A BISUBDUCTION-COLLISION OROGENIC MODEL OF EARLY-PALEOZOIC IN THE MIDDLE PART OF NORTH QILIAN AREA
Received date: 1997-06-10
Online published: 1997-08-01
A tectonic evolution model of Early Paleozoic in the middle part of North Qilian Area is put forward based on the field investigation of more than ten years, and a series of comprehensive researches, including volcanic sedimentary association, the characteristics of the complex in high pressure metamorphism zone, subduction complex rock zone, granitic magmatism and isotopic age, etc. In Sinian, paleocontinental crust broke up, and micro ocean basin was formed with remnant fragmants of continental crust. In Cambrian Ordovician, asymmetric bisubduction took place southward and northward respectively with Heihe Babaohe Zone being a spreading ridge. During the northward subduction, progressive back arc extension gave rise to a new ocean crust. This type of events took place northward repeatedly, and their correspondant products, subduction complexes, were elevated back to the surface and transformed into convergent transitional crusts. During the southward subduction, the earlier extentional transition crusts were transformed to Alaska type active continental margins which subducted southward, and subsequently arc back extensional basin was formed . In Silurian, with subduction ended and the oceanic basin disappearing, a tectonic framework with the coexistence of island chains and turbidity trough was formed. In Devonian, an orogenic belt with new continental crust was formed as the result of the convergence and collision between the Alaskan massif and the Middle Qilian massif.
ZUO Guochao，WU Hanquan . A BISUBDUCTION-COLLISION OROGENIC MODEL OF EARLY-PALEOZOIC IN THE MIDDLE PART OF NORTH QILIAN AREA[J]. Advances in Earth Science, 1997 , 12(4) : 315 -323 . DOI: 10.11867/j.issn.1001-8166.1997.04.0315
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