Mantle Zn Isotopic Heterogeneity Caused by Melt‐Rock Reaction: Evidence From Fe‐Rich Peridotites and Pyroxenites From the Bohemian Massif, Central Europe

0505049 - GLÚ 2020 RIV US eng J - Journal Article
Huang, J. - Ackerman, Lukáš - Zhang, X-CH.
Mantle Zn Isotopic Heterogeneity Caused by Melt‐Rock Reaction: Evidence From Fe‐Rich Peridotites and Pyroxenites From the Bohemian Massif, Central Europe.
Journal of Geophysical Research-Solid Earth. Roč. 124, č. 4 (2019), s. 3588-3604. ISSN 2169-9313. E-ISSN 2169-9356
Institutional support: RVO:67985831
Keywords : zinc isotopes * peridotite * pyroxenite * melt‐rock reaction * mantle heterogeneity
OECD category: Geology
Impact factor: 3.639, year: 2019
Method of publishing: Limited access
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JB017125

To investigate the effect of melt‐rock reaction on Zn isotope fractionation and mantle Zn isotopic heterogeneity, we analyzed Zn isotopic compositions of peridotites, pyroxenites, and mineral separates from the Bohemian Massif, Central Europe. The Mg‐lherzolites (Mg# = 90.9 to 89.1, FeO^T = 7.9 to 9.0 wt %) are melting residues with only moderate metasomatism and have δ⁶⁶Zn from 0.11 to 0.20‰. In contrast, the Fe‐rich peridotites (Mg# = 88.2 to 80.3, FeO^T = 10.0 to 14.5 wt %) and pyroxenites have larger ranges of δ⁶⁶Zn from 0.11 to 0.31‰ and −0.33 to 0.42‰, respectively. Large disequilibrium intermineral Zn isotope fractionation occurs in the Fe‐rich peridotites and pyroxenites with Δ⁶⁶Zn_Opx‐Ol = −0.50‰, Δ⁶⁶Zn_Grt‐Ol = −0.55 to −0.39‰, Δ⁶⁶Zn_Grt‐Opx = −0.28 to −0.05‰, and Δ⁶⁶Zn_Grt‐Cpx = −0.50 to 0.12‰. Combined with their low SiO₂ contents and radiogenic Sr‐Nd‐Os isotopic compositions, the high δ⁶⁶Zn of the Fe‐rich peridotites is attributed to reaction between Mg‐lherzolites and percolating SiO₂‐undersaturated basaltic melts that incorporated isotopically heavy crustal components. Crystallization of the isotopically heavy percolating melts migrating through the lithospheric mantle yield the high‐δ⁶⁶Zn pyroxenites. The low δ⁶⁶Zn of the pyroxenites and large intermineral Zn isotopic disequilibrium may result from kinetic Zn isotope fractionation during melt‐rock reaction. Collectively, these observations indicate that melt‐rock reaction can cause intermineral Zn isotopic disequilibrium and significant Zn isotopic heterogeneity in the mantle. This study thus highlights the potential use of Zn isotopes to trace melt‐rock reaction events in the mantle.
Permanent Link: http://hdl.handle.net/11104/0296572