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The U-Pb Geochronology and Lu-Hf Isotope Compositions of Detrital Zircons from the Nanhua Group of the Longsheng Region, South China and their Implications for Pan-African Events
Acta Geologica Sinica-English Edition ( IF 3.5 ) Pub Date : 2020-08-10 , DOI: 10.1111/1755-6724.14547 Chenglong ZHANG 1 , Ya QIN 1 , Yicheng YANG 1 , Zuohai FENG 1 , Xijun LIU 1 , Saisai LI 1 , Lei WAN 1 , Chunzeng WANG 2
Acta Geologica Sinica-English Edition ( IF 3.5 ) Pub Date : 2020-08-10 , DOI: 10.1111/1755-6724.14547 Chenglong ZHANG 1 , Ya QIN 1 , Yicheng YANG 1 , Zuohai FENG 1 , Xijun LIU 1 , Saisai LI 1 , Lei WAN 1 , Chunzeng WANG 2
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It is unclear whether the South China blocks have an affinity with continental Gondwana due to a lack of direct Pan-African magmatic and metamorphic features. In this study, we conducted U-Pb geochronological and Lu-Hf isotopic analyses for detrital zircons from a sandstone of the Chang'an Formation of the Nanhua Group in the Longsheng region of northern Guangxi, with the aim of constraining the timing of sedimentation and information as to its source, as well as seeking evidence for Pan-African events in the South China blocks. The results show that the ages of detrital zircons peaked at 654.7 ± 6.2 Ma, 773.2 ± 4.1 Ma and 821.9 ± 6.5 Ma, with some at 920–870 Ma; the youngest age indicates the existence of the Pan-African thermal event. The ∊Hf(t) and TDM2 values demonstrate that the study area has experienced three stages of crustal growth at 3.0–2.4 Ga, 2.1–1.5 Ga and 1.3–0.9 Ga. With intensively distributed Neoproterozoic mafic-ultramafic and granitic plutons emplaced at 830–810 Ma along the southwestern section of the Jiangnan Orogenic Belt and positive ∊Hf(t) values from a large group of zircon grains, it is proposed that the sediments of the Chang'an Formation (of Nanhua Group) were largely sourced from the southeastern margin of the Yangtze block. Comparison with the zircon age spectra of the Cathaysian block shows that about 79% of the Pan-African aged detrital zircon grains that have TDM2 = 1352–1031 Ma and ∊Hf(t) = 3.68–8.79, were sourced from the recycled Grenvillian crust of the Cathaysian block, suggesting that the Cathaysian block had a close connection with Gondwana.
中文翻译：
华南龙胜地区南华群碎屑锆石U-Pb年代学和Lu-Hf同位素组成及其对泛非事件的意义
由于缺乏直接的泛非岩浆和变质特征，目前尚不清楚华南地块是否与冈瓦纳大陆有亲缘关系。本研究对桂北龙胜地区南华组长安组砂岩碎屑锆石进行 U-Pb 年代学和 Lu-Hf 同位素分析，以期确定沉积时间和关于其来源的信息，以及寻找华南区块泛非事件的证据。结果表明，碎屑锆石年龄峰值分别为654.7±6.2 Ma、773.2±4.1 Ma和821.9±6.5 Ma，部分在920～870 Ma；最小的年龄表明存在泛非热事件。的ε的Hf（吨）和ŤDM2值表明研究区经历了 3.0-2.4 Ga、2.1-1.5 Ga 和 1.3-0.9 Ga 三个阶段的地壳生长。新元古代基性-超基性和花岗质岩体在 830-810 Ma 沿西南段侵位密集江南造山带和大群锆石的∊ Hf ( t ) 正值，推测长安组（南华群）沉积物主要来自扬子地块东南缘。与华夏地块的锆石年龄谱对比表明，大约 79% 的泛非时效碎屑锆石颗粒的T DM2 = 1352-1031 Ma 和∊ Hf (t ) = 3.68-8.79，来源于华夏地块再生的格伦维尔地壳，表明华夏地块与冈瓦纳有密切联系。
更新日期：2020-08-10
中文翻译：
华南龙胜地区南华群碎屑锆石U-Pb年代学和Lu-Hf同位素组成及其对泛非事件的意义
由于缺乏直接的泛非岩浆和变质特征，目前尚不清楚华南地块是否与冈瓦纳大陆有亲缘关系。本研究对桂北龙胜地区南华组长安组砂岩碎屑锆石进行 U-Pb 年代学和 Lu-Hf 同位素分析，以期确定沉积时间和关于其来源的信息，以及寻找华南区块泛非事件的证据。结果表明，碎屑锆石年龄峰值分别为654.7±6.2 Ma、773.2±4.1 Ma和821.9±6.5 Ma，部分在920～870 Ma；最小的年龄表明存在泛非热事件。的ε的Hf（吨）和ŤDM2值表明研究区经历了 3.0-2.4 Ga、2.1-1.5 Ga 和 1.3-0.9 Ga 三个阶段的地壳生长。新元古代基性-超基性和花岗质岩体在 830-810 Ma 沿西南段侵位密集江南造山带和大群锆石的∊ Hf ( t ) 正值，推测长安组（南华群）沉积物主要来自扬子地块东南缘。与华夏地块的锆石年龄谱对比表明，大约 79% 的泛非时效碎屑锆石颗粒的T DM2 = 1352-1031 Ma 和∊ Hf (t ) = 3.68-8.79，来源于华夏地块再生的格伦维尔地壳，表明华夏地块与冈瓦纳有密切联系。
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