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采用Rb-Sr方法,测定沙溪斑岩铜(金)矿成矿岩体年龄为143.37±5.17 Ma;采用~(40)Ar/~(39)Ar快中子活化定年法,测定沙溪斑岩铜(金)矿成矿年龄为123.6±0.7 Ma,成矿岩体从固结成岩到成矿经历了20 Ma。根据Rb-Sr和K-Ar同位素体系封闭温度的不同,估算出沙溪岩浆热液成矿系统热衰减速率平均为20℃/Ma。单一的由成矿小岩体所提供的热能难以维持如此长时间热液成矿活动,矿区晚期的岩浆活动是沙溪斑岩铜矿成矿的重要能量来源,这是斑岩铜矿成矿岩体多属于多阶段侵入的复式岩体的原因。斑岩铜矿成矿系统能量耗散分析显示,斑岩铜矿成矿过程中有效能量耗散效率极低,如果没有巨大的能量来源维持长时间的热液活动,斑岩铜矿难以形成。
The Rb-Sr method was used to determine the age of the ore-forming porphyry of the Shaxi porphyry copper (gold) ore deposit, which was 143.37 ± 5.17 Ma. The fasting neutron dating of ~ (40) Ar / ~ (39) The mineralization age of the rock copper (gold) deposit is 123.6 ± 0.7 Ma, and the ore-forming rock mass undergoes 20 Ma from consolidation diagenesis to mineralization. According to the different sealing temperatures of Rb-Sr and K-Ar isotope systems, the thermal decay rate of Shaxi hydrothermal mineralization system is estimated to be 20 ℃ / Ma on average. The single thermal energy provided by the ore-forming small rock mass is difficult to sustain the hydrothermal mineralization activity for a long time. The late magmatic activity of the mine area is an important energy source for the mineralization of the Shaxi porphyry copper deposit. This is the mineralization of porphyry copper deposits The rock mass belongs to the multi-stage intrusion multi-rock mass reason. The energy dissipation analysis of the porphyry copper deposit metallogenic system shows that the effective energy dissipation efficiency of the porphyry copper deposit is very low. If there is no huge energy source to maintain the hydrothermal activity for a long time, the porphyry copper deposit is difficult to form.