Early Paleozoic granitic magmatism related to the processes from subduction to collision in South Altyn, NW China

• Published in: Science China. Earth sciences Vol. 58; no. 9; pp. 1513 - 1522
• Main Authors: Liu, Liang, Kang, Lei, Cao, YuTing, Yang, WenQiang
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01.09.2015; Springer Nature B.V
• Subjects: Continental crust; Earth and Environmental Science; Earth Sciences; Geology; Magma; Marine; Metamorphic rocks; Metamorphism; Oceanic crust; Paleozoic; Plate tectonics; Review; 大陆俯冲; 岩浆活动; 早古生代; 碰撞络合物; 花岗质岩石; 超高压变质作用; 镁铁质-超镁铁质岩; 阿尔金; China; China, People's Rep; continental deep subduction; tectonic evolution; granitic magmatism; oceanic subduction; South Altyn
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-015-5151-1

Four episodes of granitic rocks at 517, 501-496, 462-451, and 426-385 Ma occurred in the South Altyn subduction-collision complex. The first episode of granite emplacement predates the formation of the ophiolite type mafic rock （〉500 Ma）, and the three subsequent episodes can be temporally correlated to high-pressure （HP） to ultrahigh-pressure （UHP） metamorphism at ca 500 Ma, retrograde granulite-facies metamorphism at ca. 450 Ma, and amphibolite-facies metamorphism at ca. 420 Ma, re- spectively. A comprehensive study of these granitic rocks, along with the regional geological background, mafic-ultramafic rocks, and HP-UHP metamorphism, indicates that the four episodes of granitic magmatism are sequentially derived from the partial melting of the earlier subducted oceanic crust at 517 Ma, the thickened continental crust due to continental subduction at ca. 500 Ma, the mid-upper crust in response to slab breakoff at ca. 450 Ma, and the tectonic transition from contraction to extension at ca. 420 Ma. The formation age of 517 Ma for oceanic adakite provides a direct constraint on the time of the oce- anic subduction in South Altyn. In addition, there is a ca. i0 Myr interval between the oceanic subduction to the continental deep subduction, suggesting that the Early Paleozoic tectonic evolution might have been a successive process in South Altyn. The four episodes of formation of granitic rocks, mafic-ultramafic rocks, and HP-UHP metamorphic rocks have fully recorded the tectonic evolution, beginning with the oceanic subduction, followed by continental subduction, and later exhumation dur- ing the Early Paleozoic in South Altyn.