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1. chinaXiv:201907.00003 [pdf]

Silurian-Devonian sub-parallel ridge-trench interaction in Western Junggar and North-Central Tianshan in NW China: Alternative genesis of archipelagic architecture

Zhang, Ji'en; Chen, Yichao; Xiao, Wenjiao; Wakabayashi, John; Windley, Brian F.; Song, Shuaihua; Yin, Jiyuan
Subjects: Geosciences >> Geology

Western Junggar and North-Central Tianshan in NW China comprise a double magmatic belt, which evolved as a result of 446-380 Ma SSZ-type gabbro-basalt-andesite-diorite-granite-rhyolite magmatism that intruded a 504-446 Ma accretionary complex in SW Junggar and coeval magmatic arc in Central Tianshan. This orogenic framework is interpreted as a product of sub-parallel ridge-trench interaction, which generated the double magmatic belt together with adakitic intrusions in the older accretionary complex. In this model, a buoyant subducted ridge stalled and separated the double magmatic belts, resulting in the opening of a new 414-325 Ma intra-arc ocean, which is represented by Nb-depleted OIB- and MORB-type ophiolites. Mafic rocks generated by sea floor spreading in the modern Gulf of California record a similar evolution and chemistry. This new ocean split the northern accretionary complex along Mt. Xiemisitai-Barleik-Mayile line, leading to deposition of Devonian shallow marine-terrestrial sediments and cessation of magmatism at 380-349 Ma; this evolution also resembles that of the late Cenozoic passive margins of Baja California. Subsequent removal of the new ocean and its ridge-subduction gave rise to an archipelagic framework in the Late Paleozoic. A worldwide analysis of published examples of sub-parallel ridge-trench interaction indicates that a ridge jump can lead to multiple episodes of subduction, which could occur long before terminal ocean closure.

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