In particular, as rocks erode, they disintegrate into sands and eventually muds made from clays. Clays tend to incorporate more heavy oxygen, explained Annie Bauer, an assistant professor and geochronologist at the University of Wisconsin–Madison who was also not involved in this study. Subducting mud and mixing it into the mantle would result in melt—and likely zircon—featuring heavier oxygen than a melt that incorporates no crustal material or crust that experienced less weathering.
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