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Wenliang Xu, Jilin University (China)
En Meng, Jilin University (China)
Fuping Pei, Jilin University (China)
Debin Yang, Jilin University (China)
Yang Yu, Jilin University (China)
Xingzhou Zhang, Jilin University (China)
Zhihong Ma, Jilin University (China)
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LA-ICP-MS U-Pb dating results for detrital and magmatic zircons from the late Paleozoic sedimentary and volcanic rocks in the eastern margin of the Jiamusi Massif, northeast China are reported to constrain the late Paleozoic tectonic evolution in the region. The detrital zircons from the lowest sandstone of the Heitai Formation display four group concordia 206Pb/238U ages, i.e., 483±2Ma, 509±1Ma, 541±2Ma and 570±6Ma, similar to ones of zircons from the Mashan Group and gneissic granites in the Jiamusi Massif (Wilde, et al., 2001, 2003), which implies that the late Paleozoic basin was formed after 483±2Ma and source of sediments was from the Jiamusi Massif. The magmatic zircons from two rhyolites of the Devonian Laotudingzi Formation (occurring above the Heitai Formation) have 206Pb/238U ages of 394±3Ma and 389±2Ma, respectively. Taken together with the basalt from the Group, it is suggested that a bimodal volcanic rocks exist in the early Devonian, implying an extensional environment. Combined with the bioclastic limestones from the early Devonian Heitai Formation and early Carboniferous Beixing Formation, it is proposed that an extensional basin was formed in the eastern margin of the Jiamusi Massif at the beginning of the late Paleozoic. However, the Permian strata mainly consist of two suites of volcanic rocks, i.e., the early Permian Erlongshan Formation and middle Permian Yanggang Formation. Their zircon LA-ICP-MS U-Pb dating results are 293±3Ma and 268±2Ma, respectively. The former is oriented in S-N direction and mainly composed of basalt-basaltic andesite-andesite and minor dacite association with high Mg# (40-59), enrichment in Na (Na2O/K2=1.26-4.25) and relatively depletion in HFSEs, implying an active continental margin tectonic setting, the latter is distributed in NE direction parallel to the Dunhua-Mishan fault and chiefly consists of dacite-rhyolite association with high SiO2 (77.2-77.5%), low MgO (0.11-0.14%) and peraluminous (ACNK=1.2-1.4), implying that the collision of the Jiamusi with the Khanka Massifs took place in the middle Permian.
Acknowledgements: This work is supported by the Natural Science Foundation of China (grant No. 40672038 and 40739905).
References: Wilde S A, Zhang X Z, Wu F Y. Tectonophysics, 2000, 328: 115-130
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