Vertical profiles of cobalt and zinc in marine sediments of the Santa Rosalía mining region, Gulf of California, Mexico.

High authigenic Co enrichment in the non‐euxinic buff‐grey and black shale of the Chandarpur Group, Chhattisgarh Supergroup: Implication for the late Mesoproterozoic shallow marine redox condition

“…A statistically significant positive correlation of Al with V, Cr and U in these samples (Table 2) reaffirms their predominantly detrital origin. This result is consistent with the majority of modern oxygenated shallow marine marginal sediments in which the bulk trace metal fraction is found in detrital aluminosilicate minerals (Hu et al, 2013;Loring, 1979;Shumilin et al, 2013;Sundby et al, 1986;Windom et al, 1989). Significant non-detrital enrichment of trace metals in the modern marine marginal sediments mostly occurs in anoxic/euxinic environments mainly led by sulfide-scavenging (Morse & Luther, 1999).…”

“…In the modern ocean, the dissolved Co abundance is extremely low, and a major fraction of it is sourced from sedimentary boundaries in the oxygen minimum zones (where dissolved oxygen concentration lies between 2 and 50 μM, for example off Peru/Chile, the Gulf of California, Arabian Sea and South Atlantic) via reductive dissolution of Fe/Mn oxyhydroxides (Tagliabue et al, 2018), whereas hydrothermal sourcing is found to be negligible. In modern shallow marine sediments, Co enrichment predominantly remains close to the crustal value (Windom et al, 1989;Hu et al, 2012Hu et al, , 2013Shumilin et al, 2013;Tagliabue et al, 2018). However, uncommon Co enrichments above UCC (EF up to 8) have been noted…”

Geochemistry in Mexico

“…The next paper reports the results of Co, Sc and Zn measurements on core sediments from the coastal zone of the Santa Rosalía mining region and the adjacent deeper areas of the Gulf of California (Shumilin et al, 2013). Co/Sc and Zn/Sc values in cores from a predominant pollution "hot spot" near Santa Rosalía port were very high, indicating that the thickness of the polluted layer exceeded the length of the cores (75-93 cm).…”