Distribution and geochemical characteristics of metal enrichment in the New Albany Shale (Devonian-Mississippian), Indiana

Abstract

Black shale beds in the uppermost part of the Clegg Creek Member of the New AlbanyShale (Devonian-Mississippian) in southern Indiana have organic C contents from • 12 to 25 wt percent and are enriched in Cu, Pb, Zn, Ni, Cd, Mo, and V. Brownish-black to olive-black shale located lower in the formation has normal metal contents and organic C abundances up to 12 wt percent. Shale units lower in the section were deposited under anaerobic conditions, but C-S-Fe relationships and sulfur isotope values suggest that the H2S-O2 boundary occurred near or at the sediment-water interface. Conversely, the carbon-and metal-rich beds near the top of the formation were deposited under strongly euxinic conditions with the chemocline located within the water column. Metal sulfide formation was limited by the availability of metals. A sharp increase in slope at 12 to 14 wt percent Corganie is observed in organic C-metal plots and is related to organic carbon preservation and metal adsorption due to the presence of an H2S-bearing water column.Sequential chemical analyses and electron microprobe studies indicate that Zn, Cu, and Cd are held in sulfide minerals, Pb as a selenide, Mo both as a sulfide (456-85%) and within kerogen (20%), Ni within kerogen (50%) and as a sulfide (45%), and V primarily within clay minerals. Petrographic studies also indicate that the beds in the upper part of the Clegg Creek Member are characterized by the highest proportion of inertinite and vitrinite found in the New Albany Shale.A conceptual model is developed whereby trace metals adsorbed on surfaces of organic material were preserved from release by oxidative degradation in the water column due to the high elevation of the H•S-O• boundary. Transition metal contents of the Clegg Creek Member may have been locally high due to an increase in the influx of terrestrial organic matter. Once delivered to the sea floor, metals took part in diagenetic reactions that produced metal sulfides and vanadiferous clays. Only Mo and Ni remained significantly enriched in kerogen. Although Ni and V contents are high in the soluble organic material from the shale, their abundance constitutes less than 1 percent each of the whole-rock metal content.

An integrated sulfur isotope model for Namibian shelf sediments

“…0.0& vs. CDT, Beier and Hayes, 1989) and 34 S-depleted pyrite (À48.2& vs. CDT) is known to be preserved in the ancient rock record (Ripley et al, 1990). Yet, significant diagenetic overprint of the solid phases would compromise the traditional interpretation of past benthic conditions and the long-term sedimentary d 34 S FeS2 record.…”

Organic Carbon and Trace Metal Distribution in the Gökçesu Shale: Eocene Basin, Bolu-Turkey

“…Sedimentation intervals and the presence of relatively low H 2 S under anoxic conditions give rise to low V and Ni concentrations in the organic phase and high concentrations of Cu, Zn, and Ni in the sulfide phase (Ripley et al, 1990).…”

“…On the basis of Ripley et al (1990) model, metals adsorbed on the OM surface are distributed over the sea floor and metallic sulfides, like vanadium-clays, are formed during the early diagenesis.…”

Influences of Terrestrial Inputs of Organic Matter on Coastal Water and Bottom Sediments in the Seto Inland Sea, Japan

“…The terrestrial nutrient input and solar insolation following flood events significantly increase the growth rate and standing stock of phytoplankton, resulting in red tide and an increase in POM in coastal seas [4][5][6]. The particulate organic matter in coastal waters and bottom sediments often absorb pollutants and heavy metals [7][8][9], and therefore the investigations of the spread of POM are especially important for coastal water and sediment management.…”