Diachronous subduction, closure of the Proto-Tethys Ocean, and collisional accretion of microcontinents: Insights from the early Paleozoic intermediate-mafic rocks in the Amdo microcontinent of the Tibetan Plateau

The Proto-Tethys Ocean played an important role in the formation and evolution of East Asian continental blocks, final closure may have led to first assembly nearly all blocks at northern margin Gondwana. However, controversy remains about reconstruction Tibetan Plateau is located Gondwana recorded entire tectonic from rift drift subduction collision during early Paleozoic. Therefore, it region which address processes Here, we present petrology, zircon U-Pb, Sr-Nd-Hf isotope, whole-rock geochemical data newly recognized intermediate-mafic magmatic rocks Amdo microcontinent central Tibet, with a view gain insights into nature geotectonic Zircon grains meta-andesites meta-basites yielded crystallization ages 490 Ma 455−450 Ma, respectively. are characterized by enrichment large ion lithophile elements (e.g., Rb, Th, U, K) depletion high field strength Nb, Ta, Ti) positive εHf(t) values (+3.4 +6.4), were probably derived partial melting depleted mantle source enriched minor fluids subducted sediments arc setting. tholeiitic exhibit both mid-ocean-ridge basalt flat rare earth element patterns) arc-like elevated Th/Yb ratios) affinities, combination negative (−4.6 −0.3) εNd(t) (−0.21 −0.45) values, suggesting that they generated varying degrees spinel peridotite ∼5%−10% crustal assimilation back-arc In this regard, favor interpretation experienced long-lasting (ca. 530−450 Ma) slab before subsequent collisional accretion microcontinents. Integrating results previous studies, propose microcontinent, South Qiangtang terrane, Qilian-Qaidam other Gondwana, arc-related magmatism along proto-Tethyan initial Proto-Tethyan been diachronous between ca. 455 430 Ma.