Late Paleozoic post-collisional magmatism in the Eastern Tianshan Belt, Northwest China new insights from geochemistry, geochronology and petrology of bimodal volcanic rocks
Coimbra, Joao Carlos; Pinto, Iraja Damiani; Wurdig, Norma Luiza; Do Carmo, Dermeval Aparecido
Lithos 127(3-4): 581-598
The Late Carboniferous to Permian marks an important phase of terrane amalgamation through accretion-collision in the Central Asian Orogenic Belt (CAOB). The Tianshan Belt forms part of this sequence, where the post-collisional event generated an E-W trending bimodal volcanic zone that extends for ca. 5km from the southern Bogda Mt. to the easternmost Tianshan Belt. Here we report the petrology, geochemistry and geochronology of the bimodal volcanic rocks to characterize the post-collisional tectonic evolution in Late Paleozoic. The major element chemistry of the basalt and rhyolite samples indicates a bimodal high-K calc-alkaline affinity. The basalts are characterized by high abundance. Highlights: A bimodal volcanic event took place in the Early Permian, at around 295Ma in the Eastern Tianshan Belt. The bimodal volcanic series was generated in an initial post-collisional setting. Basalts were likely derived from a lithospheric depleted mantle with partial incorporation of crustal components. Zircons from rhyolites yield varied ?Hf(t) values, suggesting a mixing of multiple source materials.