The Panzhihua mafic intrusion,which hosts a world-class Fe-Ti-V ore deposit,is in the western Emeishan region,SW China.The formation age(~260 Ma),and Sr and Nd isotopes indicate that the Panzhihua intrusion is part of...The Panzhihua mafic intrusion,which hosts a world-class Fe-Ti-V ore deposit,is in the western Emeishan region,SW China.The formation age(~260 Ma),and Sr and Nd isotopes indicate that the Panzhihua intrusion is part of the Emeishan large igneous province and has little crustal contamination.To assess ore genesis of the Panzhihua Fe-Ti-V ore deposit,two different models have been provided to explain the formation,namely silicate immiscibility and normal fractional crystallization.Silicate immiscibility occurring around 1,000℃at the late stage of basaltic magma evolution argues against the silicate immiscibility model.Apatite-hosted melt inclusion research indicates that silicate immiscibility occurred at the late stage of Panzhihua magma evolution,which may not have offered potential to form such large ore deposits as Panzhihua.Alternatively,continuous compositional variations of the Panzhihua intrusion and calculations using thermodynamic modelling software support the hypothesis that the Panzhihua deposit was formed by normal fractional crystallization.Reciprocal trace element patterns of the Panzhihua intrusion and nearby felsic rocks also coincide with the fractional crystallization model.Normal fractional crystallization of high-Ti basaltic magma played a key role in the formation of the Panzhihua Fe-Ti-V ore deposit.展开更多
The Panzhihua intrusion in southwest China is part of the Emeishan large igneous province and host of a large Fe-Ti-V ore deposit.In previous interpretations it was considered to be a layered,differentiated sill with ...The Panzhihua intrusion in southwest China is part of the Emeishan large igneous province and host of a large Fe-Ti-V ore deposit.In previous interpretations it was considered to be a layered,differentiated sill with the ore deposits at its base.New structural and petrological data suggest instead that the intrusion has an open S-shape,with two near-concordant segments joined by a discordant dyke-like segment. During emplacement of the main intrusion,multiple generations of mafic dykes invaded carbonate wall rocks,producing a large contact aureole.In the central segment,magmatic layering is oriented oblique to the walls of the intrusion.This layering cannot have formed by crystal settling or in-situ growth on the floor of the intrusion;instead we propose that it resulted from inward solidification of multiple,individually operating,convection cells.Ore formation was triggered by interaction of magma with carbonate wall rocks.展开更多
基金co-supported by the China Geological Survey(Grant Nos.DD20230229,DD20190011,DD20221643)the National Key Research and Development Project of China(Grant No.2018YFC0603701)。
文摘The Panzhihua mafic intrusion,which hosts a world-class Fe-Ti-V ore deposit,is in the western Emeishan region,SW China.The formation age(~260 Ma),and Sr and Nd isotopes indicate that the Panzhihua intrusion is part of the Emeishan large igneous province and has little crustal contamination.To assess ore genesis of the Panzhihua Fe-Ti-V ore deposit,two different models have been provided to explain the formation,namely silicate immiscibility and normal fractional crystallization.Silicate immiscibility occurring around 1,000℃at the late stage of basaltic magma evolution argues against the silicate immiscibility model.Apatite-hosted melt inclusion research indicates that silicate immiscibility occurred at the late stage of Panzhihua magma evolution,which may not have offered potential to form such large ore deposits as Panzhihua.Alternatively,continuous compositional variations of the Panzhihua intrusion and calculations using thermodynamic modelling software support the hypothesis that the Panzhihua deposit was formed by normal fractional crystallization.Reciprocal trace element patterns of the Panzhihua intrusion and nearby felsic rocks also coincide with the fractional crystallization model.Normal fractional crystallization of high-Ti basaltic magma played a key role in the formation of the Panzhihua Fe-Ti-V ore deposit.
基金supported by a Famous overseas professor project MS2011ZGDZ[BJ]019 through China University of Geosciences (Beijing)and by the USA NSF "Continental Geodynamics" programGeologists from the Panzhihua mining company are thanked for their logistic support
文摘The Panzhihua intrusion in southwest China is part of the Emeishan large igneous province and host of a large Fe-Ti-V ore deposit.In previous interpretations it was considered to be a layered,differentiated sill with the ore deposits at its base.New structural and petrological data suggest instead that the intrusion has an open S-shape,with two near-concordant segments joined by a discordant dyke-like segment. During emplacement of the main intrusion,multiple generations of mafic dykes invaded carbonate wall rocks,producing a large contact aureole.In the central segment,magmatic layering is oriented oblique to the walls of the intrusion.This layering cannot have formed by crystal settling or in-situ growth on the floor of the intrusion;instead we propose that it resulted from inward solidification of multiple,individually operating,convection cells.Ore formation was triggered by interaction of magma with carbonate wall rocks.
