Early history of the eastern Sibao Orogen (South China) during the assembly of Rodinia: New mica ⁴⁰Ar/³⁹Ar dating and SHRIMP U–Pb detrital zircon provenance constraints

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• 作者：Zheng-Xiang Li ; Jo-Anne Wartho ; S ; ra Occhipinti ; Chuan-Lin Zhang ; Xian-Hua Li ; Jian Wang ; Chaomin Bao
• 关键词：Sibao Orogen ; Grenville-aged ; Rodinia ; South China ; Yangtze ; Metamorphism ; Tianli Schists
• 刊名：Precambrian Research
• 出版年：2007
• 出版时间：25 October 2007
• 年：2007
• 卷：159
• 期：1-2
• 页码：79-94
• 全文大小：1660 K

文摘

The Sibao Orogen in South China is one of the poorest known Grenville-aged orogenic belts through which the Neoproterozoic supercontinent Rodinia assembled. We report here the first UV laser spot ⁴⁰Ar/³⁹Ar mica and SHRIMP U–Pb zircon ages from a rare Grenville-aged metamorphic complex, the Tianli Schists, in the eastern Sibao Orogen. Our U–Pb zircon provenance ages indicate that the protolith of the Tianli Schists was a clastic sedimentary succession most likely derived from the Yangtze Block. The depositional age of the protolith is younger than 1530 Ma, as constrained by the youngest detrital zircon grains, but is older than 1040 Ma as constrained by the oldest ⁴⁰Ar/³⁹Ar muscovite ages. The Yangtze Block provenance for the Tianli Schists suggests that the Sibaoan ophiolitic complexes in northeastern Jiangxi, the ca. 970 Ma Xiwan adakitic granite intrusions, and the ca. 900 Ma(?) Xiwan blueschists, all to the northwest of the study region, were likely formed during the closure of a back-arc basin along the margin of the Yangtze Block. Our in situ UV laser ⁴⁰Ar/³⁹Ar results from S₁ and S₂ muscovites suggest that the Tianli Schists underwent metamorphism and deformation at 1042 ± 7 Ma to 1015 ± 4 Ma, the oldest known metamorphic event in the eastern Sibao Orogen. Muscovite/biotite cooling ages of ca. 968 ± 4 and 942 ± 8 Ma are recorded by deformed and recrystallised muscovite and biotite, respectively, indicating tectonic reactivation before 900 Ma, during the later stages of the Sibao Orogeny. Together with previous results from the western Sibao Orogen, our work suggests that the closure of the ocean between the Yangtze and Cathaysia Blocks during the assembly of Rodinia was diachronous: ≥1000 Ma at the western Sibao Orogen and ca. 900 Ma at the eastern Sibao Orogen.