Geological Characteristics And Tectonic Environment Of Mesozoic Huanghuagou Granite In The Northern Margin Of The North China Craton

In this paper,the Mesozoic Huanghuagou granite in the northern margin of North China Craton is taken as the research object,and detailed field geological survey is carried out.The petrology,lithofacies,LA-ICP-MS zircon U-Pb chronology and geochemistry of Huanghuagou granite in the northern margin of North China Craton are systematically analyzed and studied.The geological characteristics,formation age and formation of Mesozoic Huanghuagou granite in the northern margin of North China Craton are determined.The petrogenesis and tectonic background of their formation are discussed,which provides a constraint for further study of Mesozoic magmatic activity and tectonic evolution in Huanghuagou area.1.Geological characteristics of the Huanghuagou graniteThrough the Huanghuagou granite detailed field geological investigation,north east to Huanghuagou ditch granite distribution,its fracture structure are well-developed,fracture in north east to distribution,also in the rock mass is divided into Medium and fine-grained hornblende monzonite and Unequal granulite monzonite,the seriate adamellite intrusive contact tip subgroups with stone formation,formed in late carboniferous epoch times.2.The formation age of the Huanghuagou granitesThe LA-ICP-MS zircon U-Pb geochronology studies have been determined for the Mesozoic Era granites in the northern margin of North China Craton.The dating results for Huanghuagou granites weighted mean ²⁰⁶Pb/²³⁸U ages of 174.7±1.8Ma?n=18?and 174.2±1.8Ma?n=24?,respectively,indicating they all formed in the Early Jurassic of Mesozoic Era3.Geochemistry of the Huanghuagou granitesThe Huanghuagou granites is characterized by high SiO₂?65.94%-75.83%?,alkali?5.86%-9.18%? and Al₂O₃?13.79%-16.54%? contents,low values of TFeO/MgO?average is 1.67?and low Rittmann index ??1.33-3.08?.The Huanghuagou granite belongs to metaluminous-weakly peraluminous high-K calc-alkaline granite with aluminium saturation index?A/CNK?from 0.90 to 1.15.The chondrite-normalized REE patterns are obviously fractionated with high?La/Yb?_N mean value?4.44?and obvious Eu anomaly.They are also enriched in Rb,Nd,Th and U,depleted in Ba,Sr,Nb,P and Ti.4.The genetic type of the Huanghuagou granitesThe Huanghuagou granites have high contents of SiO₂ and total-alkali,have negative anomalies of Sr,P and Ti,and the amounts of ?Na₂O+K₂O?/Al₂O₃?mol? ranging from 0.42 to 0.63.In addition Huanghuagou granites contain hornblende,it's the Mineralogical Discriminant marks of ?-type granites.5.The tectonic setting of the Huanghuagou granitesThe Huanghuagou ?-type granites are located in the northern margin of North China Craton.Combined with the geochemical characteristics of intraplate granites,the Huanghuagou ?-type granites emplaced at a post-collisional extensive setting after the final amalgamation of the North China block and Siberia block.