Geological Characteristics And Prospecting Prediction Of Lengshuigou Porphyry Copper-molybdenum Deposit In The Zhashui-shanyang Ore Concentration Area

The Yanshanian intermediate-acid small intrusive bodies are exposed widely in Zhashui-Shanyang ore concentration area. Most of those granite bodies are surrounded by porphyry-skarn Cu-Mo mineralization, such as Chigou porphyry Cu-Mo deposit, Xiaohekou sharn Cu deposit and Lengshuigou porphyry-skarn Cu-Mo deposit et al. In recent years, most of research about the geology and mineral resources of ore concentration are the division of strata and tectonic environment, geochemistry and isotopic characteristics, formation ages and resource of magma et al, few of further study about typical ore deposits or points. The Lengshuigou porphyry Cu-Mo deposit is selected to be systematic studied in this thesis. Basic on the field geology investigation, microscopic identification, geochemical analysis, Nd-Sr isotopic analysis and ore-forming fluid observation, analysis et al.There are poiphyry Cu,Mo(at Dongzigou and Kongqueya area), skarn Cu(at Shuanglongzhai and Yingdongya area) and structural altered rock-host Au,Ag(at Nangou and Xujiawan area) from ceter to periphery of the porphyry granite, constitute a complete porphyry metallogenic system.The geochemistry of porphyry granite shows high-K calc-alkaline ~ shoshonite series and I type or I→A transitional type. It has the feature of crust-mantle mixed, and similar to the typical porphyry metallogenic.The alterations of Lengshuigou porphyry body and wall rock are stronger, good space zonality, but unconspicuous symemetry. The alteration typies from middle to periphery are potassic, sericite-quartz, skarnized and hornfels. According to veins, metallogenic periods can be divided into four stages. They are magnetitie phase, early hydrothermal phase, medium hydrothermal phase and late hydrothermal phase. Cu and Mo occur at the early and middle of hydrothermal period.Study on fluid inclusions shows two typies of porphyry and skarn type Cu-Mo deposit. Masses of aqueous inclusions are gas-liquid two phase and few NaCl-bearing daughter crystal inclusions. The ore-forming fluid inclusions belong to mesothermal and moderate salinity. The fluid are boiling during ore-froming. H-O-S isotope compositions show that ore-forming fluids of porphyry Cu-Mo were mainly derived from magmatic water, involved a little meteoric water, and ore-forming materal was mainly originated from mantle.The tectonic setting of porphyry belongs to local stretch of extrusion background at Yanshanian,based on characteristics of porphyry bodies’ geochemistry and Nd-Sr isotope. Its original is crust-mantle mixing, and also experienced partial melting, slight assimilation contamination and crystallization.Based on comprehensive mineralization characteristcs, fluid inclusion, metallogenic physicochemical conditions and minerogenetic mechanism, then we creat a probably model of Lengshuigou Cu,Mo deposit and summarize the indicators for prospecting. Small porphyry bodies, intersection part of faults, alterationon strong area and Cu-Mo-Au-Ag-As anomaly combination area are the important indicator for prospecting. Based on the study of Lengshuigou Cu-Mo deposit, and combining geology, geochemisty, geophysic and remote data of this area, the key prospecting of Lengshuigou is Yindongya area where Cu-Mo anomaly and IP anomaly combination is well, and Dongzigou area where Cu-Mo anomaly is well and scope of alteration is large.