摘要
对天山东段尾亚麻粒岩的稀土元素和Ｓｍ－Ｎｄ同位素特征的研究表明，其原岩为１８－２０亿年地幔分异的产物，为具有岛弧特征的钙碱性岩系，以轻稀土富集为特征。并且讨论了麻粒岩原岩的形成，为交代地幔较大程度部分熔融的产物。岩浆形成和侵位过程中，有地壳物质不同程度的混染。
The isotopic and geochemical characteristics of the Weiya granulites are studied because of the great importance . of those rocks to the models of continental evolution in North Xinjiang. Discriminative diagrams indicate that most analyzed samples have igneous parentage, The igoeous protoliths apparently belong to two series, that is tholeiitic and , calc-alkaline ones, with the latter dominating over the former All REE pattems are significantly fractionated with LREE enrichment Except for one intermediate sample, most analyzed samples show apparently . negative Eu anomaly. The Nd isotopic model ages are used to estimate crust-formation age and thereby to investigate crustal growth. The Nd model ages of the most sarmples ranging from 1.7 to 2.2 Ga indicate that the crust-formation period is mainly at the Proterozoic, which corresponds to the distinct peak from 1.8 to 2.0 Ga on the histogram of Nd model ages of rocks from the Tianshan orogennic belt The Nd(0) values are presentfrom-12.4 to-19.3and the fsm/Nd values from -0.37 to-0.50,probably indicating that the rocks are derived mainly from 'depleted' mantle soruce. With the geochemical . and isotopic constraints, the mafic magma should be derived from 'metasomatic' mantle (about 2.0─ 1 .8Ga) and were contarminated with older crustal rocks (about 2.4 Ga) ,during the primary emplacement
出处
《地球化学》
CAS
CSCD
北大核心
1997年第4期70-77,共8页
Geochimica
基金
国家自然科学基金
关键词
麻粒岩
稀土族
钐
钕
同位素
granulite, rare earth elemen. Sm-Nd, eastem Tian Shan
