<i>The Planets: Their Origin and Development</i>

Urey, Harold C.; Korff, S. A.

doi:10.1063/1.3067687

Cited by 247 publications

(92 citation statements)

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“…Such a reaction scheme was originally proposed by Urey (1952Urey ( , 1956) to predict limits on atmospheric CO 2 levels over geological time. Finally, the carbonates recovered at DSDP Sites 417 and 896 were low-Mg (0-5 mol% MgC0 3 ), implying that they were formed from seawater solutions with lowered MglCa ratios (Alt and Honnorez, 1984;Teagle et aI., 1996); again, this is consistent with the chemistry of Baby Bare spring fluids, which had endmember Mg/Ca ratios of <0.02, compared to the seawater ratio of 5.1 (Table 1).…”

Section: Ridge-flank Seafloor Alterationmentioning

confidence: 99%

CO2-depleted fluids from mid-ocean ridge-flank hydrothermal springs

Sansone

Mottl

Olson

et al. 1998

Geochimica et Cosmochimica Acta

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Abstract-Hydrothermal spring fluids were collected from Baby Bare, a basement outcrop on the sedimentcovered eastern flank of the Juan de Fuca Ridge overlying 3.5 Ma-old crust. These waters are venting at 25°C but have cooled from 64°C within the upper 200-300 m of the upflow zone during their ascent. Unlike ridge-axis hydrothermal vent fluids previously sampled, the total CO 2 content of the endmember spring fluids (0.85 Mmol kg-I) is depleted with respect to bottom seawater. The very low alkalinities (0.43 rneq L-I) and high Ca 2 + concentrations (55 mmol kg-I) of endmember spring fluids suggest that the removal of C in the spring fluids is associated with carbonate precipitation in the igneous basement. Assuming that 8-20% of the total ridge-flank heat loss rate of 50 X 10 18 cal yr-I (6.6 TW) is removed by porewater advecting from the sediment at 2:25°C (an upper limit dictated by the global input rate of Mg+ 2 to the oceans; Mottl and Wheat, 1994), a maximum global carbon sink of 1.0-2.6 X lOll mol yr-I ( 1.2-3.1 Mton-C yr-I ) and a maximum global alkalinity sink of 140-340 X 10 9 eq yr-I are calculated for warm (2:25°C) ridge-flank hydrothermal circulation. This carbon flux is only 2-5% of current estimates of subaerial and submarine volcanic CO 2 emissions (-50 X 1011 mol yr-I ), indicating that hydrothermal alteration of oceanic crust on young mid-ocean ridge flanks at temperatures of a few tens of degrees Celsius is only a relatively minor sink for carbon on a global basis. It is still possible, however, that ridge-flank alteration at lower temperatures «25°C) is an important component of the global carbon budget.

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Section: Ridge-flank Seafloor Alterationmentioning

confidence: 99%

CO2-depleted fluids from mid-ocean ridge-flank hydrothermal springs

Sansone

Mottl

Olson

et al. 1998

Geochimica et Cosmochimica Acta

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“…Oxygendeficiency favoured the burial of huge amounts of organic matter in the sedimentary record as globally distributed marine black shales, which ultimately caused the drawdown of atmospheric CO 2 . However, enhanced silicate weathering is an additional mechanism for drawing down this greenhouse gas (Berner et al, 1983;Dessert et al, 2003;Raymo et al, 1988;Urey, 1952) and thereby helping to terminate the event.…”

Section: Introductionmentioning

confidence: 99%

Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)

Lechler

Strandmann

Jenkyns

et al. 2015

Earth and Planetary Science Letters

113

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An abrupt rise in temperature, forced by a massive input of CO 2 into the atmosphere, is commonly invoked as the main trigger for Oceanic Anoxic Events (OAEs). Global warming initiated a cascade of palaeoenvironmental perturbations starting with increased continental weathering and an accelerated hydrological cycle that delivered higher loads of nutrients to coastal areas, stimulating biological productivity.The end-result was widespread anoxia and deposition of black shales: the hallmarks of OAEs. In order to assess the role of weathering as both an OAE initiator and terminator (via CO 2 sequestration) during the Early Aptian OAE 1a (Selli Event, ~120 Ma) the isotopic ratio of lithium isotopes was analysed in three sections of shallowmarine carbonates from the Pacific and Tethyan realm and one basinal pelagic section from the Tethyan domain. Because the isotopic composition of lithium in seawater is largely controlled by continental silicate weathering and high-and lowtemperature alteration of basaltic material, a shift to lighter  7 Li values is expected to characterize OAEs. The studied sections illustrate this phenomenon:  7 Li values decrease to a minimum coincident with the negative carbon-isotope excursion that effectively records the onset of OAE 1a. A second negative  7 Li excursion occurs coeval with the minimum in strontium isotopes after the event. The striking similarity to the strontium-isotope record argues for a common driver. The formation and destruction (weathering) of an oceanic LIP could account for the parallel trend in both isotope systems. The double-spike in lithium isotopes is probably related to a change in weathering congruencies. Such a chemostratigraphy is consistent with the hypothesis that an increase in silicate weathering, in conjunction with organic-carbon burial, led to drawdown of atmospheric CO 2 during the early Aptian OAE 1a.

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“…On geological timescales, atmospheric carbon dioxide (CO 2 ) is largely controlled by the following generalized reaction [1][2][3]:…”

Section: Introductionmentioning

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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The Planets: Their Origin and Development

Cited by 247 publications

References 0 publications

CO2-depleted fluids from mid-ocean ridge-flank hydrothermal springs

CO2-depleted fluids from mid-ocean ridge-flank hydrothermal springs

Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)

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

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