Causes and implications of the middle rare earth element depletion in the eolian component of North Pacific sediment

Weber, Egon T.; Owen, Robert M.; Dickens, Gerald R.; Rea, David K.

doi:10.1016/s0016-7037(98)00102-1

Cited by 39 publications

(26 citation statements)

References 32 publications

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“…KNOT. Previous studies mentioned that the supply of loess particles to the interior of the western North Pacific was controlled by the atmospheric input (e.g., Nakai et al, 1993;Rea, 1994;Weber et al, 1998). However, the vertical increment of corrected loess fluxes (Fig.…”

Section: Transport Processes Of Aluminosilicates In the Western Northmentioning

confidence: 94%

“…Weber et al (1996) proposed two terrigenous materials as the provenance of North Pacific sediments, fine (<4.2 mm) Asian loess (AL) and average of basalts in the Kurile-Kamchatka Islands. Because this estimation assumes that a small part of loess undergoes dissolution in the surface water (Nakai et al, 1993;Jones et al, 1994;Asahara et al, 1995;Weber et al, 1998) and that the elemental abundance of loess changes with the grain-size Weber et al, 1996), Chinese loess (n : Gao et al, 1998;Taylor and McLennan, 1985;Shaw et al, 1986;Wedepohl, 1995), and averaged KK volcanic materials (j : Bailey, 1993) Bailey (1993) and Weber et al (1996)…”

Section: Temporal and Vertical Change Of Elemental Composition In Setmentioning

confidence: 99%

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La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

2004

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In order to understand the origins and transport processes of lithogenic aluminosilicate in the western North Pacific, time-series sediment traps were deployed at Stn. KNOT at 44∞N 155∞E (water depth: 5320 m). Annual mean content of aluminum (Al) which is a proxy of lithogenic material in settling particles was 0.38% at 1 km depth, 0.78% at 3 km depth and 1.14% at 5 km depth, respectively. Mass fluxes were corrected by 230 Th and 231 Pa activities in particles and seawater. Annual mean corrected Al fluxes at 1, 3 and 5 km depths were calculated to 0.45, 0.46 and 0.33 g/m 2 /year, respectively. Lanthanum/ytterbium (La/Yb) and thorium/scandium (Th/Sc) ratios were used as proxies for estimating the origin of lithogenic aluminosilicate in settling particles. Both La/Yb and Th/Sc ratios in settling particles increased with depth, and the seasonal variation was the smallest at 5 km depth. It was considered that variations of La/Yb and Th/Sc ratios in settling particles reflected the change of source material of lithogenic aluminosilicates. Origins of lithogenic materials in the settling particles were summarized using two end-members, loess from central Asian continent (AL) and basalts from the Kurile-Kamchatka Islands (KK). Contributions of end-members in settling particles were estimated from the La/Yb and Th/Sc ratios. The contribution of KK particles in lithogenic materials was calculated to be 84% at 1 km depth, and 61% at 3 and 5 km depths, respectively. Although the KK material was the dominant constituent of the terrigenous component in settling particles at Stn. KNOT, the KK flux decreased with depth. On the other hand, the AL flux increased with depth and the significant increase of the AL flux was presumably due to the lateral import of AL particles to the deep layer at Stn. KNOT. From these results we conclude that the distribution of lithogenic materials recorded in sediments in the western North Pacific are influenced by the northward transport of AL within the deep layer.

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Section: Transport Processes Of Aluminosilicates In the Western Northmentioning

confidence: 94%

Section: Temporal and Vertical Change Of Elemental Composition In Setmentioning

confidence: 99%

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

2004

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“…decompose, and secondary Fe-Mn oxides and hydroxides form, along with carbonate neoformation in the terrestrial dust deposits (e.g., loess, paleosols, and glacier cover). In the oceans, seawater partly dissolves unstable minerals from the deposited dust (Nakai et al, 1993;Weber et al, 1998), while other minerals (e.g., opal, silicate, etc.) are incorporated into the marine dust sediment.…”

Section: Methodsmentioning

confidence: 99%

Grain size effect on Sr and Nd isotopic compositions in eolian dust: Implications for tracing dust provenance and Nd model age

et al. 2009

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Strontium (Sr) and neodymium (Nd) isotopic compositions enable identification of dust sources and reconstruction of atmospheric dispersal pathways. The Sr and Nd isotopic compositions in eolian dust change systematically with grain size in ways not yet fully understood. This study demonstrates the grain size effect on the Sr and Nd isotopic compositions in loess and 2006 dust fall, based on analyses of seven separated grain size fractions. The analytical results indicate that Sr isotopic ratios strongly depend on the grain size fractions in samples from all types of eolian dust. In contrast, the Nd isotopic ratios exhibit little variation in loess, although they vary significantly with grain size in samples from a 2006 dust fall. Furthermore, Nd model ages tend to increase with increasing grain size in samples from all types of eolian dust. Comparatively, Sr isotopic compositions exhibit high sensitively to wind sorting, while Nd isotopic compositions show greater sensitively to dust origin. The principal cause for the different patterns of Sr and Nd isotopic composition variability with grain size appears related to the different geochemical behaviors between rubidium (Rb) and Sr, and the similar geochemical behaviors between samarium (Sm) and Nd. The Nd isotope data indicate that the various grain size fractions in loess have similar origins for each sample. In contrast, various provenance components may separate into different grain size fractions for the studied 2006 dust fall. The Sr and Nd isotope compositions further confirm that the 2006 dust fall and Pleistocene loess in Beijing have different sources. The loess deposits found in Beijing and those found on the Chinese Loess Plateau also derive from different sources. Variations between Sr and Nd isotopic compositions and Nd model ages with grain size need to be considered when directly comparing analyses of eolian dust of different grain size.

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“…This enrichment is seen as a hump in the shale-normalized ratios of REE toward the middle of the REE series (MREE, NdGd). Such MREE enrichment is typical of phosphates (Weber et al, 1998). The REE pattern in dissolved phase of river waters differ from those in the catchment rocks, a fractionation attributable to geochemical processes influencing their abundances during weathering and/or transport in the streams.…”

Section: Ree River Water Chemistrymentioning

confidence: 95%

Distribution of rare earth elements in the Yamuna and the Chambal rivers, India

Rengarajan

Sarin

2004

Geochem. J.

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We report here the first measurements of dissolved rare earth elements (REE) in the headwaters of the Yamuna river draining through the southern slopes of Himalaya. Due to intense weathering of the surface rocks of different lithologies and influence of tributaries, Yamuna river waters have variable dissolved REE contents (87 < ÂREE < 1374 ng L -1 , mean = 288.6 ng L -1 ) and exhibit negative Eu anomaly (0.49 < Eu/Eu* < 0.73, mean = 0.63). While most of the samples do not show discernable Ce anomalies; a negative Ce anomaly, however, found in a few of them, which can be explained by the colloidal pool preferentially enriched in Ce. A comparison among the river waters and bed sediments suggests that dissolved composition of REE is strongly fractionated and is enriched in MREE (Nd-Gd) with respect to sediments; presumably due to preferential dissolution of phosphate minerals such as apatite during weathering processes.Along with the Yamuna river, bed sediments from the Chambal river (a Peninsular river) have also been analyzed for REE composition. Bed sediments in the Yamuna and the Chambal river basins are characterized by ÂREE concentrations in the range of 78 to 291 mg g -1 (mean = 165 mg g -1 ) and 96 to 157 mg g -1 (mean = 134 mg g -1 ), respectively. A characteristic feature observed in the REE-normalized patterns of bed sediments is a strong HREE enrichment and a relatively positive Eu anomaly with respect to the granites in the Yamuna river catchment. In contrast, the bed sediment samples of the Chambal river show significant LREE enrichment and Eu enrichment with respect to the Deccan basalts in its catchment. The feldspars and their secondary products, which are enriched in Eu, might be the cause of the Eu anomaly. In river sediments of both these basins, the enrichment factors (EF), with respect to PAAS are £2 suggesting that REE composition is mainly derived from weathering processes. Keywords: dissolved rare earth element, MREE enrichment, Yamuna river, Chambal river, bed sediment individual cyclonic discharge events (Alexander et al., 2001) or anthropogenic inputs (Douglas et al., 2002) in controlling chemical variability and transport of major and trace elements. Likewise, studies on the dissolved load of the Ganga-Brahmaputra river system draining the

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Causes and implications of the middle rare earth element depletion in the eolian component of North Pacific sediment

Cited by 39 publications

References 32 publications

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

Grain size effect on Sr and Nd isotopic compositions in eolian dust: Implications for tracing dust provenance and Nd model age

Distribution of rare earth elements in the Yamuna and the Chambal rivers, India

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