地学前缘 ›› 2012, Vol. 19 ›› Issue (3): 240-251.

• 论文 • 上一篇    下一篇

滇西银厂坪花岗斑岩岩体的地球化学及年代学特征

丁慧霞，侯青叶，曹铁宁，刘东盛，黄丁伶，王新宇，朱洛婷   

  1. 1. 中国地质大学(北京) 地球科学与资源学院， 北京 100083 2. 有色金属矿产地质调查中心 北京矿产地质研究院， 北京 100012 3. 中国地质科学院 地球物理地球化学勘查研究所， 河北 廊坊 065000    
  • 收稿日期:2012-02-20 修回日期:2012-03-28 出版日期:2012-05-25 发布日期:2012-05-25
  • 作者简介:丁慧霞（1987—），女，硕士研究生，地球化学专业，主要从事区域地球化学研究。E-mail：dhx1987105@126.com
  • 基金资助:

    国土资源部行业专项“深部探测技术与实验研究”第四项目第二课题（SinoProbe-04-02)；国土资源部公益性行业科研专项（201011054)；国土资源部公益性行业科研专项经费项目（200911007-3）

Geochronology, geochemistry and geological significance of Yinchangping granite porphyry, Yunnan Province.

  1. 1. School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China 2. Beijing Institute of Geology for Mineral Resources, China Nonferrous Metals Resource Geological Survey, Beijing 100012, China 3. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang 065000, China
  • Received:2012-02-20 Revised:2012-03-28 Online:2012-05-25 Published:2012-05-25

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摘要：

银厂坪花岗斑岩岩体位于扬子陆块的西南缘，处于鲜水河—小江碱性岩带和金沙江—哀牢山富碱斑岩带之间。其主量元素具有高碱，高Na2O/K2O值，低TiO2特征，属于高钾钙碱性系列岩石。微量元素富集LILE，LREE和过渡金属元素(Cu、Ni、Co)，具有明显的“Ta-Nb-Ti"负异常，Eu负异常不明显。锆石LA-ICP-MS U-Pb年龄表明该区岩石的结晶年龄为(37.39±0.33) Ma。εHf(t)值为-1.8~+1.8，两阶段模式年龄为996~1 226 Ma。该区岩石具有较低的εNd(t)值（-7.4~-3.6），较高的(87Sr/86Sr)i比值（0.706 077~0.706 231），以及具有造山带铅特征的207Pb/204Pb值（15.567~15.574）和208Pb/204Pb值（38.321~38.335）。对银厂坪岩体的元素地球化学以及Sr-Nd-Pb-Hf同位素组成特征分析研究认为,研究区的花岗斑岩形成于近似大陆弧环境，同位素地球化学属于EMI-EMII过渡型源区，岩体形成于壳幔混合层。银厂坪岩体的地球化学属性更靠近安宁河碱性岩带，是该带分异末端的酸性端员组分。

关键词: U-Pb年代学, 地球化学, Sr-Nd-Pb同位素, 花岗斑岩, 扬子西南缘

Abstract:

Yinchangping granite porphyry intrusive outcrops around the southwestern segment of the Yangtze block, which is between the Xianshuihe-Xiaojiang alkaline rock zone and Jinshajiang-Ailaoshan alkali-rich porphyry rock zone. The major elements of this area show high alkaline, high ratio of Na2O/K2O and lower TiO2, presenting typical geochemical characteristic of high-K calc-alkaline rocks. Trace elements characteristics include LILE, LREE (with enrichments) and transitional elements (Cu, Ni and Co), as well as significant “Ta-Nb-Ti” negative anomaly and indistinctive Eu anomaly. LA-ICP-S zircon U-b dating shows that the emplacement age of Yinchangping granite porphyry is (37.39±0.33) Ma: εHf(t) value is in the range of  -1.8+1.8 with twostage Hf model age of 9961226 Ma; εNd(t) value is a little low within the range of -7.4-3.6; (87Sr/86Sr)i (0.706077 0.706231) is high; 207Pb/204Pb(15.56715.574) and 208Pb/204Pb(38.32138.335) present a typical characteristic of orogenic zone. All these analyses suggest that Yinchangping granite porphyry intrusion belongs to the Anninghe alkaline rocks zone  which is formed in the environment of near continental arc, where there is not only the geochemical characteristic of EM I-M II type source enrichment in mantle but also the porphyritic magma formed in “crust-antle mixed layer”. Yinchangping granite porphyry is the acid component at the end of fractional crystallization in Anninghe alkaline rock zone.

Key words:  zircon U-Pb ages, geochemistry, Sr-Nd-Pb istopes, granite porphyry, Yangtze block

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