Evidence for stable Sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern Taiwan

Abstract Serpentine alteration is recognized as an important process for element cycling, however, related silicon fluxes are unknown. Pore fluids from serpentinite seamounts sampled in the Mariana forearc region during IODP Expedition 366 were investigated for their Si, B, and Sr isotope signatures (δ30Si, δ11B, and 87Sr/86Sr, respectively) to study serpentinization in the mantle wedge and shallow serpentine alteration to authigenic clays by seawater. While serpentinization in the mantle wedge caused no significant Si isotope fractionation, implying closed system conditions, serpentine alteration by seawater led to the formation of authigenic phyllosilicates, causing the highest natural fluid δ30Si values measured to date (up to +5.2 ± 0.2‰). Here we show that seafloor alteration of serpentinites is a source of Si to the ocean with extremely high fluid δ30Si values, which can explain anomalies in the marine Si budget like in the Cascadia Basin and which has to be considered in future investigations of the global marine Si cycle.

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Ca/Sr and Sr isotope systematics of a Himalayan glacial chronosequence: carbonate versus silicate weathering rates as a function of landscape surface age

Geochimica et Cosmochimica Acta ◽

10.1016/s0016-7037(01)00755-4 ◽

2002 ◽

Vol 66 (1) ◽

pp. 13-27 ◽

Cited By ~ 71

Author(s):

Andrew D Jacobson ◽

Joel D Blum ◽

C.Page Chamberlain ◽

Michael A Poage ◽

Valerie F Sloan

Keyword(s):

Silicate Weathering ◽

Sr Isotope ◽

Weathering Rates ◽

Isotope Systematics

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Sr isotope fractionation in a karst river: case study of Krka, Croatia

10.5194/egusphere-egu21-6059 ◽

2021 ◽

Author(s):

Sonja Lojen ◽

Qasim Jamil ◽

Tea Zuliani ◽

Leja Rovan ◽

Tjaša Kanduč ◽

...

Keyword(s):

Trace Element ◽

Isotope Fractionation ◽

Solid Phase ◽

Isotope Composition ◽

Karst Water ◽

Carbonate Precipitation ◽

Sr Isotopes ◽

Sr Isotope ◽

Element Partitioning ◽

Karst River

Precipitation of calcite from water fractionates strontium (Sr) isotopes because of preferential incorporation of light (86Sr) isotopes into the solid phase, making continental carbonates one of the most 88Sr depleted reservoirs. It was suggested that carbonate precipitation is the most likely process controlling &#948;88/86Sr composition of karst water. Therefore, the 88Sr enrichment of river water could be used for the estimation of Sr and carbonate precipitation at catchment scale.In the present study, we report on trace element partitioning and Sr isotope fractionation between tufa and water in the groundwater fed karst river Krka (Croatia). Water and tufa along with samples of bedrock and soil as the main contributors of dissolved and particulate Sr at seven main waterfalls and cascades along a 33 km section of the river were analysed for trace element and Sr isotope composition (&#948;88/86Sr).The highest &#948;88/86Sr values were measured in soils and in siliciclastic rocks, while in limestone, the &#948;88/86Sr values were similar to those of old tufa precipitated in the period between 96 and 141 ky BP. Recent tufa, however, was considerably depleted in 88Sr. The isotope fractionation between water and recent tufa varied a lot and was inversely correlated with Mg and Sr partitioning coefficients, while correlations with precipitation rates and temperature were rather weak. The &#948;88/86Sr of recent tufa was strongly correlated with the stable isotope composition of organic carbon, which indicates that apart from hydrochemical, hydraulic parameters and temperature, plants and microbial communities that knowingly stimulate the tufa formation also affect the isotope fractionation of Sr.

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Iron speciation and isotope fractionation during silicate weathering and soil formation in an alpine glacier forefield chronosequence

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2011.07.008 ◽

2011 ◽

Vol 75 (19) ◽

pp. 5559-5573 ◽

Cited By ~ 44

Author(s):

Mirjam Kiczka ◽

Jan G. Wiederhold ◽

Jakob Frommer ◽

Andreas Voegelin ◽

Stephan M. Kraemer ◽

...

Keyword(s):

Isotope Fractionation ◽

Soil Formation ◽

Silicate Weathering ◽

Iron Speciation ◽

Alpine Glacier ◽

Glacier Forefield

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Magnesium isotope fractionation between brucite [Mg(OH)2] and Mg aqueous species: Implications for silicate weathering and biogeochemical processes

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2014.03.022 ◽

2014 ◽

Vol 394 ◽

pp. 82-93 ◽

Cited By ~ 57

Author(s):

Weiqiang Li ◽

Brian L. Beard ◽

Chengxiang Li ◽

Clark M. Johnson

Keyword(s):

Isotope Fractionation ◽

Silicate Weathering ◽

Biogeochemical Processes ◽

Magnesium Isotope ◽

Aqueous Species

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Stable Ca and Sr isotopes support volcanically triggered biocalcification crisis during Oceanic Anoxic Event 1a

Geology ◽

10.1130/g47945.1 ◽

2020 ◽

Author(s):

Jiuyuan Wang ◽

Andrew D. Jacobson ◽

Bradley B. Sageman ◽

Matthew T. Hurtgen

Keyword(s):

Isotope Fractionation ◽

Variable Mass ◽

Large Igneous Province ◽

Emergent Properties ◽

Ionization Mass ◽

Sr Isotope ◽

Ocean Drilling Program ◽

Oceanic Anoxic Event ◽

Anoxic Event ◽

Mass Dependent Fractionation

Large igneous province (LIP) eruptions are hypothesized to trigger biocalcification crises. The Aptian nannoconid crisis, which correlates with emplacement of the Ontong Java Plateau and Oceanic Anoxic Event 1a (OAE 1a, ca. 120 Ma), represents one such example. The Ca isotope (δ44/40Ca) system offers potential to detect biocalcification fluctuations in the rock record because Ca isotope fractionation is sensitive to precipitation rate. However, other primary and secondary processes, such as input-output flux perturbations and early diagenesis, can produce similar signals. Here, we exploit emergent properties of the stable Sr isotope (δ88/86Sr) system to resolve the origin of δ44/40Ca variability during OAE 1a. This study reports high-precision thermal ionization mass spectrometry (TIMS) δ44/40Ca, δ88/86Sr, and 87Sr/86Sr records for Hole 866A of Ocean Drilling Program Leg 143 drilled in Resolution Guyot, mid-Pacific Ocean. The samples span ~27 m.y. from the Barremian (ca. 127 Ma) to the Albian (ca. 100 Ma). The δ44/40Ca and δ88/86Sr secular trends differ from the 87Sr/86Sr record but mimic each other. δ44/40Ca and [Sr], as well as δ44/40Ca and δ88/86Sr, strongly correlate and yield slopes predicted for kinetic control, which demonstrates that variable mass-dependent fractionation rather than end-member mixing dominated the isotopic relationship between carbonates and seawater. Positive δ44/40Ca and δ88/86Sr shifts that begin before OAE 1a and peak within the interval are consistent with reduced precipitation rates. All results combined point to a cascade of effects on rate-dependent Ca and Sr isotope fractionation, which derive from the dynamic interplay between LIP eruptions and biocalcification feedbacks.

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Controls on stable Sr-isotope fractionation in continental barite

Chemical Geology ◽

10.1016/j.chemgeo.2015.07.011 ◽

2015 ◽

Vol 411 ◽

pp. 215-227 ◽

Cited By ~ 11

Author(s):

Inoka H. Widanagamage ◽

Elizabeth M. Griffith ◽

David M. Singer ◽

Howie D. Scher ◽

Wayne P. Buckley ◽

...

Keyword(s):

Isotope Fractionation ◽

Sr Isotope

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Sr isotopic characteristics in two small watersheds draining typical silicate and carbonate rocks: implication for the studies on seawater Sr isotopic evolution

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-10-8031-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 8031-8069 ◽

Cited By ~ 3

Author(s):

W. H. Wu ◽

H. B. Zheng ◽

J. D. Yang

Keyword(s):

Carbonate Rocks ◽

Chemical Weathering ◽

Silicate Weathering ◽

86Sr Ratio ◽

Sr Isotope ◽

River Catchment ◽

Weathering Rates ◽

Isotopic Compositions ◽

Isotopic Evolution ◽

The Pearl River

Abstract. We systematically investigated Sr isotopic characteristics of small silicate watershed – the tributary Xishui River of the Yangtze River, and small carbonate watershed – the tributary Guijiang River of the Pearl River. The results show that the Xishui River has relatively high Sr concentrations (0.468–1.70 μmol L−1 in summer and 1.30–3.17 μmol L−1 in winter, respectively) and low 87Sr/86Sr ratios (0.708686–0.709148 in summer and 0.708515–0.709305 in winter), which is similar to the characteristics of carbonate weathering. The Guijiang River has low Sr concentrations (0.124–1.098 μmol L−1) and high 87Sr/86Sr ratios (0.710558–0.724605), being characterized by silicate weathering. In the Xishui River catchment, chemical weathering rates in summer are far higher than those in winter, indicating significant influence of climate regime. However, slight differences of 87Sr/86Sr ratios between summer and winter show that influence of climate on Sr isotope is uncertainty owing to very similar Sr isotope values in silicate and carbonate bedrocks. As 87Sr/86Sr ratios in the Xishui River are lower than those in seawater, they will decrease 87Sr/86Sr ratio of seawater after transported into oceans. Previous studies also showed that some basaltic watersheds with extremely high chemical weathering rates reduced the seawater Sr isotope ratios. In other words, river catchments with high silicate weathering rates do not certainly transport highly radiogenic Sr into oceans. Therefore, it may be questionable that using the variations of seawater 87Sr/86Sr ratio to indicate the continental silicate weathering intensity. In the Guijiang River catchment, 87Sr/86Sr ratios of carbonate rocks and other sources (rainwater, domestic and industrial waste water, and agricultural fertilizer) are lower than 0.71. In comparison, some non-carbonate components, such as, sand rocks, mud rocks, shales, have relatively high Sr isotopic compositions. Moreover, granites accounted for only 5% of the drainage area have extremely high 87Sr/86Sr ratios with an average of over 0.8. Therefore, a few silicate components contained in carbonate rocks obviously increases the Sr isotopic compositions of the river water, and results in a positive effect on the rise of 87Sr/86Sr ratio of seawater. Therefore, the relation between Sr isotope evolution of seawater and continental weathering rate is complex, 87Sr/86Sr ratios of underlying bedrock in catchment could be an important controlling factors.

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