Middle Neoproterozoic syn-rifting volcanic rocks in Guangfeng, South China: petrogenesis and tectonic significance
Middle Neoproterozoic syn-rifting volcanic rocks in Guangfeng, South China: petrogenesis and tectonic significance
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华南广丰中新元古代同裂谷火山岩的岩石成因及构造意义
DOI：
10.1017/s0016756808004561
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发表时间：
2008-04
影响因子：
2.3
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中科院分区：
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摘要中国南方新元古代中期火成岩分布广泛，但其成因和构造意义仍有很大争议。广丰中新元古代火山-沉积岩系是在扬子地块东南部罕见的四堡期变质基底（天利片岩）上发育的。本文报道了该系列火山岩的年代学、地球化学和Nd同位素资料。火山岩由碱性玄武岩、安山岩和过铝质流纹岩组成。锆石SHRIMP U-Pb年龄测定表明，它们的喷发年龄为827±14 Ma，与华南地区广泛发生的非造山岩浆活动同期。尽管表现出相对于La和Th的Nb-Ta亏损，但碱性玄武岩的特征是高正Nd（T）值（+3.1至+6.0），相对高的TiO 2和Nb含量以及高Zr/Y和超镁铁质Nb/Ta比值，表明它们来自于陆内裂谷环境中的板片熔融交代的次大陆岩石圈地幔源。安山岩的Nd（T）值为负值（−9.3至−11.1），SiO2含量范围很广（57.6-65.6%）。它们很可能是由分离的玄武质熔体与中地壳至下地壳的中生代变质沉积岩中的长英质熔体混合而成。流纹是高度硅质和过铝质的。它们的特征是Nb、Ta、Sr、P和Ti的亏损和相对较高的Nd（T）值（−3.0至−4.8），与邻近的c。820 Ma的过铝质花岗岩类来自中元古代至新元古代早期相对较浅的沉积物源。认为广丰火山岩套是新元古代中期地幔柱活动引起的陆内裂谷作用在大陆岩石圈（包括岩石圈地幔和下、中、上地壳）不同层次上的岩浆响应。
Abstract Middle Neoproterozoic igneous rocks are widespread in South China, but their petrogenesis and tectonic implications are still highly controversial. The Guangfeng middle Neoproterozoic volcano-sedimentary succession was developed on a rare Sibaoan metamorphic basement (the Tianli Schists) in the southeastern Yangtze Block, South China. This paper reports geochronological, geochemical and Nd isotopic data for the volcanic rocks in this succession. The volcanic rocks consist of alkaline basalts, andesites and peraluminous rhyolites. SHRIMP U–Pb zircon age determinations indicate that they were erupted at 827±14 Ma, coeval with a widespread episode of anorogenic magmatism in South China. Despite showing Nb–Ta depletion relative to La and Th, the alkaline basalts are characterized by highly positive ɛNd(T) values (+3.1 to +6.0), relatively high TiO2 and Nb contents and high Zr/Y and super-chondritic Nb/Ta ratios, suggesting their derivation from a slab melt-metasomatized subcontinental lithospheric mantle source in an intracontinental rifting setting. The andesites have significantly negative ɛNd(T) values (−9.3 to −11.1) and a wide range of SiO2 contents (57.6–65.6%). They were likely generated by the mixing of fractionated basaltic melts with felsic melts derived from the Archaean metasedimentary rocks in the middle to lower crust. The rhyolites are highly siliceous and peraluminous. They are characterized by depletion in Nb, Ta, Sr, P and Ti and relatively high ɛNd(T) values (−3.0 to −4.8), broadly similar to those of the adjacent c. 820 Ma peraluminous granitoids derived from the Mesoproterozoic to earliest Neoproterozoic sedimentary source at relatively shallow levels. We conclude that the Guangfeng volcanic suite is a magmatic response of variant levels of continental lithosphere (including lithospheric mantle and the lower-middle to upper crust) to the middle Neoproterozoic intracontinental rifting possibly caused by mantle plume activity.
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影响因子：
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作者：
Jian Wang;Xian‐Hua Li;T. Duan;Dunyi Liu;B. Song;Zhongxiong Li;Yonghua Gao
通讯作者：
Jian Wang;Xian‐Hua Li;T. Duan;Dunyi Liu;B. Song;Zhongxiong Li;Yonghua Gao
DOI：
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发表时间：
2003
期刊：
--
影响因子：
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作者：
Zheng‐Xiang Li;J. Wang;X. Li;S. Zhang
通讯作者：
Zheng‐Xiang Li;J. Wang;X. Li;S. Zhang
DOI：
10.1086/341762
发表时间：
2002-09
期刊：
The Journal of Geology
影响因子：
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作者：
Mei‐Fu Zhou;A. Kennedy;M. Sun;J. Malpas;C. Lesher
通讯作者：
Mei‐Fu Zhou;A. Kennedy;M. Sun;J. Malpas;C. Lesher
影响因子：
3.8
作者：
Wenjie Li
通讯作者：
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影响因子：
3.8
作者：
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