GEOCHEMISTRY AND ITS GEOLOGICAL IMPLICATION OF THE PERMIAN GRANITE IN NUOMIN, DAXINGANLING REGION
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摘要: 大兴安岭诺敏地区大地构造位置位于兴蒙造山带的东段.该区发育大量的二叠纪花岗岩类岩石，岩性主要为二长花岗岩、钾长花岗岩.岩石地球化学分析结果表明，该区岩体具有高硅，略富铝，偏碱，低镁、钠，贫钙的特征.微量元素表现出富集Rb、Th、K、Nd、Cs和亏损U、Nb、Sr、P、Ti等特点；稀土元素具有明显的轻稀土元素富集、重稀土元素亏损和明显的负Eu异常特征.轻重稀土元素分馏程度较强.岩石总体上属于高钾钙碱性系列花岗岩.地球化学特征表明其应为S型花岗岩，可能为同源的地壳物质的部分熔融作用所形成，源岩可能为变杂砂岩和变中性火山岩.根据R1-R2与Rb-（Yb+Nb）、Rb-（Yb+Ta）等微量元素判别图解，结合该区所处的构造环境推测，该区花岗岩应形成于兴安地块与松嫩地块碰撞造山过程的后碰撞阶段.Abstract: The Nuomin area in Daxinganling is tectonically located in the east section of the Xingan-Mongolian orogenic belt, where large volumes of Permian granitic rocks, mainly monzogranite and moyite, are developed. Major element analysis shows high SiO2 and alkali content, slightly high K2O content and low MgO and CaO contents. Trace element study demonstrates the enrichment of Rb, Th, K, Nd and Cs, and depletion of Ba, U, Nb, Sr, P and Ti. The samples are enriched in LREE and depleted in HREE, with apparent negative Eu anomalies, suggesting a high degree of fractionation. The granites generally belong to the high-K calc-alkaline series. Petrogeochemistry shows that the granites are quite similar to S-type granite. They are most likely resulted from the partial melting of homologous crust, probably derived from metamorphic greywacke and intermediate volcanic rocks. According to the discrimination diagrams of R1-R2, Rb-(Yb+ Nb) and Rb-(Yb+Ta), the granites are generated in the stage of post-collision after the collision between Xingan block and Songnen block.
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Key words:
- Nuomin area /
- granite /
- geochemistry /
- crust source /
- Daxinganling
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