Petrogenesis Of The Early Permian (Strongly) Peraluminous Granites From Wuzhishan Area, Hainan And Its Geotectonic Implications

There is a great debate about the awareness of the Indo-Chinese epoch (Triassic)tectonic setting in South China (including Hainan).The article has redefined the EarlyPermian (strongly) peraluminous granite in Hainan Island. The granite is classified in(strongly) peraluminous one which has unique geochemical character and the instructivesignificance of tectonic setting， So the article take the Early Permian (strongly)peraluminous granite in Hainan Island for the research subject through petrology andgeochemistry, to discuss the genesis and forming tectonic background of the suite.In Hainan, he Early Permian (strongly) peraluminous granite, with outcropped totalarea of191km2,was distributed along the Fanyang-Changzheng-Chengpo Farm and on thenorthwest side of Wanning Huangshan Reservoir. It is composed of Garnet granite,tourmaline granite and two-mica granite (biotite) granite，The rocks shows a higervariation in their SiO2contents (SiO2=69.14%~75.84%), and is riched inalkali(12.83%~16.13%), The contents is low in their CaO、MgO、TFeO、TiO2、MnO,Therocks shows a large variation in their Na2O+K2O contents (6.49%~9.37%) and K2Ocontents (3.07%~6.9%)about two-mica granite (biotite) granite, but it shows a lower inGarnet granite, tourmaline granite. Their A/CNK values range from1.02to1.35(except0.98and0.99), most rocks of the rocks belong to (strongly) peraluminous series(A/CNKmostly>1). Their FeO＊/MgO ratios are in range (2.08~6.71).Their abundances of rare earth elements change greatly and most of them arerelatively high, with REE=77.95~450.27μg/g. The REE patterns display right-inclined,with medium-distinct differentiations between light and heavy rare earth elements. Andobvious negative Eu anomaly (δEu=0.67~0.27), The rocks are obviously enrich Rb、Th、U、K、Pb (LILE) and depleted in elements Ta、Nb、Ti.(87Sr/86Sr)iis0.71106~0.70778,εNd(t) is-7.7~-2.6, ISrand εNd(t), and the overall performance of each sample was somecorrelation, i.e. ISrlarger, the smaller the value of εNd(t)； with n(206Pb)/n(204Pb)=18.411~18.560,n(207Pb)/n(204Pb)=15.636~15.642,n(208Pb)/n(204Pb)=38.449~38.608, Itfalls on orogenic evolution of the line of the lead tectonic model diagram.This article argues that Hainan Early Permian (strongly) peraluminous granites most likely caused by anatexis of the earth’s crust mafic granulites (plagioclase amphibolite,hornblende-biotite-plagioclase leptynite or the analogues), The magma containing varyingamounts of garnet, plagioclase, biotite, quartz crystal residues. As the post-collision juststarted, the asthenosphere upwellings and lithosphere stretches, along the occurrence oflower thickening crustal and relaxation, resulting in dehydration melting.