HR: 1330h
AN: T42B-0287    [PDF]
TI: A Lower Paleozoic Plate Tectonic Model for the North Qilian Mountains, NW China
AU: * Yang, H
EM: hyyang@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan, 70101 Taiwan
AU: Tseng, C
EM: yuan1515@yahoo.com.tw
AF: Department of Earth Sciences, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan, 70101 Taiwan
AU: Zuo, G
AF: Gansu Bureau of Geology and Mineral Resources, 206 Houngxing Road, Lanzhou, 730000 China
AU: Wu, H
AF: Xi'an Institute of Geology and Mineral Resources, 166 Youyi Road, Xi'an, 710054 China
AU: Xu, Z
AF: Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037 China
AU: Yang, J
AF: Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037 China
AB: Abstract The north Qilian mountains are a strongly-lineated Caledonian fold belt. Their mountain ranges, major rivers, fold axes, fault lines, and the spatial distribution of major rock types are all more or less parallel to one another and trend in NWW-SEE direction. The Caledonian plate tectonic structures have still been well preserved despite modifications by the Indosinian and Himalayan crustal disturbances. The north Qilian mountains may be considered as a plate suture zone which sutured the Alashan craton and the central-south Qilian craton in the lower Paleozoic time. This suture zone consists of an active continental margin, a passive continental margin, and an intervening oceanic domain. The southern margin of the Alashan craton was an active continental margin in the lower Paleozoic time, on which continental margin arcs, forearc basin, forearc ridge, and accretionary prism were very well developed. The northern margin of the central-south Qilian craton was chiefly a passive continental margin, but might be active locally in the lower Paleozoic time. The intervening oceanic domain consists of oceanic island arcs, oceanic islands, oceanic ridges, major oceanic floor, and backarc basin ocean floor. A Paleo-Qilian ocean with well-developed oceanic islands and oceanic ridges is presumed to have existed during the late Proterozoic-early Cambrian period. It started to contract in the mid-Cambrian and a Mariana type subduction occurred to have formed an oceanic island arc and a backarc basin. The Andean type subduction followed in the late-Cambrian through the Silurian periods, during which the paleo-Qilian oceanic lithosphere obliquely subducted northward beneath the southern margin of the Alashan craton, converting it from passive to active, and produced continental margin arc, forearc basin, forearc ridge, and accretionary prism, accompanied by the abundant granitoid intrusions. During the same period of time, the northern margin of the central-south Qilian craton had remained largely as a passive continental margin, but the paleo-Qilian oceanic lithosphere might have also subducted southward locally probably in the middle section of the north Qilian mountains. The cessation of the northerly oblique subduction in the late Silurian-Devonian period resulted an arc-continent collision and formed a backarc basin in the eastern section, and also left behind a segment of mid-oceanic ridge, an oceanic island arc, the enclosed remnant ocean, and a backarc basin on the surface of the earth in the western section. In summary, the lower Paleozoic plate tectonic structures of the north Qilian mountains are characterized by the orderly-arranged, well preserved mid-oceanic ridges, oceanic island arcs, accretionary prism, continental margin arcs, and backarc basins, and by the occurrence of Mariana-type and Andean-type subductions, dipolar subduction, and continental reworking and reactivation.
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8102 Continental contractional orogenic belts
DE: 8150 Plate boundary--general (3040)
DE: 9320 Asia
DE: 9614 Paleozoic
SC: Tectonophysics [T]
MN: 2003 Fall Meeting