Average Chemical Compositions of Some Igneous Rocks

Nockolds, S. R.

doi:10.1130/0016-7606(1954)65[1007:accosi]2.0.co;2

Cited by 737 publications

(336 citation statements)

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“…For basalt, we use 20 000 m 2 m 22 land, the scaling value derived by Navarre-Sitchler & Brantley [44] for comparing watershed-scale weathering rates to laboratory rates on basalt substrates. Our mineralogy is that of a normal tholeittic basalt [45] and includes the Ca-and Mg-bearing minerals labradorite, augite and orthopyroxene.…”

Section: Model Developmentmentioning

confidence: 99%

Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

Taylor

Banwart

Valdes

et al. 2012

Phil. Trans. R. Soc. B

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Global weathering of calcium and magnesium silicate rocks provides the long-term sink for atmospheric carbon dioxide (CO 2 ) on a timescale of millions of years by causing precipitation of calcium carbonates on the seafloor. Catchment-scale field studies consistently indicate that vegetation increases silicate rock weathering, but incorporating the effects of trees and fungal symbionts into geochemical carbon cycle models has relied upon simple empirical scaling functions. Here, we describe the development and application of a process-based approach to deriving quantitative estimates of weathering by plant roots, associated symbiotic mycorrhizal fungi and climate. Our approach accounts for the influence of terrestrial primary productivity via nutrient uptake on soil chemistry and mineral weathering, driven by simulations using a dynamic global vegetation model coupled to an ocean -atmosphere general circulation model of the Earth's climate. The strategy is successfully validated against observations of weathering in watersheds around the world, indicating that it may have some utility when extrapolated into the past. When applied to a suite of six global simulations from 215 to 50 Ma, we find significantly larger effects over the past 220 Myr relative to the present day. Vegetation and mycorrhizal fungi enhanced climate-driven weathering by a factor of up to 2. Overall, we demonstrate a more realistic process-based treatment of plant fungal -geosphere interactions at the global scale, which constitutes a first step towards developing 'next-generation' geochemical models.

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Section: Model Developmentmentioning

confidence: 99%

Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

Taylor

Banwart

Valdes

et al. 2012

Phil. Trans. R. Soc. B

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“…FeO* : tout le fer est considéré comme étant du Fe Sources des données de granitoïdes : , , Barbero and Villaseca (1992), Barker et al (1992), Chappell and White (1992), , Collins et al (1989), Crawford and Windley (1990), Crisci et al (1979), McKenzie and Clarke (1975), Neiva (1981), Nockolds (1954), Pankhurst et al (1992), Sawyer (1987). Sources des données des verres ejqjérimentaux à partir de pélite, greywacke et psammite (T<925°C): Gardien et al (1995), Grant (2004), Montel and Vielzeuf (1997), Patifio Douce and , Patino , Patino Douce and Johnston (1991), , Stevens et al (1997), Vielzeuf and Holloway (1988).…”

Section: Figure 12: Diagramme Sioi Vs Feo* + Mgounclassified

Origines des enrichissements en biotite dans les granites de type S :

Lavaure¹

2012

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RESUMEDe nombreux travaux expérimentaux ont été effectués, au cours des dernières décennies pour recréer des magmas anatectiques felsiques à partir de la fusion par déshydratation de différents types de roches tels que des métasédiments ou des roches ignées. Cependant, les granites naturels de type S sont beaucoup plus enrichis en fer et magnésium que tous les liquides felsiques qui ont pu être obtenus expérimentalement. De plus, des analyses de liquides felsiques en inclusion dans les minéraux métamorphiques ont montré les mêmes résultats que les travaux expérimentaux. Récemment, Pentrainement de phases péritectiques lors de l'extraction du liquide a été démontré comme étant l'un des processus responsables de ces enrichissements. Seulement, un certain nombre des granites de type S riches en fer et en magnésium ne contiennent pas de minéraux tels que le grenat ou la cordiérite mais seulement un fort enrichissement enbiotite.

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“…Ignimbrite, Kaingaroa (P11802) (Steiner, 1958, anal. 40 The Na 2 0, K 2 0, and NazO + KzO contents of the Taupo volcanics are contrasted with those of Crater Lake, Lassen Peak, and the average calc-alkali rock types of Nockolds (1954) in Fig. 2.…”

Section: Variation In Major Elementsmentioning

confidence: 99%

Trace elements, variation in alkalis, and the ratio Sr⁸⁷/Sr⁸⁶in selected rocks from the Taupo Volcanic Zone

Lewis

1968

New Zealand Journal of Geology and Geophysics

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The volcanic rocks of the Taupo Zone are mostly acid tuffs and flows, with less abundant andesites, minor dacites, and rare basalts. A preliminary examination has been made of distribution of Cr, V, Sr, Rb, Cs, Li, Ba, and Zr in selected rocks from the Taupo Zone. The data support the hypothesis that the Taupo Zone volcanics belong to a continuous chemical sequence, non-porphyritic aluminous basalt-andesite--dacite--calc-alkaline rhyolite, with accumulative olivine and pyroxene andesites. Low total alkalis, low Zr, high K/Rb ratios and high Ba contents distinguish the acid rocks of the Taupo Zone from those in other New Zealand Tertiary provinces. Low concentrations of K, Rb, Cs, and Zr, high K/Rb ratios and low Rb/Sr ratios, compared with values for the average continental crust and average granite, suggest a subsialic source for the Taupo volcanics. Sr"'/Sr 8• ratios of O· 7047 for basalt and o· 7066 for rhyolite, together with the overall chemistry, indicate that the acid rocks are not the fusion products of ancient sial or reworked material derived from this and suggest a common source for both the acid and basic rocks in the Taupo Zone.

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Average Chemical Compositions of Some Igneous Rocks

Cited by 737 publications

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Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

Origines des enrichissements en biotite dans les granites de type S :

Trace elements, variation in alkalis, and the ratio Sr⁸⁷/Sr⁸⁶in selected rocks from the Taupo Volcanic Zone

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Average Chemical Compositions of Some Igneous Rocks

Cited by 737 publications

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Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

Origines des enrichissements en biotite dans les granites de type S :

Trace elements, variation in alkalis, and the ratio Sr87/Sr86in selected rocks from the Taupo Volcanic Zone

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Trace elements, variation in alkalis, and the ratio Sr⁸⁷/Sr⁸⁶in selected rocks from the Taupo Volcanic Zone