Geochemical Characteristics And Tectonic Significance Of Jurassic Granites In Eastern Wu Banner,inner Mongolia

The Dongwuqi area of Inner Mongolia is located in the southeastern part of the Greater Xing'an Mountains in northeastern China.It is located in the Xingmeng orogenic belt in the eastern part of the Central Asian orogenic belt in northeastern China.It is widely distributed with invasive rocks dominated by the extensive distribution of Phanerozoic granitic.As the main feature.At this stage,scholars generally believe that such granitic rocks were formed in the Late Paleozoic,and the Jurassic-based granites are the most representative.A large number of exposed in the Daxinganling area.The Jurassic granites in this area are widely distributed,exposed,and have many periods.However,due to the lack of accurate chronology and petrochemical data,the genesis and tectonic background evolution of Jurassic granitic intrusive rocks in this area have been seriously affected.Awareness.In this paper,the Jurassic granitoids in the study area of the Dongwuqi area in the southeastern part of the Greater Xing'an Mountains were analyzed by petrography,petrochemistry,chronology and geo-geochemistry,and the Jurassic granites in the study area were determined.Forming the age and the genesis of the rock,and further discussing the evolution process of the granite structure during the Jurassic period in the Daxinganling area.Geochemical research results show that both of them belong to the high potassiumcalc-alkalineseries.AccordingtotheLitmanindex,the calcium-calcium-alkaline rock type,A/CNK is more than 1 and less than 1.1,and the corundum content changes in CIPW standard minerals.Larger,mostly greater than1%,K₂O/Na₂O is more than 1.The intrusive rocks in this period are generally characterized by high silicon,aluminum-rich and magnesium-depleted,iron and calcium.The light rare earths are relatively enriched,and all have negative Eu anomalies.Among the trace elements,the large ion lithophile element Ba is generally depleted,high field strength.The elements P and Ti are obviously depleted.These similar geochemical characteristics and the geochemical evolution relationship between the intrusive rocks in this period indicate that the intrusive rocks in this period may be formed by different evolutions from the same source region.Structural analysis shows that some samples of late Jurassic granites fall in the granitic areas of low Sr high Yb and very low Sr high Yb.These rocks correspond to the background of less pressure.These indicate that there may be a reduction in the crust in the Late Jurassic from the middle and late in the study area.The negative anomaly of Eu in the Late Jurassic intrusive rocks in the study area has changed from early to late,which suggests that the study area experienced crustal thinning during this period.In addition,the Late Jurassic intrusive rocks in the study area contain cave granites,which are generally considered to be products of the extended background.Therefore,the early Jurassic intrusive rocks in this area should be formed in the extrusion environment in the early stage,and the late stage may be in the background of a structural system conversion.In the early part of the study area,the Late Jurassic should be in the background of the subduction of the paleo-Pacific from the southeast to the north.In the late stage,the structural system may be transformed.