Data/hora: 09/06/2024 06:00:47

Provedor de dados: 	5	
País: 	France	
Título: 	Origin of primitive ocean island basalts by crustal gabbro assimilation and multiple recharge of plume-derived melts	
Autores: 	Borisova, Anastassia Y.; Bohrson, Wendy A.; Gregoire, Michel.	
Data: 	2017-07	
Ano: 	2017	
Palavras-chave: 	Ocean island basalt; Kerguelen; Mantle plume; Ocean metagabbro xenoliths; Crustal assimilation and fractional crystallization; Magma Chamber Simulator.	
Resumo: 	Chemical Geodynamics relies on a paradigm that the isotopic composition of ocean island basalt (OIB) represents equilibrium with its primary mantle sources. However, the discovery of huge isotopic heterogeneity within olivine-hosted melt inclusions in primitive basalts from Kerguelen, Iceland, Hawaii and South Pacific Polynesia islands implies open-system behavior of OIBs, where during magma residence and transport, basaltic melts are contaminated by surrounding lithosphere. To constrain the processes of crustal assimilation by OIBs, we employed the Magma Chamber Simulator (MCS), an energy-constrained thermodynamic model of recharge, assimilation and fractional crystallization. For a case study of the 21–19 Ma basaltic series, the most primitive series ever found among the Kerguelen OIBs, we performed sixty-seven simulations in the pressure range from 0.2 to 1.0 GPa using compositions of olivine-hosted melt inclusions as parental magmas, and metagabbro xenoliths from the Kerguelen Archipelago as wallrock. MCS modeling requires that the assimilant is anatectic crustal melts (P2O5  ≤ 0.4 wt.% contents) derived from the Kerguelen oceanic metagabbro wallrock. To best fit the phenocryst assemblage observed in the investigated basaltic series, recharge of relatively large masses of hydrous primitive basaltic melts (H2O = 2–3 wt%; MgO = 7–10 wt.%) into a middle crustal chamber at 0.2 to 0.3 GPa is required. Our results thus highlight the important impact that crustal gabbro assimilation and mantle recharge can have on the geochemistry of mantle-derived olivine-phyric OIBs. The importance of crustal assimilation affecting primitive plume-derived basaltic melts underscores that isotopic and chemical equilibrium between ocean island basalts and associated deep plume mantle source(s) may be the exception rather than the rule.	
Tipo: 	Text	
Idioma: 	Inglês	
Identificador: 	https://archimer.ifremer.fr/doc/00393/50409/51128.pdf

https://archimer.ifremer.fr/doc/00393/50409/51133.pdf

https://archimer.ifremer.fr/doc/00393/50409/51134.xlsx

DOI:10.1002/2017GC006986

https://archimer.ifremer.fr/doc/00393/50409/	
Editor: 	Amer Geophysical Union	
Formato: 	application/pdf	
Fonte: 	Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2017-07 , Vol. 18 , N. 7 , P. 2701-2716	
Fonte: 	2017. American Geophysical Union. All Rights Reserved

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