海南岛前寒武纪花岗岩-绿岩系Sm-Nd同位素年龄及其地质意义

Sm-Nd Ages of the Precambrian Granitic-Greenstone Series in Hainan Island and their Geological Significance

利用Ｓｍ－Ｎｄ同位素法测试了海南岛土外山金矿区花岗－绿岩系的１５个样品，７个为绿岩中的斜长角闪片岩，８个为花岗（质）岩，分别获得了１７００．９±２０Ｍａ和１３７９．７±１７Ｍａ的Ｓｍ－Ｎｄ等时年龄，各自代表了其原岩的成岩时代。同时对花岗（质）岩获得了与１７００．９０１３２２０Ｍａ相当的１６９０～１８００Ｍａ的Ｎｄ模式年龄。对斜长角门片岩则获得２３００～２７００Ｍａ的Ｎｄ模式年龄。这些反映了海南岛于２４００Ｍａ、１７００Ｍａ、１４００Ｍａ左右发生了三次重大构造岩浆热事件。

The protolith age of the metamorphic rock in Hainan Island has never been solved for a long time. Fifteen samples including seven samples of anorthose-diastatite schist and eight samples of Hainan Island are taken to be measured by Sm-Nd radioactive isotope method in this study. Two isochron ages of 1700. 9+20 Ma and 1379. 7+17 Ma have been obtained, respectively. These ages are respectively interprered as the time of the Protolith-formation．Meanwhile granitic roock has got a Nd model age of 1691～1792 Ma which corresponds to 1700. 9+ 20 Ma， and also anorthose-diastatite-schist has obtained a Nd modelage of 2316～2689 Ma．These renflect that three important tectono-magma thermal enents took place at 2400 Ma, 1700Ma and 1400 Ma in Hainan Isiand. These events played an important role for the gold-ore formation in Precambrian granitic-greenstone belt of Hainan Island.