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Geochemistry, Geochronolgy And Tectonic Setting Of Permain Intrusive Rocks In Zhanlantun Area, Inner Mongolia

Posted on:2015-02-21Degree:MasterType:Thesis
Country:ChinaCandidate:T QinFull Text:PDF
GTID:2250330428498103Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
Late Paleozoic intrusive rocks are widely distributed in Xingan and SongnenMassifs, which formed under collision tectonic setting after the closure of paleo-AsianOcean. Based on detailed petrological, geochemical and geochronological study ofintrusive rocks for Zhalantun area, near amalgamation zone between Xingan andSongnen massifs, their rock associations and geochronological characteristics aredescribed in the paper in order to further discuss and understand petrogenesis andtectonic setting.Intrusive rocks for Zhalantun area are mainly consist of monzonitic granites,ranodiorites and syenogranites,accompanied by minor amphibole gabbros. Mostrocks are cataclasitic while minor rocks underwent ductile deformations. Most rockbrittle deformation,A few rocks occur ductile deformation.Isotope research shows Intrusive rocks formed in the early Permian in the studyarea U-Pb isotope age are respectively Gabbro285.9±3.5Ma, Granodiorite283.3±2.1Ma, Monzonitic granite285.7±4.1Ma292.0±1.9Ma, Is long granite289.3±1.9Ma.Monzonitic granite, granodiorite is aluminum-weak aluminium high potassiumcalc-alkaline granite type I, Is long weak granite is aluminum-aluminum highpotassium calc-alkaline type A granite. Granitic rock light rare earth concentration,heavy rare earth losses, Light rare earth fractionation, heavy rare earth fractionationis weak., this may be related to source area in the process of partial melting garnet,hornblende as residual phase. Enrichment of granitic rocks in large ion lithophileelements (Rb, K), the loss of high field strength elements (Nb, Ta, Ti, P).. Ba, Sr negative anomaly, negative Eu anomaly. Ba/Nb, Ba/La ratio is higher, Nb/Ta andZr/Hf ratio change is bigger, show the granitic rock has the characteristics ofcrust-mantle mixing.Gabbro rock belongs to high potassium calc-alkaline series. Mg#=0.43-0.62(Mg#=Mg2+/(Mg2++Fe2+)),Co content is41.31to47.09PPM, Ni content is47.07to138.55PPM, show hornblende gabbro experienced fractional crystallization.La/Nb=2.26-3.38, La/Ta=17.90-533.56, display the hornblende gabbro has thecharacteristics of the lithospheric mantle. La/Sm-Sm/Yb graphic display thehornblende gabbro magma source is KBI basalt not contain garnet.The early Permian intrusive rocks show characteristics of passive intrusion. Withthe characteristics of Bi-model volcanic rock. Rock combination is similar withpost-tectonic lift or collapse phase combination. Geochemical characteristics ofgabbro and orogenic environment after similar geochemical features of basalt. Type Along granite is A2type granite related to intracontinental shear extension environment.To sum up, The study area of Early Permian intrusive rocks are in post orogenictectonic environment, because of itsearly subduction fluids by metasomatism Theyare with the island arc volcano rock geochemistry. The early Early Permian Xinganand Songnen blocks are in the post collision stage, The large-scale strike slipmovement cause the early Permian intrusive emplacement.
Keywords/Search Tags:Zhalantun, Early Permian, Bi-model intrusive rocks, Post collision, Extensionalenvironment
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