The Age And Tectonic Setting Of Early Paleozoic Intrusive Rock In The Qinghai Province Xunhua Daowei Area

Qilian Orogenic Belt is an important component of the Central Orogenic Systerm. More magma activity, widely distributed of intrusive rocks and rock types diverse is a feature of Qilian Orogenic Belt. This rocks recorded between Qilian Massif and the Alashan Massif and the Qaidam Massif of the Pro-Teyhys Ocean subduction, collision and other important information. While study Caledonian magmatic rocks of Qilian Orogenic Belt has important scientific significance for revealing the Caledonian tectonic evolution of the Qilian Orogenic Belt. This article based on geology, petrology, geochemistry, geochronology research of Jishishan intrusive bodies, Leijishan intrusive bodies situated in Daowei area,Xunhua county,east part of South Qilian Orogenic Belt, achieving the following results and understanding:1?Determing five different types of intrusive rocks of Jishishan intrusive bodies,including pyroxenite, gabbro, diorite, quartz diorite, and gabbro diorite. Zircon U-Pb ages of rock is 462-464Ma, belong to the Middle Ordovician. The complex source close to the enriched lithospheric mantle, enrichment of Rb, Cs, Ba and other large-ion lithophile elements,and marked depletion of Nb, Ta, Ti, and High field strength elements, with arc magmatic rocks characteristics,which are producted of the the northern margin of Qaidam massif Ocean(Southern Qilian Ocean) northward subduction.2?Determing three different types of intrusive rocks of Leijishan intrusive bodies,including granodiorite, porphyritic monzonitic granite, monzonite granite, a few syenogranite.Zircon U-Pb ages for 443?446Ma,belong to the Late Ordovician. This granites belong to strong peraluminous S-type granites, is crustal genesis, which was formed in the Syn-collision tectonic environment. Zircon U-Pb geochronology research has also acquired 750?1400Ma inherited zircon age of the basement. Combining geochemistry and inherited zircon ages think the source area rocks as Precambrian basement, and component is equivalent to graywacke or felsic metaigneous rocks.3?Restoration and reconstruction of the Early Paleozoic tectonic evolution in the southern qilian structural belt. The tectonic evolution of northern margin of Qaidam massif-south Qilian tectonic belt based on the neoproterozoic Rodinia supercontinent splitting decomposition evolution. Splitting decomposition and ocean basin formation stage form early Neoproterozoic to the early of Early Cambrian. The oceanic crust subduction stage form the middle of Early Cambrian to the early of Middle Ordovician. Syn-collision and post-collision stage from the Late Ordovician to the Middle Devonian.