@article{TEXTUAL,
      recid = {6612},
      author = {Aarons, Sarah M. and Dauphas, Nicolas and Greber, Nicolas  D. and Roskosz, Mathieu and Bouchez, Julien and Carley,  Tamara and Liu, Xiao-Ming and Rudnick, Roberta L. and  Gaillardet, Jérôme},
      title = {Titanium transport and isotopic fractionation in the  Critical Zone},
      journal = {Geochimica et Cosmochimica Acta},
      address = {2023-05-25},
      number = {TEXTUAL},
      abstract = {Stable Ti isotopes have been applied in the detrital  sediment record to reconstruct the bulk composition of  Earth’s continental crust due to the relationship between  magmatic differentiation and Ti isotopic compositions.  However, no study has systematically evaluated the  influence of provenance, physical, and chemical weathering  on the composition of sediments relative to the protolith  they originated from. To test the influence of these  processes on Ti isotopic compositions we investigate the Ti  isotope composition of 82 surface samples including loess,  volcaniclastic rocks, river sediment, and two separate  weathering profiles through igneous rocks, collected from a  broad geographical area and a range of environmental  conditions. Limited but significant Ti isotope  fractionation exists in samples subjected to extreme  chemical weathering processes, potentially as a result of  elemental mobilization. For example, the δ<sup>49</sup>Ti  isotopic composition of bauxites developed on Columbia  River basalt varies by up to 0.1‰, becoming isotopically  heavier with increasing weathering intensity. However,  negligible variation in δ<sup>49</sup>Ti was found in a  second profile of saprolites developed on weathered  diabase. Titanium isotope variations in loess do not  correlate with chemical weathering intensity or size  sorting, but may instead be related to the provenance of  the sediment. We find that the δ<sup>49</sup>Ti of Amazon  River sediments is correlated with the Al/Zr ratio,  indicating that δ<sup>49</sup>Ti is impacted by sediment  sorting. At our study sites, the river averaged offset  between the isotopic composition of the bedload and the  suspended sediment fraction is 0.051‰, with the largest  offset being + 0.116‰. Our data suggest that during  chemical weathering, heavy Ti isotopes are preferentially  incorporated into secondary minerals producing higher  δ<sup>49</sup>Ti in intensely weathered soils. During  fluvial transport, the Ti isotopic composition of  fine-grained sediment is heavier than that of its coarser  counterpart. Crustal protolith composition and sorting  during transport and sedimentation have a stronger effect  on the Ti isotopic composition than chemical weathering.  Our results have implications for studies that utilize the  Ti elemental concentration to calculate relative enrichment  or depletion during chemical weathering and physical  transport processes in the Critical Zone and for studies  using Ti isotopes in terrigenous sediments to infer the  composition of their provenance.},
      url = {http://knowledge.uchicago.edu/record/6612},
}