Study On Characteristics Of Structures And Controls On Mineralizationg Of Jinya Gold Deposit, Guangxi

Jinya gold deposit, that is a fine disseminated (Carlin type) gold deposit, is located in the "gold-triangle" area of Yunnan-Guizhou-Guangxi. Its geotectionic position lies in the Youjiang basin of South China fold belt. Due to the insufficient in previous exploration and research, the mined gold resources are not enough at present. And new gold resources have been not discovered. The gold ore prospect in the deep location of this deposit is focused in this paper.Many scholars studied in Jinya gold and put forward different understanding. Based on field geological survey and previus conclusions achieved by fromer scholars, the characteristics of structures and controls on mineralization are studied in this paper. The principal results are summarized as following:(1) Gold mineralization hosted by the silty mudstone of Beifeng group of Middle Triassic with thickness from210m to684m, occurs in the height+850m to+200m above sea level. In present, as the prospecting height just to+528m, there is prospecting space to find other gold ore under+528m in this deposit.(2) The structural features in this district is discovered, Folds are mainly nearly NW Jinya anticline and nearly SN Nayuan anticline. Faults are mainly nearly SN trend F1, F2, F3major faults, nearly SN trend F5, No.l, No.14, No.16secondary faults and bedding sliding fractured zone in the turn end of Nayuan anticline. The gold mineralization is mainly controlled by Nayuan anticline and SN trend faults. The small-scale nearly SN trend secondary faults were grown up from the X-joints. The distribution of ore bodies were controlled by Nayuan anticline. The gold ore bodies occur in the hinge zone and both wings of Nayuan anticline. Ore bodies in the eastern wing manily tend to east, while ore bodies in the western wing manily tend west.(3) According to the stress analysis, the characteristics of structure and fault movement, Jinya anticline was frorned by NW extrusion force (σl=339°∠6°) before mineralization. And the compress-shear activites were caused by the SN major faults. Under the persistent horizontal tensile stress (σ3=94°∠6°) among mineralization, the tenso-shear activites were caused in the SN major fault and secondary faults.(4) compress-twist and expansion-twist activities on the SN trend faults were took place in the early and later mineralization periods, respectively. The mineralization of altered cataclastic rock type gold-Pyrite-arsenopyrite was controlled by the compress-twist structures of early stage. And the mineralization of the gold-bearing quartz veins, calcite veins and calcite-quartz veins was controlled by expansion-twist structures of later stage. Gold mineralization become to rich in tectonic superposition parts of two stages. (5) According to the characteristics of tectonic evolution and mineralization period, a structural ore-controlling model was established in Jinya gold deposit.(6) Based on intersecting lines occurrence of ore-bearing conjugate joints, the distribution pattern of ore body in vertical projection map, the anticline plunging direction, the kinematics characteristics of ore-controlling fracture in the mineralization period, vein orebody trended laterally to the north with the plunge angle is8-31°. Therefore the attention to gold ore prospect should be paid in the northern deep location of the each ore belt of this deposit in the future.