EARLY CORDILLERAN ARC DEVELOPMENT RECORDED IN LATE PERMIAN AND EARLY TRIASSIC PLUTONS OF THE NORTHERN MOJAVE DESERT, CALIFORNIA

AbstractPermian–Triassic boundary (PTB) volcanic ash beds are widely distributed in South China and were proposed to have a connection with the PTB mass extinction and the assemblage of Pangea. However, their source and tectonic affinity have been highly debated. We present zircon U–Pb ages, trace-element and Hf isotopic data on three new-found PTB volcanic ash beds in the western Hubei area, South China. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircons yields ages of 252.2 ± 3.6 Ma, 251.6 ± 4.9 Ma and 250.4 ± 2.4 Ma for these three volcanic ash beds. Zircons of age c. 240–270 Ma zircons have negative εHf(t) values (–18.17 to –3.91) and Mesoproterozoic–Palaeoproterozoic two-stage Hf model ages (THf2) (1.33–2.23 Ga). Integrated with other PTB ash beds in South China, zircon trace-element signatures and Hf isotopes indicate that they were likely sourced from intermediate to felsic volcanic centres along the Simao–Indochina convergent continental margin. The Qinling convergent continental margin might be another possible source but needs further investigation. Our data support the model that strong convergent margin volcanism took place around South China during late Permian – Early Triassic time, especially in the Simao–Indochina active continental margin and possibly the Qinling active continental margin. These volcanisms overlap temporally with the PTB biocrisis triggered by the Siberian Large Igneous Province. In addition, our data argue that the South China Craton and the Simao–Indochina block had not been amalgamated with the main body of Pangea by late Permian – Early Triassic time.

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Morphological Evolution of Claraia Species from the Late Permian (Changhsingian) to the Early Triassic (Induan) and the Response to the Permian–Triassic Stressed Environment

Springer Geology - STRATI 2013 ◽

10.1007/978-3-319-04364-7_197 ◽

2014 ◽

pp. 1035-1038

Author(s):

Weihong He ◽

Kexin Zhang ◽

Tinglu Yang ◽

Shunbao Wu

Keyword(s):

Morphological Evolution ◽

Early Triassic ◽

Late Permian

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The Late Permian-Early Triassic Khuff Formation in the Middle-East: Sequence Biostratigraphy and Palaeoenvironments by Means of Calcareous Algae and Foraminifers

10.2523/iptc-11743-abstract ◽

2007 ◽

Cited By ~ 7

Author(s):

Jeremie Gaillot

Keyword(s):

Middle East ◽

Calcareous Algae ◽

Early Triassic ◽

Late Permian

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Final-Stage Magmatic Record of Paleo-Asian Oceanic Subduction? Insights from Late Permian to Early Triassic Intrusive Rocks in the Yanbian Area, Easternmost Central Asian Orogenic Belt

Minerals ◽

10.3390/min10090799 ◽

2020 ◽

Vol 10 (9) ◽

pp. 799

Author(s):

Chao Zhang ◽

Franz Neubauer ◽

Zheng-Hong Liu ◽

Fang-Hua Cui ◽

Qing-Bin Guan

Keyword(s):

Partial Melting ◽

Granitic Rocks ◽

Early Triassic ◽

Crustal Material ◽

Late Permian ◽

The North ◽

Wide Range ◽

Intrusive Rocks ◽

Subduction Setting ◽

T Values

This paper reports new zircon LA–ICP–MS U–Pb and Hf isotope data, and whole-rock major and trace element data for Late Permian to Early Triassic intrusive rocks in the Yanbian area, NE China. These data provide new insights into the timing of the final subduction of the Paleo-Asian Ocean beneath the North China Craton. The zircon U–Pb age data indicate that a suite of Late Permian to Early Triassic intrusive rocks related to subduction is present within the Yanbian area. The Late Permian intrusive rocks consist of diorites while the Early Triassic granites and hornblende gabbros constitute a geochemically bimodal igneous rock association. Furthermore, the Early Triassic granites show the geochemical characteristics of shoshonitic rocks. All the rocks are characterized by enrichment in LILEs and LREEs, and depletion in HREEs and HFSEs, suggesting they formed in a subduction setting. Zircons from the Early Triassic gabbros have εHf(t) values and TDM2 ages of +7.6 to +10.7 and 735–1022 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of lithospheric mantle material that had been previously modified by subduction-related fluids. The Late Permian diorites have εHf(t) values and TDM2 ages of +0.5 to +9.5 and 853 to 1669 Ma, respectively, while they have high contents of Al2O3, Fe2O3, and low contents of SiO2, Cr, and Ni, indicating Late Permian diorites should derive from the mantle and are influenced by some crustal material. Early Triassic granitic rocks have a wide range of εHf(t) values and TDM2 ages of −4.8 to +9.4 and 852 to 2136 Ma, respectively. Their zircons imply that the Early Triassic granites could be mainly derived from partial melting of the crust, with minor contribution of the crustal material of an ancient crust. The Early Triassic bimodal intrusive rocks in Yanbian area, combined with the regional geologic information; therefore, record a final post-subduction extensional environment due to the break-off of the previously subducted slab.

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