四川大陆槽稀土矿床碳酸岩-英碱正长岩锆石U-Pb年代学和Hf同位素性质及其地质意义  

Zircon U-Pb ages, Hf isotopic compositions and geological significance:A case study of carbonatite and nordmarkite from the Dalucao REE deposit,Sichuan province.

作　　者：田世洪[1,2] 侯增谦[3] 杨竹森[1] 杨志明[3] 袁忠信[1] 王彦斌[3,4] 谢玉玲[5] 刘英超[1] 李政[5] 

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]中国地质科学院地质研究所,北京100037 [4]北京离子探针中心,北京100037 [5]北京科技大学土木与环境工程学院,北京100083

出　　处：《岩石学报》2008年第3期544-554,共11页Acta Petrologica Sinica

基　　金：国家杰出青年基金(编号:40425014);国家自然科学青年基金(编号:40603012);国家重点基础研究发展规划项目(编号:2002CG412610);中央级公益性科研院所基本科研业务费专项资金(编号:K0802);南京大学内生金属矿床成矿机制研究国家重点实验室资金(编号:13-7-5);国家自然科学面上基金(编号:40573035);中国地质科学院重点开放实验室专项资金(编号:KL05-9)联合资助.

摘　　要：川西冕宁-德昌稀土成矿带是中国最重要的稀土成矿带之一,所有稀土矿床均与碳酸岩-正长岩杂岩体有关。前人研究表明,牦牛坪、木落寨和里庄碳酸岩-碱性杂岩体成岩年龄与其相应矿床的成矿年龄基本一致,而大陆槽正长岩年龄与REE 矿床的成矿年龄相差甚远。本文对大陆槽碳酸岩、英碱正长岩进行了 SHRIMP U-Pb 锆石年代学和 LA-MC-ICPMS 锆石Hf 同位索原位测量,它们的形成年龄分别为12.99±0.94Ma、14.53±0.31Ma,表明两者是同时形成的,且与其成矿年龄基本一致。碳酸岩和正长岩的ε_(Hf)(t)值、Hf 模式年龄与它们的ε_(Nd)(t)值、Nd 模式年龄所展现出来的特征一致,说明在其形成过程中有地壳物质的加入。The Mianning-Dechang REE belt in western Sichuan, SW China is one of the most significant REE belt in China. The REE mineralization is associated with the carbonatite-alkalic complexes. The formers＇ results indicate that diagenetic ages of carbonatite-alkalic complex from Maoniuping, Muluozhai and Lizhuang are consistent with their corresponding metallogenic ages, while the age of syenite from Dalucao is markedly different from its metallogenic ages. In this work, we present SHRIMP U-Pb zircon dating and LA-MC-ICPMS zircon in-situ Hf isotopes for the carbonatite and nordmarkite from Dalucao. The ages for carbonatite and nordmarkite are 12.99 ±0. 94Ma, 14. 53 ±0. 31Ma, respectively. These dating results suggest that they formed at the same time and corresponded with their metallogenic ages. Coupling with zircon Hf isotopes and published Nd isotopes data of carbonatite and nordmarkite imply that they underwent contamination by crustal materials during their formation.

关 键 词：SHRIMP U-Pb锆石定年 LA-MC-ICPMS锆石Hf同位素 碳酸岩-英碱正长岩 四川 大陆槽稀土矿床 

分 类 号：P597.3[天文地球—地球化学] P588.15[天文地球—地质学]