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文章选取8件闪锌矿、3件方铅矿和1件黄铁矿样品,采用Rb-Sr等时线定年方法测定天堂铜铅锌多金属矿床的成矿时代。获得闪锌矿等时线年龄为(98.1±1.6)Ma,闪锌矿+方铅矿等时线年龄为(99±2)Ma,闪锌矿+方铅矿+黄铁矿等时线年龄为(98.2±1.3)Ma,闪锌矿+黄铁矿等时线年龄为(97.87±0.96)Ma,方铅矿+黄铁矿等时线年龄为(98.6±4.2)Ma。Rb-Sr定年结果表明,天堂铜铅锌多金属矿床的成矿时代为98Ma左右,矿床形成于晚白垩世早期,可能与135Ma之后太平洋板块的运动方向发生转向,使得中国大陆包括华南板块在内均处于持续伸展阶段有关。硫化物矿石Rb-Sr所得的Sr同位素初始比(87Sr/86Sr)i平均值为0.7117,小于陆源硅酸盐的值(0.720),高于地幔Sr的初始值0.707,结合笔者对该矿床所做的S、Pb等同位素组成特征研究,显示成矿物质来源于壳幔混合。研究表明,利用特定矿床的主要矿石矿物,采用Rb-Sr等时线定年方法通过共生矿物组合和单矿物相互约束,可以有效地确定成矿时代,这对了解矿床的成矿背景等具有一定的指示意义。
In this paper, 8 samples of sphalerite, 3 galena and 1 pyrite were selected and the metallogenic epoch of the Tiantuo Cu-Pb-Zn polymetallic deposit was determined by the Rb-Sr isochron method. The isochron age of sphalerite was (98.1 ± 1.6) Ma, the isochron age of sphalerite + galena was (99 ± 2) Ma, the isochron age of sphalerite + galena + pyrite (98.2 ± 1.3) Ma, the isochron age of sphalerite + pyrite is (97.87 ± 0.96) Ma, and the isochron age of galena + pyrite is (98.6 ± 4.2) Ma. The results of Rb-Sr dating show that the mineralization age of the Tiantuo Cu-Pb-Zn polymetallic deposit is about 98Ma. The deposit formed in the early Late Cretaceous and may turn with the direction of the Pacific plate movement after 135Ma, making the mainland China including the South China Plate Are in the stage of sustained expansion related. The average Sr isotope ratio (87Sr / 86Sr) i obtained from sulphide ore Rb-Sr is 0.7117, less than the value of terrestrial silicate (0.720), which is higher than the initial value of mantle Sr of 0.707. S, Pb and other isotopic composition characteristics of studies show that ore-forming materials derived from the crust and mantle mixing. The results show that the ore-forming age can be effectively determined by using the Rb-Sr isochron-dating method by using the main ore minerals in a particular deposit and by the mutual restraint of the intergrowth mineral assemblages and the single minerals. This is of great significance for understanding the metallogenic background of the ore deposit, Indicate the meaning.