Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains

Abstract Zircon of crustal origin found in mantle-derived rocks is of great interest because of the information it may provide about crust recycling and mantle dynamics. Consideration of this requires understanding of how mantle temperatures, notably higher than zircon crystallization temperatures,...

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Autores principales:	Fernando Bea, Pilar Montero, Jose Francisco Molina Palma
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2018
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/0426d09772154fa1886e03154b610e9e
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spelling	oai:doaj.org-article:0426d09772154fa1886e03154b610e9e2021-12-02T15:08:18ZExperimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains10.1038/s41598-018-30934-42045-2322https://doaj.org/article/0426d09772154fa1886e03154b610e9e2018-08-01T00:00:00Zhttps://doi.org/10.1038/s41598-018-30934-4https://doaj.org/toc/2045-2322Abstract Zircon of crustal origin found in mantle-derived rocks is of great interest because of the information it may provide about crust recycling and mantle dynamics. Consideration of this requires understanding of how mantle temperatures, notably higher than zircon crystallization temperatures, affected the recycled zircon grains, particularly their isotopic clocks. Since Pb2+ diffuses faster than U4+ and Th+4, it is generally believed that recycled zircon grains lose all radiogenic Pb after a few million years, thus limiting the time range over which they can be detected. Nonetheless, this might not be the case for zircon included in mantle minerals with low Pb2+ diffusivity and partitioning such as olivine and orthopyroxene because these may act as zircon sealants. Annealing experiments with natural zircon embedded in cristobalite (an effective zircon sealant) show that zircon grains do not lose Pb to their surroundings, although they may lose some Pb to molten inclusions. Diffusion tends to homogenize the Pb concentration in each grain changing the U-Pb and Th-Pb isotope ratios proportionally to the initial 206Pb, 207Pb and 208Pb concentration gradients (no gradient-no change) but in most cases the original age is still recognizable. It seems, therefore, that recycled crustal zircon grains can be detected, and even accurately dated, no matter how long they have dwelled in the mantle.Fernando BeaPilar MonteroJose Francisco Molina PalmaNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 8, Iss 1, Pp 1-10 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Fernando Bea Pilar Montero Jose Francisco Molina Palma Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains
description	Abstract Zircon of crustal origin found in mantle-derived rocks is of great interest because of the information it may provide about crust recycling and mantle dynamics. Consideration of this requires understanding of how mantle temperatures, notably higher than zircon crystallization temperatures, affected the recycled zircon grains, particularly their isotopic clocks. Since Pb2+ diffuses faster than U4+ and Th+4, it is generally believed that recycled zircon grains lose all radiogenic Pb after a few million years, thus limiting the time range over which they can be detected. Nonetheless, this might not be the case for zircon included in mantle minerals with low Pb2+ diffusivity and partitioning such as olivine and orthopyroxene because these may act as zircon sealants. Annealing experiments with natural zircon embedded in cristobalite (an effective zircon sealant) show that zircon grains do not lose Pb to their surroundings, although they may lose some Pb to molten inclusions. Diffusion tends to homogenize the Pb concentration in each grain changing the U-Pb and Th-Pb isotope ratios proportionally to the initial 206Pb, 207Pb and 208Pb concentration gradients (no gradient-no change) but in most cases the original age is still recognizable. It seems, therefore, that recycled crustal zircon grains can be detected, and even accurately dated, no matter how long they have dwelled in the mantle.
format	article
author	Fernando Bea Pilar Montero Jose Francisco Molina Palma
author_facet	Fernando Bea Pilar Montero Jose Francisco Molina Palma
author_sort	Fernando Bea
title	Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains
title_short	Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains
title_full	Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains
title_fullStr	Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains
title_full_unstemmed	Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains
title_sort	experimental evidence for the preservation of u-pb isotope ratios in mantle-recycled crustal zircon grains
publisher	Nature Portfolio
publishDate	2018
url	https://doaj.org/article/0426d09772154fa1886e03154b610e9e
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Experimental evidence for the preservation of U-Pb isotope ratios in mantle-recycled crustal zircon grains

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