宁芜盆地花岗岩类的锆石U-Pb年龄、同位素特征及其意义
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国家自然科学基金项目(40830426,40803015,40672062)、国家重点基础研究发展规划973项目(2007CB411405)、新世纪优秀人才支持计划项目(NCET-10-0324)、安徽省地质勘查专项费项目(2005-51,2007-1,2009-g-22,2009-13)、澳大利亚塔斯马尼亚大学国家优秀矿床研究中心科研基金(CODES2009 P2-3)和安徽省优秀青年科技基金资助项目(08040106907,04045063)


Zircon U-Pb ages and isotopic characteristics of the granitoids in the Ningwu basin, China
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    摘要:

    宁芜盆地中花岗岩类侵入体出露零星,以石英二长岩和花岗岩为主,研究程度薄弱。本文对盆地内主要的5个花岗岩类侵入体牛迹山岩体、霍里岩体、姑山岩体(姑山铁矿床钻孔中)、小石山岩体和娘娘山岩体进行了年代学、锆石Lu-Hf同位素、Nd-Sr同位素分析研究。这5个花岗岩类侵入体的LA-ICPMS锆石U-Pb年龄依次为128.0±1.7、126.4±1.3、129.8±1.6、130.1±1.5Ma、128.3±1.8Ma,形成于126~130Ma之间,均为早白垩世岩浆活动的产物,与姑山、娘娘山旋回火山岩活动时限相当,与玢岩型铁矿的成矿时代也相似。Nd-Sr同位素指示,宁芜盆地花岗岩类源于交代地幔源区,其性质接近于EMI型富集地幔,其形成与古板块的俯冲交代作用有关;姑山铁矿床钻孔中的姑山岩体锆石εHf(t)均为正值(7.644~13.910),可能指示了更多的地幔组分参与才是铁富集成矿的有利因素。盆地中的花岗岩类形成于中国东部岩石圈减薄高峰期的地球动力学背景,为典型张性构造应力体制的产物。

    Abstract:

    There are few outcrops of granitic intrusions in the Ningwu basin, composed mainly of quartz monzonite and granite. Few works have been done on these granitic intrusions. This paper presents a detail study of some granitic intrusions by means of LA-ICPMS zircon dating, Lu-Hf isotope of zircon and Sr-Nd isotope analyses. The chronology results show that the ages of Niujishan pluton (128.0±1.7 Ma), Huoli pluton (126.4±1.3 Ma), Gushan pluton (sampling from drill core in the Gushan iron deposit, 129.8±1.6 Ma), Xiaoshishan pluton (130.1±1.5Ma) and Niangniangshan pluton (128.3±1.8Ma), which indicates the granitic intrusive activities took place in 126~130Ma, belong to the early Cretaceous. The ages are corresponding with those of the Gushan and Niangniangshan Formations volcanic rocks and the mineralization ages of the porphyry iron deposits in the Ningwu basin. The Nd-Sr isotope results suggest that the granitic intrusions derived from the metasomatic mantle, compositionally closing to the EMI, which has relationship with the subduction of the pacific plate. TheεHf(t)of the ziron from the Gushan pluton is 7.644~13.910, implies that the more percentage of mantle composition is favorable for the iron mineralization. The granitic plutons in the Ningwu basin are the products of extensional geodynamic setting, which responded by the lithospheric thinning in the eastern of China.

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袁峰,周涛发,范裕,张乐骏,马良,钱兵.2011.宁芜盆地花岗岩类的锆石U-Pb年龄、同位素特征及其意义[J].地质学报,85(5):821-833.
yuan feng, ZHOU Taofa, ZHANG Lejun, FAN Yu, MA Liang, QIAN Bing.2011. Zircon U-Pb ages and isotopic characteristics of the granitoids in the Ningwu basin, China[J]. Acta Geologica Sinica,85(5):821-833.

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  • 收稿日期:2011-03-28
  • 最后修改日期:2011-03-28
  • 录用日期:2011-04-01
  • 在线发布日期: 2011-05-16
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