Investigation of magnesium isotope fractionation during basalt differentiation: Implications for a chondritic composition of the terrestrial mantle

Teng, Fang‐Zhen; Wadhwa, M.; Helz, Rosalind Tuthill

doi:10.1016/j.epsl.2007.06.004

Cited by 332 publications

(341 citation statements)

References 29 publications

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“…is isotopically heavy appears to contradict the occurrence of isotopically light Mg in most Earth surface fluids; the δ 26/24 Mg composition of bulk silicate Earth is -0.23 ‰, whereas the average continental runoff is -1.09 ‰ and that of modern seawater is -0.82 ‰ (Teng et al, 2007;Bourdon et al, 2010;Young and Galy, 2004;Tipper et al, 2006;Ling et al, 2011). We note that the 0.25 ‰ fractionation observed in this experiment is small relative to the ~1.2 ‰ range observed in global rivers (e.g.…”

Section: Implications For Surface Water Mg Isotope Compositionsmentioning

confidence: 97%

The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at Earth surface conditions

Oelkers

Benning

Lutz

et al. 2015

Geochimica et Cosmochimica Acta

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Section: Implications For Surface Water Mg Isotope Compositionsmentioning

confidence: 97%

The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at Earth surface conditions

Oelkers

Benning

Lutz

et al. 2015

Geochimica et Cosmochimica Acta

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“…Despite this, and in contrast to many stable isotope systems that show little resolvable isotope fractionation as a result of high-temperature igneous processes, i.e. Mg (Teng et al, 2007) or Li (Tomascak et al, 1999), there appears to be resolvable, equilibrium-controlled Si isotope fractionation during magmatic differentiation, whereby an increase in SiO 2 content is accompanied by a concentration of the heavier Si isotopes (Fig 1; Savage et al, 2011). The magnitude of fractionation between the basaltic and rhyolitic end-members is D 30 Si $0.20&.…”

Section: Introductionmentioning

confidence: 94%

The silicon isotope composition of granites

Savage

Georg

Williams

et al. 2012

Geochimica et Cosmochimica Acta

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Because weathering results in preferential incorporation of the lighter Si isotopes into clay minerals, the Si in magmas derived from (meta)sedimentary lithologies enriched in such phases should also be isotopically light, relative to melts derived from igneous sources. With the advent of new high precision techniques it should therefore be possible to resolve such differences. Hence, Si isotopes have to potential to distinguish between, and characterise, different magmatic source regions.To explore this, here we report the Si isotopic compositions of a suite of Phanerozoic I-, S-and A-type granites and mineral separates, as well as samples of associated country rock. The whole-rock data fall between δ30Si = −0.40 and −0.11 ± 0.04‰ (95% s.e.). This range is more limited than that defined by previous low precision measurements of granites, but is significantly broader than that displayed by more recent, high precision, measurements of high-Si extrusive igneous rocks. As predicted, S-type granites are, on average, isotopically lighter than I-and A-type samples, and negative correlations with alumina saturation index (ASI) values and initial 87Sr/86Sr provide evidence that Si isotope variations in granites can be explained by variable incorporation of an enriched sedimentary component. However, the relatively small isotopic perturbations and apparent degree of overlap between granite affinities suggest that Si isotopes are not as sensitive to sedimentary input, relative to more established proxies such as, for example, O isotopes. The average Si isotope value of all granites analysed in this study is δ30Si = −0.23 ± 0.15‰ (2 s.d.), which is entirely consistent with a recently published estimate for the continental crust, based on an andesitic bulk composition and the well defined relationship between Si isotopes and magmatic fractionation. AbstractBecause weathering results in preferential incorporation of the lighter Si isotopes into clay minerals, the Si in magmas derived from (meta)sedimentary lithologies enriched in such phases should also be isotopically light, relative to melts derived from igneous sources. With the advent of new high precision techniques it should therefore be possible to resolve such differences. Hence, Si isotopes have to potential to distinguish between, and characterise, different magmatic source regions.To explore this, here we report the Si isotopic compositions of a suite of Phanerozoic I-, S-and A-type granites and mineral separates, as well as samples of associated country rock. The whole-rock data fall between d 30 Si = À0.40 and À0.11 ± 0.04& (95% s.e.). This range is more limited than that defined by previous low precision measurements of granites, but is significantly broader than that displayed by more recent, high precision, measurements of high-Si extrusive igneous rocks. As predicted, Stype granites are, on average, isotopically lighter than I-and A-type samples, and negative correlations with alumina saturation index (ASI) values and initial 87 Sr/ 86 Sr provide e...

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“…Magnesium isotopic analyses were carried out at the Isotope Laboratory of the University of Arkansas, Fayetteville. Chemical procedures and instrumental analyses followed those reported in previous studies (Teng et al 2007Yang et al 2009;Li et al 2010;Liu et al 2010b). All chemical procedures were performed in a class 10,000 clean laboratory, equipped with a class 100 laminar-flow exhaust hood ).…”

Section: Major and Trace Elements Zircon And U-pb Datingmentioning

confidence: 99%

Destruction of the North China Craton Induced by Ridge Subductions

Ling

Li²,

Ding

et al. 2013

The Journal of Geology

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A B S T R A C TThe destruction of the North China Craton (NCC) mainly occurred in the Cretaceous and has been attributed to a "top-down" rapid delamination, "bottom-up" long-term thermal/chemical erosions, or hydration by subductionreleased fluids. On the basis of the distribution of one Jurassic and two Early Cretaceous adakite belts and the drifting history of the paleo-Pacific Plate, we propose that three ridge subduction events dominated the large-scale decratonization in the NCC. Both physical erosion and magmatism induced by ridge subduction contributed to the destruction of the NCC; the last ridge subduction, at Ma, was the key driving force in the final destruction. We present 130 ‫ע‬ 5 mineralogical, geochemical, and isotopic data in support of the ridge subduction model: flat subduction of a spreading ridge resulted in stronger physical erosion on the thick lithosphere mantle of the NCC. Consequently, slab melting occurred during ridge subduction, forming adakites with mantle Mg isotope compositions, followed by A-type granites as a result of asthenosphere upwelling. Delaminated lower continental crust was also partially melted after reacting with hydrous magmas, as indicated by eclogite xenoliths, resulting in a zircon age spectrum similar to that of the NCC and some adakitic samples with chemical characteristics similar to those of the Dabie adakites. The final decratonization was triggered by the last ridge subduction, with both physical erosion (flat subduction) and thermal erosion (adakitic and A-type magmatisms). Given that ridge subduction has occurred throughout Earth's history, the associated decratonization processes are presumably a common phenomenon that modified the chemical compositions of the continental crust.

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Investigation of magnesium isotope fractionation during basalt differentiation: Implications for a chondritic composition of the terrestrial mantle

Cited by 332 publications

References 29 publications

The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at Earth surface conditions

The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at Earth surface conditions

The silicon isotope composition of granites

Destruction of the North China Craton Induced by Ridge Subductions

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