(Table 1) Chemical and lithological composition of rocks from DSDP Hole 465A


Uranium and thorium are concentrated in Cretaceous limestone, chert, ash, basalt, and other rock types at Deep Sea Drilling Project Site 465 located on the southern Hess Rise in the central North Pacific. U concentrations, up to 194 ppm on a carbonate-free basis, are among the highest recorded for any deep-sea deposits. U was initially derived from seawater and concentrated by absorption on terrigenous (humic) organic matter in limestone in a shallow marine environment. U and Th were probably concentrated further by low-temperature hydrothermal fluids emanating from the basaltic basement. Mainly montmorillonite, an alteration product of basalt and ash, and organic matter in sedimentary rocks acted as hosts for U and Th.The unique combination of sediments rich in humic organic matter, abundant smectite in altered ash and basalt, and warm hydrothermal solutions provided the necessary conditions for migration and concentration of U and Th. To better understand the conditions limiting the migrating and concentration of U and Th, other rocks deposited during the ocean-wide Cretaceous anoxic events should be analyzed for these elements.

In the sample 465A-40-1, 145 (calcareous ash / sulfide-rich fraction) contents of major oxides were measured by quantitative emission spectroscopy; in the samples 465A-40-2, 62 (altered ash) and 465A-40-2, 62 (altered ash, <1 µm fraction) contents of major oxides were measured by semi-quantitative emission spectroscopy.

Supplement to: Hein, James R; Koski, Randolph A; Morgenson, Lisa A (1982): Uranium and thorium enrichment in rocks from the base of DSDP Hole 465A, Hess Rise, Central North Pacific. Chemical Geology, 36(3-4), 237-251

DOI https://doi.org/10.1594/PANGAEA.696416
Related Identifier https://doi.org/10.1016/0009-2541(82)90050-X
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.696416
Creator Hein, James R; Koski, Randolph A; Morgenson, Lisa A
Publisher PANGAEA
Publication Year 1982
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 278 data points
Discipline Earth System Research
Spatial Coverage (178.919 LON, 33.821 LAT); North Pacific/CONT RISE