REE and ε Nd of clay fractions in sediments from the eastern Pacific Ocean: Evidence for clay sources

Clay fractions in the non-calcareous surface sediments from the eastern Pacific were analyzed for clay minerals, REE and 143Nd/144Nd. Montmorillonite/illite ratio (M/I ratio), total REE contents (ΣREE), LREE/HREE ratio and cerium anomaly (δCe) may effectively indicate the genesis of clay minerals. Clay fractions with M/I ratio 0.85, ΣREE 1, δCe=0.86 to 1.5, ΣREE=200 to 350 μg/g, LREE/HREE ratio ≈6 and REE distribution patterns similar to that of China loess are identified as terrigenous clay fraction. The 143Nd/144Nd ratios or ɛNd values of clay fractions inherit the features of terrigenous sources of clay minerals. Clay fractions are divided into 4 types according to ɛNd values. Terrigenous clay minerals of type I with the ɛNd values of ™8 to ™6 originate mainly from North American fluvial deposits. Those of type II with the ε Nd values of ™9 to ™7 are mainly from the East Asia and North American fluvial deposits. Those of type III with ε Nd values of ™6 to ™3 could come from the central and eastern Pacific volcanic islands. Those of type IV with ε Nd values of ™13 to ™12 may be from East Asia eolian. The terrigenous and autogenetic mixed clay fractions show patchy distributions, indicating that there are volcanic or hot-spot activities in the eastern Pacific plate, while the terrigenous clay fractions cover a large part of the study area, proving that the terrigenous clay minerals are dominant in the eastern Pacific.