TY - JOUR
T1 - Extreme Zr stable isotope fractionation during magmatic fractional crystallization
AU - Ibañez-Mejia, Mauricio
AU - Tissot, François L.H.
N1 - Funding Information:
We thank D. McGee for access to the MIT Nu Plasma II and J. DesOrmeau for the scanning electron microscopy imaging at U. Nevada in Reno. We thank E. Bloch and M. Méheut for comments to an earlier version of the manuscript. G. Gaetani, H. Marshall, and three anonymous reviewers provided comments that greatly helped improve the manuscript. Funding: This research was supported by NSF-EAR grants 1823748 (to M.I.-M.) and 1824002 (to F.L.H.T.), and startup funds to M.I.-M. provided by U. Rochester.
Publisher Copyright:
Copyright © 2019 The Authors, some rights reserved;
PY - 2019/12/18
Y1 - 2019/12/18
N2 - Zirconium is a commonly used elemental tracer of silicate differentiation, yet its stable isotope systematics remain poorly known. Accessory phases rich in Zr4+ such as zircon and baddeleyite may preserve a unique record of Zr isotope behavior in magmatic environments, acting both as potential drivers of isotopic fractionation and recorders of melt compositional evolution. To test this potential, we measured the stable Zr isotope composition of 70 single zircon and baddeleyite crystals from a well-characterized gabbroic igneous cumulate. We show that (i) closed-system magmatic crystallization can fractionate Zr stable isotopes at the >0.5% level, and (ii) zircon and baddeleyite are isotopically heavy relative to the melt from which they crystallize, thus driving chemically differentiated liquids toward isotopically light compositions. Because these effects are contrary to first-order expectations based on mineral-melt bonding environment differences, Zr stable isotope fractionation during zircon crystallization may not solely be a result of closed-system thermodynamic equilibrium.
AB - Zirconium is a commonly used elemental tracer of silicate differentiation, yet its stable isotope systematics remain poorly known. Accessory phases rich in Zr4+ such as zircon and baddeleyite may preserve a unique record of Zr isotope behavior in magmatic environments, acting both as potential drivers of isotopic fractionation and recorders of melt compositional evolution. To test this potential, we measured the stable Zr isotope composition of 70 single zircon and baddeleyite crystals from a well-characterized gabbroic igneous cumulate. We show that (i) closed-system magmatic crystallization can fractionate Zr stable isotopes at the >0.5% level, and (ii) zircon and baddeleyite are isotopically heavy relative to the melt from which they crystallize, thus driving chemically differentiated liquids toward isotopically light compositions. Because these effects are contrary to first-order expectations based on mineral-melt bonding environment differences, Zr stable isotope fractionation during zircon crystallization may not solely be a result of closed-system thermodynamic equilibrium.
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U2 - 10.1126/sciadv.aax8648
DO - 10.1126/sciadv.aax8648
M3 - Article
C2 - 31897427
AN - SCOPUS:85076708578
SN - 2375-2548
VL - 5
JO - Science Advances
JF - Science Advances
IS - 12
M1 - eaax8648
ER -