Post-collisional granitoids from the Dabie orogen: New evidence for partial melting of a thickened continental crust

被引：305

作者：

He, Yongsheng ^{[1
,2
]}

Li, Shuguang ^{[1
]}

Hoefs, Jochen ^{[2
]}

Huang, Fang ^{[1
,3
]}

Liu, Sheng-Ao ^{[1
]}

Hou, Zhenhui ^{[1
]}

机构：

[1] Univ Sci & Technol China, CAS Key Lab Crust Mantle Mat & Environm, Sch Earth & Space Sci, Hefei 230026, Anhui, Peoples R China

[2] Univ Gottingen, Dept Geosci, D-37077 Gottingen, Germany

[3] ETH, Inst Geochem & Petrol, CH-8092 Zurich, Switzerland

来源：

GEOCHIMICA ET COSMOCHIMICA ACTA | 2011年 / 75卷 / 13期

基金：

中国国家自然科学基金;

关键词：

U-PB AGE; MAFIC-ULTRAMAFIC INTRUSIONS; PRESSURE METAMORPHIC ROCKS; TRONDHJEMITE-GRANODIORITE TTG; EARLY CRETACEOUS GRANITOIDS; CENTRAL CHINA IMPLICATIONS; INTERMEDIATE-FELSIC ROCKS; ANCIENT LOWER CRUST; O-ISOTOPE EVIDENCE; TRACE-ELEMENT;

D O I：

10.1016/j.gca.2011.04.011

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

The geological implications of granitoid magmas with high Sr/Y and La/Yb are debated because these signatures can be produced by multiple processes. This study presents comprehensive major and trace element compositions and zircon SHRIMP U-Pb age data of 81 early Cretaceous granitoids and 4 mafic enclaves from the Dabie orogen to investigate partial melting of the thickened lower continental crust (LCC). On the basis of Sr/Y ratios, granitoids can be grouped into two magma series: (i) high Sr/Y granitoids (HSG) and (ii)Normal granitoids with low Sr/Y. Relative to normal granitoids, HSG display the following distinct chemical features: (1) at given SiO2 and CaO contents, the HSG have significantly higher Sr than normal granitoids, defining two different trends in Sr versus SiO2, CaO diagrams; (2) highly depleted heavy rare earth element (REE) relative to middle and light REE with (Dy/Yb)(N) and (La/Yb)(N) up to 3.2 and 151, respectively; (3) variable and higher Nb/Ta; and (4) positive correlations among Sr/Y, (Dy/Yb)(N), (La/Yb)(N), and Nb/Ta. High Sr/Y, (La/Yb)(N), (Dy/Yb)(N), and Sr/CaO of HSG do not correlate with major elements (e.g., SiO2). Large variations in these ratios at a given SiO2 content indicate that these features do not reflect magma mixing or fractionation. HSG have higher Sr at a given CaO content and larger variation of (Dy/Yb)(N) than old crustal rocks (including exposed basement, global mafic LCC xenoliths, high Sr/Y TTG suites, and adakites in modern arcs). This precludes inheritance of the HSG chemical features from these source rocks. Instead, the chemical features of the HSG are best explained by partial melting of the thickened LCC with garnet-dominant, plagioclase-poor, and rutile-present residual lithologies. The coupled chemical features of the HSG are not observed in post-collisional granitoids younger than ca.130 Ma, indicating removal of the eclogitic source and/or residuum of HSG underneath the orogen. These characteristic chemical relationships in the Dabie HSG may be applied to distinguish partial melts of thickened LCC from high Sr/Y intermediate-felsic magmatic rocks which do not show clear indications for melting depth. (C) 2011 Elsevier Ltd. All rights reserved.

引用

页码：3815 / 3838

页数：24

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