Application of Orthogonal Functions Fitting to the Exploration of Massive Sulfide Deposits in Ashele,Xinjiang
运用正交函数拟合预测新疆阿舍勒地区块状硫化物矿床

The large copper-rich deposit in exploring in Ashele,Xinjiang,is a typical vulcanogenic massivesulfide deposit.Thick, large and lenticular orebodics exhibit the stratabound character,and there isappreciable difference in density between orebodies and country rocks.Ground geophysical methods,mainly the gravity method,have been proved to be the most effective methods for the reconnaissanceof hidden massive sulfide deposits,But the Ashele ore district is characterized by complex geologicalstructures. As the gravity effects due to gravitational bodies at different depths and with different den-sities overlaps each other,the gravity anomalies produced by orebodies,particularly by the deep-scatedones, are usually masked.In order to solve the knotty problem,the proper orthogonal functions fitted to the Bougueranomaly can be selected in the ore district,so as to separate the local gravity anomalies due to the orehorizons from the measured anomalies.On that basis,we outlined successfully a tectono-metallogenicbelt,unveiled the structures in the ore district,delineated eleven local gravity anomalies,and chartedthe interested area in ore prospecting.The average densities of the rocks and the ores from table lshows that the minimum density of the ores is higher than the maximum one of the country rocks inthe ore district.Therefore, it may be considered that"wherever there are ores in a area,there isbound to be manifestation of gravity anomaly there",and the gravity data processing by means of themethod can be used in ore prospecting dircctly in such ore districts as Asheic.