Thermal constraints on the distribution of long-lived radioactive elements in the Earth

1979 ◽  
Vol 291 (1381) ◽  
pp. 269-275 ◽  
Keyword(s):  
Heat Generation ◽  
Heat Production ◽  
Upper Mantle ◽  
High Heat ◽  
Geochemical Data ◽  
Radioactive Elements ◽  
The Core ◽  
Thermal Constraints ◽  
The Earth ◽  
Qualitative Models

Geochemical data show that radioactive heat production in the crust plus upper mantle (which is defined seismically to terminate at a depth of 415 km) cannot account for the heat escaping from the Earth. Deeper sources must be invoked, and a number of qualitative models of the variation of radioactive heat generation with depth are suggested. Preferred models involve a narrow zone of high heat production about halfway between the crust and the core.

scholarly journals Exercise activates compensatory thermoregulatory reaction in rats: a modeling study

2015 ◽  
Vol 119 (12) ◽  
pp. 1400-1410 ◽  
Author(s):  
Yeonjoo Yoo ◽  
Michelle LaPradd ◽  
Hannah Kline ◽  
Maria V. Zaretskaia ◽  
Abolhassan Behrouzvaziri ◽  
...  
Keyword(s):  
Body Temperature ◽  
Heat Generation ◽  
Heat Production ◽  
Core Body Temperature ◽  
Heat Stroke ◽  
The Body ◽  
Model Parameters ◽  
The Core ◽  
Treadmill Speed ◽  
Core Body

The importance of exercise is increasingly emphasized for maintaining health. However, exercise itself can pose threats to health such as the development of exertional heat shock in warm environments. Therefore, it is important to understand how the thermoregulation system adjusts during exercise and how alterations of this can contribute to heat stroke. To explore this we measured the core body temperature of rats ( Tc) running for 15 min on a treadmill at various speeds in two ambient temperatures ( Ta = 25°C and 32°C). We assimilated the experimental data into a mathematical model that describes temperature changes in two compartments of the body, representing the muscles and the core. In our model the core body generates heat to maintain normal body temperature, and dissipates it into the environment. The muscles produce additional heat during exercise. According to the estimation of model parameters, at Ta = 25°C, the heat generation in the core was progressively reduced with the increase of the treadmill speed to compensate for a progressive increase in heat production by the muscles. This compensation was ineffective at Ta = 32°C, which resulted in an increased rate of heat accumulation with increasing speed, as opposed to the Ta = 25°C case. Interestingly, placing an animal on a treadmill increased heat production in the muscles even when the treadmill speed was zero. Quantitatively, this “ready-to-run” phenomenon accounted for over half of the heat generation in the muscles observed at maximal treadmill speed. We speculate that this anticipatory response utilizes stress-related circuitry.

A model for Archean tectonism. Part I. The thermal conditions

1979 ◽  
Vol 16 (10) ◽  
pp. 1942-1950 ◽  
Author(s):  
G. F. West ◽  
J.-C. Mareschal
Keyword(s):  
Heat Production ◽  
Upper Mantle ◽  
Temperature Jump ◽  
Thermal Conditions ◽  
Thermal Modelling ◽  
Superior Province ◽  
Clear Separation ◽  
One Dimensional ◽  
Tectonic Model ◽  
The Earth

The feasibility of a tectonic model that would explain some of the major features of the Archean Superior Province is examined. This model assumes that about 3.5 Ga (1 Ga = 109 years) ago, a thin granitoid crust covered most of the Earth and there was no clear separation into oceans and continents. Basalts would partially melt in the upper mantle and rise to the surface forming thick volcanic plateaus. After cooling, the dense volcanics (2.9 g/cm3) overlying the granitic crust (2.65 g/cm3) would sink if both materials' viscosity were reduced. A succession of cycles of volcanism and vertical tectonism may have lasted until the Kenoran orogeny. One-dimensional thermal modelling shows that under reasonable assumptions, the temperature jump which follows the deposition of a volcanic layer at −3.2 Ga is sufficient to reduce the viscosity by five orders of magnitude. This was no longer the case under post Kenoran conditions when radioactive heat production was lower, and deep erosion had reduced even further the amount of radioactivity in the crust.

scholarly journals U–Pb Geochronology of Hydrothermal Monazite from Uraniferous Greisen Veins Associated with the High Heat Production Mount Douglas Granite, New Brunswick, Canada

Geosciences ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 224 ◽  
Author(s):  
Nadia Mohammadi ◽  
Christopher R. M. McFarlane ◽  
David R. Lentz
Keyword(s):  
New Brunswick ◽  
Heat Production ◽  
Inductively Coupled Plasma ◽  
Radioactive Decay ◽  
High Heat ◽  
Ore Deposits ◽  
Geochemical Data ◽  
Scattered Electron ◽  
Radiogenic Heat ◽  
Radiogenic Heat Production

A combination of in situ laser ablation inductively coupled plasma–mass spectrometry (LA ICP–MS) analyses guided by Scanning Electron Microscope–Back-Scattered Electron imaging (SEM–BSE) was applied to hydrothermal monazite from greisen veins of the Late Devonian, highly evolved, uraniferous Mount Douglas Granite, New Brunswick, Canada. Understanding the uraniferous nature of the suite and characterizing the hydrothermal system that produced the associated mineralized greisen veins were the main goals of this study. The uraniferous nature of the Mount Douglas Granite is evident from previous airborne radiometric surveys, whole-rock geochemical data indicating high U and Th (2–22 ppm U; 19–71 ppm Th), the presence of monazite, zircon, xenotime, thorite, bastnaesite, and uraninite within the pluton and the associated hydrothermal greisen veins, as well as anomalous levels of U and Th in wolframite, hematite, and martite within greisen veins. New U–Pb geochronology of hydrothermal monazite coexisting with sulfide and oxide minerals yielded mineralization ages ranging from 344 to 368 Ma, with most of them (90%) younger than the crystallization age of the pluton (368 ± 3 Ma). The younger mineralization age indicates post-magmatic hydrothermal activities within the Mount Douglas system that was responsible for the mineralization. The production of uraniferous greisen veins by this process is probably associated with the High Heat Production (HHP) nature of this pluton, resulting from the radioactive decay of U, Th, and K. This heat prolongs post-crystallization hydrothermal fluid circulation and promotes the generation of hydrothermal ore deposits that are younger than the pluton. Assuming a density of 2.61 g/cm3, the average weighted mean radiogenic heat production of the Mount Douglas granites is 5.9 µW/m3 (14.1 HGU; Heat Generation Unit), in which it ranges from 2.2 µW/m3 in the least evolved unit, Dmd1, up to 10.1 µW/m3 in the most fractionated unit, Dmd3. They are all significantly higher than the average upper continental crust (1.65 µW/m3). The high radiogenic heat production of the Mount Douglas Granite, accompanied by a high estimated heat flow of 70 mW/m2, supports the assignment of the granite to a ‘hot crust’ (>7 HGU) HHP granite and highlights its potential for geothermal energy exploration.

5. Rocks in the deep

2016 ◽  
pp. 66-79
Author(s):  
Jan Zalasiewicz
Keyword(s):  
Magnetic Fields ◽  
Upper Mantle ◽  
Lower Crust ◽  
Seismic Waves ◽  
Direct Experience ◽  
Rock Fragments ◽  
The Core ◽  
The Earth ◽  
Deep Earth ◽  
Volcanic Processes

It is over 6,000 km to the centre of the Earth, but our direct experience of its rocks goes to little more than 3 km below the surface in the deepest mines on Earth. ‘Rocks in the deep’ shows that we can find out more by assessing rock fragments brought from deeper levels by tectonic or volcanic processes; by analysing patterns of change in the gravitational and magnetic fields; by detecting seismic waves that have travelled through the Earth; or by recreating conditions of the deep Earth in the laboratory. It describes what is known about the lower crust, the upper mantle, the deep mantle, and the core.

Universal dispersion tables

1969 ◽  
Vol 59 (4) ◽  
pp. 1667-1693
Author(s):  
Don L. Anderson ◽  
Robert L. Kovach
Keyword(s):  
Upper Mantle ◽  
Free Oscillation ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Average Density ◽  
Earth Model ◽  
The Core ◽  
The Earth ◽  
Small Change ◽  
Dominant Parameter

Abstract The effect of a small change in any parameter of a realistic Earth model on the periods of free oscillation is computed for both spheroidal and torsional modes. The normalized partial derivatives, or variational parameters, are given as a function of order number and depth in the Earth. For a given mode it can immediately be seen which parameters and which regions of the Earth are controlling the period of free oscillation. Except for oSo and its overtones the low-order free oscillations are relatively insensitive to properties of the core. The shear velocity of the mantle is the dominant parameter controlling the periods of free oscillation and density can be determined from free oscillation data only if the shear velocity is known very accurately. Once the velocity structure is well known free oscillation data can be used to modify the average density of the upper mantle. The mass and moment of inertia are then the main constraints on how the mass must be redistributed in the lower mantle and core.

Composition of Earth

2021 ◽  
Author(s):  
H. Palme
Keyword(s):  
Upper Mantle ◽  
Core Formation ◽  
Formation Model ◽  
Major Element Composition ◽  
The Core ◽  
The Earth ◽  
The 1960S ◽  
Isotope Analyses ◽  
Uniform Composition

Early models of the composition of the Earth relied heavily on meteorites. In all these models Earth had different layers, each layer corresponded to a different type of meteorite or meteorite component. Later, more realistic models based on analyses of samples from Earth began with Ringwood’s pyrolite composition in the 1960s. Further improvement came with the analyses of rare MgO rich peridotites from a variety of occurrences all over the Earth, as xenoliths enclosed in melts from the upper mantle or as ultramafic massifs, tectonically emplaced on the Earth’s surface. Chemical systematics of these rocks allow the determination of the major element composition of the primitive upper mantle (PUM), the upper mantle after core formation and before extraction of basalts ultimately leading to the formation of the crust. Trace element analyses of upper mantle rocks confirmed their primitive nature. Geochemical and geophysical evidence argue for a bulk Earth mantle of uniform composition, identical to the PUM, also designated as “bulk silicate Earth” (BSE). The formation of a metal core was accompanied by the removal of siderophile and chalcophile elements into the core. Detailed modeling suggests that core formation was an ongoing process parallel to the accretion of Earth. The composition of the core is model dependent and thus uncertain and makes reliable estimates for siderophile and chalcophile element concentrations of bulk Earth difficult. Improved stable isotope analyses show isotopic similarities with noncarbonaceous chondrites (NCC), while the chemical composition of the mantle of the Earth indicates similarities with carbonaceous chondrites (CC). In detail, however, it can be shown that no single known meteorite group, nor any mixture of meteorite groups can match the chemical and isotopic composition of Earth. This conclusion is extremely important for any formation model of the Earth.

The deficiency of siderophile elements in the Moon

1977 ◽  
Vol 285 (1327) ◽  
pp. 569-575 ◽  
Keyword(s):  
High Heat ◽  
Metallic Nickel ◽  
The Moon ◽  
Nickel Iron ◽  
Natural Processes ◽  
The Core ◽  
The Earth ◽  
Successive Passage ◽  
Direct Formation ◽  
Siderophile Elements

The deficiency of siderophiles in the crust of the Earth is customarily attributed to leaching by metallic nickel-iron, which eventually sank to form the core. A similar deficiency exists in the Moon, which has, at best, a very much smaller core. Hence it is logical to consider the hypothesis that the Moon formed from the mantle of the Earth, after the siderophiles had been removed. It is shown that the non-hydrostatic figure of the Moon, and the requirement that the mascons must be supported, together with the high heat-flow, imply that the metal of the Moon is collected in the core. It probably amounts to less than 1 % of the Moon’s mass. Calculations show that if the core is in chemical equilibrium with the lunar silicates, then the nickel has been removed from the Moon as a whole to an extent which is greater than can be explained by theories of direct formation from a nebula. The only salvation for the idea of direct formation from a nebula appears to be an efficient process of extraction of the siderophiles by successive passage of small amounts of reduced metal through the silicate portion of the Moon. Since natural processes do not usually operate with the required efficiency, it can be concluded that the formation of the Moon by the fission of the Earth is geochemically plausible.

The first 800 million years of Earth's history

1981 ◽  
Vol 301 (1461) ◽  
pp. 401-422 ◽  
Keyword(s):  
Heat Flow ◽  
Upper Mantle ◽  
Calc Alkaline ◽  
Radiogenic Heat ◽  
Crustal Rocks ◽  
The Core ◽  
The Earth ◽  
Equilibrium Data ◽  
Geochemical Transport ◽  
Lunar Basins

The Earth grew initially from hot planetesimals of reduced material, and began to differentiate early into a metal-rich core, a silicate-rich mantle and a volcanic surface. Accretion ended with volatile-rich oxidized material, which did not interact with the core because of a mantle barrier. Quenching of magmas at the surface and foundering of cool material was effective in cooling the Earth by 1600 J per gram of magma. Magmas transported radioactive elements and volatiles to the outer 50 km. The lower mantle became stranded below the critical adiabat for melting. The core may have been fully molten. Radiogenic and non-radiogenic heat sources produced a surface heat flow that decreased from ca . 1.3 x 10 14 W at 4.45 Ga B.P . to the present value of 4 x 10 13 W. In spite of uncertainties in the production and transport of heat, it seems safe to conclude that intense volcanism occurred throughout the pre-Archaean era before survival of crust. From phase-equilibrium data for peridotites and calc-alkaline rocks, it is deduced that a range of ultrabasic to basic magmas was produced from a peridotitic upper mantle, and that calc-alkaline magmas were produced during foundering of crust. An anorthositic crust was not formed. From observations of lunar basins, it is concluded that a minimum of ca . 500-1000 impact basins were formed on Earth in ca . 100—200 Ma before 3.95 Ga B.P. Plausible calculations suggest that ca . 20 times as many basins were formed in the preceding ca . 300 Ma. Impact debris would be cooled by water in wet crustal rocks and oceans. It is assumed that after 4.0 Ga B.P. impacts would have only temporary local effects on the crust, and emphasis is placed on upper-mantle convection as the main driving force for geochemical transport. Sedimentation and metamorphism were important factors during foundering of crust. ‘Oceanic' and ‘continental' regions developed above up-welling and down-welling segments of convection cells, and these regions resembled greenstone belts and high-grade regions of the Archaean era. As heat flow declined, polygonal tectonics was replaced by symmetrical linear tectonics during the Archaean era, and then by asymmetrical linear tectonics during the Proterozoic era.

Geochemical Constraints on the Early Thermal History of the Earth

1989 ◽  
Vol 44 (10) ◽  
pp. 883-890 ◽  
Author(s):  
Michael J. Drake
Keyword(s):  
Upper Mantle ◽  
Partition Coefficients ◽  
Current Theory ◽  
Gravitational Potential Energy ◽  
The Moon ◽  
The Core ◽  
The Earth ◽  
History Of ◽  
Geochemical Constraints ◽  
Origin Of The Moon

Abstract Theories of the formation of the Earth strongly suggest that the Earth should have been substantially molten during and immediately after accretion. Estimates of the composition of the upper mantle indicate that many elements are present in chondritic ratios. Experimental measurements of element partition coefficients show that segregation of perovskite, majorite garnet, or olivine would fractionate the ratios of these elements away from chondritic values. The implication of these geochemical observations is that the Earth did not undergo extensive fractionation during and immediately following accretion. One possibility is that the Earth did not become substantially molten. Alternatively, if the Earth was indeed substantially molten, then it is possible that minerals were entrained in magma and were unable to segregate. In the former case, the accretional process must have delivered gravitational potential energy more slowly than current theory predicts, and an origin of the Moon in a giant impact would be unlikely. In the latter case, the high Mg/Si ratio in the upper mantle of the Earth relative to most classes of chondrites would be intrinsic to the silicate portion of the Earth. Unless significant amounts of Si exist in the core, the high Mg/Si ratio is a bulk planetary property, implying that the accretional process did not mix material between 1 AU and 2-4 AU.

Heat Generation and Transport in the Earth

2010 ◽  
Author(s):  
Claude Jaupart ◽  
Jean-Claude Mareschal
Keyword(s):  
Heat Generation ◽  
The Earth
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