of carbonates, hydrothermal solutions and river waters

摘要: We present strontium (Sr) isotope ratios that, unlike traditional 87 Sr/ 86 Sr data, are not normalized to a fixed 88 ratio of 8.375209 (defined as d 88/86 = 0 relative NIST SRM 987). Instead, we correct for fractionation during mass spectrometry with Sr– 84 double spike. This technique yields two independent and that reported ( Sr*) (d Sr), respectively. The difference between the radiogenic 8.375209) new Sr* values reflect natural mass-dependent fractionation. In order constrain glacial/interglacial changes in marine budget compare composition modern seawater (( Sr*, Sr)Seawater) biogenic carbonates Sr)Carbonates) corresponding river waters Sr)River) hydrothermal solutions Sr)HydEnd) triple plot. measured Sr)River selected rivers together account � 18% global discharge yield flux-weighted mean (0.7114(8), 0.315(8)&). average Sr)HydEnd from Atlantic Ocean (0.7045(5), 0.27(3)&). contrast, Sr)Carbonates representing output (0.70926(2), 0.21(2)&). estimate sources at (0.7106(8), 0.310(8)&). estimated Sr)input Sr)output reflects disequilibrium respect inputs outputs. contrast ocean, equilibrium outputs last glacial maximum (10–30 ka before present) can be explained by invoking three times higher uniquely “glacial” source: weathering shelf exposed low sea levels. Our data also consistent “weathering peak” hypothesis invokes enhanced resulting postglacial exposure abundant fine-grained material. 2010 Elsevier Ltd. All rights reserved.