Geology topics

G. Price Russ

Publications and source records attributed to G. Price Russ.

4 recordsLinked to original sources

USGS1992

Interoceanic variation in the rare earth, major, and trace element depositional chemistry of chert: Perspectives gained from the DSDP and ODP record

Rare earth element (REE), major, and trace element abundances and relative fractionations in forty nodular cherts sampled by the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) indicate that the REE composition of chert records the interplay between terrigenous sources and scavenging from the local seawater. Major and (non-REE) trace element ratios indicate that the aluminosilicate fraction within the chert is similar to NASC (North American Shale Composite), with average Pacific chert including ~7% NASC-like particles, Indian chert ~ 11% NASC, Atlantic chert ~ 17% NASC, and southern high latitude (SHL) chert 53% NASC. Using La as a proxy for ∑REE, approximations of La ex (the amount of La in excess of that supplied by the detrital aluminosilicate fraction) indicate that Pacific chert contains the greatest La ex (85% of La total ) and SHL chert the least (38% of La total ). As shown by interelement associations, this La ex is most likely an adsorbed component onto aluminosilicate and phosphatic phases. Accordingly, chert from the large Pacific Ocean, where deposition occurs relatively removed from significant terrigenous input, records a depositional REE signal dominated by adsorption of dissolved REEs from seawater. Pacific chert CeCe * ⪡ 1 and La n Yb n ~ 0.8-1, resulting from adsorption of local Ce-depleted seawater and preferential adsorption of LREEs from seawater (e.g., La n Yb n ~ 0.4), which increases the La n Yb n ratio recorded in chert. Chert from the Atlantic basin, a moderately sized ocean basin lined by passive margins and with more terrigenous input than the Pacific, records a mix of adsorptive and terrigenous REE signals, with moderately negative Ce anomalies and La n Yb n "> La n Yb n ratios intermediate to those of the Pacific and those of terrigenous input. Chert from the SHL region is dominated by the large terrigenous input on the Antarctic passive margin, with inherited Ce Ce * ~1 "> CeCe * ~1 and inherited La n Yb n "> La n Yb n values of ~1.2–1.4. Ce Ce * "> ~1.2–1.4.CeCe * does not vary with age, either throughout the entire data base or within a particular basin. Overall, Ce Ce * "> CeCe * does not correlate with P 2 O 5 concentrations, even though phosphatic phases may be an important REE carrier. This and previous studies of the large-scale controlling parameters of sedimentary REEs across ocean basins collectively indicate that REE indices of depositional regime (e.g., Ce Ce * "> CeCe * , La n Yb n "> La n Yb n , La ex ) are reproducible in a variety of sediment and rock lithologies, ages, and ocean basins, and present a coherent tool for paleoceanographic and tectonic basin reconstructions.

Geochimica et Cosmochimica Acta↗

USGS1992

Rare earth, major, and trace element composition of Monterey and DSDP chert and associated host sediment: Assessing the influence of chemical fractionation during diagenesis

Chert and associated host sediments from Monterey Formation and Deep Sea Drilling Project (DSDP) sequences were analyzed in order to assess chemical behavior during diagenesis of biogenic sediments. The primary compositional contrast between chert and host sediment is a greater absolute SiO 2 concentration in chert, often with final SiO 2 ≥ 98 wt%. This contrast in SiO 2 (and Si Al "> SiAl ) potentially reflects precursor sediment heterogeneity, diagenetic chemical fractionation, or both. SiO 2 concentrations and Si Al "> SiAl ratios in chert are far greater than in modern siliceous oozes, however and often exceed values in acid-cleaned diatom tests. Compositional contrasts between chert and host sediment are also orders-of-magnitude greater than between multiple samples of the host sediment. Calculations based on the initial composition of adjacent host, observed porosity reductions from host to chert and a postulated influx of pure SiO 2 , construct a chert composition which is essentially identical to observed SiO 2 values in chert. Thus, precursor heterogeneity does not seem to be the dominant factor influencing the current chert composition for the key elements of interest. In order to assess the extent of chemical fractionation during diagenesis, we approximate the precursor composition by analyzing host sediments adjacent to the chert. The SiO 2 concentration contrast seems caused by biogenic SiO 2 dissolution and transport from the local adjacent host sediment and subsequent SiO 2 reprecipitation in the chert. Along with SiO 2 , other elements are often added (with respect to Al) to Monterey and DSDP chert during silicification, although absolute concentrations decrease. The two Monterey quartz chert nodules investigated, in contrast to the opal-CT and quartz chert lenses, formed primarily by extreme removal of carbonate and phosphate, thereby increasing relative SiO 2 concentrations. DSDP chert formed by both carbonate/phosphate dissolution and SiO 2 addition from the host. Manganese is fractionated during chert formation, resulting in MnO Al 2 O 3 "> MnOAl2O3 ratios that no longer record the depositional signal of the precursor sediment. REE data indicate only subtle diagenetic fractionation across the rare earth series. Ce Ce ∗ "> CeCe* values do not change significantly during diagenesis of either Monterey or DSDP chert. Eu Eu ∗ "> EuEu* decreases slightly during formation of DSDP chert. La n Yb n "> LanYbn is affected only minimally as well. During formation of one Monterey opal-CT chert lens, REE Al "> REEAl ratios show subtle distribution changes at Gd and to a lesser extent near Nd and Ho. REE compositional contrasts between diagenetic states of siliceous sediment and chert are of a vastly smaller scale than has been noted between different depositional environments of marine sediment, indicating that the paleoenvironmental REE signature is not obscured by diagenetic overprinting.

Geochimica et Cosmochimica Acta↗

USGS1992

Rare earth, major and trace element composition of Leg 127 sediments

The relative effects of paleoceanographic and paleogeographic variations, sediment lithology, and diagenetic processes on the final preserved chemistry of Japan Sea sediments are evaluated by investigating the rare earth element (REE), major element, and trace element concentrations in 59 squeeze-cake whole-round and 27 physical-property sample residues from Sites 794, 795, and 797, cored during ODP Leg 127. The most important variation in sedimentary chemical composition is the increase in SiO2 concentration through the Pliocene diatomaceous sequences, which dilutes most other major and trace element components by various degrees. This biogenic input is largest at Site 794 (Yamato Basin), moderately developed at Site 797 (Yamato Basin), and of only minor importance at Site 795 (Japan Basin), potentially reflecting basinal contrasts in productivity with the Yamato Basin recording greater biogenic input than the Japan Basin and with the easternmost sequence of Site 794 lying beneath the most productive waters. There are few systematic changes in solid-phase chemistry resulting from the opal-A/opal-CT or opal-CT/quartz silica phase transformations. Most major and trace element concentrations are controlled by the aluminosilicate fraction of the sediment, although the effects of diagenetic silica phases and manganese carbonates are of localized importance. REE total abundances (IREE) in the Japan Sea are strongly dependent upon the paleoceanographic position of a given site with respect to terrigenous and biogenic sources. REE concentrations at Site 794 overall correspond well to aluminosilicate chemical indices and are strongly diluted by SiO2 within the upper Miocene-Pliocene diatomaceous sequence. Eu/Eu* values at Site 794 reach a maximum through the diatomaceous interval as well, most likely suggesting an association of Eu/Eu* with the siliceous component, or reflecting slight incorporation of a detrital feldspar phase. XREE at Site 795 also is affiliated strongly with aluminosilicate phases and yet is diluted only slightly by siliceous input. At Site 797, ΣRE E is not as clearly associated with the aluminosilicate fraction, is correlated moderately to siliceous input, and may be sporadically influenced by detrital heavy minerals originating from the nearby rifted continental fragment composing the Yamato Rise. Ce/Ce* profiles at all three sites increase essentially monotonically with depth and record progressive diagenetic LREE fractionation. The observed Ce/Ce* increases are not responding to changes in the paleoceanographic oxygenation state of the overlying water, as there is no independent evidence to suggest the proper Oceanographic conditions. Ce/Ce* correlates slightly better with depth than with age at the two Yamato Basin sites. The downhole increase in Ce/Ce* at Sites 794 and 797 is a passive response to the diagenetic transfer of LREE (except Ce) from sediment to interstitial water. At Site 795, the overall lack of correlation between Ce/Ce* and La/Y^ suggests that other processes mask the diagenetic behavior of all LREEs. First-order calculations of the Ce budget in Japan Sea waters and sediment indicate that ~20% of the excess Ce adsorbed by settling particles is recycled within the water column and that an additional -38% is recycled at or near the seafloor. Thus, because the remaining excess Ce is only -10% of the total Ce, there is not a large source of Ce to the deeply buried sediment, further suggesting that the downhole increase in Ce/Ce* is a passive response to diagenetic behavior of the other LREEs. The REE chemistry of Japan Sea sediment therefore predicts successive downhole addition of LREEs to deeply buried interstitial waters.

Conference Paper↗

USGS1991

Rare earth elements in Japan Sea sediments and diagenetic behavior of Ce/Ce∗: results from ODP Leg 127

The relative effects of paleoceanographic and paleogeographic variations, sediment lithology, and diagenetic processes on the recorded rare earth element (REE) chemistry of Japan Sea sediments are evaluated by investigating REE total abundances and relative fractionations in 59 samples from Ocean Drilling Program Leg 127. REE total abundances (ΣREE) in the Japan Sea are strongly dependent upon the paleoceanographic position of a given site with respect to terrigenous and biogenic sources. REE concentrations at Site 794 (Yamato Basin) overall correspond well to aluminosilicate chemical indices and are strongly diluted by SiO 2 within the late Miocene-Pliocene diatomaceous sequence. Eu/Eu* values at Site 794 reach a maximum through the diatomaceous interval as well, most likely suggesting an association of Eu/Eu* with the siliceous component, or reflecting slight incorporation of a detrital feldspar phase. ΣREE at Site 795 (Japan Basin) also is affiliated strongly with aluminosilicate phases, yet is diluted only slightly by siliceous input. At Site 797 (Yamato Basin), REE is not as clearly associated with the aluminosilicate fraction, is correlated moderately to siliceous input, and may be sporadically influenced by detrital heavy minerals originating from the nearby rifted continental fragment composing the Yamato Rise. The biogenic influence is largest at Site 794, moderately developed at Site 797, and of only minor importance at Site 795, reflecting basinal contrasts in productivity such that the Yamato Basin records greater biogenic input than the Japan Basin, while the most productive waters overlie the easternmost sequence of Site 794. Ce/Ce* profiles at all three sites increase monotonically with depth, and record progressive diagenetic LREE fractionation. The observed Ce/Ce* record does not respond to changes in oxygenation state of the overlying water, and Ce/Ce* correlated slightly better with depth than with age. The downhole increase in Ce/Ce* at Site 794 and Site 797 is a passive response to diagenetic transfer of LREE (except Ce) from sediment to interstitial water. At Site 795, the overall lack of correlation between Ce/Ce* and L (l n /Yb n suggests that other processes are occurring which mask the diagenetic behavior of all LREEs. First-order calculations of the Ce budget in Japan Sea waters and sediment indicate that ~20% of the excess Ce adsorbed by settling particles is recycled within the water column, and that an additional ~38% is recycled at or near the seafloor (data from Masuzawa and Koyama, 1989). Thus, because the remaining excess Ce is only ~10% of the total Ce, there is not a large source of Ce to the deeply buried sediment, further suggesting that the downhole increase in Ce/Ce* is a passive response to diagenetic behavior of the other LREEs. The REE chemistry of Japan Sea sediment therefore predicts successive downhole addition of LREEs to deeply-buried interstitial waters.

Geochimica et Cosmochimica Acta↗