Characteristics And Their Petrogenesis Of Basic And Ultrabasic Intrusions In Wengeqi, Guyang Area, Inner Mongolia

Inner Mongolia is one of the most important area in China to research the northern fringe of North China Platform,where basic and ultrabasic rocks controlled by deep fault can be found.Wengeqi intrusions are the basic and ultrabasic rocks controlled by Linhe-Jining fault in the northern fringe of North China Platform.In this paper,Wengeqi intrusions were studied by Petrography,Mineralogy and Geochemistry in single mineral etc.Understandings below were obtained in this research.1.Wengeqi intrusions are composed of Pyroxenolite and Hornbledite.Including magnetite-Pyroxenolite,biotite-Pyroxenolite,amphibole-Pyroxenolite,pyroxene-Hornbledite, zonal Hornbledite,apatite-chlorite-Hornbledite and a little of magnetite pyroxene-Biotitite.2.Essential minerals of Wengeqi intrusions are diopside,amphibole,apatite. Minor minerals are biotite,magnetite,epidote,chlorite,calcite,albite garnet etc.3.The characteristics of diopsite are enriched in light REE,with weak negative Eu anomaly and with high level of Ca,Si and low level of Al,Ti,Mn.It is also characterized by relative enrichment in Hf,Zr,Sr,Pb and depletion in Nb,Ta,U,Th, Ba,K,Rb.And by lower Cr,Ni and higher V,Ti,Sc contents.4.Amphibole is characterized by high Fe,alkali and low Mn,Cr,enrichment in LREE with unclear Eu anomaly.Zonal amphibole is common,the core of zone is pargasite,the rim is ferroan pargasite.Nine dots on the line which through the zone from left to right are named as B1 to B9.B4 to B6 belongs to core dots,B3 and B7 are the transition dots.The content of those elements:La to Sm,Ba,Nb,Ta,V,Ti is highest level at B2 and B8.the highest summit of Eu to Lu is B3 and B7.differently, the content summit of Rb,K,Pb,Zr,Hf is B1 and B9,the tendency from summit to center is gradually reduced.The summit of Sc and Ni belongs to B4.5.The geochemistry of apatite is characterized by high level of total REE,The average is 2961.77ppm,enriched in LREE,with slight to medium negative Eu anomaly.The curve of rare earth element is in accord with the pattern of intermediate rocks and basic rocks6.The crystallization temperature of hornbledite is 350℃～400℃,the crystallization temperature of amphibole-pyroxenolite and biotite-pyroxenolite is 700℃～800℃;and the average temperature of Pyroxenolite is 1082℃.The average crystallized pressure is 44Gpa,the same as 17.5 kilometer.7.Hornbledite and pyroxenolite are caused by magma rather than skarn.The two rocks may crystallize from two different degrees of molten magma respectively.