| Tianshan orogenic belt is part of the Central Asian giant complex, north and south sideswere clamped in the Tarim Basin and Junggar Basin. The area,the Tianshan divided into Eastand West,roughly east-west to Urumqi-Korla line as the boundary, while the West Tianshanhas been divided into three parts,the Northern Tianshan, Middle Tianshan and SouthernTianshan. The Southern Tianshan is Located on the border between Tarim plate andKazakhstan plate,extension of the Urals-South Tianshan orogenic belt of China, it is atypical Paleozoic orogenic belt and it is an Paleozoic collision zone evolved from an openocean basin that between the Tarim plate and Kazakhstan plate, Quruqtagh in the northernmargin of the Tarim block and the southern margin of the Central Asian Orogenic Beltbinding site Tianshan orogenic system, and its structure and properties of the formation andevolution has important significance for resolve the relationship between the Central AsianOrogenic Belt and the Tarim craton, South Tianshan orogenic belt and the formation andevolution of structural properties.In this paper, homologous magmatic evolution and plate tectonics theory, based onprevious regional information Systematic research and author personally involved in1/50000of the regional geological survey project, View domestic research, It has been analyzedsystemly focuses on petrology, geochronology, geochemistry and geological background ofQuruqtagh widely developed western part of the Paleozoic intrusive belt.The main research results and cognition are as follows:1) Disintegrated the western part of the intrusion Quruqtagh, and established the "intrusive mapping unit"Observations detailedfull on Intrusions distributed in the western part of the intrusionQuruqtagh zonal, based on the theory that different levels of tectonic magmatic unit formedon homologous magmatic evolution, magma intrusion intruded upward,totally disintegratedeight Paleozoic tectonic magmatic units,they are Eastern middle Ordovician ust Teng Gawlerbiotite granite (O2), late Ordovician ust fine Proton high Lexi Ministry adamellite (O3), late Silurian Tiemenguan southeast porphyritic granodiorite (S3),/late Silurian ExpoSternberg Township quartz diorite (S3/o), early Devonian WstTengGawler gabbro (green)rock (D1v), early Devonian World Tiemenguan East adamellite (D1), early Devonian ustTeng Gawler adamellite (D1) and early Carboniferous imam was opened in Southadamellite (C1).2) Analyzed systemly focuses on petrology, geochronology, geochemistry and tectonicenvironment of granitic intrusions developed from Quruqtagh widely developed western partof the Paleozoic intrusive beltFrom the analysis of rock association, the western part of the Quruqtagh has a series ofacidic rock combination,there is gabbro (gabbro-diabase)-quartz diorite-granodiorite-adamellite-K-feldspar granite from mafic-neutral-acidic; and obtained the intrusion’sLA-ICP-MS U-Pb zircon dating of western part of the intrusion Quruqtagh, the ages were:middle Ordovician (463.5±5.8Ma,458±3Ma) late Ordovician (454.6±4.6Ma,454.2±9.5Ma),late Silurian (419.2±3.1Ma,418±2.7Ma), early Devonian (415.5±4.3Ma), late Devonian (withSiO2(51%~65%~69%~74%) on the geochemistry,K2O(1.4%~2.8%~3.5%~;400.6±1.6Ma,399.9±1.5Ma),Geochemistry characteristics shows SiO2(51%~65%~69%~74%) K2O(1.4%~2.8%~3.5%~4.5%),K2O/SiO2(0.03~0.04~0.05~0.06)andK2O/Na2O(0.55~1.30~1.69~2.72) successively adding, According to the polarity of the active continental margincomponent characteristics inferred the characteristics is formed by the subduction retreat diveSuccessively away from the Magmatic belt.Mostly produced by high-angle subduction; The source identification show that, theOrdovician, Silurian and Devonian granites were melting of the source rock containingplagioclase-hornblende Stone-source rock sec tion pyroxene granulite melting in the lowercrust, and the early Carboniferous peraluminous S-type granites melting of sandstone ormetamorphic rocks which rich biotite and muscovite at high temperatures and pressureconditions; the characteristics of Yb gradually increased, and Carboniferous intrusive rockshave a tendency to increase in order shows that there has more crustal material participatedmagmatic activity with Subduction occurred and crust vertical sustainable growth,goes step further to explain the subduction is sustainable/ongonging; the products of subductionenvironment are middle Ordovician (O2) to early Devonian (D1) intrusive rocks belong to thecalc-alkaline-Kcalc-alkaline I-type granites type, quasi Aluminum-weakly peraluminousseries, Petrography and trace element geochemical characteristics shows that the properties ofarc granite; the early carboniferous (C1) is strongly peraluminous granite "S" type granite,formed in the land-continental collision tectonic environment, the main reasons of this kindof granitic magma may be caused by crustal thickening crust remelting of matter;3)Constraints on evolution of southern Tianshan oceanic basin and the structuralproperties of Quruqtagh plotsAccording achievements of Quruqtagh evolution of the western part of the Paleozoicgranite and regional achievements, infered the transition of southern edge of the southernTianshan oceanic tectonic from extensional environment to squeeze environment at least inthe Middle Ordovician (O2),start north-sorth bilateral subduction with the nature of the activeedge of the continent,through Silurian(S), Devonian(D) to early Carboniferous(C1) continuedsubduction, resulting in the formation of the two rims arc granitic intrusions, the method ofsouthern subduction mainly for back type with high angle, and the northern edge is relativelyslow. Different subduction angle lead to different activity intensity of north and south edgesmagmatic,the northern greater than the southern edge and then into the contraction phase,and closed in the Early Carboniferous (C1) ocean basin, into the intraplate geologicalevolution stage.In addition, the intrusive rock belt with active epicontinental magmatic arc properties,its causes related with the southern Tianshan oceanic crust under the Tarim plate subduction(Ordovician-Devonian) ocean basin closure and post-collision (Carboniferous) orogeny, so itshould not be used as part of the stability Tarim craton, but as the proliferation plots of Tarimplatform. |
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