodong area, Shandong Province
图 2 胶东及邻区布格重力异常(据1∶20万山东省胶东地区布格重力Δg等值线平面图①编制)
a.布格重力异常, 等值线间距5×10-5 m/s2; b.剩余重力异常, 等值线间距5×10-5 m/s2
Fig. 2. Bouguer gravity anomaly in Jiaodong and neighboring region, Shandong Province
图 3 胶东及邻区航磁异常(据1：10万山东中郎及东部航空盛判△T平面刹面图①编制)
a.探部磁异常.等值线问距20 nT; b.找部磁异常, 等值线间距50nT; .金“床(点)
Fig. 3. Aronmagnetic anmly ia Jaodog and nigboring rgion, Shandong Povine
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