Geology and geochronology of the Shijia gold deposit, Jiaodong Peninsula, China

Abstract

The Shijia gold deposit, classified as a Linglong-type (quartz vein-type) gold deposit, is located in the north of Qixia-Penglai gold belt in the Jiaodong Peninsula. The orebodies predominantly occurring as quartz-sulfide veins are hosted in the Early Cretaceous Guojialing amphibole-bearing monzogranite and strictly controlled by NNE- to NE-striking high-angle faults. Hydrothermal minerals include K-feldspar, quartz, sericite, pyrite, sphalerite, galena, chalcopyrite, calcite and fluorite. Based on the mineralogical, textural and field cross-cutting relationships, the mineralization process can be divided into three stages: (I) quartz-sericite-pyrite stage, (Ⅱ) quartz-sulfide-gold stage and (III) quartz-calcite-fluorite stage. Field investigation shows that the orebodies have undergone several times of deformation after their formation, resulting in the deformation and discontinuity of the orebodies. Early Cretaceous dykes, including granite pegmatite, lamprophyre, diabase and granite porphyry, are developed in the Shijia gold deposit. The crosscutting relationship between orebodies and various mafic-felsic dykes shows that their formation sequence is granite pegmatite, Au orebody, lamprophyre, diabase and granite porphyry. LA-ICP-MS zircon U-Pb dating shows that the emplacement ages of granite pegmatite, lamprophyre, diabase, and granite porphyry are 129.7 ± 1.6 Ma, 129.3 ± 1.4 Ma, 128.3 ± 1.3 Ma and 120.0 ± 1.1 Ma, respectively. These dating results are consistent with the crosscutting phenomenon observed in the field, indicating that the mineralization time of the Shijia gold deposit is between 129.7 Ma and 129.3 Ma. The timing of gold mineralization at Shijia coincides with the large-scale thinning of the lithosphere in the North China Craton during the Early Cretaceous, indicating that the formation of the deposit is mainly controlled by extensional tectonics. Because the gold mineralization was predated the emplacement of lamprophyre and diabase dykes, there might be not a direct genetic relationship between the gold mineralization and the mafic dykes in the Shijia gold deposit.