摘要
通过钐—钕同位素测定,抱板群中的斜长角闪片岩、混合花岗片麻岩及其中的暗色包体等时线年龄分别为1.7Ga、1.4Ga和2.9Ga.用单矿物铅同位素测斜长角闪片岩、混合花岗片麻岩年龄分别为1.1～1.2Ga和940Ma.铷—锶全岩等时线法测得抱板群斜长角闪片岩和石碌群、抱板群中的云母片岩为1.3Ga和1.2Ga。因此,海南岛存在着前寒武纪地层,其中,具有花岗—绿岩且含有玄武质科马提岩组合的抱板群是前寒武纪结晶基底或前地槽构造层.石碌群是地槽早期发展阶段形成的构造亚层。海南岛大地构造演化经历了前地槽(X)、地槽(Ⅰ)、地台(Ⅱ)、地洼(Ⅲ)等多个发展阶段。
In this paper according to the systematic studies of Sm-Nd isochronic lines, the absol ute ages of plagioclase-hornblend and mi gmatic granitic gneiss of the Baoban Group are 1. 7 Ga and 1. 4 Ga respectively , and the absolute age of mianthite occurring in the migmatitic granite is 2. 9 Ga. These ages illustrate that these rocks were formed 1. 4 and 2. 9 Ga ago. Thirdly,the single-stage Pb-model isotopic ages of feldspar selected from the plagioclase-hornblend schist and migmatic granitic gneiss of the Baoban Group are 1.1 to 1. 2 Ga and 940 Ma respectively. Based on the results of the Rb-Sr whole -rock isochronic line, the metamorphic ages of the plagioclase hornblend schist in the Baoban Group and mica schist in the Baoban Group and the Shilu Group are 1. 34 Ga and 1. 22 Ga respectivly.Among the Precambrian strata in Hainan Island, the Bao.ban Group having the characteristics of granite-greenstone and containing basaltic komatiite makes up the Precambrian cristalline basement or the pre-geosynclinal structural layer, and the Shilu Group consisting of turbidite, felsic volcanis and sedimentary rocks and a Fe-bearing formation is a structural sublayer formed during the early stage of geosynclinal development.The evidence and characteristics ogeotectonisc evoluting of Hainan Island has undergone four stages, that is , pre-geosynclinal, geosynclinal, platform, diwa.
关键词
前寒武纪
大地构造
地层
Precambrian, pre-geosyncline tectonic strata, Geotectonic evolution Hainan Island
