| 青海东昆仑西段阿克楚克赛地区新元古代片麻状黑云二长花岗岩成因及其地质意义：地球化学、年代学及Hf同位素制约 |
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| 引用本文： | 赵拓飞,林博磊,陈昌昕,王超,李良.青海东昆仑西段阿克楚克赛地区新元古代片麻状黑云二长花岗岩成因及其地质意义：地球化学、年代学及Hf同位素制约[J].吉林大学学报(地球科学版),2022,52(5):1540-1557. |
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| 作者姓名： | 赵拓飞 林博磊 陈昌昕 王超 李良 |
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| 作者单位： | 1.中国自然资源经济研究院，北京1011492.中国地质大学（北京）经济管理学院，北京1000833.自然资源部信息中心，北京1008124.中国地质科学院，北京1000375.自然资源部深地科学与探测技术实验室, 北京1000946.吉林省地质调查院，长春1300617.云南大学地球科学学院，昆明 650504 |
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| 摘 要： | 青海东昆仑西段阿克楚克赛地区基础地质研究较薄弱，为了厘定该区花岗片麻岩侵入体的形成时代及岩石成因，本文对其进行了岩石地球化学、锆石U-Pb年代学以及Hf同位素研究。研究结果表明：该岩石岩性为片麻状黑云二长花岗岩，SiO2质量分数为74.44%～76.36%，Na2O与K2O质量分数分别为0.06%～0.07%和3.89%～4.35%，Al2O3质量分数为9.76%～10.95%，过铝指数（A/CNK）为0.92～1.09，TiO2与MnO质量分数分别为0.32%～0.38%和0.10%～0.13%；CaO质量分数为2.70%～3.46%，Mg#值为25.42～29.69；样品稀土元素质量分数较高， w（ΣREE）为200.04×10-6～215.30×10-6，LREE/HREE为6.94～7.88，Rb、U、Th、K明显富集，Nb、Ta、P、Ti、Sr明显呈“V”型亏损。岩石形成时代为新元古代早期（（966±3）Ma，MSWD=4.1），锆石εHf(t)为-3.38～3.14，Hf同位素二阶段模式年龄（TDM2）为2 033～1 625 Ma。岩石地球化学和Hf同位素研究结果显示，阿克楚克赛片麻状黑云二长花岗岩为准铝质-弱过铝质高钾钙碱性I型花岗岩，岩浆源区以新生玄武质地壳为主，有古元古代硅铝质地壳物质的加入，可能为古元古界金水口岩群斜长角闪岩、片麻岩部分熔融。岩石地球化学特征显示阿克楚克赛片麻状黑云二长花岗岩形成于新元古代早期俯冲向碰撞转换的构造背景下。结合区域构造演化，综合分析认为东昆仑地区普遍存在新元古代岩浆-构造活动，时间上响应全球罗迪尼亚超大陆聚合事件，本次研究样品是罗迪尼亚超大陆聚合在青海东昆仑西段碰撞形成的具体体现，说明本地区在约966 Ma时正在由俯冲向碰撞造山阶段转换。
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| 关 键 词： | 东昆仑造山带 I型花岗岩 岩石地球化学 锆石U-Pb定年 Hf同位素 |
| 收稿时间： | 2022-03-31 |
Petrogenesis and Geological
Significance of Neoproterozoic Gneissic Biotite Monzogranite in Akechukesai
Area,Western Segment of the East Kunlun Orogenic Belt,Qinghai Province:
Constraints from Geochemistry,Zircon U-Pb Chronology and Hf Isotopes |
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| Zhao Tuofei,Lin Bolei,Chen Changxin,Wang Chao,Li Liang.Petrogenesis and Geological
Significance of Neoproterozoic Gneissic Biotite Monzogranite in Akechukesai
Area,Western Segment of the East Kunlun Orogenic Belt,Qinghai Province:
Constraints from Geochemistry,Zircon U-Pb Chronology and Hf Isotopes[J].Journal of Jilin Unviersity:Earth Science Edition,2022,52(5):1540-1557. |
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| Authors: | Zhao Tuofei Lin Bolei Chen Changxin Wang Chao Li Liang |
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| Abstract: | The basic geological research of Akchukesai
area in the western Segment of the East Kunlun orogenic belt is weak. The
granite gneiss in this area was designated as the Jinshuikou Group by
predecessors. In field work, it was found that the Jinshuikou Group gneiss
should be a granite gneiss intrusion. In order to determine the geochronology
and petrogenesis of the intrusion， the rock geochemistry, zircon U-Pb geochronology and
Hf isotope studies were carried out in this paper. The results show that: the
lithology of the sample is gneissic biotite monzogranite, major element data
show that the SiO2 content is 74.44%-76.36%, Na2O and K2O
contents are respectively 0.06%-0.07% and 3.89%-4.35%, Al2O3 content is 9.76%-10.95%, A/CNK is 0.92-1.09，TiO2 and MnO contents are respectively
0.32%-0.38% and 0.10%-0.13%；CaO content is
2.70%-3.46%，Mg# is
25.42-29.69；The rare earth
elements of the samples are higher, ΣREE is 200.04×10-6-215.30×10-6, LREE/HREE is 6.94-7.88. Trace
elements show the characteristics of enriched in Rb, U, Th, K and Nb, Ta, P,
Ti, Sr showed“V”type depleted. The age of formation is Early
Neoproterozoic ((966±3)Ma，MSWD=4.1), zricon in situεHf(t)=-3.38-3.14,
Hf isotope two-stage model ages TDM2 range from 2 033-1 625 Ma. Petrogeochemical and Hf isotopic results show that
the gneissic biotite monzogranite is peraluminous-weak peraluminous high-K
calc-alkaline I-Type granite. The magma source area should be dominated by new
basaltic crust, with the addition of Paleoproterozoic silical-aluminum crust,
which may be the partial melting of plagioamphibole and gneiss of Paleoproterozoic Jinshuikou Group. The
petrogeochemical characteristics show that the samples were formed under the
tectonic background of subduction to collision transformation in the Early
Neoproterozoic. Based on the comprehensive analysis of regional tectonic
background, it is concluded that Early Neoproterozoic magmatism and tectonic
activity are prevalent in the East Kunlun region, which responds to the global
Rodinia supercontinent convergence event. The samples studied in this study are
the concrete manifestation of the collision formation of Rodinia supercontinent
convergence in the western segment of East Kunlun, this indicates that the
region was transitioning from subduction to collision orogenic stage at about 966 Ma. |
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| Keywords: | Eastern Kunlun orogenic belt I-type granite petrogeochemistry zircon U-Pb geochronology Hf isotopes |
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