Geochronology,geochemistry and petrogenesis of two-stage Indosinian granites from the Xiajiang uranium ore deposit,Jiangxi Province: Implication for Indosinian tectonics and genesis of uranium-bearing granites in South China
Geochronology,geochemistry and petrogenesis of two-stage Indosinian granites from the Xiajiang uranium ore deposit,Jiangxi Province: Implication for Indosinian tectonics and genesis of uranium-bearing granites in South China
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发表时间：
2013
影响因子：
1.8
通讯作者：
Zhao Kui-dong;Li Jiren;Ling Hongfei;Chen Pei-rong;Chen Weifeng;S. Tao
中科院分区：
文献类型：
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作者：
Zhao Kui-dong;Li Jiren;Ling Hongfei;Chen Pei-rong;Chen Weifeng;S. Tao
江西省峡江铀矿床是华南地区花岗岩型铀矿床之一。铀矿体位于江西省金坛花岗岩基体中。野外地质调查和锆石U-Pb测年表明，金坛岩基由两期印支期花岗岩组成。含U二云母花岗岩的侵位时间为239±1Ma,斑状黑云母花岗岩的侵位时间为226±2Ma。二云母花岗岩的SiO 2 含量较高(74. 09%～74. 53%)，而TiO 2 、CaO、MgO含量较低。花岗岩的A/CNK值在1. 20至1. 46之间变化,这与花岗岩中含有白云母和石榴石相一致。二云母花岗岩属于典型的强过铝质S型花岗岩。然而，斑状黑云母花岗岩表现出不同的地球化学特征。其HFSE和REE含量相对较高，Rb/Sr比值较低，Eu负异常不太明显。斑状黑云母花岗岩的 A / CNK 值范围为 1. 05 至 1. 13。两种花岗岩均具有较低的 e Nd(t) 值（双云母花岗岩为-9. 0 至-8. 8，斑状黑云花岗岩为-9. 8 至-9. 4），古元古代模式年龄为 1. 73 ~ 1. 75Ga。二云母花岗岩和1. 77～1. 80Ga为斑状黑云母花岗岩）。地球化学和同位素特征表明，二云母花岗岩和斑状黑云母花岗岩均属于S型花岗岩。然而，二云母花岗岩应来源于富含粘土的泥质岩的深熔作用，而斑状黑云母花岗岩则应来源于贫粘土的砂岩的部分熔融。我们认为二云母花岗岩较早在同碰撞挤压环境下由地壳脱水熔融形成，斑状黑云母花岗岩较晚在碰撞后伸展环境下形成。二云母花岗岩含铀量较高,其矿物学和地球化学特征与华南典型含铀花岗岩相似。对比研究表明，华南印支期含铀花岗岩很可能是由同碰撞挤压构造时期的泥质岩深熔形成的。
The Xiajiang uranium ore deposit in Jiangxi Province is one of the granite-hosted uranium ore deposits in South China. The uranium orebodies are hosted by the Jintan granitic batholith in the Jiangxi Province. Field geological survey and zircon U-Pb dating indicated that the Jintan batholith is composed of two stage Indosinian granites. The U-bearing two-mica granite was emplaced at 239 ± 1Ma,and the porphyritic biotite granite was emplaced at 226 ± 2Ma. The two-mica granite has high SiO 2 contents( 74. 09% ~ 74. 53%) and low TiO 2,CaO and MgO contents. A/CNK values of the granites vary from 1. 20 to 1. 46,which is consisted with that the granite contains muscovite and garnet. The two-mica granite belongs to typical strongly peraluminous S type granite. However,the porphyritic biotite granite shows different geochemical characteristics. It has relatively higher HFSE and REE contents,lower Rb / Sr ratios and less pronounced negative Eu anomalies. A / CNK values of the porphyritic biotite granite vary from 1. 05 to 1. 13. Both of the granites have low e Nd( t) values(-9. 0 to-8. 8 for the two-mica granite and-9. 8 to-9. 4 for the porphyritic biotite granite) with Paleo-proterozoic model ages( 1. 73 ~ 1. 75Ga for the two-mica granite and 1. 77 ~ 1. 80Ga for the porphyritic biotite granite). Geochemical and isotopic characteristics indicate that both the two-mica granite and the porphyritic biotite granite belong to S-type granite. However,the two-mica granite should be derived from anatexis of clay-rich pelitic rocks and the porphyritic biotite granite from partial melting of clay-poor psammitic rocks. We suggested that the two-mica granite formed earlier from dehydrate-melting of crust at syn-collisional compressional environment and the porphyritic biotite granite formed later at the post-collisional extensitional environment. The two-mica granite contains higher U contents,and its mineralogical and geochemical characteristics are similar to those of typical U-bearing granites in South China. Comparative studies indicate that Indosinian U-bearing granites in South China are likely formed from anatexis of pelitic rocks during syn-collisional compressional tectonic regime.