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基于海南地块各类型岩石的 63个样品Nd和Pb同位素分析数据 ,研究了海南地块元古宙地壳变质基底的时代、特征和演化。研究结果表明 ,海南岛元古宙变质基底成熟度低 ,基底变质岩系的母岩物质来源于长期亏损的地幔源区 ,主要形成时代为古元古宙晚期—新元古宙 ;不同时代花岗岩具有较高的εNd(t)值和较低的Nd模式年龄 ,主要形成于幔源物质参与下的或含地幔成分较多的初生地壳再循环。地壳增生具幕式增生的特点 ,并在 2 .0Ga、1.7Ga、1.2Ga出现高峰 ;Pb同位素组成既不同于扬子地块又不同于华夏地块 ,介于两地块之间 ,和Nd同位素特征具有一致或耦合关系。结合海南岛地质特征 ,初步认为不能单纯地将海南岛基底理解为华南地块统一南延部分或是华夏古陆的部分 ,可能为不同的构造块体。
Based on the Nd and Pb isotope data of 63 samples from various types of rocks in Hainan block, the epoch, metamorphism and evolution of Proterozoic crustal metamorphism in Hainan block are studied. The results show that the metamorphic basement of the Proterozoic in Hainan Island is low in maturity. The parent rocks of the basement metamorphic rocks are derived from long-term depleted mantle source areas. The main forming age is the late Paleoproterozoic-Neoproterozoic granite The higher εNd (t) value and lower age of Nd model are mainly formed by primary crustal reclamation with the participation of mantle source materials or with more mantle components. Crustal hyperplasia with episodic hyperplasia and peaked at 2.0Ga, 1.7Ga and 1.2Ga. The Pb isotopic composition is different from that of the Yangtze block and the Huaxia block, between the two blocks, and that of Nd isotopes Features are consistent or coupled. Based on the geological characteristics of Hainan Island, it is preliminarily believed that the basement of Hainan Island can not be interpreted simply as a part of South China block unified southern part or Huaxia ancient continent, which may be different tectonic blocks.