scholarly journals Diamond ascent by rift-driven disruption of cratonic mantle keels

2021 ◽  
Author(s):  
Thomas Gernon ◽  
Stephen Jones ◽  
Sascha Brune ◽  
Thea Hincks ◽  
Anne Glerum ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Mantle Source ◽  
Small Volume ◽  
Dynamic Models ◽  
Return Flow ◽  
Asthenospheric Mantle ◽  
Earth’S Mantle ◽  
The Past ◽  
Convective Instabilities ◽  
Cratonic Mantle

Abstract Diamonds are erupted at Earth’s surface in volatile-rich magmas called kimberlites1,2,3. These enigmatic magmas, originating from depths exceeding 150 kilometres in Earth’s mantle1, occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity4. Whether their mobilization is driven by mantle plumes5 or mechanical weakening of cratonic lithosphere4,6 remains unclear. Here we show that most kimberlites spanning the past billion years erupted approximately 25 million years after the onset of continental fragmentation, suggesting an association with rifting processes. Our dynamic models show that physically steep lithosphere-asthenosphere boundaries formed during terminal rifting (necking) generate convective instabilities in the asthenosphere that slowly migrate many hundreds of kilometres inboard of the rift, causing destabilization of cratonic mantle keel tens of kilometres thick. Displaced lithosphere is replaced by hot, upwelling asthenosphere in the return flow, causing partial melting of carbonated mantle and variable assimilation of lithospheric material. The resulting small-volume kimberlite magmas ascend rapidly and adiabatically, exsolving amounts of carbon dioxide (CO2) that are consistent with independent constraints7. Our model reconciles diagnostic kimberlite features including association with cratons and geochemical characteristics that implicate a common asthenospheric mantle source contaminated by cratonic lithosphere8. Together, these results provide a quantitative and mechanistic link between kimberlite episodicity and supercontinent cycles via progressive disruption of cratonic keels.

A Comparison of Two Sub-structuring Techniques for Representing the Modal Properties of Tires

2001 ◽  
Vol 29 (1) ◽  
pp. 23-43 ◽  
Author(s):  
D. Tsihlas ◽  
T. Lacroix ◽  
B. Clayton
Keyword(s):  
Automobile Industry ◽  
Dynamic Models ◽  
Transfer Functions ◽  
Component Mode Synthesis ◽  
Numerical Techniques ◽  
The Past ◽  
Custom Made ◽  
Modal Behavior ◽  
Noise Vibration ◽  
Reduced Dynamic

Abstract Different numerical sub-structuring techniques for the representation of tire modal behavior have been developed in the past 20 years. By using these numerical techniques reduced dynamic models are obtained which can not only be used for internal studies but also be provided to the automobile industry and linked to reduced dynamic vehicle models in order to optimize the coupled vehicle-tire response for noise vibration and harshness purposes. Two techniques that have been developed in a custom-made finite element code are presented: 1) the component mode synthesis type models for which the wheel center interface is free and 2) the Craig and Bampton type models for which the wheel center interface is fixed. For both techniques the interface between the tire and the ground is fixed. The choice of fixed or free wheel center boundary condition is arbitrary. In this paper we will compare the formulation of these two numerical methods, and we will show the equivalency of both methods by showing the results obtained in terms of frequency and transfer functions. We will show that the two methods are equivalent in principle and the reduced dynamic models can be converted from one to the other. The advantages-disadvantages of each method will be discussed along with a comparison with experimentally obtained results.

Links between atmospheric carbon dioxide, the land carbon reservoir and climate over the past millennium

2015 ◽  
Vol 8 (5) ◽  
pp. 383-387 ◽  
Author(s):  
Thomas K. Bauska ◽  
Fortunat Joos ◽  
Alan C. Mix ◽  
Raphael Roth ◽  
Jinho Ahn ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
The Past ◽  
Carbon Reservoir ◽  
Atmospheric Carbon ◽  
Past Millennium

scholarly journals The thermal conductivity of some gases at 0° C

1934 ◽  
Vol 144 (853) ◽  
pp. 496-513 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Thermal Conductivity ◽  
Kinetic Theory ◽  
Molecular Changes ◽  
The Past ◽  
Comprehensive Account ◽  
The Absolute ◽  
Relative Measurements ◽  
Gas Conduction ◽  
Heat Transfers

During recent years an increased interest has been displayed in the phenomena of gas conduction, particularly in their application to the observation of molecular changes and chemical dissociations. While relative measurements usually suffice for these purpose, there have also been carefully planned researches on the absolute thermal conductivities of gases, the results of which are of value in the development of the kinetic theory. A comprehensive account of the methods which have been employed in the past for the measurement of the thermal conductivity of gases is given in a recent paper by Trautz and Zündel, who include also a table of the available data to 1931 for air, hydrogen, and carbon dioxide. The lack of agreement between the values obtained by different workers shown in this table can be explained by the smallness of the quantity measured, and by the difficulty of eliminating the heat transfers by convection and by radiation, one or both of which are always present.

scholarly journals Green Rust: The Simple Organizing ‘Seed’ of All Life?

Life ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 35 ◽  
Author(s):  
Michael Russell
Keyword(s):  
Carbon Dioxide ◽  
Hydrothermal Vents ◽  
Green Rust ◽  
Iron Sulfides ◽  
Banded Iron Formations ◽  
Variable Valence ◽  
Earth’S Mantle ◽  
Nickel Cobalt ◽  
Iron Formations ◽  
Emergence Of Life

Korenaga and coworkers presented evidence to suggest that the Earth’s mantle was dry and water filled the ocean to twice its present volume 4.3 billion years ago. Carbon dioxide was constantly exhaled during the mafic to ultramafic volcanic activity associated with magmatic plumes that produced the thick, dense, and relatively stable oceanic crust. In that setting, two distinct and major types of sub-marine hydrothermal vents were active: ~400 °C acidic springs, whose effluents bore vast quantities of iron into the ocean, and ~120 °C, highly alkaline, and reduced vents exhaling from the cooler, serpentinizing crust some distance from the heads of the plumes. When encountering the alkaline effluents, the iron from the plume head vents precipitated out, forming mounds likely surrounded by voluminous exhalative deposits similar to the banded iron formations known from the Archean. These mounds and the surrounding sediments, comprised micro or nano-crysts of the variable valence FeII/FeIII oxyhydroxide known as green rust. The precipitation of green rust, along with subsidiary iron sulfides and minor concentrations of nickel, cobalt, and molybdenum in the environment at the alkaline springs, may have established both the key bio-syntonic disequilibria and the means to properly make use of them—the elements needed to effect the essential inanimate-to-animate transitions that launched life. Specifically, in the submarine alkaline vent model for the emergence of life, it is first suggested that the redox-flexible green rust micro- and nano-crysts spontaneously precipitated to form barriers to the complete mixing of carbonic ocean and alkaline hydrothermal fluids. These barriers created and maintained steep ionic disequilibria. Second, the hydrous interlayers of green rust acted as engines that were powered by those ionic disequilibria and drove essential endergonic reactions. There, aided by sulfides and trace elements acting as catalytic promoters and electron transfer agents, nitrate could be reduced to ammonia and carbon dioxide to formate, while methane may have been oxidized to methyl and formyl groups. Acetate and higher carboxylic acids could then have been produced from these C1 molecules and aminated to amino acids, and thence oligomerized to offer peptide nests to phosphate and iron sulfides, and secreted to form primitive amyloid-bounded structures, leading conceivably to protocells.

scholarly journals Mantle Dynamics of the Central Atlantic Magmatic Province (CAMP): Constraints from Platinum Group, Gold and Lithophile Elements in Flood Basalts of Morocco

2019 ◽  
Vol 60 (8) ◽  
pp. 1621-1652 ◽  
Author(s):  
Christian Tegner ◽  
Sandra A T Michelis ◽  
Iain McDonald ◽  
Eric L Brown ◽  
Nasrrddine Youbi ◽  
...  
Keyword(s):  
Mantle Source ◽  
Gold Mineralization ◽  
Potential Temperature ◽  
Primitive Mantle ◽  
Mantle Melting ◽  
Flood Basalts ◽  
Asthenospheric Mantle ◽  
Central Atlantic Magmatic Province ◽  
Platinum Group ◽  
Central Atlantic

Abstract Mantle melting dynamics of the Central Atlantic Magmatic Province (CAMP) is constrained from new platinum group element (PGE), gold (Au), rare earth element (REE), and high field strength element (HFSE) data and geochemical modelling of flood basalts in Morocco. The PGE are enriched similarly to flood basalts of other large igneous provinces. The magmas did not experience sulphide saturation during fractionation and were therefore fertile. The CAMP is thus prospective for PGE and gold mineralization. The Pt/Pd ratio of the Moroccan lavas indicates that they originated by partial melting of the asthenospheric mantle, not the subcontinental lithospheric mantle. Mantle melting modelling of PGE, REE and HFSE suggests the following: (1) the mantle source for all the lavas was dominated by primitive mantle and invariably included a small proportion of recycled continental crust (<8%); (2) the mantle potential temperature was moderately elevated (c. 1430°C) relative to ambient mantle; (3) intra-lava unit compositional variations are probably a combined result of variable amounts of crust in the mantle source (heterogeneous source) and fractional crystallization; (4) mantle melting initially took place at depths between c. 110 and c. 55 km and became shallower with time (c. 110 to c. 32 km depth); (5) the melting region appears to have changed from triangular to columnar with time. These results are best explained by melting of asthenospheric mantle that was mixed with continental sediments during the assembly of Pangaea, then heated and further mixed by convection while insulated under the Pangaea supercontinent, and subsequently melted in multiple continental rift systems associated with the breakup of Pangaea. Most probably the CAMP volcanism was triggered by the arrival of a mantle plume, although plume material apparently was not contributing directly (chemically) to the magmas in Morocco, nor to many other areas of CAMP.

Contribution of a net transmembrane HCO3- flux to intracellular acid-base regulation

1977 ◽  
Vol 43 (6) ◽  
pp. 931-935 ◽  
Author(s):  
D. R. Strome ◽  
R. L. Clancy ◽  
N. C. Gonzalez
Keyword(s):  
Carbon Dioxide ◽  
Small Volume ◽  
Elevated Carbon Dioxide ◽  
Ringer Solution ◽  
Carbon Dioxide Tension ◽  
Acid Base ◽  
Initial Cell ◽  
Intracellular Acid

Experiments were performed to determine the relative effects of a net extracellular-to-intracellular HCO3- flux and of elevated carbon dioxide tension (PCO2) on cellular acid-base regulation. Isolated rabbit hearts were perfused by recirculating a small volume of Ringer solution in which the PCO2 and the HCO3- concentration could be independently altered. Net HCO3- flux was assessed by the disappearance of HCO3- from perfusate. Between 40 and 100 Torr PCO2, a HCO3- flux into the cell occurs only when perfusate HCO3- concentration is increased. Therefore, by selective manipulation of perfusate HCO3- and PCO2 it is possible to induce hypercapnia with or without an accompanying HCO3- flux. When perfusate HCO3- concentration was increased from 20 to 36 mM, cellular HCO3- concentration increased from 22.5 +/- 0.8 to 26.1 +/- 1.0 mM at 40 Torr PCO2 and from 27.8 +/- 0.7 to 34.1 +/- 1.4 mM at 98 Torr PCO2. These increases can be accounted for by the amount of HCO3- that disappeared from the perfusate. The results suggest that most of the initial cell CO2 buffering is provided by the net HCO3- flux in addition to the passive physicochemical buffering.

scholarly journals Catalytic Conversion of Carbon Dioxide through C-N Bond Formation

Molecules ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 182 ◽  
Author(s):  
Jing-Yuan Li ◽  
Qing-Wen Song ◽  
Kan Zhang ◽  
Ping Liu
Keyword(s):  
Carbon Dioxide ◽  
Catalytic Mechanism ◽  
Bond Formation ◽  
Catalytic Efficiency ◽  
Chemical Fixation ◽  
Catalytic Systems ◽  
Formation Reaction ◽  
Metal Free ◽  
The Past ◽  
Regulatory Strategies

From the viewpoint of green chemistry and sustainable development, it is of great significance to synthesize chemicals from CO2 as C1 source through C-N bond formation. During the past several decade years, many studies on C-N bond formation reaction were involved, and many efforts have been made on the theory. Nevertheless, several great challenges such as thermodynamic limitation, low catalytic efficiency and selectivity, and high pressure etc. are still suffered. Herein, recent advances are highlighted on the development of catalytic methods for chemical fixation of CO2 to various chemicals through C-N bond formation. Meanwhile, the catalytic systems (metal and metal-free catalysis), strategies and catalytic mechanism are summarized and discussed in detail. Besides, this review also covers some novel synthetic strategies to urethanes based on amines and CO2. Finally, the regulatory strategies on functionalization of CO2 for N-methylation/N-formylation of amines with phenylsilane and heterogeneous catalysis N-methylation of amines with CO2 and H2 are emphasized.

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