The Regularitis Of The Mineralization Enrichment And Ore Prediction Of The Xiaoshuijing Gold Deposit In Middle Yunnan

Based on the studies of geological setting , ore-controlling geological structures, geological characteristics of ore deposits, geochemical and geophysical anomalies, metallogenic fluid characteristics and contrasted with neighboring gold deposit, the paper summarizes regional metallogenic regulations, mineralization enrichment rules, origin types of ore deposits, a metallogenic model, a prospecting model, regulations of ore prognosis and prospecting criteria . Gold prospective areas at Xiaoshuijing district and outskirt of it have been predicted. The study results provide scientific evidences for arrangement of prospection work.Xiaoshuijing gold deposit is located to the eastern margin of the conjunction of the Yangtze platform and Lanping-Simao fold belt, i.e. the eastern margin of Ailao Mountain metamorphic belt and Honghe shear zone. Regionally, there are four metallogenic stages which resulted in, respectively, early Proterozoic marine volcanic-sedimentary-metamorphic iron-copper deposits, lateritic iron (gold) deposits with their ages ranging from middle Proterozoic to Triassic, hydrothermal vein gold deposits and lead-zinc (silver) deposits controlled by shear zones formed in the period from Yanshanian to early Himalayan, late Himalayan sedimentary sandstone and conglomerate hosted gold deposit overlapped and modified by hydrothermal fluids. The deposits in the area are characterized by the ore deposit assemblage of the four mineralisation styles.The gold deposits in the area are dominated by the structurally controlled ore deposits. The structural systems at different orders respectively control the distribution of regional gold belts, ore fields, ore deposits, ore bodies and ore types. The Xiaoshuijing fault zone (at the third order) controls Xiaoshuijing gold deposit. The suborder fault zones, shear zones, interlayer fractures control distribution of ore bodies. The ore-controlling structures belong to brittle-ductile shear zones. The places where orientation of a fault zone changes or faults crosscut each other or a fault zone gets wide are favorable locations where the thick and lenticular gold ore bodies occurred. Ore bodies often get thin or thin out, or become veins in the places where an ore-controlling fault zone obviously becomes narrow. Gold ore bodies at Xiaoshuijing gold deposit occurred at the levels from 1740m to 2045m. The deposit formed in a ductile-brittle shear zone and resulted from a mixture of mesothermal and epithermal hydrothermal fluids cycling at the shallow parts of the shear zone. The deposit is an altered fault rock type gold deposit. The strata consisting of basement and adjacent source rocks are rich in gold. The tectonic activities forced fluids from the mantle to rise upward, and forced metamorphic hydrothermal fluids, hydrothermal fluids derived from meteoric water and groundwater, and magmatic fluids to pass through the fault zone. The cycling hydrothermal fluids activated gold in the strata along the passage and forced it to migrate. Gold precipitated from the hydrothermal fluids and was enriched in the locations where a fault zone gets wide or the orientation of a fault zone changes from the gentle to the steep.A model of mineralisation controlled by structures at different orders, a model of mineralisation enrichment regulations controlled by structures, a model of shapes and orientations of ore bodies controlled by structures, a model of mineralization and alteration zoning, a model of mineralization controlled jointly by rocks and structures, a dynamic model of mineralization, a comprehensive model of applying geophysical and geochemical techniques to search for mineral resources have been outlined. It is pointed out that the integration of multiple exploration methods involving geological, geochemical and geophysical techniques, and drilling and tunneling is an efficient way to discover and prove the gold deposit of this kind.It is predicated that there is no potentiality for prospecting gold in the northern part of the prospecting line 14 and in the southern part of the prospecting line 93 at Xiaoshuijing gold district. There is a good potentiality for prospecting gold in the zone between the line 14 and the line 93. The prospective zone with its elevation above 1740m is 2 kilometers long and the potential gold resources within the zone can reach more than 10 tones of gold, whereas there is a limited potentiality for prospecting gold beneath the elevation 1740m. It is also predicated that it is sure that new gold deposits can be discovered at Subu adjacent to Xiaoshuijing gold deposit and at the zone between Dakanzi and Guanlanshan in the northern part of Xiaoshuijing gold deposit. These areas are prospective targets for further prospection.