Asian continental nature of87Sr/86Sr ratios in north central Pacific sediments

Strontium isotopic compositions were determined for silicate detritus in 152 deep-sea and continental shelf surface sediment samples from the Pacific Ocean to trace their provenance. The major characteristics of the spatial variation of the Sr isotopes and the interpretation of this variation may be summarized as follows: (1) Sediments in the Pacific have a lower average87Sr/86Sr ratio (0.7112) with a narrower range (0.703–0.724) than in the Atlantic (0.7166; 0.704–0.743). Many western Pacific volcanoes together with young continental crust supply material with low87Sr/86Sr ratios to the Pacific, in contrast to the large old cratonic crust that supplies material with high Sr ratio to the Atlantic. (2) The87Sr/86Sr ratio is high in the north central Pacific (0.711–0.719). The Izu-Ogasawara and Mariana arcs supply low87Sr/86Sr material to the western Pacific, but farther to east the abundant supply of loess carried by middle-latitude westerlies from the Asian continent (87Sr/86Sr=ca.0.720) dominates the north central Pacific.