Metallogenic Prediction And Prospective Direction Of Gangcha-Kemo Gold Deposit In Hezuo,Gansu Province

Western Qinling is a main gold metallogenic belt in northwest China,with variety types of mineral deposit and remarkable mining potential.Gangcha gold deposit,Gansu is located in the Western Qinling orogenic belt.It has characteristics of epithermal deposit,and shows geological characteristics that lead to existence of cryptoexplosive breccia deposit and porphyry deposit in deep.The exploration work indicates that the Gangcha gold deposit has a medium scale of reserves.Kemo area in the southern part of the Gangcha gold deposit also shows favorable metallogenic conditions,and has a potential of further expanding the reserves.Therefore this article studies Gangcha-Kemo area for metallogenic prediction,and tries to support the evaluation of ore district potential by geochemical and geophysical survey.Geochemical survey is an effective measure for mineral exploration.The elements association of secondary halo and primary halo have been measured and analyzed by using handheld rapid element analyzer(XRF).The result shows strong elements association anomalies of Au-Ag-As-Sb-Pb-Zn occured in an area surrounded by the NNE trended Xiajiamen gully,the NEE trended Gchangcha River and the huge NW trended fault.It is suggested that this triangle region in the south Gangcha gold deposit is a favorable location for gold mineralization and one of the target areas for further exploration.In addition,according to the regular pattern of spatial distribution of the mineral veins and faulted structures in the Gangcha gold field,most of the mineral veins are obviously controlled by the north-south trending faulted structures.Faulted structures can create migration pathways for ore fluid,and become favorable space for ore accumulation.Thus it is of great importance to research attitudes and space distribution of the faulted structures.Faults to which the Gangcha Au-1,Au-2 and Au-3 gold mineral veins belong are traced by Controlled Source Audio Magnetotellurics(CSAMT).It is now confirmed that the faults extended southward into the triangle region,where great geochemical anomalies of Au-Ag-As-Sb-Pb-Zn occurred,that mentioned above,and connected with the concentrated faults in the triangle region.This indicates that the ore-controlling fault system of the Gangcha gold field has extended to the triangle region in the south.In order to verify the mineral-bearing potentiality of extended fault system in triangle region,induced polarization intermediate gradient method of geophysics survey is performed in Gangcha gold deposit and its southern-extended district.The result shows there are low resistivity and high polarizability characteristics in the shallow part of north Gangcha deposit and the deep part of south Gangcha deposit.It is suggested that the mineral-bearing potentiality of north-south trending faulted structure has a lateral prostration to the south.To sum up,there can be a favorable ore area in the south of Gangcha gold deposit.This provided a new evidence for deep prospecting.In conclusion,there can be a hydrothermal activity center in the triangle region which surrounded by Gchangcha River,Xiajiamen gully and the northwest trended huge fault.This triangle region has a great potential of mineralization,and deep ore exploration should be carried out in this region.