Petrological Characteristics And Tectonic Significance Of The Early Cretaceous Volcanic Rocks In Taibaiwei Mountain And Tadi, Lingqiu, Shanxi Province

Lingqiu is located in the southwestern end of Yanshan tectonic belt，thetransition/conversion of the north near EW Yanshan mountains and south NETaihang mountains.On the basis of detailed geological field work,and bystudying the geological characteristics、the spatial and temporal characteristicsand petrography of Taibai Mountains volcanic basins and Tadi volcanicdepressions, combining with its major elements, REE and trace elementgeochemistry analysis, the auther discussed the Volcanic edifice features、thepetrological characteristics and the causes of volcanic rocks, magmatic materialsources, tectonic environment and dynamic background of early Cretaceousvolcanic rocks in Taibai mountains and Tadi,I have mainly obtained thefollowing options:1. The volcanic rocks in Taibai mountains and Tadi are the product of thesame period that both of which are formed in the Early Cretaceous. the mainrock types in qiangfengling body of zhangjiakou group of Taibai mountain aretrachyte, mattedacite,rhyolite and few volcanic clastic rock`and the main rock types in xiangyangcun body of which are rhyolite and Rhyoliticignimbrite;While in Tadi, the qiangfengling body are mainly consist of Thepyroclastic rock and Terrigenous clastic rock and the xiangyangcun body aremainly consist of pyroclastic rock. The intensity of volcanism in the two placesare different. Taibai Mountain is characterized by strong volcanic eruption,accompanied by lava flows while the volcanism in Tadi is relatively weak,it wascharacterized by the deposit of pyroclastic rock and Terrigenous clastic rock inthe early and the overflow of the volcano effect characteristics of late.2. The volcanic rocks in Taibai mountains and Tadi are mainly a series ofacid and mid-acid rocks,with a evolution characteristics of transition fromcalc-alkaline to alkaline potassium, high potassium calc-alkaline to Shoshonite.3. The volcanic rocks of qiangfengling body in Taibai mountain are richedin potassium, magnesium, and aluminum while are poor in magnesium, withhigh La/Yb ratio and No Eu anomaly; They are relatively enriched in large ionlithophile elements(LILE) Rb, Ba and K;High field strength elements((HFSE)Nb, Ta, Zr, Hf, Ti are sharply depleted. High Sr, Sr/Y ratio, high La/Ybratio,lean Y and Yb. Its genetic type is C-type high potassium calc-alkalineadakitic volcanic rocks. The volcanic rocks of xiangyangcun body inZhangjiakou group of Taibai mountains and Tadi are both relatively enriched insilicon,potassium, alkali, iron and poor in magnesium; Both of them haveright-wing type distribution pattern and strongly negative Eu anomaly; they areboth rich in high field strength elements while are depleted Nb, Ta, Zr, Hf, Ti. Its genetic type is equivalent to aluminum volcanic rock A-type granite.4. The volcanic rocks of Zhangjiakou group in Taibai mountains and Tadiformed in the structure conversion process of extruded mountain-extension andthinning of Mesozoic in the east of North China Craton. The subduction of theancient Pacific plate and the Eurasian plate caused the erosion of the activemantle heat flow system to the bottom of the lithosphere. At the bottom of theintracontinental thickened crust in the late stage of orogenic, partial melting ofthelower-moderate degree of the basement of crustal formed C-type Kcalc-alkaline adakite of qiangfengling body in Taibai mountain.In the stage ofintracontinental extensional stretching process after orogenic,the partial meltingunder low pressure of the felsic igneous rocks formed the A2type granitoids inmetaluminous or weakly peraluminous of xiangyangcun body in the Taibaimountains and Tadi Zhangjiakou group. So,the deep of the Linqiu experienced aprocess of magmatism of partial melting of basic low crust and siliconaluminum layer of crust in Late Mesozoic.