Petrogenesis Of The Dongsai Ring Shaped Intrusive Complex And Its Tectonic Implications Within Shangyi County,North Hebei Area

The Dongsai zonal complex is located in the Shangyi area of the northern part of the northern part of the North China Craton.The study of the petrography,geochemistry and isotope geochronology of the zonal complex can not only explore the evolution between different rock types.The evolutionary relationship can further constrain the time limit for the final closure of the ancient Asian Ocean through a series of subduction collisions.The ring-shaped complex rock body is composed of five types of rock types: fine-grained granite,plaque-like granite,medium-grained granite,quartz monzonite and hornblende monzonite.Among them,fine-grained granite is distributed in Nangou Village,with fine-grained granitic structure and massive structure.The main mineral combination is plagioclase(Pl)+quartz(Q)+micro-plagioclase(Mic);plaque-like granite It is distributed in Xisai Village and develops like a plaque structure and a massive structure.The feldspar phenophyllite in the local area develops a ring-spotted structure.The main mineral combination is plagioclase(Pl)+ quartz(Q)+ potassium feldspar(Kfs);The medium-grained granite is distributed in the west of Huazigou Village.It has medium-grained granitic structure and massive structure.The main mineral combination is plagioclase(Pl)+quartz(Q)+potassium feldspar(Kfs);quartz monzonite is distributed in In the area of Dongyingpan,it has a fine-grained structure and a massive structure.The main mineral combination is plagioclase(Pl)+potassium feldspar(Kfs)+quartz(Q)+hornblende(Hb);the hornblende monzonite is distributed in In the area of the field and ditch,the development of fine-grained structure and massive structure,the main mineral combination is plagioclase(Pl)+ potassium feldspar(Kfs)+ hornblende(Hb).The five rock types in the zonal complex show a right-dip mode with light rare earth element enrichment and heavy rare earth element loss.The three rocks of Huazigou medium-grain granite,Xisai-like porphyritic granite and Nangou fine-grain granite obvious Eu negative anomaly,the field sag hornblende and Dongyingpan quartz feldspar are relatively enriched in Rb,Ba and K,and depleted in Nb,P and Ti,and have the characteristics of type I granite;The Xisai-like porphyritic granite and the Nangou fine-grained granite are enriched in Rb and K,and the relative losses are Ba,Sr,P and Ti,which are characterized by obvious A-type granite.According to the comprehensive analysis,the zonal complex is evolved by homologous magma,and magma may be mixed during its formation.Combined with field geological survey,petrographic characteristics,petrochemical characteristics and isotope geochronology analysis,the formation of the ring-shaped complex can be divided into four stages: the first stage is the field-ditch horn flashing monzonite(243 ±2.9Ma)and Dongyingpan quartz diorite(247±3.2Ma).Although the U-Pb harmonic age-weighted average of the two rocks in this period is different,it is still within the error tolerance.After comprehensive analysis,The two rocks are considered to be the evolution of the facies belt;the second stage is the Huazigou medium-grained granite with a zircon U-Pb age of 246±2.1 Ma;the third stage is a Xisai-like porphyritic granite with zircon U-Pb age is 240±2.2 Ma;the last stage is Nangou fine-grained granite formed at 235±2.1Ma.Based on the analysis of the tectonic setting and regional tectonic features of the zonal complex,the DongSai ring intrusive complex is formed in the tectonic setting of the Late Triassic Early Paleo-Asian Ocean and finally stretched.The stress state is extended.The Lord is the response to the regional tectonic movement transition event.