Phyllosilicate controls on magnesium isotopic fractionation during weathering of granites: Implications for continental weathering and riverine system

Continental weathering is a fundamental process in releasing magnesium (Mg) from crystalline rocks to the hydrosphere and biosphere. Mg isotopes can be substantially mobilized, re-distributed, fractionated during weathering, therefore used as powerful tool trace biogeochemical cycle of Mg. Causes significant isotopic fractionation behaviors silicate are still not well understood, hindering further application probe different geological processes. In this study, we demonstrate that dissolution formation phyllosilicates main control sub-tropical granite. Furthermore, mechanisms for same mineral phase could also cause variations magnitude directionality fractionation. incipient supergene form mainly through topotactic transformation. Vermiculitization parental chlorite tends release 24Mg causes 26Mg enrichment saprock. an advanced stage compositions more influenced by interaction with soil solutions. Minerals formed dissolution-precipitation mechanism neoformed dominantly sourced contemporary would firstly incorporated into phyllosilicates, such vermiculite, interstratified biotite/vermiculite chlorite/vermiculite. Therefore, solutions became enriched depth pedolith, which relatively 24Mg-rich form. However, saprolite, precipitation illite may have preferentially scavenged 24Mg, enriching 26Mg. Varying relative abundances phyllosilicate minerals along profile large regolith. Our study shows composition slightly weathered materials significantly heavy. Hence, entrainment 26Mg-rich but alternative explain high ?26Mg recorded some sedimentary rocks, especially aeolian source. Whereas low widely archived groundwater river water alternatively explained saprock scavenging transformation, instead severe depletion due intense vast secondary minerals, previously suggested. Comprehensive characterization processes resultant products essential interpret observed