Signatures and Significance of Lithogenic, Hydrothermal, Biogenic, and Authigenic Mineral Fractions in Ridge Flank Sediments of the East Pacific Rise

The complex mineralogy and dynamic geochemical processes make the sediments of the Clarion-Clipperton Zone in the eastern Pacific an important research target. Although the sediments and depositional conditions in the study area have been investigated recently, there are still unresolved issues due to the heterogeneity of the sediments. By combining rock magnetic properties and elemental composition data of sediment core SO240-69SL (12° 39.855' N, 119° 13.374' W, water depth of 4275 m) with endmember modeling we aim at contributing to a better understanding of the origin and genesis of the sediments.

Based on magnetostratigraphy, the sediments retrieved at this site are backdated to 3.59 Ma and show pronounced changes in sedimentary input through time. The multi-proxy approach reveals four major sediment components: (1) a bottom current-transported lithogenic source derived from weathering of crustal rocks, (2) a low-temperature hydrothermal component of iron-rich clay minerals, (3) a calcareous fraction restricted to the lower part of the core, and (4) authigenic iron-manganese precipitates found at present and past redox boundaries.

The sedimentary input from 3.59 to 2.82 Ma is dominated by the low-temperature hydrothermal component and preservation of biogenic carbonates. Endmember modeling shows that the hydrothermal component decreases upward, which is indicative of an increasing distance of the site from the hydrothermal source. From 2.41 to 1.14 Ma, a pronounced change in sediment color and magnetic properties (ARM, ARM/IRM) as well as geochemical properties (Fe/Ti, Si, Al) marks a pause in sedimentation. Thereafter, the sedimentary environment shifts towards lithogenic-dominated sediments with constant content of biogenic magnetite, accompanied by a decrease in sedimentation rate from 1.02 to 0.25 cm ka^-1.

This study demonstrates the potential of using combined rock magnetic and geochemical approaches to reconstruct the complex depositional and early diagenetic history of abyssal sediments. It provides new insights into the sediment formation, mineralogy, and highlights the importance of low-temperature hydrothermal and authigenic minerals, in addition to lithogenic and biogenic sources, on (magnetic) sediment properties.