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TitlePermian back-arc basin formation and arc migration in the southern Central Asian Orogenic Belt, Northwest China
AuthorSantos, G S; Hong, T; Van Staal, C S; Bédard, J H; Lin, S; Wang, K
SourceGeological Journal 2022 p. 1-11,
Alt SeriesNatural Resources Canada, Contribution Series 20220241
Mediapaper; digital; on-line
File formatpdf; html
Lat/Long WENS 94.3333 96.3333 41.5000 40.6667
SubjectsScience and Technology; tectonics; Central Asian Orogenic Belt; Permian
Illustrationslocation maps; diagrams; photographs; stratigraphic columns; cross-plots; cross-sections
Released2022 10 09
AbstractThe 290-280 Ma mafic Liuyuan Complex, embedded in the terranes constituting the southern edge of the Central Asian Orogenic Belt, has been interpreted to be either an ophiolite or an intracontinental large igneous province. Our detailed mapping shows that the Liuyuan Complex preserves an almost complete oceanic crustal section, with basal troctolite cumulates, varitextured gabbro affected by intense sub-seafloor hydrothermal circulation, a newly discovered, and laterally-continuous sheeted dyke complex, capped by basaltic pillows. This architecture is inconsistent with a continental rift-layered intrusion model for the Liuyuan Complex, which we interpret as oceanic crust formed by seafloor spreading. The trace element ratios (Th/Yb, V/Ti, La/Sm, and La/Nb) of the lavas is consistent with a back-arc basin environment. We suggest that the slab subducting to the north and forming the Ganquan arc system rolled back around 292 Ma, opening a back-arc basin (the Liuyuan Complex). This oceanic basin started to close from ca. 281 Ma, with north dipping subduction under the accreted terranes constituting the southern active margin of Composite Siberia. The Liuyuan Complex was eventually obducted southwards over the Ganquan arc as part of the upper plate during the final closure of the back-arc basin.
Summary(Plain Language Summary, not published)
New mapping and geochemical work show that the Liuyuan Complex of NW China is an ophiolite that formed at 290-280 Ma. This allows the history of closure of the Central Asian Orogenic Belt to be reinterpreted.

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