The Carboniferous Arc Granites In Sonidzuoqi,inner Mongolia

On the basis of the“Inner Mongolia 1:50000 Zhunheremuyin Sumu six pieces of regional geological survey”project,the late Paleozoic granite in the Sonidzuoqi of Inner Mongolia was studied.The study area is located in sunidzuoqi,Inner Mongolia North western border region,the tectonic location belongs to the Central Asian orogenetic belt east of Xingmeng orogenetic belt.The Paleozoic tectonic activity in the area is frequent,and the magmatic activity is strong.The regional tectonic units belong to Xing Meng orogenetic belt of northern orogenetic belt,the south wing to Er Lian-HEGENSHAN fracture belt is bounded on the north is a Siberian active continental margin.The Paleozoic in the study area belongs to the paleo Asian Ocean tectonic domain,and it is in the Western Pacific tectonic domain.Xing Meng Orogen Paleozoic tectonic activity is frequent,intense magmatic activity,the formation of parallel distribution of regional tectonic magmatic belt to the north east.Combined with spatial and temporal distribution of intrusive rocks,rock composition,geochemical characteristics,our regional geological survey work from the study area exposed to the north east of the Carboniferous magmatic belts disintegration granodiorite-syenogranite sequence of Carboniferous gabbro diorite-granodiorite sequence,alkali feldspar granite Carboniferous and Permian porphyry independent rock sequence.Carboniferous granodiorite-granite syenite intrusive series constitute the main body of the late Paleozoic intrusive rock band.Granodiorite-syenogranite sequence main rock types include medium-grained granodiorite,medium-grained hornblende monzonite granite,medium-grained biotite monzonite granite,fine-grained biotite monzonite granite and medium-thin grain syenogranite.Magnesia and magnesium hornblende biotite typical mineral assemblage of the sequence intrusions appear,lack of mineral-rich aluminum,generally containing a trace of diorite xenoliths,showing I-type granites features.System zircon isotopic data obtained show that our new,granodiorite-adamellite-syenogranite sequence emplacement age range 321.4³06.2Ma,shall Late Carboniferous.The age range is consistent with the group Po district gaomiao Sec volcanic age range?326.3³07.4Ma?.SiO₂ content range granodiorite sequence is 64.31⁷7.38wt%,full-alkali content?K₂O+Na₂O?Changes in 6.29⁸.81wt%,the larger Mg#range?65 to 11?,show calc-alkaline magma geochemical characteristics.Granite has a larger Al₂O₃content range?17.70¹1.13 wt%?,A/CNK and A/NK were 0.89 to 1.26 and 1.09to 1.67,showing the weak from the quasi-series aluminum series evolutionary trend.With the SiO₂ content increased,MgO,Al₂O₃,TiO₂,TFe₂O₃,CaO and P₂O₅ content of granite presented a consistent decreasing trend,reflecting their common parent magma.granodiorite sequence compatible with low trace elements?Ni,Co,V,Sc?and a high content of incompatible trace elements?Rb,Th?content.Granite light/heavy rare earth separation obviously,on the whole have LREE-MREE rightist segment,nearly flat MREE-HREE REE pattern.The sequence showing a significant change in the scope of Eu anomaly,granodiorite of most samples Eu/*Eu values in the vicinity of 1,while the two long granite and syenite granite has a clear negative Eu anomaly,reflecting the plagioclase crystals were separated process.Granite strong enrichment of incompatible elements?Cs,Rb,Ba,Th,U,K?and a fluid-activated elements Pb,high field strength elements?Nb,Ta,Ti?relative loss of form on the incompatible elements with a bipartite graph significant peak Pb and Nb-Ta and Ti negative anomalies,geochemical characteristics of magmatic arc display.Carboniferous granodiorite-granite syenite intrusive rocks with high sequence Rb,Th content and low high field strength elements?Nb,Ta,Hf?and heavy rare earth elements?Yb,Y?.On the trace element partition structure diagrams,granite samples are concentrated in an arc volcanic area.Thus,the system of rock and geochemical data indicate that the sequence of rock formed in arc magma intrusion,and Bao Li Gao Miao group Sec related spatial and temporal distribution of volcanic arc volcanism represents a year process.Combined with regional geological data,this study is to identify the Carboniferous arc on or after the Early Palaeozoic island arc-arc basin development background secondary margin volcanic arc.The work identified in the study area and the eastern side of the Carboniferous arc granites Xilinhot Carboniferous arc granites?Chen et al.,2009?jointly determining the presence of suture Suolun Carboniferous arc,which stretches west to south-east Mongolia?Blight et al.2010?.The volcanic arc and Suolun suture the northern margin of the North China Craton south east-west arc Carboniferous?324³02Ma;Zhang et al,2009.?To form a substantially uniform age range.This table Ming Suolun symmetrically north and south sides of the suture Carboniferous continental margin volcanic arc reflects Paleoasian bidirectional subduction system in order to provide an effective constraint Xingmeng for tectonic evolution pattern.