Phase Equilibria Constraints on Relations of Ore-bearing Intrusions with Flood Basalts in the Panxi Region,Southwestern China

【摘要】 <正>There are two types of temporally and spatially associated intrusions within the Emeishan large igneous province(LIP);namely,small ultramafic subvolcanic sills that host magmatic Cu-Ni-Platinum Group Element(PGE)-bearing sulfide deposits and large mafic layered intrusions that host giant Ti-V magnetite deposits in the Panxi region.However,except for their coeval ages,the genetic relations between the ore-bearing intrusions and extrusive rocks are poorly understood.Phase equilibria analysis(Q-Pl-Ol-Opx-Cpx system)has been carried out to elucidate whether ore-bearing Panzhihua,Xinjie and Limahe intrusions are co-magmatic with the picrites and flood basalts (including high-Ti,low-Ti and alkali basalts),respectively.In this system,the parental magma can be classified as silica-undersaturated olivine basalt and silica-saturated tholeiite.The equivalents of the parental magma of the Xinjie and Limahe peridotites and picrites and low-Ti basalts are silica-undersaturated, whereas the Limahe gabbro-diorites and high-Ti basalts are silica-saturated.In contrast,the Panzhihua intrusion appears to be alkali character.Phase equilibria relations clearly show that the magmas that formed the Panzhihua intrusion and high-Ti basalts cannot be co-magmatic as there is no way to derive one liquid from another by fractional crystallization.On the other hand,the Panzhihua intrusion appears to be related to Permian alkali intrusions in the region,but does not appear to be related to the alkali basalts recognized in the Longzhoushan lava stratigraphy. Comparably,the Limahe intrusion appears to be a genetic relation to the picrites,whereas the Xinjie intrusion may be genetically related to be low-Ti basalts.Additionally,the gabbro-diorites and peridotites of the Limahe intrusion are not co-magmatic,and the former appears to be derived liquid from high-Ti basalts.更多还原

【Abstract】 There are two types of temporally and spatially associated intrusions within the Emeishan large igneous province(LIP);namely,small ultramafic subvolcanic sills that host magmatic Cu-Ni-Platinum Group Element(PGE)-bearing sulfide deposits and large mafic layered intrusions that host giant Ti-V magnetite deposits in the Panxi region.However,except for their coeval ages,the genetic relations between the ore-bearing intrusions and extrusive rocks are poorly understood.Phase equilibria analysis(Q-Pl-Ol-Opx-Cpx system)has been carried out to elucidate whether ore-bearing Panzhihua,Xinjie and Limahe intrusions are co-magmatic with the picrites and flood basalts (including high-Ti,low-Ti and alkali basalts),respectively.In this system,the parental magma can be classified as silica-undersaturated olivine basalt and silica-saturated tholeiite.The equivalents of the parental magma of the Xinjie and Limahe peridotites and picrites and low-Ti basalts are silica-undersaturated, whereas the Limahe gabbro-diorites and high-Ti basalts are silica-saturated.In contrast,the Panzhihua intrusion appears to be alkali character.Phase equilibria relations clearly show that the magmas that formed the Panzhihua intrusion and high-Ti basalts cannot be co-magmatic as there is no way to derive one liquid from another by fractional crystallization.On the other hand,the Panzhihua intrusion appears to be related to Permian alkali intrusions in the region,but does not appear to be related to the alkali basalts recognized in the Longzhoushan lava stratigraphy. Comparably,the Limahe intrusion appears to be a genetic relation to the picrites,whereas the Xinjie intrusion may be genetically related to be low-Ti basalts.Additionally,the gabbro-diorites and peridotites of the Limahe intrusion are not co-magmatic,and the former appears to be derived liquid from high-Ti basalts.更多还原