Geological Event Sequences Of Wengeqi Mafic-ultramafic Complex,Guyang Area,Inner Mongolia

There are many Paleozoic mafic-ultramafic complex in the north margin of North China Craton.A lot of Cu-Ni(PGE)sulfide deposit occure in these complex.This paper made the thoroughly study on Petrography,Mineralogy and Diagenetic mineralization process for Wengeqi complex,the main conclusions are as followings:1.Wengeqi complex are composed of Pyroxenolite and Hornbledite.Including Pyroxenolite,magnetite-Pyroxenolite,amphibole-Pyroxenolite,biotite-Pyroxenolite,biotite-hornblende-Pyroxenolite,Hornbledite,zonal Hornbledite,pyroxene-Hornbledite.2.The Diagenetic process of Wengeqi rock mass can be devided into three periods:Magma cumulus pile period,Post-magmatic hydrothermal fluids period,Retrograde metamorphism period.3.The mineral assemblage of Magma cumulus pile period is:diopside +pargasite + apatite,chalcopyrite + pyrrhotine ± pentlandite + PGM.The mineral assemblage of early Post-magmatic hydrothermal fluids period is:ferropargasite+albite+epidote+calcite+apatite,pyrite+magnetite,pyrite+kotulskite,pyrite+ sudburyite,magnetite + sperrylite;The mineral assemblage of late Post-magmatic hydrothermal fluids period(That is Skarn stage)is:hornblende +garnet,hornblende + allanite + apatite,magnetite and ilmenite.The mineral assemblage of Retrograde metamorphism period is:epidote + actinolite + albite+ chlorite + biotite,Albite + epidote + sericite + calcite.4.The temperature pressure conditions of every Diagenetic period of Wengeqi complex is that:Magma cumulus pile period:T?1150?,P?0.40GPa,the main combination is Di+Prg+Ap.Post-magmatic hydrothermal fluids period can be divided into two part,the early stage:T ?700 ?,and the main combination is Am+Ab+Cc+Ep+Ap;the later stage:T?350-500?,this part is equivalent to Skarn period.Retrograde metamorphism period:T?350?,P?0.25GPa.The meaning of fuild-crystal is that mineral crystal formed directly by the fuild,and the pure fluid product did not react with the surrounding rock.