江西城门山铜矿铼-锇同位素年龄研究

Re Os ISOTOPIC AGE STUDY OF THE CHENGMENSHAN COPPER DEPOSIT,JIANGXI PROVINCE

城门山铜矿中，侵入到花岗闪长岩中的石英斑岩，其Ｒｅ－Ｏｓ法同位素测年结果为１４０×１０６ａ，进而确定了该区二次岩浆侵入活动时间相隔约１０×１０６ａ，在这期间内，岩浆由中酸性演变为酸性；与其相应的成矿作用则从夕卡岩型铜、硫矿化演变为细脉浸染型铜、金矿化，构成了一个演化序列。在细脉浸染型辉钼矿化作用中，石英细脉中辉钼矿比石英斑岩中浸染状辉钼矿形成略早，二者在空间上呈正消长，而整个成矿过程大约经历了４×１０６～３×１０６ａ。

There are two stages of magmatic intrusion in the Chengmenshan copper ore district, namely the early stage granodiorite prophyry and the late stage quartz porphyry. The age of the former porphyry is 150×10 6 a, and the Re Os isochron age of the latter porphyry determined by the authors is 140×10 6 a, suggesting that the interval between these two stages of magmatic activity is some 10×10 6 a. During this period, magmatic activity evolved from intermediate acid to acid, whereas the ore forming process developed from skarn type copper sulfur mineralization to veinlet disseminated molybdenum gold mineralization, constituting a metallogenic evolutionary series. In the process of the veinlet disseminated mineralization, molybdenite was produced in two forms:one was veinlet or stockwork molybdenite with Re Os isochron age 3(141±3)×10 6 a, the other was in dissemination form with Re Os isochron age (137±3)×10 6 a. It is obvious that the veinlet or stockwork molybdenite was formed earlier than the disseminated molybdenite, and that the whole ore forming process of molybdenite spanned a period of 4×10 6 a～3×10 6 a.