U-Pb zircon ages for a collision-related K-rich complex at Shidao in the Sulu ultrahigh pressure terrane, China.

Abstract

The Shidao complex at the eastern extremity of the Sulu ultrahigh pressure (UHP) terrane is composed of oldest pyroxene syenite, quartz syenite and youngest granite intrusives of the K-rich shoshonitic series. U-Pb zircon dating yields nearly concordant ages of 225 ± 2, 211 ± 3 and 205 ± 5 Ma for pyroxene syenite, quartz syenite and granite, respectively. The ages closely postdate the 240 to 220 Ma UHP metamorphism and correspond to the rapid cooling and exhumation of UHP rocks. A close genetic relation may exist between the formation of the Shidao intrusives and the continental collision and UHP metamorphism. However, the K-rich Shidao intrusive rocks are different from common syn-collisional granites in association of K-rich and granitic magmatism. A breakoff model is postulated to explain the formation of the complex. The breakoff of the subducting slab caused the rapid exhumation of the UHP terrane. Mantle upwelling resulted in basaltic magmatism and formation of the K-rich complex. Formation of the Shidao complex marked the cessation of the UHP metamorphism and the oldest ages of 225 ± 2 Ma of the complex is the minimum timing for the UHP metamorphism.

Destruction of North China Craton: Insights from temporal and spatial evolution of the proto-basins and magmatism

“…In addition, the tectonic amalgamation of the Yangtze Plate with the North China Craton is spatially well coupled with the division of lithospheric mantle region of the North China Craton (Figure 8). Magmatism on the eastern and southern margins of the North China Craton in Late Triassic is a representation of cratonic destruction on the margins, no matter they were products in post-collisional extension background or melting of the lithosphere mantle induced by asthenospheric upwelling through the slab window formed by slab breakoff of the deep subducted plate [63,64].…”

Origin of early Cretaceous calc-alkaline lamprophyres from the Sulu orogen in eastern China: implications for enrichment processes beneath continental collisional belt

“…In this respect, the carbonate-and rutile-rich melt metasomatism beneath the Sulu orogen was unlikely to have been simultaneous to continental subduction. Alternatively, seismic investigations on the DabieSulu belt and U -Pb dating results of collision-related K-rich complex from the Sulu orogen suggested that slab breakoff occurred after the Triassic collision (Xu et al, 1999;Chen et al, 2003), which could be a likely mechanism for the metasomatic event. Following slab breakoff, asthenospheric upwelling and lithospheric extension caused the rapid exhumation of the UHP terranes (e.g., Li et al, 1999) and would provide heat supply to melt the trapped subducted continental crust.…”

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

“…There are also the same episode of alkali granites in the Dabie-Sulu orogenic belt [56,57], which also show the similar patterns of arc-like REE and trace element distribution [5,[58][59][60]. The Neoproterozoic age of inherited zircons in the CB granite indicates that its source is a product of mid-Neoproterozoic rift magmatism along the northern margin of the South China Block.…”