Petrogenesis and tectonic significance of a Mesozoic granite-syenite-gabbro association from inland South China
Petrogenesis and tectonic significance of a Mesozoic granite-syenite-gabbro association from inland South China
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华南内陆中生代花岗岩-正长岩-辉长岩组合的岩石成因及构造意义
DOI：
10.1016/j.lithos.2010.08.016
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发表时间：
2010-10
期刊：
影响因子：
3.5
通讯作者：
中科院分区：
文献类型：
--
作者：
通过对华南内陆一个花岗岩-正长岩-辉长岩组合的锆石U-Pb年龄、Hf同位素组成、全岩元素和Sr-Nd同位素组成的研究，探讨了其源区和构造环境。龙源坝黑云母花岗岩的平均年龄为240 Ma，龙源坝二云母花岗岩、陂头碱长花岗岩、含角闪石碱长花岗岩、塔北正长岩、黄埠正长岩、车埠辉长岩、成龙辉长岩的平均年龄为178 Ma，而大风脑正长岩的平均年龄为165 Ma。龙源坝黑云母花岗岩和二云母花岗岩具有S型特征，可能为新元古代壳源。成龙辉长岩具有类OIB微量元素特征和高亏损同位素组成（εHf（t）=10.0±1.3; εNd（t）=5.2），表明其母岩熔体来源于软流圈，地壳同化作用不明显。然而，地壳污染需要解释的同位素组成的车布辉长岩。正长岩的成分为钾玄岩，具有亏损的Sr-Nd-Hf同位素特征，我们认为这是软流圈地幔和交代岩石圈地幔混合源区的产物。正如预期的那样，地壳同化的信号在更演化的正长岩的岩石成因中是显著的。陂头碱长花岗岩和含角闪石的碱长花岗岩分别具有I型和A型特征。它们比S型龙源坝花岗岩的同位素更亏损。我们认为，它们可能是通过岩浆混合的主要幔源熔体与新元古代地壳。侏罗纪花岗岩-正长岩-辉长岩组合是软流圈-岩石圈-地壳相互作用的产物，记录了华南早燕山期软流圈地幔上涌在地幔和地壳岩浆生成中的主要作用。它们可能是古太平洋板块俯冲早期，板块边缘对远场应力的构造响应，形成于板内裂谷环境。早侏罗世完成了特提斯造山体制向古太平洋体制的构造转换，燕山早期岩浆活动应与古太平洋构造体制有成因联系。
A granite–syenite–gabbro association from inland South China has been studied for zircon U–Pb ages and Hf isotopic compositions as well as whole-rock elemental and Sr–Nd isotopic compositions to constrain their sources and tectonic settings. These rocks have distinctive crystallization ages: the Longyuanba biotite granites have a mean age of ~240Ma, the Longyuanba two-mica granites, Pitou alkali-feldspar granites and amphibole-bearing alkali-feldspar granites, Tabei and Huangbu syenites and Chebu and Chenglong gabbros have a similar age of ~178Ma, whereas the Dafengnao syenite gives a mean age of ~165Ma. The Longyuanba biotite granites and two-mica granites exhibit S-type characteristics, probably derived from a Neoproterozoic crustal source. The Chenglong gabbro has OIB-like trace element and highly depleted isotope compositions (εHf(t)=10.0±1.3; εNd(t)=5.2), suggesting its parental melt to be of asthenospheric origin with insignificant crustal assimilation. However, crustal contamination is required to explain the isotopic compositions of the Chebu gabbro. The syenites are shoshonitic in composition, and have depleted Sr–Nd–Hf isotopic signatures, which we interpret to have resulted from a mixed source of asthenospheric mantle and metasomatized lithospheric mantle. As expected, the signals of crustal assimilation are conspicuous in the petrogenesis of the more evolved syenites. The Pitou alkali-feldspar granite and amphibole-bearing alkali-feldspar granite exhibit I-type and A-type characteristics, respectively. They are isotopically more depleted than the S-type Longyuanba granites. We suggest that they may have formed through magma mixing of predominantly mantle-derived melts with the Neoproterozoic crust. The Jurassic granite–syenite–gabbro association was the product of asthenosphere–lithosphere–crust interactions, which records the primary role of asthenospheric mantle upwelling in magma generation both in the mantle and in the crust in the Early Yanshanian time in South China. They probably occurred in an intraplate rift-like environment as a tectonic response to far-field stress at plate margins during the early stage of the paleo-Pacific plate subduction. The tectonic transition from the Tethys orogenic regime to the paleo-Pacific regime was accomplished in the Early Jurassic, and the early Yanshanian magmatism should be genetically associated with the paleo-Pacific tectonic regime.
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影响因子：
5.3
作者：
D. McKenzie
通讯作者：
D. McKenzie
DOI：
--
发表时间：
2008
期刊：
Acta Geological Sinica
影响因子：
--
作者：
X. Guang-fu
通讯作者：
X. Guang-fu
影响因子：
5.8
作者：
A. Draut;P. Clift
通讯作者：
A. Draut;P. Clift
影响因子：
56.9
作者：
E. Scherer;C. Münker;K. Mezger
通讯作者：
E. Scherer;C. Münker;K. Mezger
DOI：
10.2973/odp.proc.sr.176.011.2002
发表时间：
2002
期刊：
--
影响因子：
--
作者：
Y. Niu;T. Gilmore;S. Mackie;A. Greig;W. Bach
通讯作者：
Y. Niu;T. Gilmore;S. Mackie;A. Greig;W. Bach