Origin of metalliferous sediments from the East Pacific Rise

doi:10.1016/0012-821X(73)90179-9

Earth and Planetary Science Letters

Volume 19, Issue 1, May 1973, Pages 75-82

https://doi.org/10.1016/0012-821X(73)90179-9 Get rights and content

Abstract

The distribution of several metals in East Pacific Rise sediments, when normalized to Al₂O₃, exhibit stronger maxima near the rise crest than when simply plotted on a carbonate-free basis. The similarity (1) between the distribution of metals in ridge sediments and previously measured mean heat flow values and (2) between the composition of crestal sediments and terrestrial ore bodies associated with greenstone belts, strongly supports a hydrothermal origin for rise crest sediments.

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Intense reducing conditions during the last deglaciation and Heinrich events (H1, H2, H3) in sediments from the oxygen minimum zone off Goa, eastern Arabian Sea
2017, Marine and Petroleum Geology
Citation Excerpt :
There is a large variations in the La(n)/Yb(n) ratio ranging from 0.8 to 1.35 in the cores (Fig. 10). In both the sediment cores the La(n)/Yb(n) ratio is < 1 during the last 10 ka suggesting depletion of the light lanthanide compared to the heavy lanthanide, whereas between 14 and 10 ka this ratio is almost constant and is close to 1, indicating the presence of terrigenous derived material (Piper, 1973; Nath et al., 1992). During last deglaciation and Heinrich events, the La(n)/Yb(n) ratio is > 1 and reaches a maximum of 1.35 whereas Ce/Ce* becomes more negative, reaching lowest value of ∼0.75.
Two sediment cores, ABP-32/GC-01R and ABP-32/GC-03 were collected at a water depth of 642 m and 1086 m off Goa from the present day Oxygen Minimum Zone (OMZ) of eastern Arabian Sea (EAS) cover time span of last 18 ka and 32 ka respectively were analysed for multi-proxy redox-sensitive elements to understand the variation in the redox conditions and factors responsible for its development.
Redox-sensitive elements concentration and their normalized ratios (Mn/Al, U/Th, Mo/Al and Ce/Ce*) suggest that sediment core ABP-32/GC-01R is under more reducing conditions due to its location within the centre of OMZ compared to core ABP-32/GC-03 which is at the base of OMZ. Sediments from the EAS are of non-euxinic environments where dissolved sulfide is present but restricted to the sediment pore-waters. Lack of significant correlation (r=< 0.1) of organic carbon with U and Mo suggest that productivity may not have control on the development of reducing conditions. The lowest Mn/Al ratio, strong negative Ce/Ce* anomaly and remarkable enrichment of U/Th and Mo/Al ratios during the last deglaciation, and Heinrich events (H1, H2, H3) indicate intense reducing conditions probably due to poor ventilation by oxygen depleted bottom waters from Subantarctic Mode Waters (SAMW) - Antarctic Intermediate waters (AAIW). There is a distinct lathanide fractionation in the sediment cores where, La_(n)/Yb_(n) ratio is <1, ≈1 and >1 during the last 10 ka (Holocene), 14–10 ka (includes-Younger Dryas and Bǿlling-Allerǿd), 18–14 ka (last deglaciation) and Heinrich events suggesting less reducing, terrigenous dominated and intense reducing condition respectively.
Geochemical and Sr-Nd isotopic variations in palaeoflood deposits at mainstem-tributary junction, western India: Implications on late Holocene flood events
2016, Catena
Citation Excerpt :
The plots were normalised with Al as elemental concentrations are relative and prone to changes even due to change in sedimentation rates. Al and Ti are weathering resistive elements and there will be little change from source to sink in ideal conditions (Piper, 1973). The advantage of normalisation is that the real trend of chemical changes can be identified by ratio vs. ratio plots, such as enrichment and depletion of some elements because Al is an immobile element on the Earth surface in most scenarios.
Element geochemistry and Sr–Nd isotopes have been used to characterise the palaeoflood sediments at a tributary junction in lower Narmada Valley archiving the Little Ice Age (LIA) and to determine the present day sources for the mainstem and the tributary sediments. The major and trace element concentrations show minor variations in values post 360 Cal yr BP. The ⁸⁷Sr/⁸⁶Sr and ε_Nd values of palaeoflood sediments range from 0.7122 to 0.7191 and − 2.89 to + 6.28 respectively. The bed sediments from the mainstem river (Narmada) and its tributary (Karjan) yield ⁸⁷Sr/⁸⁶Sr values of 0.72394 and 0.7113 and ε_Nd values of − 7.18 and + 6.09 respectively. Potential sources of palaeoflood sediments have been investigated from Sr and Nd isotope compositions and mixing of the mainstem as well as the tributary sediments is suggested. Pronounced contribution from the Deccan Basalt during the early part of the Little Ice Age is inferred. The more radiogenic Nd values indicate a contribution from the weathering of younger Deccan basalts, especially the Poladpur formations. The control of weathering intensity and mineral sorting is observed in ‘higher than the source rock’ ⁸⁷Sr/⁸⁶Sr ratios of the sediments. The major and trace element variations during the last 700 years are not conclusive although, isotopic signatures of the flood sediments help in constraining the flux from the tributaries. Sr and Nd isotopic composition of the palaeoflood sediments can be used to track the monsoon intensity and pattern but their concentrations in a fluvial system remain primarily controlled by mineral sorting processes and mixing of sources.
Integrated assessment of metal contamination in sediments from two tropical estuaries
2014, Ecotoxicology and Environmental Safety
Citation Excerpt :
Differences between control and field-collected sediments in chronic toxicity data were evaluated using one-way ANOVA followed by the Dunnett post hoc test (α=0.05). In order to minimize ambiguities in interpreting the spatial distribution of contaminants, grain size bias was removed by normalizing metal concentrations to Al (Piper, 1973). Prior to the normalization of metal concentrations to Al, multivariate analyses were performed to investigate the relationship between environmental variables, toxicity and benthic community using the BIOENV procedure (Clarke and Ainsworth, 1993) based on a Spearman rank correlations between Bray–Curtis similarity matrix and environmental data.
In order to evaluate if sediment metal contamination is responsible for benthic degradation and identify possible reference sites in Todos os Santos Bay (TSB), comparisons between a highly impacted (Subaé) and less impacted (Jaguaripe) estuarine systems were made based on (i) field assessment of macrobenthic assemblage, (ii) sediment metal concentrations and (iii) chronic toxicity test with the tropical copepod Nitokra sp. Data were integrated by multivariate analysis (BIOENV and PCA) and the ratio-to-mean (RTMe) approach. Estuaries were divided into four different salinity zones to avoid misclassification of benthic conditions. Salinity was the main variable correlated to the benthic distribution in both estuaries, indicating that categories based on salinity features seem to be suitable in TSB. Correspondence among lines of evidence differed in low and high metal contaminated systems. Chronic toxicity was found along both the entire systems, being considerably higher in Jaguaripe. However, there was no clear evidence of metal contamination and benthic alteration in most stations of Jaguaripe. Although the concentrations of Sr and Cu were correlated to the benthic assemblage in Jaguaripe, it is unlikely that toxicity has been caused by these elements. The benthic assemblage distribution of Jaguaripe seems to be rather related to natural stressful conditions of transitional waters. Even though the Jaguaripe estuary might not be pristine, it can be used as a reference estuary for benthic assessment in TSB. Regarding the Subaé estuary, toxicity and Zn were also correlated to the benthic assemblage and most stations showed signs of benthic alteration and metal contamination. All lines of evidence were in agreement providing evidences that metal contamination might be responsible for benthic degradation in Subaé.
The Woxi W-Sb-Au deposit in Hunan, South China: An example of Late Proterozoic sedimentary exhalative (SEDEX) mineralization
2012, Journal of Asian Earth Sciences
Citation Excerpt :
Banded quartz–scheelite–stibnite ores and individual quartz bands from the ore are distinctly enriched in W, Au, As and Sb, but depleted in most of the other trace elements, especially those that are mostly of terrigenous origin, e.g. Hf, Sc, Th, Ta, Y, Zr, Nb and the REEs (Table 1, Fig. 12). This is consistent with many ancient polymetallic sulfide deposits (e.g., Lottermoser, 1991; Xue et al., 1995; Liu et al., 1996; Han and Sun, 1999; Qi, 2002) and modern hydrothermal metalliferous sediments formed on the sea-floor (e.g., Bostrom and Peterson, 1966; Piper, 1973; Piper and Graef, 1974; Rona, 1984; Marchig et al., 1982, 1986; Bischoff et al., 1983; Alt, 1988). The high concentrations of W, Au, As and Sb are commonly interpreted to be of hydrothermal origin, whereas the low contents of the other trace elements are attributed to rapid accumulation rates and rapid burial of hydrothermal precipitates in the sediment pile (Lottermoser, 1991).
The Woxi W–Sb–Au deposit in Hunan, South China is hosted by Proterozoic metasedimentary rocks, a turbiditic sequence of graywacke, siltstone, sandy slate and slate. The deposit has two principal styles of mineralization: stratiform and stockwork. The stratiform ores, which account for about 75% of the total proven ore reserves, are composed predominantly of interbedded, massive to laminated Au-bearing quartz, stibnite, scheelite, pyrite, and silty clays. Fine layering, at the macro- to microscale, is the most striking feature of the ores, with individual mm- to cm-scale bands traceable over distances of several meters to a few hundred meters along strike. Structures indicative of soft-sediment deformation due to slumping and synsedimentary sliding are commonly observed in the banded ores and the barren quartz–carbonate beds in the adjacent host rocks. The stockwork mineralization accounts for about 25% of the total ore reserves and is restricted to a 3–10 m-thick zone immediately beneath the stratiform ores. It is characterized by numerous quartz + pyrite ± scheelite stringer veins that are either subparallel or near perpendicular to the overlying stratiform ore layers. Alteration at Woxi occurs as semiconformable, tabular blankets asymmetrically enveloping the orebodies along their entire length, and, is dominated by a quartz + sericite + chlorite ± carbonate assemblage. The footwall alteration is generally more intense and somewhat thicker than the hanging-wall alteration. Geochemical data show that, with distance above and below the mineralized horizons, contents of W, Au, As, and Sb systematically decrease, whereas concentrations of other trace elements such as Hf, Sc, Th, Ta, Y, Zr, Nb and REEs gradually increase. This may reflect a decreasing hydrothermal input in the sediments and an increasing dominance of detrital and seawater-derived components. The chondrite-normalized REE patterns of both bulk ores and individual minerals are comparable to those of many SEDEX-type deposits and associated exhalites, implying similar mineralizing fluids for these deposits. Sulfides from the ore have negative and variable δ³⁴S values (from −12.3‰ to −1.2‰), suggesting a dominant sulfur contribution of bacterial sulfate reduction. A syngenetic (SEDEX) model is thus proposed for the formation of the Woxi deposit. Convective seawater circulated through the sediment pile and episodically vented metalliferous hydrothermal fluids onto the sea floor. Each exhalative episode was preceded by a period dominated by chemical and turbiditic sedimentation (footwall alteration blanket), followed by a peak release of hot metalliferous brines (stratiform ores and associated stringers), and terminated by a waning influx of hydrothermal fluids accompanying burial by later turbidites (hanging-wall alteration blanket).
Chapter Fourteen Elemental Proxies for Palaeoclimatic and Palaeoceanographic Variability in Marine Sediments: Interpretation and Application
2007, Developments in Marine Geology
Citation Excerpt :
The degree of major element enrichment in ridge crest sediments can be seen in the exceptionally high Fe/Al, Mn/Al and Si/Al ratios in a transect across the East Pacific Rise (Figure 6). Similar relative enrichments of other metals and metalloids, including As, B, Cd, Cu, Ni, Pb, Tl and Zn, are found on other EPR transects (Piper, 1973). The enriched metals accumulate at significantly higher rates compared with hydrogenous sedimentation in the central ocean basins (Bender et al., 1971; Dymond & Veeh, 1975).
This chapter discusses the elemental proxies for palaeoclimatic and palaeoceanographic variability in marine sediments. Physical and biological processes during deposition coupled with post-depositional chemical reactions yield a complex component mixture that can provide significant palaeoceanographic and palaeoclimatic information to complement and strengthen interpretations derived from the study of microfossils and the isotopic compositions of sedimentary components. The chapter reviews the application of sedimentary geochemistry to the reconstruction of climatic and oceanographic changes over the Cenozoic, with emphasis on the Late Pleistocene. Records from both pelagic regimes and ocean margin provinces are used to show how information on both ocean conditions and terrestrial climates can be assembled from the major, minor and trace element composition of sea-floor deposits. The chapter provides background sedimentary information, and describes some common data manipulation techniques that are used to construct and study palaeoclimatic and palaeoceanographic records in marine sediments.
Manganese deposits in the global lithogenetic system: Quantitative approach
1992, Ore Geology Reviews
A computerized data base, including 330 localities and believed to represent at least 95% of the presently recorded spot accumulations of ore-grade Mn on land, is the basis for a quantitative analysis of terrestrial Mn resources. This file is reprinted in full (Appendix).
The present subaerially exposed global ore Mn resources are calculated as 17.9 × 10⁹ t Mn¹. In this figure are included the actually mineable straight Mn deposits (8.7 × 10⁹ t Mn); potentially mineable land-based Mn accumulations (9.2 × 10⁹ t Mn), and actual or potential Mn that could be extracted as a byproduct of mining other metals (0.6 × 10⁹ t Mn). This distribution is strongly influenced by giant accumulations, where the single, exceptional Kalahari Mn field contains over 50% of the presently economic Mn ore reserves, or 23.42% of the global land Mn resources.
A set of attributes has been selected to treat the global ore Mn population in terms of genesis, geotectonic and environmental setting, and lithologic associations. In terms of genesis, precipitation from aqueous solutions was responsible for at least 99% of the contemporaneous, and probably also the past Mn accumulations now exposed on land. Weathering of Mn orebodies has left its mark on 93% of the Mn localities, and 24% are now represented entirely by supergene assemblages. Less than 0.01% of the ore Mn resources, however, are formed by weathering-related accumulation over silicate rocks (ultramafics).
In terms of geotectonic environments, the bulk of the land-based Mn deposits (97%) formed in intraplate and stable continental margin settings; 3.1% formed along Pacific-type and rift-type continental margins; and only 0.00045% of the deposits formed in an oceanic setting. This is in contrast with the outstanding Mn-accumulating capacity of the present ocean and is a consequence of the low preservation potential of the oceanic domain.
In terms of lithologic associations, 96% of the Mn in land-based deposits is present in marine-sedimentary associations (70% of Mn is in banded iron formations, 14.4% is in detrital and 11.1% is in carbonate-dominated associations). Chert and jasper, limestone, sandstone, shale, and banded iron formation are statistically the most common immediate hosts to Mn ores with recorded hosting frequencies of 79, 50, 45, 37 and 35, respectively.
In terms of geological history, the lower Proterozoic accounts for 58.9% of the prreserved ore Mn on land, followed by Oligocene (17.2%), Jurassic (6.2%) and middle Proterozoic (4.5%). In terms of the intensity of Mn accumulation per one million years of geological time, Oligocene (110 × 10⁶ t Mn/ma) is two orders of magnitude greater than the nearest time periods: Jurassic (8.9 × 10⁶ t Mn/ma) and lower Proterozoic (6.5 × 10⁶ t Mn/ma).
The historical distribution pattern of the land-based Mn deposits seems to indicate that accumulation of the bulk of the present ore-grade Mn is the result of repeated recycling with a land → ocean trend, abruptly initiated at the time of early cratonization (about 2.5 Ga). This has been supplemented by a substantially less significant, but remarkably steady reverse trend of addition of juvenile Mn released from the mantle into the crust. Mafics and particularly basalts are the most important intermediaries in the cumulative secular increase of liberated and accumulated Mn in the crust. Direct to indirect, proven to hypothetical spatial coincidence of “basalts” and Mn ores can be demonstrated on at least 169 localities out of 330 (= 51%) evaluated.

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Origin of metalliferous sediments from the East Pacific Rise

Abstract

Mar. Geol.

Geochim. Cosmochim. Acta

Nature

Mar. Geol.

Earth Planet. Sci. Letters

Geol. Soc. Am. Abstr.

J. Geophys. Res.

Geochim. Cosmochim. Acta

Doklady Akad. Nauk SSSR

Geochemistry of three cores from the East Pacific Rise

Earth Planet. Sci. Letters

On the thermal balance of mid-ocean ridges

Geophys. J. Roy. Astron. Soc.

The oxygen isotope geochemistry of submarine greenstones

Trans. Am. Geophys. Un.

Aluminum-poor ferromanganoan sediments on active ocean ridges

J. Geophys. Res.

Instrumental activation analysis of standard rocks with high-resolution γ-ray detectors

Geochim. Cosmochim. Acta

The diatomaceous sediments of the Gulf of California