Genetic Mineralogy Of Pyroxene In Mesozoic Intrusive Rocks In Han-Xing Area,South Taihang

Hanxing area is located in the southwest of Hebei Province,and the geotectonics is located in the middle and south of the central orogenic belt of the North China Craton.A large number of Mesozoic intrusive rocks are developed in this area,in which the high magnesium diorite is one of the important responses to the failure of the North China Craton,which is of great significance to the study of the failure of the North China Craton.With the occurrence of Hanxing skarn iron ore is an important type of rich iron ore in China,with high economic value.Therefore,the study of the genesis and evolution of high magnesium diorite is of great significance for the study of the failure and prospecting of the North China Craton.In recent years,many scholars have studied the genesis of high magnesium diorite in Hanxing area from the point of view of rock geochemistry and chronology,but there are few systematic genetic mineralogical studies.This paper will take the study of genetic mineralogy as the main method,through detailed petrographic study,EPMA and LA-ICP-MS,to analyze the genetic mineralogy of pyroxene with different rock mass,lithology and occurrence.The temperature range of pyroxene in this area is calculated by using different empirical formulas of pyroxene thermometer,and its genesis is discussed,which lays a foundation for the formation and evolution of high magnesium diorite.The experimental results show that the main element characteristics of pyroxene in this area show that the samples in Hanxing area are rich in Ca,Mg,poor in Na and Al.All pyroxene belongs to Ca-Mg-Fe clinopyroxene and most of them are diopside.SiO₂-Al₂O₃projection shows that the pyroxene magma genesis in all samples belongs to sub-alkaline series and belongs to tholeiite basalt.The trace element test results of pyroxene in this region show that the contents of rare earth elements and trace elements are different in different samples.The rare earth partition curve shows that the samples with low total amount of rare earth crystallize earlier,in the trace element spider web diagram.Most of the samples are deficient high field strength elements and enrich large ion lipophilic elements.The genesis of pyroxene is discussed by establishing the typomorphic of pyroxene.According to the structure,there are three kinds of pyroxene in this area:type ? pyroxene with self-shaped structure,type ? pyroxene with reaction edge structure and type ? pyroxene with inclusion structure.Through further geochemical analysis and discussion,it is found that there are four different genesis in the authigenic crystals of type ? pyroxene:they are the authigenic crystals crystallized during the emplacement of the basic rocks,The authigenic crystals of the intermediate-acid mixed magma crystallized in the deep and shallow magmatic chamber respectively,and the authigenic crystals crystallized directly during the emplacement of the intermediate-acid mixed magma.There are two kinds of genesis of type ? pyroxene captive crystals:one is the crystal in the basic magma before magma mixing,and the other is the crystal in the acidic magma before magma mixing.The genesis of the captive crystals of type ? pyroxene is the crystals of pyroxene crystallized in the deep magmatic chamber along with the magma in the basic rocks.In addition,the correlation between the major elements of pyroxene indicates the evolution of magma,in which pyroxene is dominated by magmatic mixing in Qicun rock mass and crystallization differentiation in Hongshan rock mass.The crystallization differentiation of pyroxene does not play a leading role in Fushan rock mass.