地学前缘 ›› 2011, Vol. 18 ›› Issue (2): 85-99.

• 论文 • 上一篇    下一篇

大别山鲁家寨花岗岩地球化学、锆石年代学和Hf同位素特征：扬子克拉通北东缘新元古代岩浆活动证据

孙洋，马昌前，张超   

  1. 1. 中国地质大学（武汉） 地球科学学院， 湖北 武汉430074
    2. 中国地质大学 地质过程与矿产资源国家重点实验室， 湖北 武汉430074
    3. 汉诺威大学 矿物学系， 德国 汉诺威  D30167
  • 收稿日期:2010-06-01 修回日期:2010-12-30 出版日期:2011-03-15 发布日期:2011-04-15
  • 作者简介:孙洋(1985—),女,博士研究生，岩石学、矿物学、矿床学专业。E-mail: cugsunyang@gmail.com
  • 基金资助:

    科学技术部国际科技合作与交流专项(20071077);国家自然科学基金重点项目(40334037); 教育部和国家外国专家局高等学校学科创新引智计划(B07039); 湖北省自然科学基金重点项目(2009CDA004)

Geochemistry, zircon geochronology and Hf isotopes of Lujiazhai granites from the Dabie Orogen: Evidence for the Neoproterozoic magmatism along the northeastern margin of Yangtze Block.

  1. 1. Faculty of Earth Sciences, China University of Geosciences（Wuhan）, Wuhan 430074, China
    2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
    3. Institut für Mineralogie, Leibniz Universitt Hannover, D30167 Hannover, Germany
  • Received:2010-06-01 Revised:2010-12-30 Online:2011-03-15 Published:2011-04-15

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摘要：

摘要：对大别山造山带的鲁家寨花岗岩进行了锆石UPb年代学、锆石Hf同位素和岩石地球化学研究。锆石LAICPMS UPb定年结果表明鲁家寨花岗岩形成于新元古代（(816±17) Ma）。鲁家寨花岗岩总体具有高硅 (SiO2 6913%~7547%)、准铝弱过铝(A/CNK=098~101)的化学组成特征。稀土元素总量(∑REE)为（2743~16066）×10-6，稀土元素配分曲线呈右倾型，具有弱的负Eu异常—正Eu异常。高场强元素 (P、Nb、Ti等)强烈亏损，大离子亲石元素 (K、Ba、Sr等)相对富集。锆石Hf同位素组成研究表明，鲁家寨新元古代花岗岩可能主要来源于与扬子陆核类似的大别山早前寒武纪变质基底的部分熔融，幔源岩浆不仅为古老地壳物质的部分熔融作用提供了热量，可能还直接参与了花岗岩的成岩作用。综合Rodinia超大陆古地理复原资料，推测扬子板块北东缘新元古代早期为接受大洋俯冲的活动大陆边缘，而形成于816 Ma的鲁家寨岩体具有后碰撞岩浆活动的特征，是弧陆碰撞造山带构造(重力/拉张)垮塌产物。

关键词: 鲁家寨花岗岩, 锆石U-Pb年龄, 锆石Hf同位素, 大别造山带, 新元古代岩浆活动

Abstract:

The Lujiazhai granitic pluton located in the southern Dabie Orogen was studied by zircon LAICPMS UPb dating, zircon Hf isotope and bulk geochemistry analyses. LAICPMS zircon UPb dating gave the age of 816±17 Ma for the Lujiazhai granites, revealing that the pluton was emplaced in the Neoproterozoic. All bulk samples are high in SiO2 (6913%—7547%), with moderate A/CNK values (098—101, averaged at 10), inferring an Itype granite affinity. The concentration of total rare earth elements (REEs) varies in the range of 2743×10-6 to 16066×10-6. The Lujiazhai granites are characterized by an enriched LREE pattern with slightly negative to positive Eu anomalies. They are enriched in large ion lithophile elements (e.g. K, Ba, Sr), but depleted in high field strength elements (e.g. P, Nb, Ti). Zircon Hf isotopic data indicate that the Lujiazhai Neoproterozoic granitic pluton in the southern Dabie Orogen was likely formed by magmas derived from partial melting of Early Precambrian metamorphic complex, accompanied by the heating and possible assimilation of mantlederived magmas. By combining studies of the paleogeographic reconstruction of the Rodinia supercontinent, we propose that since the early Neoproterozoic, the northeastern margin of the Yangtze block might have been under an active continental margin setting induced by subduction of an oceanic plate. In this tectonic regime, the Lujiazhai granites were derived by partial melting of ancient crustal materials induced by the underplating or intracrustal heating of hot mantlederived magmas. After the cease of subduction and consequent continentarc collision, this area was then likely dominated by postcollisional extension or rifting tectonically, related to the breakup of the Rodinia supercontinent.

Key words: Lujiazhai pluton, zircon UPb age, zircon Hf isotopes, Dabie Orogen, Neoproterozoic magmatism

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