Geochemical Characteristics And Tectonic Magmatic Evolution Of Granitoids In Fengqing Area Of Yunnan

Lincang granite batholith,located in the western Yunnan,is the largest complex batholith and also an important component of Paleo-Tethys,which has been drawn great attention both at home and northern of lincang granite of Fenqing located in the northern section of Lincang granite batholith,overalling north-south trending.East side connected to the Yangtze microcontinent through the Lancang Jiang Fault Zone and west side to the Sibumasu microcontinent through the Shantouhou Fault and Xiqianjie Fault.Based on actual profile measurement,the thesis focus on the research in petrography,mineral chemistry and rock geochemical characteristics of northern of lincang granite in the northwest of Fengqing,and compares with the Lincang granite batholith, then diseussed the seientific problems such as sources,mechanisms of genesis, deep dynamic processes and tectonic magmatism evolutions.The Lincang granite is mostly biotitic monzogranite in terms of lithology,The 15 representative samples have shown that Plagioclase in Permian rocks An = 26.45 48.28,To neutral plagioclase, development of band structure; Potassium feldspar as orthoclase,The Or content is higher 92.91 96.46%.Biotite is rich Al₂O₃, FeO, the characteristics of low TiO₂, For magnesia biotite, with the trend of transition to a black mica iron, is greater than the shell type granite rock mass MF average MF?0.5?value, speculates that mantle source material mixed with. Triassic eta gamma of plagioclase in rocks the An = 8.23 0.34, sodium feldspar; Potassium feldspar as orthoclase, Or content is 88.34 99.12%; Biotite equally rich Al₂O₃, FeO, the characteristics of low TiO₂, as the iron biotite, indicates that the host magma from the earth's crust. MF value of 0.36 to 0.36, with an average of 0.39, shall be the transformation type granite. Lincang granite base northern rock SiO₂ average content of 68.95%, has the rich aluminum?Al₂O₃, an average of 15.36%?, potassium rich?K₂O, an average of 4.54%?, poor calcium?CaO, an average of 1.66%?, the characteristics of the aluminum A/CNK saturation index value of 1.41 3.31, on average, 1.84 terman index with A mean of 1.76, in the high performance for aluminium potassium calc-alkalic rock; Lincang granite enrichment large ion lithophile elements such as northern rock?U, Th, K and Pb?, apparent loss of high field strength elements?Nb, Ta, Sr, Zr and Ti?, relative to the Rb and Th losses of Ba.? REE averaged 235.49 x 10-6; LREE/HREE 9.68, show the light rare earth concentration, heavy rare earth losses, relatively large ion lithophile elements, the characteristics of the transition elements relative loss. Obvious negative Eu anomaly,it shows that after partial melting by crustal material, experienced a moderate degree of crystallization differentiation. Geochemical characteristics show that the northern end of the lincang granite base should belong to S type granite rock mass; Lincang granite material sources of the northern rock mass is mainly for the poor clay arenite,Triassic source rock material shall be the poor clay shale rock; La La/Sm illustrations,both show the equilibrium partial melting rather than the characteristics of fractional crystallization, Harker diagram of different sex and combining with the primitive mantle standardization spider diagram of trace element and ree chondrite standardized distribution diagram, Triassic granitic mass and northern of lincang granite rock mass is at the same time under the action of syntectonic after partial melting by the different shell source, through the form of a certain degree of crystallization differentiation.To the late carboniferous to the early Permian, chang ning a Meng Lianyang basin cut, the eastward subduction in the Permian, lancang river belt formed subduction type synchronous low potassium 1 k arc calc-alkaline intermediate-acid volcanic rock. And formed in the early part of the lincang granite base, Permian has the feature of arc granite diorite YanYanJi. Since the late Triassic period to the cretaceous upwelling asthenosphere and early rock sediments transformation enrichment enclosure and interactions, including the enrichment of sediment reforming enclosure slower molten rock that is formed in the late Triassic and cretaceous low magnesium and high aluminum magma.