四川里庄稀土矿床岩浆碳酸岩的地球化学  

Geochemistry of Carbonatites in the Lizhuang REE Deposit, Sichuan Province

作　　者：田世洪[1,2] 张桂兰[3] 侯增谦[1,2] 丁悌平[1,2] 邹天人[1] 袁忠信[1] 白鸽[1] 谢玉玲[4] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]国土资源部同位素地质重点实验室,北京100037 [3]内蒙古自治区国土资源信息院,内蒙古呼和浩特010020 [4]北京科技大学土木与环境工程学院,北京100083

出　　处：《地球学报》2005年第B09期151-155,共5页Acta Geoscientica Sinica

基　　金：本文得到国家重点基础研究发展规划项目（编号：2002CG412610和G1999043211）和国家杰出青年基金项目（编号：40425014）联合资助.

摘　　要：里庄稀土矿床位于四川冕宁县西南方向49km，为侵位于碱性杂岩体申的碳酸岩脉状矿床。本文从稀土元素地球化学和同位素地球化学的角度探讨了碳酸岩与地幔过程之间的关系。研究表明，碳酸岩的∑REE为（9236．2-5943．6）×10^-6，为LREE富集型，与典型岩浆碳酸岩特征相似；碳酸岩的C、O同位素组成非常稳定，其δ^13Cv-PDB和δ^18Ov-SMOW分别为-3．9‰～-5．3‰和8．7‰～11．9‰，均落在“原生碳酸岩”的C、O同位素组成范围之内；碳酸岩的Pb、Sr同位素组成比较均一，其^87Sr／^86Sr、^206Pb／^206Pb、^207Pb／^2004Pb、^208Pb／^204Pb分别为0．706305～0．706997、18．197～18．220、15．601～15．604、38．401-38．434，与EMⅠ型地幔源区的同位素组成基本一致。所有这些特征均表明岩石来自交代富集地幔源区。The Lizhuang REE deposit, located about 49 km southwest of Mianning County, Sichuan Province, is a carbonatite veintype deposit hosted in alkali complex rocks. In order to find out the relationship between the carbonatites and the mantle processes, the authors made a systematic study of REE geochemistry and C, O, Sr, and Pb isotopes. The ∑REE contents of carbonatites range from 8 393 × 10^-6 to 8 402 × 10^-6, with smooth right-dipping distribution patterns that are similar to those of the well-established magmatic carbonatite. The C and O isotopic compositions of the calcite samples from the carbonatite stocks in the Lizhuang REE deposit vary in a very limited range, with the δ^13 Cv-PDB and δ^18Ov-SMOW values varying in the range of - 3.9‰- - 5. 3‰ and 8.7‰ - 11. 9‰, respectively. They are fallen into the range of the “primary igneous carbonatites”. The Sr and Pb isotopic compositions of the calcite samples from the carbonatite in the Lizhuang REE deposit are relatively constant, with the ^87Sr/^86Sr, ^206Pb/^204Pb, ^207Pb/ ^204Pb and ^208Pb/^204Pb values varying in the range of 0. 706305 ± 0. 706997, 18. 197-18. 220, 15. 601 - 15. 604, and 38. 401 - 38. 434, respectively. The similarity of Sr and Pb isotopic compositions of the carbonatite with those of EM Ⅰ suggests an enriched mantle source for the mineralization of rare earth elements. All of these data suggest that the rocks were derived from the metasomatic enriched mantle.

关 键 词：岩浆碳酸岩 稀土元素 同位素地球化学 EMⅠ 四川里庄稀土矿床 碳酸岩 稀土矿床 岩浆 四川 稀土元素地球化学 

分 类 号：P597[天文地球—地球化学] P588.245[天文地球—地质学]