汉南杂岩余家山铜镍矿成矿时代与岩浆源区性质研究r——来自锆石U-Pb测年和Lu-Hf同位素的制约

摘要

汉南杂岩余家山铜镍矿位于望江山基性岩体的西南部,地处扬子克拉通北缘西端.矿区内出露的岩体成岩成矿时代和源区性质不明,从而影响了对本矿床成因的认识.本文分析了矿区内出露的典型含矿岩体和围岩的LA-ICP-MS锆石U-Pb年代学和原位Lu-Hf同位素数据,结果表明其成矿时代接近或稍晚于约(791±4)Ma,成岩时代约为(808±7)Ma.且含矿岩体的εHf(t)值在+9.5~+10.9之间,平均值为+10.7,一阶段Hf模式年龄为924~974 Ma;围岩的εHf(t)值在+8.7~+11.1之间,平均值为+9.9,一阶段Hf模式年龄为927~1018 Ma.结合前人研究成果表明,余家山铜镍矿基性岩体由中元古代晚期至新元古代早期亏损地幔物质部分熔融生成,可能形成于活动大陆边缘环境.%The Yujiashan Cu-Ni deposit of Hannan complex is located in the southwest of the Wangjiangshan basic massif, in the west of the northern margin of the Yangtze craton. There is less study on the diagenesis age, mineralization age and the nature of magma source of the outcropped rock mass, which affects the understanding of the deposit genesis. The data of LA-ICP-MS zircon U-Pb dating and in-situ Lu-Hf isotope of the typical outcropped ore-bearing and surrounding rocks were analyzed in the study. The results show that the mineralization age is about or a little late than ( 791 ± 4 ) Ma, and the diagenesis age is about ( 808 ± 6. 8 ) Ma. Furthermore, the in-stiu zircon Hf isotopic analysis indicates that the εHf (t) values of ore-bearing rock range from +9. 5~ +10. 9, with an average value of +10. 7 and Hf model ages ranging from 924 Ma to 974 Ma;theεHf ( t) values of surrounding rock range from +8. 7~ +11. 1 , with an average value of +9. 9 and Hf model ages ranging from 924 Ma~974 Ma. Coupled with the available published data, it is proposed that the basic massif of the Yujiashan Cu-Ni deposit maybe derived from the partial melting of depleted mantle materials of late Middle Proterozoic-Neoproterozoic age in the active continental margins setting.