Testing final closure time of the Paleo-Asian Ocean along the Solonker
suture by a transition of compressional and extensional setting
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Abstract
The giant Central Asian Orogenic Belt is an extensive accretionary orogen, of which the Solonker suture, as a
major regional suture, coincides closely with an early Permian paleobiogeographical boundary. This suture is
considered to mark the location of the final closure of the Paleo-Asian Ocean between the North China Craton and
the Mongolian Terrane. Although the closure time of the Paleo-Asian Ocean along the Solonker suture has
generally been regarded as Late Permian–Early Triassic, uncertainty remains because of a lack of typical collisionrelated
features (e.g., high-grade regional metamorphism and well-developed fold–thrust structures) and a
scarcity of outcrops.
The present study reports Early Permian foliated gabbros and dikes (288–275 Ma) and Middle-Late Permian
undeformed layered gabbros, strongly peraluminous granites, and I-type granites (265–254 Ma) in the Xinhure
area along the northern margin of the North China Craton. The Early Permian foliated intrusions have a
subduction-related geochemical signature and were derived from partial melting of lithospheric mantle modified
by subduction-related melts or fluids at the active margin of the North China Craton. In contrast, the Late Permian
undeformed layered gabbros and strongly peraluminous granites were derived from partial melting of lithospheric
mantle and middle–upper crust, respectively, triggered by asthenospheric upwelling. Therefore, a transition from
an end-compressional to an extensional environment according to a transition from collision termination to postcollision
of the North China Craton and Mongolian Terrane may have occurred between 275 Ma and 262 Ma. This
time span can be considered as the final closure time of the Paleo-Asian Ocean along the Solonker suture.
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