Zircon U-Pb dating, trace element and Sr-Nd-Hf isotope geochemistry of Paleozoic granites in the Miao¡¯ershan-Yuechengling batholith, South China: Implication for petrogenesis and tectonic-magmatic evolution

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• 作者：Kui-Dong Zhao ; Shao-Yong Jiang ; Tao Sun ; Wei-Feng Chen ; Hong-Fei Ling ; Pei-Rong Chen
• 关键词：Zircon U&ndash ; Pb dating ; Sr&ndash ; Nd&ndash ; Hf isotopes ; Geochemistry ; Paleozoic granites ; Wuyi&ndash ; Yunkai orogeny ; South China
• 刊名：Journal of Asian Earth Sciences
• 出版年：2013
• 出版时间：25 September, 2013
• 年：2013
• 卷：74
• 期：Complete
• 页码：244-264
• 全文大小：5950 K

文摘

The Miao¡¯ershan-Yuechengling batholith (MYB) is one of the largest granitic batholiths in South China. At least five individual phases have been identified for the Paleozoic granites in the MYB. SHRIMP and LA-ICP-MS zircon U-Pb dating results imply that these granites were emplaced at 435 ¡À 4 Ma, 427 ¡À 3 Ma, 417 ¡À 6 Ma, 404 ¡À 6 Ma and 382 ¡À 2 Ma, respectively. The ages gradually decreased from the southeast to the northwest, implying that the MYB was incrementally emplaced from the southeast to the northwest lasting from early Silurian to late Devonian. Most granites are metaluminous to weakly peraluminous, and contain low P₂O₅ contents (<0.15 % ). These granites show enrichment of Rb, Th, U and depletion of Ba, Sr, Eu, Ti. They show relatively high (⁸⁷Sr/⁸⁶Sr)_i ratios (>0.715), low ¦Å_Nd(t) values (?8.9 to ?6.7), and low zircon ¦Å_Hf(t) values (?9.5 to ?4.0). These geochemical and isotopic characteristics indicate that these granites may have formed from partial melting of Paleoproterozoic basement rocks. Slight geochemical differences between different phases can be interpreted as resulting from partial melting of heterogeneous sources or different proportion mixing of meta-igneous and meta-sedimentary rocks. Zircon Hf isotope model ages vary from 1.77 to 1.93 Ga, with an average value of 1.84 ¡À 0.07 Ga. These data indicate that crust growth in this region took place mainly during the Paleoproterozoic (ca. 1.84 Ga), and the basement in the MYB should belong to the Cathaysia Block. The formation of the Paleozoic granites in the MYB was suggested to be related to the late orogenic magmatism of the Wuyi-Yunkai orogeny. Thus, the late orogenic magmatism in the northwestern part of the Wuyi-Yunkai orogeny must have lasted until ca. 381 Ma and took place also to the east of the Anhua-Luocheng Fault.