Early Silurian Trench-arc-basin System in Northwestern Margin of the North Qilian Orogen, China: Constraints from U–Pb Zircon Geochronology of Tuffs and Sandstones

The North Qilian Orogen is considered as a representative oceanic suture zone formed by the closure of the North Qilian Ocean, which forms the northern part of the Proto-Tethys Ocean along the northern margin of the eastern Gondwana during the Early Paleozoic. However, the time interval of Early Pal...

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Published inGeochemistry international Vol. 60; no. 13; pp. 1415 - 1438
Main Authors Liang, Wei, Mou, Chuanlong, Hou, Qian
Format Journal Article
LanguageEnglish
Published Moscow Pleiades Publishing 01.12.2022
Springer
Springer Nature B.V
Subjects
Accretion
Chronology
Deposition
Earth and Environmental Science
Earth Sciences
Geochemistry
Geochronology
Geochronometry
Gondwana
Isotopes
Oceanic trenches
Orogeny
Paleoceanography
Paleozoic
Radiometric dating
Rock
Rocks
Rocks, Sedimentary
Sandstone
Silurian
Subduction
Tuff
Volcanic ash, tuff, etc
Zircon
China
Early Silurian
LA‑ICP-MS U–Pb dating
North Qilian Orogen
Angzanggou Formation
Tuff and detrital zircons
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Summary:The North Qilian Orogen is considered as a representative oceanic suture zone formed by the closure of the North Qilian Ocean, which forms the northern part of the Proto-Tethys Ocean along the northern margin of the eastern Gondwana during the Early Paleozoic. However, the time interval of Early Paleozoic subduction system remains controversial, especially the part along the northwest margin where it is connected to the Alxa Block. Here we explored the whole rock geochemistry and LA-ICP-MS zircon U–Pb geochronology on a suite of tuff and clastic rocks from the Angzanggou Formation in the west margin of the North Qilian Orogen. Zircon U–Pb dating of tuff samples yielded the eruption ages of ca. 438 Ma. Detrital zircon from clastic rocks have revealed three age populations: 0.4–0.6 Ga (peak at 438 Ma), 0.7–0.9 Ga (peak at 875 Ma), and 0.93–1.1 Ga (peak at 984 Ma). Zircons with U–Pb ages of 0.4–0.6 Ga are markedly different from those of North China Block and Alxa Block, but are similar to zircon ages determined for Qilian Paleozoic arc-related magmatic rocks. Based on previous geochemical and geochronological data from the early Paleozoic igneous and clastic rocks, we believed that the subduction-accretion processes in North Qilian Orogen lasted until the Angzanggou Formation in the Early Silurian, thus leading to the formation of a fore-arc basin.
ISSN:0016-7029
1556-1968
DOI:10.1134/S0016702922130079