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| Assimilation of carbonate country rock by the parent magma of the Panzhihua Fe-Ti-V deposit（SW China）：Evidence from stable isotopes | |
| 作者姓名： | Clement Ganino Chris Harris Nicholas T.Arndt Stephen A.Prevec Geoffrey H.Howarth |
| 作者单位： | [1]Geoazur, Universite de Nice - Sophia Antipolis, CNRS/IRD, 250 rue Albert Einstein 06560 Valbonne, France [2]Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa [3]ISTerre, Grenoble Universites, CNRS/IRD BP 53 38041 Grenoble CEDEX 9, France [4]Department of Geology, Rhodes University, Grahamstown 6140, South Africa |
| 基金项目： | The project benefited from a PROCORE Hong Kong-France exchange grant to Arndt and Zhou and a grant from the US National Science Foundation |
| 摘 要： | The Panzhihua intrusion in southwest China is part of the Emeishan Large Igneous Province and host of a large Fe-Ti-V ore deposit.During emplacement of the main intrusion,multiple generations of mafic dykes invaded carbonate wall rocks,producing a large contact aureole.We measured the oxygen-isotope composition of the intrusions,their constituent minerals,and samples of the country rock.Magnetite and plagioclase from Panzhihua intrusion haveδ18O values that are consistent with magmatic equilibrium, and formed from magmas withδ18O values that were 1-2‰higher than expected in a mantle-derived magma.The unmetamorphosed country rock has highδ18O values,ranging from 13.2‰（sandstone） to 24.6-28.6‰（dolomite）.The skarns and marbles from the aureole have lowerδ18O andδ13C values than their protolith suggesting interaction with fluids that were in exchange equilibrium with the adjacent mafic magmas and especially the numerous mafic dykes that intruded the aureole.This would explain the alteration ofδ18O of the dykes which have significantly higher values than expected for a mantle-derived magma.Depending on the exactδ18O values assumed for the magma and contaminant, the amount of assimilation required to produce the elevatedδ18O value of the Panzhihua intrusion was between 8 and 13.7 wt.%,assuming simple mixing.The exact mechanism of contamination is unclear but may involve a combination of assimilation of bulk country rock,mixing with a melt of the country rock and exchange with CO2-rich fluid derived from decarbonation of the marls and dolomites.These mechanisms,particularly the latter,were probably involved in the formation of the Fe-Ti-V ores. |
| 关 键 词： | Panzhihua Stable isotopes Carbonates Assimilation Contamination |
| 收稿时间： | 14 September 2012 |
http://www.sciencedirect.com/science/article/pii/S1674987112001557 |
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| Clement Ganino,Chris Harris,Nicholas T.Arndt,Stephen A.Prevec,Geoffrey H.Howarth.http://www.sciencedirect.com/science/article/pii/S1674987112001557[J].Geoscience Frontiers,2013,4(5):547-554. | |
| Authors: | Clément Ganino Chris Harris Nicholas TArndt Stephen APrevec Geoffrey HHowarth |
| Institution: | 1. Geoazur, Université de Nice-Sophia Antipolis, CNRS/IRD, 250 rue Albert Einstein 06560 Valbonne, France 2. Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa 3. ISTerre, Grenoble Universités, CNRS/IRD BP 53 38041 Grenoble CEDEX 9, France 4. Department of Geology, Rhodes University, Grahamstown 6140, South Africa |
| Abstract: | The Panzhihua intrusion in southwest China is part of the Emeishan Large Igneous Province and host of a large Fe-Ti-V ore deposit. During emplacement of the main intrusion, multiple generations of mafic dykes invaded carbonate wall rocks, producing a large contact aureole. We measured the oxygen-isotope composition of the intrusions, their constituent minerals, and samples of the country rock. Magnetite and plagioclase from Panzhihua intrusion have δ18O values that are consistent with magmatic equilibrium, and formed from magmas with δ18O values that were 1–2‰ higher than expected in a mantle-derived magma. The unmetamorphosed country rock has high δ18O values, ranging from 13.2‰ (sandstone) to 24.6–28.6‰ (dolomite). The skarns and marbles from the aureole have lower δ18O and δ13C values than their protolith suggesting interaction with fluids that were in exchange equilibrium with the adjacent mafic magmas and especially the numerous mafic dykes that intruded the aureole. This would explain the alteration of δ18O of the dykes which have significantly higher values than expected for a mantle-derived magma. Depending on the exact δ18O values assumed for the magma and contaminant, the amount of assimilation required to produce the elevated δ18O value of the Panzhihua intrusion was between 8 and 13.7 wt.%, assuming simple mixing. The exact mechanism of contamination is unclear but may involve a combination of assimilation of bulk country rock, mixing with a melt of the country rock and exchange with CO2-rich fluid derived from decarbonation of the marls and dolomites. These mechanisms, particularly the latter, were probably involved in the formation of the Fe-Ti-V ores. |
| Keywords: | Panzhihua Stable isotopes Carbonates Assimilation Contamination |
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