Petrogenesis of Triassic granite from the Jintan pluton in Central Jiangxi Province, South China: implication for uranium enrichment
Petrogenesis of Triassic granite from the Jintan pluton in Central Jiangxi Province, South China: implication for uranium enrichment
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江西省中部金坛岩体三叠纪花岗岩的岩石成因：对铀富集的意义
DOI：
10.1016/j.lithos.2018.09.003
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发表时间：
2018-11
期刊：
影响因子：
3.5
通讯作者：
Xu Zhitian
中科院分区：
文献类型：
--
作者：
Tao Jihua;Li Wuxian;Wyman Derek A.;Wang Andong;Xu Zhitian
华南内陆三叠纪出露大量的黑云母花岗岩和二云母花岗岩，其中部分具有高铀含量，被认为是后期热液成矿的矿源。因此，它们的岩石成因对于限制铀富集的可能来源至关重要。本文报道了赣中金滩岩体新的LA-ICPMS锆石U-Pb年龄、黑云母和白云母的矿物地球化学、全岩地球化学结果以及Sr、Nd、Hf同位素数据。LA-ICPMS锆石U单键Pb定年结果表明，金滩岩体中的黑云母花岗岩（BG）和二云母花岗岩（TMG）的结晶年龄均为~220 Ma。TMG的U含量（7.85 ~ 48.90 ppm，平均18.44 ppm）高于BG（4.99 ~ 17.72 ppm，平均8.64 ppm）。BG和TMG的全岩εNd（t）和锆石εHf（t）值均为负值，并含有继承锆石。TMG为强过铝质（A/CNK = 1.13-1.33），含有丰富的原生白云母，在YvsRb和ThvsRb图上显示S型亲合性，属S型花岗岩。BG在YvsRb和ThvsRb图上也显示出S型花岗岩的亲合性。这些岩套显示出相似的Sr单键Nd同位素组成（BG初始87 Sr/86 Sr值= 0.711389至0.714225，εNd（t）= −9.91至−9.16; TMG初始87 Sr/86 Sr值= 0.711832，εNd（t）= −10.02），并且在空间上是相关的，表明BG也应该被划分为S型花岗岩。TMG的锆石εHf（t）值（−6.4 ~ −1.1）高于BG（−8.7 ~ −3.7），表明TMG和BG可能来自相似的沉积物，但可能具有某些不同的源区特征。BG具有较高的全稀土、轻稀土和MgO含量，其化学成分呈线性协变; TMG具有较宽的成分变化范围，但全稀土、轻稀土和MgO含量较低。黑云母地球化学特征表明TMG形成于比BG更还原的岩浆体系中。锆石饱和测温结果表明，BG的岩浆温度明显高于TMG。TMG具有较高的Al_2 O_3/TiO_2比值和较低的CaO/Na_2 O比值，但Sr/Y和La/Yb比值较高。地球化学和岩石学数据表明，BG来自于更深层次的粘土贫砂质岩源，具有较高的温度和较高的氧逸度，并经历了广泛的分离结晶，而TMG来自于更高层次的粘土丰富的泥质岩源，具有较低的温度和氧逸度，只有有限的分离结晶。结果表明，TMG中铀的富集与铀源、低部分熔融温度或低部分熔融程度、还原环境及岩浆中稀土元素和轻稀土元素含量低等物理化学条件的综合作用有关。
Numerous Triassic biotite granites and two-mica granites crop out in the interior of South China, and some of them possess high U contents, which have been regarded as the sources for later hydrothermal mineralization. Their petrogenesis is therefore crucial for constraining the possible origins of the U enrichment. Here we report new LA-ICPMS zircon Usingle bondPb ages, mineral geochemistry of biotite and muscovite, whole rock geochemical results and Srsingle bondNd and zircon Hf isotope data from the Jintan pluton in Central Jiangxi Province, South China. LA-ICPMS zircon Usingle bondPb dating indicates that both biotite granite (BG) and two-mica granite (TMG) in the Jintan pluton crystallized at ~220 Ma. The TMG have higher U contents (7.85 to 48.90 ppm, average18.44 ppm) than theBG (4.99 to 17.72 ppm, average 8.64 ppm). Both BG and TMG show negative whole-rock εNd(t)and zircon εHf(t)values and contain some inherited zircons. The TMG are strongly peraluminous (A/CNK = 1.13–1.33), contain abundant primary muscovite, and display S-type affinity on plots of YvsRb and ThvsRb, suggesting that they are S-type granites. The BG also display S-type granite affinities on plots of YvsRb and ThvsRb. The suites display similar Srsingle bondNd isotope compositions (BG initial87Sr/86Sr values = 0.711389 to 0.714225 and εNd(t) = −9.91 to −9.16, TMG initial87Sr/86Sr values = 0.711832 and εNd(t) = −10.02) and are spatially associated, suggesting that the BG should also be classified as S-type granites. The TMG have higher zircon εHf(t)values (−6.4 to −1.1) than the BG (−8.7 to −3.7), indicating the TMG and BG might be derived from similar sediments but possibly with some distinct characteristics in their sources. The BG exhibit linear covariations in chemical compositions with relatively high total REE and light REE contents and MgO contents, while the TMG displays broader compositional variations but with relatively low total REE, light REE and MgO contents. Biotite geochemistry indicates the TMG formed in a more reduced magmatic system than the BG. The temperatures estimated by zircon saturation thermometry indicate the BG had distinctly higher magmatic temperatures than the TMG. The TMG display relatively high Al2O3/TiO2ratios and low CaO/Na2O ratios than the BG but have higher Sr/Y and La/Yb ratios. The geochemical and petrological data suggest the BG were derived from clay-poor psammite sources at deeper levels with higher temperatures and higher oxygen fugacity, and underwent an extensive fractional crystallization, while the TMG was derived from clay-rich pelitic sources at higher levels and lower temperatures and oxygen fugacity with only limited fractional crystallization. We conclude that the combination of U-rich sources, physical-chemical conditions such as low partial melting temperature or low degrees of partial melting, a reduced environment and low REE and LREE contents of magmas controlled the U enrichment in TMG.
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影响因子：
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作者：
J. A. Speer
通讯作者：
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影响因子：
1.8
作者：
Zhao Kui-dong;Li Jiren;Ling Hongfei;Chen Pei-rong;Chen Weifeng;S. Tao
通讯作者：
Zhao Kui-dong;Li Jiren;Ling Hongfei;Chen Pei-rong;Chen Weifeng;S. Tao
DOI：
--
发表时间：
2002
期刊：
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影响因子：
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作者：
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通讯作者：
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影响因子：
6.1
作者：
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通讯作者：
Yuejun Wang;W. Fan;Guowei Zhang;Yanhua Zhang
影响因子：
56.9
作者：
E. Scherer;C. Münker;K. Mezger
通讯作者：
E. Scherer;C. Münker;K. Mezger