The deep continental crust has a larger Mg isotopic variation than previously thought

Abstract

Magnesium isotope compositions of the bulk continental crust is a key to understand Mg isotope behaviors during crustal processes, and is the prerequisite to study mantle-crust material exchange/reaction by Mg isotopes. However, thus far, little is known about Mg isotopic compositions of the middle and lower continental crust. In the article by Yang et al. in this issue entitled "Magnesium isotopic composition of the deep continental crust," the authors present high-precision Mg isotopic analyses of highgrade metamorphic terrane samples and granulite xenoliths from China, which represent the middle and lower continental crust, respectively. Large Mg isotopic variation is observed in the deep continental crust, reflecting the combination of several processes, such as continental weathering, involvement of supracrustal materials, and fluid metasomatism. In addition, this article also provides an average Mg isotope composition of the bulk continental crust, which is crucial to future applications of Mg isotopes.

Effects of cone combinations on accurate and precise Mg‐isotopic determination using multi‐collector inductively coupled plasma mass spectrometry

“…A large number of biological, geological, and physicochemical processes can result in significant Mg‐isotopic fractionation . With the use of a homogeneous isotope reference material (DSM‐3), Mg isotopes are increasingly employed to provide ubiquitous traceability in the fields of geochemistry, speleology, hydrology, oceanography, paleoclimatology, cosmochemistry, and biology, such as understanding biogeochemical processes, tracing fluid/melt‐mineral interaction, characterizing chemical weathering, exploring earth and planetary evolution, and reconstructing climate history . To date, a range of ~6‰ in the 26 Mg/ 24 Mg ratios has been observed in various types of natural samples .…”

“…employed to provide ubiquitous traceability in the fields of geochemistry, speleology, hydrology, oceanography, paleoclimatology, cosmochemistry, and biology, [3][4][5][6][7][8][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] such as understanding biogeochemical processes, 6,14,17,28 tracing fluid/melt-mineral interaction, 29 characterizing chemical weathering, 5,11,12 exploring earth and planetary evolution, 3,4,13 and reconstructing climate history. 5,15,16 To date, a range of~6‰ in the 26 Mg/ 24 Mg ratios has been observed in various types of natural samples.…”