Geochemical characteristics of sediments from the COMRA registered pioneer area (CRPA), equatorial northeastern Pacific Ocean

COMRA (China Ocean Mineral Resources Association) registered pioneer area (CRPA) is located in the western part of the area between the Clarion and Clipperton Fraction Zones (CCFZs).Based on distinctive color and bio-disturbing properties, two layers are recognized in the sediment columns from the CRPA:a pale brown layer (Unit A) on the top and a dark brown layer (Unit B) in the lower part. Color division between them can be explained as a hiatus. As a result, the two units are different to each other in chemical composition and sediment properties. It is found that contents of P₂O₅, MnO₂, CaO, Na₂O in sediments of older Unit B are higher, but SiO₂ content is slightly lower.Based on correlation analysis, Mn and Fe in the sediments have different origins. The former is mainly precipitated in authigenic process, whilst the latter is closely related to terrigenous detritus. Therefore,the differences in chemical composition of the sediments are caused by different sedimentation settings.