山西省刁泉银铜矿床地质特征及成因机制

GEOLOGICAL CHARACTERISTICS AND GENETICMECHANISM OF THE DIAOQUAN SILVER COPPER DEPOSIT,SHANXI PROVINCE

刁泉大型银铜矿床产于由黑云母石英二长岩、花岗斑岩、石英斑岩等组成的复式岩体的夕卡岩带中，矿化呈环带状展布。矿体严格受火山口构造控制。由银铜矿的地质特征、矿物组成、微量元素、稳定同位素、包裹体地球化学特征等研究表明刁泉银铜矿是与次火山岩体有关的夕卡岩型银铜矿床。

The Diaoquan silver copper deposit,a large sized deposit recently discovered in northeastern Shanxi,occurs in the skarn zone around a neck facies complex rock body.Orebodies in zonal distribution are strictly controlled by crater structure.Composed of quartz porphyry,granite porphyry,biotite quartz monzonite and gabbro,the complex rock body intruded into Middle and Upper Cambrian and Lower and Middle Ordovician carbonate strata which contain relatively high minor elements such as Ag,Au,Pb and Zn.The Cu,Ag,Au,Pb,Zn,As and Mo contents of granite porphyry and quartz porphyry are 4～9 times higher than their Vinogradov's values in acid rocks,and their whole rock Rb Sr isotopic isochron age is 130 9×10 6,indicating products of Yanshanian period.The initial ratio of strontium isotopes( 87 Sr/ 86 Sr) 0 is 0 7061,suggesting that the rock body is of mixed crust mantle type.The lead isotopic characteristics of rocks give the same conclusion. The orebodies have complicated mineral composition,with 47 metallic minerals already observed.The formation of minerals might be divided into two metallogenic periods and four ore forming stages.Sulfur isotopic composition( δ 34 S) of minerals is between 0 5‰ and 5 7‰,showing hydrothermal characteristics of magma.The lead isotopic composition of Diaoquan ores and the characteritic values of the source area are similar to those of biotite quartz monzonite and granite porphyry.δ 18 O H 2O of ore forming fluids is 3 66‰,and δ D is -91‰,exhibiting characteritstics of initial magmatic water.Meteoric water entered the ore forming fluids at the late ore forming stage.When the ore fomring temperature of fluids was 120～400℃ and 120～220℃,the salinity of fluids was 3 5%￣3 8%NaCl;when the ore forming temperature was 325￣400℃,the salinity of fluids was 40%￣ 46%NaCl.The Diaoquan silver copper deposit was a skarn type silver copper deposit related to the subvolcanic rock body.Copper and gold mineralization took place relatively early,but the principal ore forming process occurred somewhat later and was related to volcanic epithermal mesothermal solution.