The Geochemistry Study Of The Mesozoic Volcanic Rocks In Hellers Tai,Inner Mongolia

Dong Ujimqin banner of Inner Mongolia Hellers Tai area is located in central of the great Xing'an range. It is collision between Siberian plate and North China plate formation of Xing Meng orogenic belt part. Hellers Tai chung Cenozoic volcanic rocks are widely distributed. According to lithology, contact relationship and regional stratigraphic correlation, combined with isotopic dating results, the formation of Hellers Tai is redefined to, the late Jurassic mani spit group?J3mn? and early Cretaceous white tone high old group?K1b? were reclassified as early Cretaceous white tone high old group A?K₁b¹?, B?K₁b²?.The white tone high old group?K₁b¹? a neutral trachyandesite, trachyandesitic tuff rock,and a new formation sound high old group second segment?K₁b²? for a set of acidic volcanic rock combination, lithology to rhyolitic pyroclastic rocks and rhyolite mainly interbedded with thin volcanic sedimentary rocks.Take the typical samples of Mesozoic volcano rock, Hellers Tai, was discovered in two by a group of Portland, volcanic rocks major elements showed the characteristics of high alkali, poor calcium, magnesium, Gao Jia low, Baiyingaolao group A?K₁b¹? in the TAS classification map all fall in the nearby area and dacite andesite area boundary, overall in alkaline and sub alkaline region, enrichment of large ion lithophile elements?LILE? Rb, Th and HFSE Ce, depleted in high field strength elements?HFSE? Nb, Zr, Y, Nb/Ta ratio and loss of Ba element, the ratio of Zr/Hf rock were 10.55-16.20 and 35.46-42.89, the ratio of Th/U?2.78-3.87? lower than average value of 3.8?Taylor SR, Mclenann, 1985?, neutral volcano rock REE was right, LREE, hree relative loss, with weak negative Eu anomalies;Baiyingaolao group two?K₁b²? in the TAS classification of investment in the region to sub alkaline rhyolite, high potassium calc alkaline series and kalibasalic series, enriched in large ion lithophile elements?LILE? Rb, K, Ba, Th, and depleted in HFSE?HFSE? Nb, Zr,Hf and Y, Nb/Ta ratio and Zr/Hf ratio of rock were 9.00-13.43 and 23.34-33.48, the ratio of Th/U?2.52-4.96? are higher than the average of 3.8, acidic volcano rock, right inclined REE,LREE, hree relative loss, with strong negative Eu anomalies that may contain a small amount of plagioclase and garnet the residue magma source, may have experienced plagioclase crystallization during magma ascent.Geochemical analysis show that the crustal material joining and mantle source components in the process of rock of Mesozoic volcanic and are the product of mantle materials and crust derived material mixing, the difference is that the crust mantle mixing proportions between the two may be slightly different.