Magmatism Of Mesozoic In The Wuxilike Area Of Altay,Xinjiang:Petrogenesis Mechanism And Tectonic Setting

The study area is located in the Wuxilike area of Xinjiang Altay Orogenic Belt,and located in the Altay paleozoic plutonic magmatic arc of the Altay terrigenous mobile belt in the Siberian plate,granite is widely distributed very much and with very unique geological significance in this area.Altay orogenic belts produced multiple magmatic activities and recorded the history of the orogenic belt's formation and evolution during the structural evolution process.In order to further determine the period of magmatism,type of rock genetic and structural evolution and many more problem of the Altay Orogenic Belt,this paper selects the detailed zircon U-Pb isotopic chronology and lithogeochemistry to the Horemudek,the Mankeyidingshayi and the Huitengarshan Plutons in the Central part of the Altay orogenic belt of China,and analyses the three rock masses.The formation age and the geochemical characteristics of rock and geochemistry,combined with previous research results,discuss the major geological problems,such as the source rock type,genetic mechanism and geotectonic environment of rock masses.The results of the zircon U-Pb dating show that the Horemudek pluton formed at222.3±3.5Ma?MSWD=2.1?,andtheMankeyidingshayiplutonformedat217.9±2.3Ma?MSWD=1.4?,The Huitengarshan pluton formed at 203.1±2.1Ma?MSWD=3.3?,all of which belong to the Late Triassic intrusive rocks,which provided a new basis for the tectonic settings and evolution of the Altay region.The geochemical characteristics of the rocks indicate that the rocks general have high silicon?SiO₂=67.31⁷5.34%,the average is 72.03%?and alkali?ALK=8.03¹2.47%,the average is 9.23%?,high potassium and low sodium?K₂O/Na₂O=0.91².92,the average is 1.65?,low titanium?TiO₂=0.04⁰.50%,the average is 0.20%?and other characteristics,the rock Al₂O₃content is high?Al₂O₃=13.64¹7.48%,the average is 15.04%?,aluminum saturation index?A/CNK?ranged from 1.03 to 1.26 with an average of 1.12,the average Rithmann index???is 3.05,and the alkalinity rate?AR?averaged is 3.70;the ratio of light to heavy rare earths to heavy rare earths was greater in all rocks.Large?LREE/HREE=1.21⁶.70,the average is 3.91?and significant negative Eu anomalies?the average of?Eu is 0.62?;A more consistent distribution pattern was generally shown on the primitive mantle-normalized spider diagrams of the trace elements in the granites.Ba,K,Nb,Sr,P,Ti and so on elements exhibited significant negative anomalies,and Rb,Th,U,Ta,La,Ce,Nd,Zr,Sm,and Y elements showed significant changes positive exception.The overall character-ristics of the magmatic source rocks are rich in potassium,have a crust-origin,and non-orogenic S-type granites.The Huitengarshan pluton also has the characteristics of the A-typegranite and should be attributed to the granite between the S-type and the A-type.Granitoid magma is mainly formed by the crust source and mixed with a small amount of mantle material on thelow-melting,there is remnants of plagioclase of rich in calcium in the source area,and there may be apatite Separation and crystallization of ilmenite,etc.By using R₁-R₂,Rb-Hf-Ta,Yb+Nb-Rb and other diagrams of the tectonic setting combined with Sr-Nd isotope test results and previous research results,after comprehensive analysis and research,it is speculated that the granitic plutons are formed in the intraplate?intracontinental?extension setting.During the ascent of mantle plume,metapelites derived from the crust?with a small amount of mantle material added to the Huitengarshan pluton?and some deposits such as miscellaneous sandstones are partially melted.