Genesis of Neoproterozoic Amphibolite in Diancangshan, West Yunnan: Evidence from Zircon U-Pb Age and Whole-Rock Geochemistry

被引：2
作者：
Ma Y. [1 ]
Cai Y. [1 ,2 ]
Ma L. [1 ]
Zhou Y. [1 ]
Zhao K. [1 ]
机构：
[1] Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin
[2] Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi, Guilin University of Technology, Guilin
来源：
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2021年 / 46卷 / 08期
关键词：
Amphibolite; Back-arc basin; Diancangshan; Geochemistry; Geochronology; Neoproterozoic; Zircon U-Pb dating;
D O I：
10.3799/dqkx.2020.288
中图分类号：
学科分类号：
摘要：
The current research on Neoproterozoic magmatism on the southwestern Yangtze Block is still weak, which restricts the complete understanding of the Neoproterozoic tectonic evolution of the South China Plate. Detailed zircon U-Pb geochronological and whole-rock geochemical analyses of amphibolite in the Diancangshan area in western Yunnan were carried out in this study. The amphibolite samples can be divided into two groups based on their Nb/La ratios. Group 1 has Nb/La ratios of 0.75-0.76, greater than 0.5, resembling those of Nb-enriched basalt, while Group 2 has Nb/La ratios of 0.20-0.21, and shows obvious negative Nb and Ta anomalies, and thus are similar to those of arc basalt. The group 1 samples have SiO2 contents of 52.4%-52.6%, MgO of 4.1%-4.2%, FeOt of 8.7%-8.8%, and Mg# of 53. The group 2 samples are characterized by lower SiO2 contents (47.4%-47.5%), and higher MgO (5.4%-5.5%), FeOt (9.8%-9.9%) contents, and Mg# (57). Both of the two group samples show slightly high degree of fractionation. The group 1 samples have (La/Yb)cn ratios of 3.0-3.2, and (Gd/Yb)cn ratios of 1.42-1.51, and show negative Eu anomalies (δEu =0.75-0.76). The group 2 samples have (La/Yb)cn ratios of 14.0-14.3, and (Gd/Yb)cn ratios of 1.85-1.93, and show unobvious Eu anomalies (δEu =0.99-1.13). LA-ICP-MS zircon U-Pb dating results show that two representative amphibolite samples yield ages of 764±6 Ma and 779±9 Ma, suggesting that there is mafic magmatic activity in the Diancangshan area during the Neoproterozoic. Integrated with regional data, the amphibolite was likely to be produced in a back-arc basin which was caused by oceanic crustal subduction along the southwestern Yangtze Block in the Neoproterozoic. © 2021, Editorial Department of Earth Science. All right reserved.
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页码：2860 / 2872
页数：12
相关论文
共 56 条
[1]  
Beguelin P., Bizimis M., Beier C., Et al., Rift-Plume Interaction Reveals Multiple Generations of Recycled Oceanic Crust in Azores Lavas, Geochimica et Cosmochimica Acta, 218, pp. 132-152, (2017)
[2]  
Cai Y. F., Wang Y. J., Cawood P. A., Et al., Neoproterozoic Subduction along the Ailaoshan Zone, South China: Geochronological and Geochemical Evidence from Amphibolite, Precambrian Research, 245, pp. 13-28, (2014)
[3]  
Cai Y. F., Wang Y. J., Cawood P. A., Et al., Neoproterozoic Crustal Growth of the Southern Yangtze Block: Geochemical and Zircon U-Pb Geochronological and Lu-Hf Isotopic Evidence of Neoproterozoic Diorite from the Ailaoshan Zone, Precambrian Research, 266, pp. 137-149, (2015)
[4]  
Cai Y.F., Wang Y.J., Liu H.C., Et al., Geochronological and Geochemical Characteristics of the Neoproterozoic Amphibolite from Ailaoshan Zone, Western Yunnan and Its Tectonic Implications, Geotectonica et Metallogenia, 38, 1, pp. 168-180, (2014)
[5]  
Campbell I. H., Griffiths R. W., Implications of Mantle Plume Structure for the Evolution of Flood Basalts, Earth and Planetary Science Letters, 99, 1-2, pp. 79-93, (1990)
[6]  
Dai Z.W., Li G.M., Ding J., Et al., Late Cretaceous Adakite in Nuri Area, Tibet: Products of Ridge Subduction, Earth Science, 43, 8, pp. 2727-2741, (2018)
[7]  
Dong Y. P., Liu X. M., Santosh M., Et al., Neoproterozoic Accretionary Tectonics along the Northwestern Margin of the Yangtze Block, China: Constraints from Zircon U-Pb Geochronology and Geochemistry, Precambrian Research, 196-197, pp. 247-274, (2012)
[8]  
Li B.L., Ji J.Q., Wang D.D., Et al., Neoproterozoic Magmatism in South Yunnan: Evidence from SHRIMP Zircon U-Pb Geochrological Results of High-Grade Metamorphic Rocks in the Yaoshan Group, Acta Geologica Sinica, 86, 10, pp. 1584-1591, (2012)
[9]  
Li X.H., Liu Y., Tu X.L., Et al., Precise Determination of Chemical Compositions in Silicate Rocks Using ICP AES and ICP MS: A Comparative Study of Sample Digestion Techniquesof Alkali Fusion and Acid Dissolution, Geochimica, 31, 3, pp. 289-294, (2002)
[10]  
Li Z. X., Li X. H., Kinny P. D., Et al., Geochronology of Neoproterozoic Syn-Rift Magmatism in the Yangtze Craton, South China and Correlations with Other Continents: Evidence for a Mantle Superplume that Broke up Rodinia, Precambrian Research, 122, 1-4, pp. 85-109, (2003)
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