| Early Indosinian Weiya Gabbro in Eastern Tianshan, China： Elemental and Sr-Nd-O Isotopic Geochemistry, and Its Tectonic Implications |
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| 作者姓名： | ZHANG Zunzhong GU Lianxing WU Changzhi |
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| 作者单位： | [1]State Key Laboratory of Mineral Deposit Research （Nanjing University）, Department of Earth Sciences, Nanjing University, Nanjing, Jiangsu 210093 [2]School of the Environment, Nanjing University, Nanjing, Jiangsu 210093 |
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| 基金项目： | 国家自然科学基金;国家重点基础研究发展计划(973计划);中国博士后科学基金 |
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| 摘 要： | The Weiya gabbro in eastern Tianshan was formed during the early Indosinian. This rock, with low ratios of Ce/Pb （5.74-10.16）, is notably characterized by enrichment in large ion lithophile elements （LILE）, such as Rb, K, Ba and Pb, and in high field strength elements （HSFE）, such as U and Th, but depletion in Nb and Ta. All samples of the Weiya gabbro display similar chondrite-normalized patterns with moderate enrichment in LREE （72.58-135.61ppm）, moderate depletion in HREE （15.26-25.31ppm） and mild fractionation between LREE and HREE （L/ H=4.09-5.98）. The average initial Sr value of the rock is 0.7069, and δ18O values of the rock range from 5.67‰-8.04‰. In terms of Nd isotope ratios, the Weiya gabbro is characterized by positive eNd（t） values （0.52-0.76）. All these characteristics indicate that the source region of the Weiya gabbro was metasomatized by fluids released from subducted young continental crust, with limited crustal contamination during magma ascent and emplacement. Continental （A-type） subduction was induced by northward subduction of the Paleo-Tethyan oceanic plate during the latest Permian to Triassic. From this point of view, it is supposed that tectonic conversion from the Paleo-Asian to the Paleo-Tethys regime occurred during the latest Permian or earliest Triassic.
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| 关 键 词： | 辉长岩 交代作用 新疆 地质 |
| 修稿时间： | 2005-12-052006-08-08 |
Early Indosinian Weiya Gabbro in Eastern Tianshan, China: Elemental and Sr-Nd-O Isotopic Geochemistry, and Its Tectonic Implications |
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| Authors: | ZHANG Zunzhong GU Lianxing WU Changzhi ZHAI Jianping LI Weiqiang and TANG Junhua State Key Laboratory of Mineral Deposit Research |
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| Institution: | Nanjing University |
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| Abstract: | The Weiya gabbro in eastern Tianshan was formed during the early Indosinian. This rock, with low ratios of Ce/Pb (5.74-10.16), is notably characterized by enrichment in large ion lithophile elements (LILE), such as Rb, K, Ba and Pb, and in high field strength elements (HSFE),such as U and Th, but depletion in Nb and Ta. All samples of the Weiya gabbro display similar chondrite-normalized patterns with moderate enrichment in LREE (72.58-135.61ppm), moderate depletion in HREE (15.26-25.31ppm) and mild fractionation between LREE and HREE (L/H=4.09-5.98). The average initial Sr value of the rock is 0.7069, and δ18O values of the rock range from 5.67‰-8.04‰. In terms of Nd isotope ratios, the Weiya gabbro is characterized by positive εNd(t) values (0.52-0.76). All these characteristics indicate that the source region of the Weiya gabbro was metasomatized by fluids released from subducted young continental crust, with limited crustal contamination during magma ascent and emplacement. Continental (A-type)subduction was induced by northward subduction of the Paleo-Tethyan oceanic plate during the latest Permian to Triassic. From this point of view, it is supposed that tectonic conversion from the Paleo-Asian to the Paleo-Tethys regime occurred during the latest Permian or earliest Triassic. |
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| Keywords: | Weiya gabbro mantle metasomatism intra-continental subduction easternTianshan Xinjiang |
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