| SIMS zircon U-Pb ages, geochemistry and Nd-Hf isotopes of ca. 1.0 Ga mafic dykes and volcanic rocks in the Huili area, SW China: Origin and tectonic significance | |
| Wei-Guang Zhu; Hong Zhong; Zheng-Xiang Li; Zhong-Jie Bai; Yi-Jin Yang | |
| 2016 | |
| 发表期刊 | Precambrian Research
 |
| 卷号 | 273期号:1页码:67-89 |
| 摘要 | Late Mesoproterozoic to early Neoproterozoic igneous rocks (ca. 1100 Ma to >860 Ma) are sparse in the southwestern Yangtze Block, hindering our understanding of South China's position during the late Mesoproterozoic to early Neoproterozoic assembly of the supercontinent Rodinia. We report here Cameca secondary ion mass spectrometry (SIMS) zircon U-Pb ages, geochemistry, and Nd-Hf isotopic data for mafic dykes that intruded in the lower Tianbaoshan Formation, and that of intermediate to felsic volcanic rocks from the upper Tianbaoshan Formation of the Huili Group in southwestern Yangtze Block. The mafic dykes were formed at 1023 +/- 6.7 Ma. The volcanic rocks were dated at 1025 +/- 13 Ma and 1021 +/- 6.4 Ma, contemporaneous to the mafic dykes. The mafic dykes show weakly positive epsilon(Nd)(t) values (+0.41 to +1.6) and positive epsilon(Hf)(t) values (+7.0 to +10.3). They are characterized by slightly LREE-enriched and HREE-depleted patterns and the trace element patterns with typical depletion of Nb and Ta and slightly enrichment of Th relative to La. The parental magma for the mafic rocks exhibits affinity of low-Ti tholeiitic basaltic magma generated by melting of a depleted asthenospheric mantle source. The primary magma of these mafic rocks likely underwent variable degrees of the fractional crystallization and crustal contamination. The intermediate to felsic volcanic rocks in the Tianbaoshan Formation are characterized by significantly LREE-enriched and slightly HREE-depleted patterns, showing negative Nb-Ta, Eu, Sr, P and Ti anomalies in the primitive mantle-normalized multi-element plot. In addition, the volcanic rocks display variably elevated Ga, Rb, Zr, REE, and Y concentrations, and high Ga/Al ratios (2.31-2.64), consistent with the geochemical characteristics of A(2)-type granites. The volcanic rocks exhibit negative epsilon(Nd)(t) values (-5.1 to-7.1) and variable epsilon(Hf)(t) values (-0.67 to +3.9). They give two-stage Nd model ages (T(Nd)2DM) and two-stage Hf model ages (T-2Dm(Hf)) of 1.83-1.99 Ga and 1.62-1.91 Ga, respectively. The Nd-Hf isotopic signatures indicate that the primitive magma for the Tianbaoshan intermediate to felsic volcanic rocks was probably derived from partial melting of the granulite-facies lower crust driven by underplating of mafic magmas, and underwent extensive fractional crystallization during emplacement. The studied 1.02 Ga felsic volcanic rocks and mafic dykes at Huili are interpreted to have formed in an impactogen setting during the initial stage of collision between the Yangtze and Cathaysia blocks prior to the Sibao Orogeny. |
| 学科领域 | 矿床地球化学 |
| 收录类别 | SCI |
| 语种 | 英语 |
| 文献类型 | 期刊论文 |
| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/6089 |
| 专题 | 矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文 |
| 推荐引用方式 GB/T 7714 | Wei-Guang Zhu,Hong Zhong,Zheng-Xiang Li,et al. SIMS zircon U-Pb ages, geochemistry and Nd-Hf isotopes of ca. 1.0 Ga mafic dykes and volcanic rocks in the Huili area, SW China: Origin and tectonic significance[J]. Precambrian Research,2016,273(1):67-89. |
| APA | Wei-Guang Zhu,Hong Zhong,Zheng-Xiang Li,Zhong-Jie Bai,&Yi-Jin Yang.(2016).SIMS zircon U-Pb ages, geochemistry and Nd-Hf isotopes of ca. 1.0 Ga mafic dykes and volcanic rocks in the Huili area, SW China: Origin and tectonic significance.Precambrian Research,273(1),67-89. |
| MLA | Wei-Guang Zhu,et al."SIMS zircon U-Pb ages, geochemistry and Nd-Hf isotopes of ca. 1.0 Ga mafic dykes and volcanic rocks in the Huili area, SW China: Origin and tectonic significance".Precambrian Research 273.1(2016):67-89. |
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