Comparative Researchs On Volcanic Rocks From Manitu Formation On The East And West Slopes Of Da Hingan Range

This article is based on“1:250000Suolun-Wulanhaote geological resurvey project,InnerMongolia”.The Manitu Formation nearby Suolun town on the east slope of Da Hingan Range iscarried out a detailed geological survey together with observations on lithology,geochemistryand isotopic geochronology.Comparing the feather with Manitu Formation from Dongwuqi onthe west slope of Da Hingan Range,Main achievements have been made as follows:1.Manitu Formation nearby Suolun town has carbonate-andesite,pyroxene dacite, Daciticrhyolitic and acidic tuff,which is from Dongwuqi is composed of andesite, andesitic porphyry,dacitic volcanic rocks.Combined with regional data, there are the andesite,trachyte,latite,rhyolite,basaltic andesite,tuff in Manitu Formation.2.The volcanic rocks from Manitu Formation nearby Suolun town belong to high-Kcalc-alkaline series.They have higher total rare earth elements.The light and heavy rare earthelements have high degree of fractionation.Mafic rocks has basically no Eu anomaly and rhyolitewith Eu negative anomaly.Trace elements enrich LILE elements such as Rb,Ba,K,Th and loss inHFSE such as Ta, Nb, Ti. Formed extensional environment is within the plate.3.The volcanic rocks from Manitu Formation in Dongwuqi belong to high-K calc-alkalineseries.They have higher total rare earth elements.The light and heavy rare earth elements havehigh degree of fractionation.They have Eu negative anomaly.Trace elements enriched LILEelements such as Rb,Ba,K,Th and loss in HFSE such as Ta, Nb, Ti. The volcanic rock should bethe intraplate orogenic belt volcanic rocks.4.By zircon U-Pb isotopic dating and regional ages of volcanic rocks from ManituFormation,the author found the ages are mainly distributed in the range of two section:125~138Ma and146~158Ma.5.By comparing volcanic rocks from Manitu Formation assemblage,geochemistry,theformation age on the both of slopes of Da Hingan Range,Mesozoic volcanic rocks in Da HinganRange area relate to Da Hingan Range extensional orogenic process.Da Hingan Range East,thewest slope of the Manitu volcanic rocks were formed in an intraplate environment,theasthenosphere upwelling diapirs,causes the surface uplift, the Da Hingan Range in the high angle normal faults based on both sides of the rapid rise,the corresponding settlement,the lower cruststretched to the sides in the migration process accompanied by delamination of the crustaland thefurther thinning and detachment,molten magma along the surfacezone of ejection forming. Theeast are more abundantly distributed than the west slope of Da Hingan Range.It is connectedwith the lithospheric thinning rate.