Neodymium and strontium isotopic constraints on soil sources in Barbados, West Indies

doi:10.1016/S0016-7037(96)00252-9

Geochimica et Cosmochimica Acta

Volume 60, Issue 21, November 1996, Pages 4193-4206

https://doi.org/10.1016/S0016-7037(96)00252-9 Get rights and content

Abstract

Neodymium and strontium isotopic compositions and $Sm Nd$ ratios are used to constrain the sources of silicate-rich soils developed on uplifted Pleistocene coral-reef limestones on Barbados, West Indies. The geographic and geologic setting of Barbados facilitates the application of these tracers to the evaluation of the following soil sources: (1) Pleistocene reef limestone regolith, (2) Tertiary carbonate rocks, sandstones, and mudstones that are exposed in northeastern Barbados, (3) volcanic ash erupted from the Lesser Antilles arc, (4) Saharan dust transported by trade winds, and (5) fertilizer. The soils have ϵ_Nd values that range from −6.6 to −1.9, $^{87} Sr^{86} Sr$ values of 0.70890 to 0.71067, and $Sm Nd$ ratios of 0.223–0.260. The Pleistocene limestone component is the most significant source of Sr in the soils and a negligible source of Nd. Comparison of Sm and Nd concentrations and neodymium isotopic compositions of soil samples that are weathered to varying extents indicates that Sm and Nd are relatively unfractionated and retained in the soils during weathering. ϵ_Nd and $Sm Nd$ variations in the soils, therefore, primarily reflect the compositions and proportions of the silicate sources. Mass balance calculations based on Sm‐Nd systematics require that the silicate soil components contain between 30–85% volcanic ash, with the remaining silicate fraction comprised of old, continentally-derived sediment. In contrast to Sm and Nd, Sr is mobilized and removed from the soils during weathering. Strontium from volcanic and carbonate sources is preferentially removed relative to continental silicate sources. The strontium isotopic compositions of the soils, therefore, reflect the combined effects of the degree of weathering and the compositions and proportions of the soil sources. Mass balance calculations indicate that at least 35–60% of the initial Sr in the soils has been removed by weathering. These results illustrate (1) the utility of radiogenic isotopes in identifying and quantifying soil sources and weathering processes, (2) the compositional influence of numerous sources on soils, even those developed in a relatively isolated area such as Barbados, and (3) the domination of Barbados soil Sm‐Nd systematics by nonregolith eolian components.

References (67)

J.L. Banner et al.
Uranium-series evidence on diagenesis and hydrology in Pleistocene carbonates of Barbados, West Indies
Earth Planet. Sci. Lett.
(1991)
J.J. Braun et al.
Cerium anomalies in lateritic profiles
Geochim. Cosmochim. Acta
(1990)
G.H. Brimhall et al.
Constitutive mass balance relations between chemical composition, volume, density, porosity, and strain in metasomatic hydrochemical systems: Results on weathering and pedogenesis
Geochim. Cosmochim. Acta
(1987)
W. Chesworth et al.
The weathering of basalt and relative mobilities of the major elements at Belbex, France
Geochim. Cosmochim. Acta
(1981)
J.C. Faugeres et al.
Quaternary deposits on the South Barbados accretionary prism
Mar. Geol.
(1991)
R.A. Glaccum et al.
Saharan aerosols over the tropical North Atlantic-Mineralogy
Mar. Geol.
(1980)
L.P. Gromet et al.
The “North American shale composite”: Its compilation, major and trace element characteristics
Geochim. Cosmochim. Acta
(1984)
F.E. Grousset et al.
Neodymium isotopes as tracer in marine sediments and aerosols, North Atlantic
Earth Planet. Sci. Lett.
(1988)
F.E. Grousset et al.
Origins of peri-Saharan dust deposits traced by their Nd and Sr isotopic composition
Paleogeol. Paleoeclim. Paleoecol.
(1992)
J.S. Marsh
REE fractionation and Ce anomalies in weathered Karoo dolerite
Chem. Geol.
(1991)

D.K. McDaniel et al.

Resetting of neodymium isotopes and redistribution of REEs during sedimentary processes: The early Proterozoic Chelmsford Formation, Sudbury Basin, Ontario, Canada

Geochim. Cosmochim. Acta

(1994)

J.J. Middelburg et al.

Chemical processes affecting the mobility of major, minor, and trace elements during weathering of granitic rocks

Chem. Geol.

(1988)

D.R. Muhs et al.

Geochemical evidence of Saharan dust parent material for soils developed on Quaternary limestones of the Caribbean and western Atlantic islands

Quat. Geol.

(1990)

M. Ohr et al.

Mobility and fractionation of rare earth elements in argillaceous sediments: Implications for dating diagenesis and low-grade metamorphism

Geochim. Cosmochim. Acta

(1994)

J.J. Scholten et al.

Morphology, genesis and classification of three soils over limestone, Jamaica

Geoderma

(1986)

H.F. Shaw et al.

Sm‐Nd in marine carbonates and phosphates: Implications for Nd isotopes in seawater and crustal ages

Geochim. Cosmochim. Acta

(1985)

E. Sholkovitz et al.

The incorporation of rare earth elements in modern coral

Geochim. Cosmochim. Acta

(1995)

S.E. Topp et al.

Vertical distribution of trace elements in laterite soil (Suriname)

Chem. Geol.

(1984)

N. Ahmad et al.

Occurrence of aluminous laterite soils (bauxites) in the Bahamas and Cayman Islands

Econ. Geol.

(1969)

N. Ahmad et al.

Genesis, chemical properties and mineralogy of limestone-derived soils, Barbados, West Indies

Trop. Agric.

(1969)

J.F. Banfield et al.

Apatite replacement and rare earth mobilization, fractionation, and fixation during weathering

Clays Clay Mineral.

(1989)

J.L. Banner et al.

Rare earth element and Nd isotopic variations in regionally extensive dolomites of the Burlington-Keokuk Fm. (Miss.): Implications for carbonate diagenesis

J. Sediment. Petrol.

(1988)

J.L. Banner et al.

Tracing groundwater evolution in a limestone aquifer using Sr isotopes: Effects of multiple sources of dissolved ions and mineral-solution reactions

Geology

(1994)

J.L. Banner et al.

A high resolution temporal record of Holocene groundwater evolution: Tracing the links between climate and hydrology

Geology

(1996)

M.L. Bender et al.

Uranium-series dating of the Pleistocene reef tracts of Barbados, West Indies

Geol. Soc. Amer. Bull.

(1979)

P.W. Birkeland

Soils and Geomorphology

(1984)

P.E. Biscaye et al.

Rb‐Sr, $^{87} Sr^{86} Sr$ isotope system as an index of provenance of continental dusts in the open Atlantic Ocean

J. Res. Atmos.

(1974)

L.E. Borg et al.

Constraints on soil sources and weathering processes in the Pleistocene limestone aquifer of Barbados, West Indies from Nd and Sr isotopic analyses of soils and soil leachates

G.H. Brimhall

Metal enrichment in bauxites by deposition of chemically mature aeolian dust

Nature

(1988)

L.J. Chubb

Bauxite genesis in Jamaica

Econ. Geol.

(1963)

J.P. Davidson

Isotopic and trace element constraints on the petrogenesis of subduction-related lavas from Martinique, Lesser Antilles

J. Geophys. Res.

(1986)

J.S. Diller et al.

Volcanic dust and sand from St. Vincent caught at sea and on Barbados

Science

(1902)

J.R. Duddy

Redistribution and fractionation of rare earth and other elements in a weathering profile

Chem. Geol.

(1980)

Cited by (102)

Resetting of soil compositions by irrigation in urban watersheds: Evidence from Sr isotope variations in Austin, TX
2023, Science of the Total Environment
Human activities in urban areas disturb the natural landscape upon which they develop, disrupting pedogenic processes and ultimately limiting the ecosystem services urban soils provide. To better understand the impacts on and resiliency of soils in response to urban development, it is essential to understand the processes by which and degree to which soil physical and chemical properties are altered in urban systems. Here, we apply the source-tracing capabilities of Sr isotopes (⁸⁷Sr/⁸⁶Sr) to understand the impacts of urban processes on the composition of soils in eight watersheds in Austin, Texas. We evaluate natural and anthropogenic Sr sources in watersheds spanning a wide range of urbanization, comparing soils by variations in their natural (including mineralogy, thickness, soil type, and watershed) and anthropogenic (including irrigation, soil amendments, and fertilization) characteristics. A strong positive correlation between soil thickness and ⁸⁷Sr/⁸⁶Sr is observed among unirrigated soils (R² = 0.83). In contrast, this relationship is not observed among irrigated soils (R² = 0.004). 95 % of 42 irrigated soil samples have ⁸⁷Sr/⁸⁶Sr values approaching or within the range for municipal supply water. These results indicate soil interaction with municipal water through irrigation and/or water infrastructure leakage. Soils irrigated with municipal water have elevated ⁸⁷Sr/⁸⁶Sr values relative to unirrigated soils in seven of eight watersheds. We propose that original soil ⁸⁷Sr/⁸⁶Sr values are partially to completely reset by irrigation with municipal water via ion exchange processes. Our results demonstrate that in urban systems, Sr isotopes can serve as an environmental tracer to assess the overprint of urbanization on natural soil characteristics. In the Austin region, resetting of natural soil compositions via urban development is extensive, and the continued expansion of urban areas and irrigation systems may affect the ability of soils to retain nutrients, filter contaminants, and provide other ecosystem services that support environmental resilience.
Global spatio-temporal variations and metallogenic diversity of karst bauxites and their tectonic, paleogeographic and paleoclimatic relationship with the Tethyan realm evolution
2022, Earth-Science Reviews
Karst bauxites over the world have significant economic value and the geodynamic controls of their formation have attracted wide attention. These deposits are distributed over a vast region in the Tethyan realm, formed in diverse geological times and tectonic settings under a relatively monotonous warm and humid paleoclimate. This study reviews the spatio-temporal distribution of karst bauxites and their geodynamic and paleoclimatic settings based on paleogeographic reconstruction of the Tethyan realm. We show that karst bauxites were mainly formed in three orogenic domains: (1) the Ural-Central Asia belt, which formed at low paleolatitudes during the Cambrian through Devonian controlled by the Proto-Tethys and the Paleo-Asian Ocean, and later during Carboniferous and Cretaceous-Paleogene at mid-high paleolatitudes influenced by the heat transport from Paleo-Tethys and Neo-Tethys via seaways, (2) the Carboniferous to Permian Eastern Asia belt and westerly younger late Permian to Jurassic Turkey-Iran-Afghanistan-Pakistan belt formed in low paleolatitudes within the region of Paleo-Tethys, and (3) the Late Cretaceous-Paleogene Mediterranean belt and Neogene Caribbean belt controlled by the evolution of Neo-Tethys. The spatial shift of bauxitization with time was controlled by the paleogeographic evolution of Tethys and the resulting changes of oceanic current circulation and paleoclimate. We identify common scenarios of diverse metallogenic models in specific geodynamic phases through a combined analysis of chronological data on detrital zircons and local sedimentological sequences. In the continental extension phase, basement rocks were exposed to provide dominant materials for the formation of bauxite deposits on eroded carbonate platforms along continental margins. In the oceanic subduction phase, the arc volcanism provided abundant volcaniclastic materials, especially for the bauxite deposits on isolated carbonate platforms. In the arc accretion phase, weathered remnants were transported from complex nappes into intracontinental carbonate depressions. The karst bauxite deposits originally formed in a specific tectonic stage were superimposed by later tectonic reworking, and were metamorphosed, or exposed, disrupted, eroded, redeposited and altered during later continental collision stage, whereas incipient bauxite accumulation restarted during post-collisional extension phase. These processes occurring within the similar favorable paleoclimatic background define a unified metallogenic system concomitant with Wilson cycle that explains the spatio-temporal distribution of karst bauxites in the Tethyan realm.
Application of hydrochemical and multi-isotopic (87Sr/86Sr, δ13C-DIC, δ2H-H<inf>2</inf>O, δ18O-H<inf>2</inf>O) tools to determine contamination sources and processes in the Guadalhorce River Basin, southern Spain
2022, Science of the Total Environment
The integrated use of multi-isotopic (⁸⁷Sr/⁸⁶Sr, δ¹³C-DIC, δ²H-H₂O, δ¹⁸O-H₂O) and hydrochemical data was applied in the highly anthropized Guadalhorce river basin, southern Spain, to improve the knowledge about water contamination sources and processes and to achieve improved water resource management. The results obtained highlight the importance of the use of isotopes as tracers of pollutants. DIC, δ²H-H₂O, δ¹⁸O-H₂O and δ¹³C-DIC allowed differentiating two water recharge end members: direct rainwater, infiltrated into the upper and lower detritic aquifers of the sub-basins, and the Guadalhorce dam system, which act as a source in some groundwater and surface waters of the lower sub-basin. ⁸⁷Sr/⁸⁶Sr data supported the existing conclusions in relation to pollution sources in the study area. The Triassic basement (evaporites) of the carbonate and detritic aquifers of the basin generally controls the natural ⁸⁷Sr/⁸⁶Sr composition in waters of the upper sub-basin. Only one groundwater sample reflects the influence of a human organic source (sewage) in its composition. On the other hand, mixing of human inorganic (fertilizers and detergents) strontium sources is required to explain the ⁸⁷Sr/⁸⁶Sr contents of the lower sub-basin waters. Discriminating the use of domestic detergents as another anthropogenic source of strontium and sulphate in waters is a novel finding in this research. The conclusions reached can be extrapolated to other anthropized basins.
Fate and availability of dust-borne phosphorus in a sub-humid temperate forest
2022, Chemical Geology
Aeolian dust deposition is an important phosphorus (P) input to terrestrial ecosystems, but it lacks evidence of how dust inputs supply available P and affect P geochemistry and dynamics in soils of sub-humid ecosystems. We determined soil P speciation using P K-edge X-ray absorption near edge spectroscopy and P availability using modified Hedley sequential chemical extractions in a weakly acidic soil profile (2.5 m thick) in a sub-humid temperate forest ecosystem. The soil profile receives substantial dust inputs that account for 34.8% - 53.5% of the soil mass at depths based on a Sr isotope analysis. The acidic topsoils (5 < pH < 5.5) contain Ca-bound P (Ca-P) that accounts for 4%–18% of total soil P. Since Ca-P compounds are unstable and transform to other forms at pH < 5.5, continuous inputs of dust materials rich in Ca-P must occur to sustain the considerable Ca-P in the topsoils. Across all depths, soil Ca-P positively correlates with soil labile P_i (both resin and NaHCO₃ extracted) in proportion, suggesting that dissolution of dust-borne Ca-P compounds replenishes the labile P_i pool. On the other hand, weathering of the Fe-rich dusts leads to formation of abundant iron oxides that in turn favors formation of occluded P (44–85%) and Fe (and Al)-bound P (57–83%), which may fix released P from the dust-borne Ca-P dissolution and reduce soil P availability in a long term. Interestingly, the saprolite layer has an unexpectedly high weathering degree with nearly depleted Ca-P, likely caused by dust inputs that increase soil moisture and microbial activities and accordingly weathering. Our study identifies that continuous deposition and subsequent dissolution of dust-borne Ca-P compounds in acidic soils sustain soil P availability. The study also highlights that aeolian dust inputs affect soil P availability and dynamics in a sub-humid forest ecosystem not only by acting as a bioavailable P source but also altering soil chemistry and weathering.
Variations and significance of Mg/Sr and 87Sr/86Sr in a karst cave system in southwest China
2021, Journal of Hydrology
The geochemical compositions of cave drip water and speleothems such as Mg, Sr, Mg/Ca, Sr/Ca, and ⁸⁷Sr/⁸⁶Sr are considered to be responsive to changes in the local climate and hydrological conditions. Systematic monitoring was performed on the Mg and Sr contents, Mg/Sr ratio and ⁸⁷Sr/⁸⁶Sr of soil, soil water, cave drip water, and the active speleothems (AS) in Furong Cave in Chongqing, southwest China, during 2009–2018 (A.D). The results were interpreted in conjunction with the changes in the ⁸⁷Sr/⁸⁶Sr ratios to explore the main sources and controlling factors of Sr and other trace elements in drip water. (1) Due to the decrease in winter and spring rainfall, the residence time of water in the soil was prolonged, which resulted in increasing of Mg and Sr concentrations and ⁸⁷Sr/⁸⁶Sr ratios in soil water. It indicates that the trace element contents of soil water reflect seasonal changes of the rainfall. (2) The Mg and Sr contents were higher in drip water than in the soil water, as well as the ⁸⁷Sr/⁸⁶Sr ratios of the cave drip-water was closer to that of the bedrock, which indicated that the overlying bedrock was the main source of the trace elements in the drip water and the speleothems in Furong Cave. (3) Mg contents and Mg/Sr ratios in drip water and AS showed decreasing trend, which may be affected by the shorter water-rock contact time due to the increasing annual rainfall in the monitoring period. (4) The Sr contents in AS might be affected by the growth rate of AS because of the similar increasing trend. (5) The Mg and Sr contents and the Mg/Sr ratios of the drip water and AS did not exhibit seasonal variations due to the mixing of the fissure water and complex hydrology condition of the overlying bedrock, however, the geochemical indexes (Mg and Mg/Sr ratio) showed an opposite trend to the annual rainfall variation. In short, this study highlights the responses of the changes of Mg, Sr contents and Mg/Sr ratios of drip water and AS to the rainfall on the multi-year timescale, which contributes critical insights into the paleoclimate interpretation of proxies of speleothems in the cave with hundreds of meters’ thick bedrock.
The occurrence and distribution of strontium in U.S. groundwater
2021, Applied Geochemistry
Groundwater samples from 32 principal aquifers across the United States (U.S.) provide a broad spatial scope of the occurrence and distribution of strontium (Sr) and are used to assess environments and factors that influence Sr concentration. Strontium is a common trace element in soils, rocks, and water and is ubiquitous in groundwater with detectable concentrations in 99.8% of samples (n = 4,824; median = 225 μg/L). Concentrations in 2.3% of samples exceeded the 4,000 μg/L health-based screening level. The relative importance of controlling factors on Sr concentration are spatially variable and partly dependent on the type of groundwater well. Three case settings illustrate controls on Sr concentration. For drinking-water supply wells, most high concentrations (>4,000 μg/L) were measured in samples from carbonate aquifers that resulted from water-rock interaction with Sr-bearing rocks and minerals. High Sr concentrations from monitoring wells were more common in unconsolidated sand and gravel aquifers in arid or semi-arid setting where shallow groundwater is affected by irrigation and evaporative concentration of dissolved constituents in combination with lithologic or applied Sr sources. Upwelling saline groundwater is also a source of Sr in some locations. Total dissolved solids concentration is an indicator of high Sr in all settings. An estimated 2.2 million people in the conterminous U.S. are potentially supplied water from public-supply wells with high Sr concentration, ~86% of whom use carbonate aquifers (with more than half supplied by the Floridan aquifer system). An additional 120,000 people are potentially supplied high-Sr-concentration water from domestic wells, more than half of whom (~58%) are in Texas. This study markedly expands the coverage of previous surveys of Sr in groundwater and is of interest given potential adverse human-health effects related to elevated concentrations of Sr and consideration of Sr for drinking-water regulation. Case settings with elevated Sr described for U.S. groundwater are likely indicative of settings and processes affecting Sr concentration in groundwater globally.

View all citing articles on Scopus

^∗: Present address: SN4/NASA Johnson Space Center, Houston, TX 77058, USA.

View full text

Neodymium and strontium isotopic constraints on soil sources in Barbados, West Indies

Abstract

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Mar. Geol.

Mar. Geol.

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Paleogeol. Paleoeclim. Paleoecol.

Chem. Geol.

Geochim. Cosmochim. Acta

Chem. Geol.

Quat. Geol.

Geochim. Cosmochim. Acta

Geoderma

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Chem. Geol.

Occurrence of aluminous laterite soils (bauxites) in the Bahamas and Cayman Islands

Econ. Geol.

Genesis, chemical properties and mineralogy of limestone-derived soils, Barbados, West Indies

Trop. Agric.

Apatite replacement and rare earth mobilization, fractionation, and fixation during weathering

Clays Clay Mineral.

Rare earth element and Nd isotopic variations in regionally extensive dolomites of the Burlington-Keokuk Fm. (Miss.): Implications for carbonate diagenesis

J. Sediment. Petrol.

Tracing groundwater evolution in a limestone aquifer using Sr isotopes: Effects of multiple sources of dissolved ions and mineral-solution reactions

Geology

A high resolution temporal record of Holocene groundwater evolution: Tracing the links between climate and hydrology

Geology

Uranium-series dating of the Pleistocene reef tracts of Barbados, West Indies

Geol. Soc. Amer. Bull.

Soils and Geomorphology

Rb‐Sr, 87Sr86Sr isotope system as an index of provenance of continental dusts in the open Atlantic Ocean

J. Res. Atmos.

Constraints on soil sources and weathering processes in the Pleistocene limestone aquifer of Barbados, West Indies from Nd and Sr isotopic analyses of soils and soil leachates

Metal enrichment in bauxites by deposition of chemically mature aeolian dust

Nature

Bauxite genesis in Jamaica

Econ. Geol.

Isotopic and trace element constraints on the petrogenesis of subduction-related lavas from Martinique, Lesser Antilles

J. Geophys. Res.

Volcanic dust and sand from St. Vincent caught at sea and on Barbados

Science

Redistribution and fractionation of rare earth and other elements in a weathering profile

Chem. Geol.

Rb‐Sr, $^{87} Sr^{86} Sr$ isotope system as an index of provenance of continental dusts in the open Atlantic Ocean