Massive magnesium depletion and isotope fractionation in weathered basalts

Liu, Xiao Ming; Teng, Fang‐Zhen; Rudnick, Roberta L.; McDonough, William F.; Cummings, Michael L.

doi:10.1016/j.gca.2014.03.028

Cited by 124 publications

(116 citation statements)

References 57 publications

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“…4), but the general trend in  Huang et al, 2012;Liu et al, 2014;Teng et al, 2010;Tipper et al, 2010 (Wimpenny et al, 2014).…”

Section: Fractionating Geochemical Reactions Within the Regolithmentioning

confidence: 97%

“…6). These observations and the few studies other studies including pore water, bulk regolith and stream δ 26 Mg data in silicate catchments, indicate that the Mg isotope composition of pore water exported to the streams will evolve over kyr time scales, from the stage when rock has just been exposed to chemical weathering (Tipper et al, 2012), and fastreacting minerals are still available (Trostle et al, 2014;Dessert et al, 2015), to the extreme weathering stage where atmospheric inputs, changes in redox conditions within the regolith, and hydrological factors become comparatively more important (e.g., our B1S1 site; Dessert et al, 2015;Liu et al, 2014). We clearly need more studies to refine our interpretation, especially at intermediate weathering stages, but rough patterns can be already be noted in Figure 12.…”

Section: Implications For the Mg Isotope Exports From Tropical Catchmmentioning

confidence: 99%

“…Furthermore, Mg isotopes ( 24 Mg,25 Mg and 26 Mg) are fractionated by chemical weathering (e.g. Liu et al, 2014;Pogge von Strandmann et al, 2012;Teng et al, 2010) and by the uptake by vegetation (e.g. Black et al, 2008;Bolou-Bi et al, 2012;Bolou-Bi et al, 2010;Tipper et al, 2010;Tipper et al, 2012b), thus making it a promising tracer of both the geochemical and environments, leading water to flow laterally along high-permeability, near-surface flowpaths or via saturation-excess overland flow during intense rain events (Elsenbeer, 2001;Schellekens et al, 2004;Goller et al, 2005;Bonell, 2005;Kurtz et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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The influence of critical zone processes on the Mg isotope budget in a tropical, highly weathered andesitic catchment

Lara

Buss

Strandmann

et al. 2017

Geochimica et Cosmochimica Acta

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In order to assess the effects of critical zone processes on Mg concentrations and isotopic signatures of tropical streams, we studied a well constrained, highly weathered andesitic volcaniclastic catchment in the Luquillo Critical Zone Observatory, Puerto Rico. Our results indicate that dissolved Mg concentrations and isotope ratios in the regolith pore water are mainly controlled by rain input, with weathering inputs being more important at sites with thinner regolith (2.7 to 0.9 m deep) and at

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“…4), but the general trend in  Huang et al, 2012;Liu et al, 2014;Teng et al, 2010;Tipper et al, 2010 (Wimpenny et al, 2014).…”

Section: Fractionating Geochemical Reactions Within the Regolithmentioning

confidence: 97%

Section: Implications For the Mg Isotope Exports From Tropical Catchmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The influence of critical zone processes on the Mg isotope budget in a tropical, highly weathered andesitic catchment

Lara

Buss

Strandmann

et al. 2017

Geochimica et Cosmochimica Acta

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“…It is well known that the variation of Mg isotope compositions is limited during high-temperature geological processes (Teng et al 2007(Teng et al , 2010aHandler et al 2009;Yang et al 2009;Bourdon et al 2010;Dauphas et al 2010;Pogge von Strandmann et al 2011;Xiao et al 2013), but is quite large during low-temperature processes (Pogge von Strandmann et al 2008;Teng et al 2010b;Tipper et al 2010;Huang et al 2012;Liu et al 2014). Just like other fluid-mobile elements, Mg displays a highly variable and remarkably discrepant isotope composition in the upper continental crust (Shen et al 2009;Huang et al 2013) and the hydrosphere (Tipper et al 2006;Foster et al 2010;Ling et al 2011) when compared with the relatively homogeneous mantle (d 26 Mg = -0.25 ± 0.07‰, Teng et al 2010a).…”

mentioning

confidence: 99%

“…Just like other fluid-mobile elements, Mg displays a highly variable and remarkably discrepant isotope composition in the upper continental crust (Shen et al 2009;Huang et al 2013) and the hydrosphere (Tipper et al 2006;Foster et al 2010;Ling et al 2011) when compared with the relatively homogeneous mantle (d 26 Mg = -0.25 ± 0.07‰, Teng et al 2010a). The main processes responsible for such large isotopic variation are continental weathering and/or carbonate deposition that occurred among sedimentary systems/ upper continental crust and hydrosphere (Pogge von Strandmann et al 2008;Teng et al 2010b;Tipper et al 2010;Huang et al 2012;Liu et al 2014). During continental weathering, light Mg isotopes favor the hydrosphere to weathered residue, whereas during carbonate deposition, light Mg isotopes prefer carbonate minerals to the hydrosphere.…”

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confidence: 99%

The deep continental crust has a larger Mg isotopic variation than previously thought

Zhang

2016

American Mineralogist

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Magnesium isotope compositions of the bulk continental crust is a key to understand Mg isotope behaviors during crustal processes, and is the prerequisite to study mantle-crust material exchange/reaction by Mg isotopes. However, thus far, little is known about Mg isotopic compositions of the middle and lower continental crust. In the article by Yang et al. in this issue entitled "Magnesium isotopic composition of the deep continental crust," the authors present high-precision Mg isotopic analyses of highgrade metamorphic terrane samples and granulite xenoliths from China, which represent the middle and lower continental crust, respectively. Large Mg isotopic variation is observed in the deep continental crust, reflecting the combination of several processes, such as continental weathering, involvement of supracrustal materials, and fluid metasomatism. In addition, this article also provides an average Mg isotope composition of the bulk continental crust, which is crucial to future applications of Mg isotopes.

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Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

Liu

Wang

et al. 2017

JGR Solid Earth

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Tracing and identifying recycled carbonates is a key issue to reconstruct the deep carbon cycle. To better understand carbonate subduction and recycling beneath the southeastern Tibetan Plateau, high‐K cal‐alkaline volcanic rocks including trachy‐basalts and trachy‐andesites from Tengchong were studied using Mg and Ca isotopes. The low δ26Mg (−0.31 ± 0.03‰ to −0.38 ± 0.03‰) and δ44/40Ca (0.67 ± 0.07‰ to 0.80 ± 0.04‰) values of these volcanic rocks compared to those of the mantle (−0.25 ± 0.07‰ and 0.94 ± 0.05‰, respectively) indicate the incorporation of isotopically light materials into the mantle source, which may be carbonate‐bearing sediments with low δ26Mg and δ44/40Ca values. In addition, no correlations of δ26Mg and δ44/40Ca with either SiO2 contents or trace element abundance ratios (e.g., Sm/Yb and Ba/Y) were observed, suggesting that limited Mg and Ca isotopic fractionation occurred during cal‐alkaline magmatic differentiation. A binary mixing model using Mg–Ca isotopes shows that 5–8% carbonates dominated primarily by dolostone were recycled back into the mantle. Since Tengchong volcanism is still active and probably related to ongoing plate tectonic movement, we propose that the recycled carbonates are derived from oceanic crust related to the ongoing subduction of the Indian plate.

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Massive magnesium depletion and isotope fractionation in weathered basalts

Cited by 124 publications

References 57 publications

The influence of critical zone processes on the Mg isotope budget in a tropical, highly weathered andesitic catchment

The influence of critical zone processes on the Mg isotope budget in a tropical, highly weathered andesitic catchment

The deep continental crust has a larger Mg isotopic variation than previously thought

Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

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