Open AccessLimited magnesium isotope fractionation during metamorphic dehydration in metapelites from the Onawa contact aureole, Maine
Author(s) -
Li WangYe,
Teng FangZhen,
Wing Boswell A.,
Xiao Yilin
Publication year - 2014
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2013gc004992
Subject(s) - protolith , geology , metamorphic rock , geochemistry , equilibrium fractionation , isotope fractionation , fractionation , isotope , sedimentary rock , clastic rock , mineralogy , chemistry , physics , organic chemistry , quantum mechanics
Knowledge on the behavior of Mg isotopes during metamorphic dehydration is the prerequisite for applying Mg isotopes as tracers for crustal recycling. Here we report Mg isotopic compositions of metapelites from the Onawa contact aureole, Maine. Except one sample, all metapelites across the aureole, from the wall‐rock regional metamorphic rocks to the partially melted rocks adjacent to the pluton, have similar Mg isotopic compositions (δ 26 Mg = −0.09 to +0.12‰). This observation indicates limited Mg isotope fractionation during metamorphic dehydration and fluid‐rock interaction, due to the low Mg concentration in fluids relative to rocks. Our results suggest that Mg isotopic compositions of metapelites can record those of their protoliths and, hence, recycled clastic sedimentary materials may preserve their low‐temperature Mg isotopic signatures through subduction zones. Therefore, Mg isotopes may serve as new tracers for crustal recycling, for example, tracing components experienced weathering cycles within granite sources.