Origin and geotectonic setting of the porphyritic quartz diorite in Qiandi area of Linxi County,Inner Mongolia
The porphyritic quartz diorite in Qingdi area of Linxi County,Inner Mongolia is a kind of granite closely related to mineralization.In this paper,the genetic types,the source of magma,and the geotectonic setting of formation of the porphyritic quartz diorite in this area are preliminarily studied by the characteristics of rock geochemistry,and the results of previous studies on isotopic dating.The results show that the rocks are of characteriscts of high K,low Na,rich in Mg-Fe and poor in Si-Al.They belong to the rocks with high K calc-alkaline series and have the characteristics of I-type granite.The large ionic lithoophile trace elements such as Rb,Sr,Ba,and U were enriched,and the high field strength elements such as K,Th,Nb,Ta and P are depleted,REE present a right-leaning distribution pattern showing the large curve slope with enrichment of light rare earth elements and depletion of heavy rare earth elements.Eu shows normal or weakly positive Europium Anomaly.The rocks are formed by partially melting of basic rocks in a tectonic setting of paleosubduction zones.The U-Pb apparent age of Zircon is 239Ma,it is suggested that the formation of the porphyritic quartz diorite may be related to the subduction and accretion orogeny between the Siberia plate and the North-china plate in North-south direction.
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