Division To The Tectofacies In The Caledonian Tectonic Belt In Lapeiquan Area In Altun Mountain

Based on the tectofacies division in the Caledonian Orogenic zone in Lapeiquan region in Altun mountain,and using of the predecessor's fruit ,we can divide the tectonic slices into 10 tectonic facies from the different tectonic environment in our study region ,such as continental rift facies, MORB facies,OIB facies, Deep-sea Basin facies, island-arc volcanic facies, back-arc basin facies, carbonic rock platform facies, arc intrusive rock facies, continental marginal volcanic arc facies and postorogenic intrusion facies.These tectonic facies show us the process of the dispersion,convergence and collision during the Caledonian orogenic evolution in Altun mountain.The continental rift mainly contains the Suoerkuli group which include shore-shallow sea facies and carbonic rock sedimentary formation. MORB facies mainly consists of ophiolite slices, which consists of serpentinite, Pyroxene peridotite, pyroxenite ,meta-basalt and etc. OIB facies constitutes by basic volcanic rock which under low greenschist facies-greenschist facies metamorphic process always co-existence with MORB facies. Deep-sea Basin facies consists of radiolarian chert and siliceous limestone.Island-arc volcanic facies consists of acidic-intermediate acidic volcanics which under low greenschist facies-greenschist facies metamorphic process. Back-arc basin facies constitutes by the continental margin clastic rocks-Flysch formation.Carbonic rock platform facies constitutes by extremely thick metamorphic carbonate rock and metamorphosed detrital rock. Continental marginal volcanic arc facies consititues by clastic rock and acidic volcanic rock formation. Arc intrusive rock facies mainly constitutes by base-acidic rocks and consists of gabbro, diorite, tonalite, granodiorite and monzonitic granite. Postorogenic intrusion facies mainly consists of porphyritic monzonitic granite, tonalite and a little syenite-granite.Based on the tectofacies division,we found a formation and evolution model of the Orogenic zone in Altun mountain. During late Mesoproterozoic, the southern margin of Tarim plate began to split, it follows that sedimentary rock and basic intrusive rock in the rift valley had been emplaced. During early Cambrian period or Precambrian(>510Ma)the ocean basin began to spreading and finally formed the Noth Altun ocean,then MORB,OIB and siliceous rock been emplaced. During Middle Cambrian-early Ordovician(510-450Ma), the Noth Altun ocean basin began to shrinking,then rock association in island-arc volcanic facies, back-arc basin facies, carbonic rock platform facies, continental marginal volcanic arc facies and arc intrusive rock facies had been emplaced. After early Ordovician(400-450Ma), collisional orogeny occurred and Oceanic evolution ended and Postorogenic magmaticrock facies emplaced, and then porphyritic monzonitic granite, tonalite and syenite-granite of had been emplaced.