Reconciling Orogenic Drivers for the Evolution of the Bangong‐Nujiang Tethys During Middle‐Late Jurassic. Issue 2 (12th February 2020)

• Record Type: Journal Article
• Authors: Li, Shi‐Min; Wang, Qing; Zhu, Di‐Cheng; Cawood, Peter A.; Stern, Robert J.; Weinberg, Roberto; Zhao, Zhidan; Mo, Xuan‐Xue
• Is Part Of: Tectonics. Volume 39:Issue 2(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-02-12
• Subjects: arc magmatism -- detrital zircon ages -- orogenic divers -- arc‐trench system -- subparallel ridge subduction -- Bangong‐Nujiang suture; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2019TC005951
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Identifying arc‐trench systems along with spatial and temporal variations in their record of tectono‐magmatic events is crucial for determining the orogenic divers and evolution of orogenic systems. New geochronological and geochemical data of Jurassic igneous rocks, as well as detrital zircon data from contemporaneous sedimentary units, within the eastern Bangong‐Nujiang suture in central Tibet indicate the existence of an approximately 1, 200‐km Middle‐Late Jurassic magmatic arc system. This arc system can be divided into two distinct along‐strike segments, which are characterized by magmatic activity extending from 166 to 160 Ma in the east and 170–148 Ma in the west, followed by magmatic gaps at 160–120 and 148–125 Ma, respectively. An accretionary prism, magmatic arc, and retro‐arc sedimentary units are identified from south to north in the eastern segment. The 166–160 Ma arc includes high‐K calc‐alkaline granitoids, and high‐Mg andesites, dacites, and rhyolites, which collectively can be interpreted to originate from partial melting of ancient lower crust and mélange diapirs above a north dipping subduction zone. Our analysis reveals the existence of an overall compressional arc‐trench system along strike, which overlaps with a phase of 170–160 Ma ophiolite generation and a rock association of 160–148 Ma slab‐derived adakites and oceanic island basalt‐type rocks, and is followed by an overall magmatic gap during 148–125 Ma with subsequent 125–105 Ma extensive magmatism. We infer that these records may reflect sequential tectonic events, including subparallel ridge‐trench collision (170–160 Ma), slab window formation (160–148 Ma), subsequent subduction termination (148–125 Ma), and final Lhasa‐Qiangtang amalgamation (125–105 Ma). Key Points: An ~1, 200‐km‐long Middle‐Late Jurassic magmatic arc flanked by coeval sedimentary units An overall compressional convergent margin overlapping with ophiolite generation and slab window magmatism, and followed by a magmatic gap Sequential events including subparallel ridge‐trench collision, slab window formation, subduction termination, and Lhasa‐Qiangtang amalgamation