Neutrino Geophysics: Proceedings of Neutrino Sciences 2005
Abstract
This volume presents a collection of recent articles primarily documenting the nascent science of neutrino geophysics. Most of the articles followed from talks given at Neutrino Sciences 2005: Neutrino Geophysics held at the University of Hawaii in December 2005. However, several other key contributions were solicited to make the collection as comprehensive as possible, enhancing the value of this book.
The book offers a unique status report on neutrino geophysics to the expert researcher, as well as a comprehensive introduction into this new field of science to graduate students.
Chapters (24)
Long distance detection of electron anti-neutrinos from reactors at distances of order 200 km has been achieved with the 1000 ton liquid scintillator-based KamLAND instrument in Japan. In summer 2005 the KamLAND group reported the first detection of anti-neutrinos from the natural radioactivity of the earth. These measurements are due to uranium and thorium decays dominantly from the nearby crust in Japan, and are expected to have only a small contribution from the earth’s mantle (and core). Several new detectors are under consideration around the world for measurements which when taken together can reveal the location of these heavy elements, which are expected to contribute a major share of the internal earth’s heating via their radioactivity. This heating is of course associated with providing the power to drive the geomagnetic field and plate tectonics. Geologists have only indirect evidence about the deep earth, mostly from seismic wave velocity and inferences from a few meteorites. Anti-neutrino detection, on the other hand, yields direct information about earth’s interior. The location and magnitude of the earth’s uranium and thorium are crucial to understanding the origin and evolution of the earth and present day activity.
I shall summarize the marvellous accomplishments in neutrino physics of the past decade, very briefly sketch our current understanding of these elusive particles and provide a personal list of the most important challenges that remain in this discipline, given in (my) order of priority. Because the following discussion is more provocative than novel, I must apologize in advance for the inevitable omissions, distortions, inequities and iniquities resulting from my ignorance or infirmitude, inattention or ineptitude and unintended arrogance.
The radioactivity of the earth is an important parameter in understanding the dynamics of the planet and the evolution of the crust-mantle-core system but geochemical and geophysical approaches have had only a limited success in defining it. The opportunity of a direct estimate of the radioactivity of the earth by measurement of the geoneutrino flux takes on an added significance in this context. Such an independent new measurement will help resolve and/or clarify a number of questions about global scale processes in the earth and will help advance earth sciences.
In this paper we discuss the Herndon hypothesis that a nuclear reactor is operating at the center of the Earth. Recent experimental evidence shows that some uranium can have partitioned into the core. There is no viable mechanism for the small amount of uranium that is dissolved in the molten metal to crystallize as a separate uranium phase (uranium metal or uranium sulfide) and migrate to the center of the core. There is no need for an extra heat source, as the total heat leaving the core can be easily provided by “classical” heat sources, which are also more than adequate to maintain the Earth’s magnetic field. It is unlikely that nuclear georeactors (fast breeder reactors) are operating at the Earth’s center.
To appreciate the essential scientific reasons for the possible existence of a nuclear reactor at Earth’s center, it is necessary to understand precisely the oxidation state of the deep interior of the Earth as well as the nature and probable circumstances of Earth’s origin, which led to that state of oxidation. For example, in referring to the quote from Wheeler et al. (2006), “the transfer of U from metal sulfide to silicate under our experimental conditions is so complete that insufficient U would remain so as to be of any importance to the core’s heat budget,” Schuiling neglected to note that the silicate used in the laboratory experiment contained 8% FeO. A more highly reduced silicate — nearly devoid of FeO, such as MgSiO3, consistent with the enstatite-chondritic deep interior of the Earth — would have yielded a significantly different laboratory result. Similarly, in referring to elemental behavior using Goldschmidt’s term “chalcophile,” Schuiling fails to mention that chalco-philicity is related to state of oxidation. Even making use of some condensation model, as Schuiling does, necessitates assuming a particular pressure, which leads to a particular range of oxygen fugacities. Schuiling adopts without reservation the so-called standard model of solar system formation, evidently without realizing that the resulting state of oxidation in that contemporary formation model would inevitably lead to Earth having an insufficiently massive core.
Only three processes, operant during the formation of the Solar System, are responsible for the diversity of matter in the Solar System and are directly responsible for planetary internal-structures, including planetocentric nuclear fission reactors, and for dynamical processes, including and especially, geodynamics. These processes are: (i) Low-pressure, low-temperature condensation from solar matter in the remote reaches of the Solar System or in the interstellar medium; (ii) High-pressure, high-temperature condensation from solar matter associated with planetary-formation by raining out from the interiors of giant-gaseous protoplanets, and; (iii) Stripping of the primordial volatile components from the inner portion of the Solar System by super-intense solar wind associated with T-Tauri phase mass-ejections, presumably during the thermonuclear ignition of the Sun. As described herein, these processes lead logically, in a causally related manner, to a coherent vision of planetary formation with profound implications including, but not limited to, (a) Earth formation as a giant gaseous Jupiter-like planet with vast amounts of stored energy of protoplanetary compression in its rock-plus-alloy kernel; (b) Removal of approximately 300 Earth-masses of primordial volatile gases from the Earth, which began Earth’s decompression process, making available the stored energy of protoplanetary compression for driving geodynamic processes, which I have described by the new whole-Earth decompression dynamics and which is responsible for emplacing heat at the mantle-crust-interface at the base of the crust through the process I have described, called mantle decompression thermal-tsunami; and, (c) Uranium accumulations at the planetary centers capable of self-sustained nuclear fission chain reactions.
Earth shines in antineutrinos produced from long-lived radioactive elements: detection of this signal can provide a direct test of the Bulk Silicate Earth (BSE) model and fix the radiogenic contribution to the terrestrial heat flow. In this paper we present a systematic approach to geo-neutrino production based on global mass balance, supplemented by a detailed geochemical and geophysical study of the region near the detector, in order to build theoretical constraints on the expected signal. We show that the prediction is weakly dependent on mantle modeling while it requires a good description of the crust composition in the region of the detector site. In 2005 the KamLAND experiment proved that the technique for exploiting geo-neutrinos in the investigation of the Earth’s interior is now available. After performing an analysis of KamLAND data which includes recent high precision measurements of the 13C(α, n)16O cross section, we discuss the potential of future experiments for assessing the amount of uranium and thorium in different reservoirs (crust, mantle and core) of the Earth.
Geo-neutrinos emitted by heat-producing elements (U, Th and K) represent a unique probe of the Earth interior. The characterization of their fluxes is subject, however, to rather large and highly correlated uncertainties. The geochemical covariance of the U, Th and K abundances in various Earth reservoirs induces positive correlations among the associated geo-neutrino fluxes, and between these and the radiogenic heat. Mass-balance constraints in the Bulk Silicate Earth (BSE) tend instead to anti-correlate the radiogenic element abundances in complementary reservoirs. Experimental geo-neutrino observables may be further (anti)correlated by instrumental effects. In this context, we propose a systematic approach to covariance matrices, based on the fact that all the relevant geo-neutrino observables and constraints can be expressed as linear functions of the U, Th and K abundances in the Earth’s reservoirs (with relatively well-known coefficients). We briefly discuss here the construction of a tentative “geo-neutrino source model” (GNSM) for the U, Th, and K abundances in the main Earth reservoirs, based on selected geophysical and geochemical data and models (when available), on plausible hypotheses (when possible), and admittedly on arbitrary assumptions (when unavoidable). We use then the GNSM to make predictions about several experiments (“forward approach”), and to show how future data can constrain a posteriori the error matrix of the model itself (“backward approach”). The method may provide a useful statistical framework for evaluating the impact and the global consistency of prospective geo-neutrino measurements and Earth models.
The Kamioka liquid scintillator antineutrino detector (KamLAND), which consists of 1000 tones of ultra-pure liquid scintillator surrounded by 1879 photo-multiplier tubes (PMT), is the first detector sensitive enough to detect geoneutrinos. Earth models suggest that KamLAND observes geoneutrinos at a rate of 30 events/1032-protons/year from the 238U decay chain, and 8 events/1032-protons/year from the 232Th decay chain. With 7.09 × 1031 proton-years of detector exposure and detection efficiency of 0.687±0.007, the ‘rate-only’ analysis gives 25
−18+19 geoneutrino candidates. Assuming a Th/U mass concentration ratio of 3.9, the ‘rate + shape’ analysis gives the 90% confidence interval for the total number of geoneutrinos detected to be from 4.5 to 54.2. This result is consistent with predictions from the Earth models. The 99% C.L. upper limit is set at 1.45 × 10−31 events per target proton per year, which is 3.8 times higher than the central value of the model prediction that gives 16 TW of radiogenic heat production from 238U and 232Th. Although the present data have limited statistical power, they provide by direct means an upper limit for the Earth’s radiogenic heat of U and Th.
A natural nuclear fission reactor operating in the center of the Earth has been proposed by Herndon (Hollenbach and Herndon, 2001) as the energy source that powers the geo-magnetic field. The upper limit on the expected geo-reactor power is set by the estimated 12 TW (Buffett, 2003) heat flow from the Earth’s core. If it exists, a nuclear reactor of that size emits a strong anti-neutrino flux. Emitted electron anti-neutrinos can be detected by the Kamioka liquid scintillator anti-neutrino detector (KamLAND) (Raghavan, 2002), and the geo-reactor power level is proporional to the anti-neutrino emission rate. KamLAND measures the geo-reactor power as a constant positive offset in detected anti-neutrino rate on top of the varying anti-neutrino rate coming from man-made reactors. Here we present the first attempt to measure the geo-reactor power. Based on a 776 ton-year exposure of KamLAND to electron anti-neutrinos, the detected flux corresponds to (6±6) TW. The upper limit on the geo-reactor power at 90% confidence level is 18 TW, which is below the lower limit of the total Earth’s radiogenic heat, estimated to be between 19 and 31TW (Anderson, 2003).
Decays of radionuclides throughout the earth’s interior produce geothermal heat, but also are a source of antineutrinos; these geoneutrinos are now becoming observable in experiments such as KamLAND. The (angle-integrated) geoneutrino flux has been shown to provide a unique probe of geothermal heating due to decays, and an integral constraint on the distribution of radionuclides in the earth. In this paper, we calculate the angular distribution of geoneutrinos, which opens a window on the differential radial distribution of terrestrial radionuclides. We develop the general formalism for the neutrino angular distribution. We also present the inverse transformation which recovers the terrestrial radioisotope distribution given a measurement of the neutrino angular distribution. Thus, geoneutrinos not only allow a means to image the earth’s interior, but offer a direct measure of the radioactive earth, both revealing the earth’s inner structure as probed by radionuclides, and allowing a complete determination of the radioactive heat generation as a function of radius. Turning to specific models, we emphasize the very useful approximation in which the earth is modeled as a series of shells of uniform density. Using this multishell approximation, we present the geoneutrino angular distribution for the favored earth model which has been used to calculate the geoneutrino flux. In this model the neutrino generation is dominated by decays of potassium, uranium, and thorium in the earth’s mantle and crust; this leads to a very “peripheral” angular distribution, in which 2/3 of the neutrinos come from angles θ ≳ 60° away from the nadir. We note that a measurement of the neutrino intensity in peripheral directions leads to a strong lower limit to the central intensity. We briefly discuss the challenges facing experiments to measure the geoneutrino angular distribution. Currently available techniques using inverse beta decay of protons require a (for now) unfeasibly large number of events to recover with confidence the forward scattering signal from the background of subsequent elastic scatterings. Nevertheless, it is our hope that future large experiments, and/or more sensitive techniques, can resolve an image of the earth’s radioactive interior.
The possibility of terrestrial antineutrino directionality studies is considered for future unloaded liquid scintillator detectors. Monte-Carlo simulations suggest that the measurable displacement between prompt and delayed antineutrino signals makes such studies possible. However, it is estimated that on the order of 1000 terrestrial antineutrino events are required to test the simplest models, demanding detectors of 100 kt size to collect sufficient data in a reasonable period of time.
This paper describes the Borexino detector and the high-radiopurity studies and tests that are integral part of the Borexino technology and development. The application of Borexino to the detection and studies of geoneutrinos is discussed.
There are plans to fill the Sudbury Neutrino Observatory with liquid scintillator after measurements with heavy water are completed. The new experiment, known as SNO+, would make an excellent detector for geo-neutrinos. SNO+ would be located amidst a thick and uniform region of continental crust, away from nuclear power reactors. As a result, the geo-neutrino signal to reactor background ratio in SNO+ will exceed that from previous measurements. Geo-neutrino measurements by SNO+ will shed light on the amount of uranium and thorium radioactivity in the crust, as well as deeper inside the Earth. Spectral information from SNO+ geo-neutrino detection will provide the first direct measurement of the U/Th ratio.
A significant fraction of the 44TW of heat dissipation from the Earth’s interior is believed to originate from the decays of terrestrial uranium and thorium. The only estimates of this radiogenic heat, which is the driving force for mantle convection, come from Earth models based on meteorites, and have large systematic errors. The detection of electron antineutrinos produced by these uranium and thorium decays would allow a more direct measure of the total uranium and thorium content, and hence radiogenic heat production in the Earth. We discuss the prospect of building an electron antineutrino detector approximately 700 m3 in size in the Homestake mine at the 4850’ level. This would allow us to make a measurement of the total uranium and thorium content with a statistical error less than the systematic error from our current knowledge of neutrino oscillation parameters. It would also allow us to test the hypothesis of a naturally occurring nuclear reactor at the center of the Earth.
We consider the detector size, location, depth, background, and radio-purity required of a mid-Pacific deep-ocean instrument to accomplish the twin goals of making a definitive measurement of the electron anti-neutrino flux due to uranium and thorium decays from Earth’s mantle and core, and of testing the hypothesis for a natural nuclear reactor at the core of Earth. We take the experience with the KamLAND detector in Japan as our baseline for sensitivity and background estimates. We conclude that an instrument adequate to accomplish these tasks should have an exposure of at least 10 kilotonne-years (kT-y), should be placed at least at 4 km depth, may be located close to the Hawaiian Islands (no significant background from them), and should aim for KamLAND radio-purity levels, except for radon where it should be improved by a factor of at least 100. With an exposure of 10 kT-y we should achieve a 25% measurement of the flux of U/Th neutrinos from the mantle plus core. Exposure at multiple ocean locations for testing lateral heterogeneity is possible.
A future large-volume liquid scintillator detector such as the proposed 50 kton LENA (Low Energy Neutrino Astronomy) detector would provide a high-statistics measurement of terrestrial antineutrinos originating from β-decays of the uranium and thorium chains. Additionally, the neutron is scattered in the forward direction in the detection reaction \(
\bar v_e + p \to n + e^ +
\). Henceforth, we investigate to what extent LENA can distinguish between certain geophysical models on the basis of the angular dependence of the geoneutrino flux. Our analysis is based on a Monte-Carlo simulation with different levels of light yield, considering an unloaded PXE scintillator. We find that LENA is able to detect deviations from isotropy of the geoneutrino flux with high significance. However, if only the directional information is used, the time required to distinguish between different geophysical models is of the order of severals decades. Nonetheless, a high-statistics measurement of the total geoneutrino flux and its spectrum still provides an extremely useful glance at the Earth’s interior.
As a possible design of a future geoneutrino detector, a KamLAND-type, monolithic, liquid scintillator detector with a thicker veto and a method for particle identification to reject neutron and 9Li background from cosmic-ray muon spallation is considered. Assuming such a detector, the possibility for geoneutrino observation at a depth of around 300 meters of water equivalent is investigated.
The Double Chooz reactor neutrino experiment will be built in the forthcoming years. Eventhough not dedicated to geo-neutrino detection, it is based on similar experimental methods. By pushing current technology to the limits an unprecedented precision will be reached due to careful reduction and control of systematic errors below the percent level. The experience and technical innovation achieved by this project could be valuable for future geo-neutrino experiments. After discussing the Double Chooz detector design we focus on progress achieved on scintillating oils and compatible materials.
Because the propagation of neutrinos is affected by the presence of Earth matter, it opens new possibilities to probe the Earth’s interior. Different approaches range from techniques based upon the interaction of high energy (above TeV) neutrinos with Earth matter, to methods using the MSW effect on the oscillations of low energy (MeV to GeV) neutrinos. In principle, neutrinos from many different sources (sun, atmosphere, supernovae, beams etc.) can be used. In this talk, we summarize and compare different approaches with an emphasis on more recent developments. In addition, we point out other geophysical aspects relevant for neutrino oscillations.
The result of a study on the use of an array of large anti-neutrino detectors for the purpose of monitoring rogue nuclear activity is presented. Targeted regional monitoring of a nation bordering large bodies of water with no pre-existing legal nuclear activity may be possible at a cost of about several billion dollars, assuming several as-yet-untested schemes pan out in the next two decades. These are: (1) the enabling of a water-based detector to detect reactor anti-neutrinos by doping with GdCl3; (2) the deployment of a KamLAND-like detector in a deep-sea environment; and (3) the scaling of a Super-Kamiokande-like detector to a size of one or more megatons. The first may well prove feasible, and should be tested by phase-III Super-Kamiokande in the next few years. The second is more of a challenge, but may well be tested by the Hanohano collaboration in the coming decade. The third is perhaps the least certain, with no schedule for construction of any such device in the foreseeable future. In addition to the regional monitoring scheme, several global, untargeted monitoring schemes were considered. All schemes were found to fail benchmark sensitivity levels by a wide margin, and to cost at least several trillion dollars.
The main effort in Europe to evaluate the interest for IAEA of neutrinos detectors close to nuclear power stations is made within the Double Chooz experiments. Specific simulation of diversion scenarios as well as new experimental measurements of neutrinos emitted are underway.
Antineutrino data constrain the concentrations of the heat producing elements U and Th as well as potentially the concentration of K. Interpretation is similar to but not homologous with gravity. Current geoneutrino physics efficiently asks simple questions taking advantage of what is already known about the Earth. A few measurements with some sites in the ocean basins will constrain the concentration of U and Th in the crust and mantle and whether the mantle is laterally heterogeneous. These results will allow Earth science arguments about the formation, chemistry, and dynamics of the Earth to be turned around and appraised. In particular, they will tell whether the Earth accreted its expected share of these elements from the solar nebula and how long radioactive heat will sustain active geological processes on the Earth. Both aspects are essential to evaluating the Earth as a common or rare habitable planet.
The KamLAND liquid scintillator detector demonstrated the detection of antineutrinos produced by natural radioactivities in the Earth, so-called geoneutrinos. Although this first result of geo-neutrinos is consistent with current geophysical models, more accurate measurements are essential to provide a new window for exploring the inside of the Earth. In this article I would like to discuss the future prospects of KamLAND geoneutrino detection, and the possibility of directional measurement of incoming geoneutrinos. It is interesting to consider the application of geoneutrino detectors to measurements of other neutrino signals. The possibility of detecting the solar 7Be, pep and CNO neutrinos is discussed. A new type detector concept is proposed not only to explore the precise measurement of reactor neutrino oscillations but also to enable us to realize the neutrino tomography inside the Earth.
... An introduction is given in Bowden [7], where the focus is upon close-in reactor monitoring. Remote monitoring of reactor activity will be possible out to hundreds of kilometers with next generation instruments, and some can envisage a worldwide network of neutrino monitors contributing to antinuclear weapons proliferation efforts in the future [36]. ...
The detection of electron anti-neutrinos from natural radioactivity in the earth has been a goal of neutrino researchers for about half a century. It was accomplished by the KamLAND Collaboration in 2005, and opens the way towards studies of the Earth's radioactive content, with very important implications for geology. New detectors are operating (KamLAND and Borexino), building (SNO+) and being proposed (Hanohano, LENA, Earth and others) that will go beyond the initial observation and allow interesting geophysical and geochemical research, in a means not otherwise possible. Herein we describe the approaches being taken (large liquid scintillation instruments), the experimental and technical challenges (optical detectors, directionality), and prospects for growth of this field. There is related spinoff in particle physics (neutrino oscillations and hierarchy determination), astrophysics (solar neutrinos, supernovae, exotica), and in the practical matter of remote monitoring of nuclear reactors.
Analytical techniques can be distinguished between passive ones, taking profit of the inherent activity of the sample, and those which are interactive in character.
Intense devolatilization and chemical-density differentiation attended accretion of planetesimals on the primordial Earth. These processes gradually abated after cooling and solidification of an early magma ocean. By 4.3 or 4.2 Ga, water oceans were present, so surface temperatures had fallen far below low-pressure solidi of dry peridotite, basalt, and granite, ~1300, ~1120, and ~950 °C, respectively. At less than half their T solidi, rocky materials existed as thin lithospheric slabs in the near-surface Hadean Earth. Stagnant-lid convection may have occurred initially but was at least episodically overwhelmed by subduction because effective, massive heat transfer necessitated vigorous mantle overturn in the early, hot planet. Bottom-up mantle convection, including voluminous plume ascent, efficiently rid the Earth of deep-seated heat. It declined over time as cooling and top-down lithospheric sinking increased. Thickening and both lateral extensional + contractional deformation typified the post-Hadean lithosphere. Stages of geologic evolution included (i) 4.5–4.4 Ga, magma ocean overturn involved ephemeral, surficial rocky platelets; (ii) 4.4–2.7 Ga, formation of oceanic and small continental plates were obliterated by return mantle flow prior to ~4.0 Ga; continental material gradually accumulated as largely sub-sea, sialic crust-capped lithospheric collages; (iii) 2.7–1.0 Ga, progressive suturing of old shields + younger orogenic belts led to cratonal plates typified by emerging continental freeboard, increasing sedimentary differentiation, and episodic glaciation during transpolar drift; onset of temporally limited stagnant-lid mantle convection occurred beneath enlarging supercontinents; (iv) 1.0 Ga–present, laminar-flowing asthenospheric cells are now capped by giant, stately moving plates. Near-restriction of komatiitic lavas to the Archean, and appearance of multicycle sediments, ophiolite complexes} alkaline igneous rocks, and high-pressure–ultrahigh-pressure (HP–UHP) metamorphic belts in progressively younger Proterozoic and Phanerozoic orogens reflect increasing negative buoyancy of cool oceanic lithosphere, but decreasing subductability of enlarging, more buoyant continental plates. Attending supercontinental assembly, density instabilities of thickening oceanic plates began to control overturn of suboceanic mantle as cold, top-down convection. Over time, the scales and dynamics of hot asthenospheric upwelling versus lithospheric foundering + mantle return flow (bottom-up plume-driven ascent versus top-down plate subduction) evolved gradually, reflecting planetary cooling. These evolving plate-tectonic processes have accompanied the Earth’s thermal history since ~4.4 Ga.
Neutrino geophysics is an emerging interdisciplinary field with the potential to map the abundances and distribution of radiogenic heat sources in the continental crust and deep Earth. To date, data from two different experiments quantify the amount of Th and U in the Earth and begin to put constraints on radiogenic power in the Earth available for driving mantle convection and plate tectonics. New improved detectors are under construction or in planning stages. Critical testing of compositional models of the Earth requires integrating geoneutrino and geological observations. Such tests will lead to significant constraints on the absolute and relative abundances of U and Th in the continents. High radioactivity in continental crust puts limits on land-based observatories' capacity to resolve mantle models with current detection methods. Multiple-site measurement in oceanic areas away from continental crust and nuclear reactors offers the best potential to extract mantle information. Geophysics would benefit from directional detection and the detectability of electron antineutrinos from potassium decay.
Aims: We present neutrino light curves and energy spectra for two
representative type Ia supernova explosion models: a pure deflagration and a
delayed detonation. Methods: We calculate the neutrino flux from
processes using nuclear statistical equilibrium abundances convoluted with
approximate neutrino spectra of the individual nuclei and the thermal neutrino
spectrum (pair+plasma). Results: Although the two considered thermonuclear
supernova explosion scenarios are expected to produce almost identical
electromagnetic output, their neutrino signatures appear vastly different,
which allow an unambiguous identification of the explosion mechanism: a pure
deflagration produces a single peak in the neutrino light curve, while the
addition of the second maximum characterizes a delayed-detonation. We
identified the following main contributors to the neutrino signal: (1) weak
electron neutrino emission from electron captures (in particular on the protons
Co55 and Ni56) and numerous beta-active nuclei produced by the thermonuclear
flame and/or detonation front, (2) electron antineutrinos from positron
captures on neutrons, and (3) the thermal emission from pair annihilation. We
estimate that a pure deflagration supernova explosion at a distance of 1 kpc
would trigger about 14 events in the future 50 kt liquid scintillator detector
and some 19 events in a 0.5 Mt water Cherenkov-type detector. Conclusions:
While in contrast to core-collapse supernovae neutrinos carry only a very small
fraction of the energy produced in the thermonuclear supernova explosion, the
SN Ia neutrino signal provides information that allows us to unambiguously
distinguish between different possible explosion scenarios. These studies will
become feasible with the next generation of proposed neutrino observatories.
Uranium and thorium within the Earth produce a major portion of terrestrial heat along with a measurable flux of electron antineutrinos. These elements are key components in geophysical and geochemical models. Their quantity and distribution drive the dynamics, define the thermal history, and are a consequence of the differentiation of the Earth. Knowledge of uranium and thorium concentrations in geological reservoirs relies largely on geochemical model calculations. This article describes the methods and criteria to experimentally determine average concentrations of uranium and thorium in the continental crust and in the mantle by using site-specific measurements of the terrestrial antineutrino flux. Optimal, model-independent determinations involve significant exposures of antineutrino detectors remote from nuclear reactors at both a midcontinental and a midoceanic site. This would require major, new antineutrino detection projects. The results of such projects could yield a greatly improved understanding of the deep interior of the Earth.
• geochemistry
• geoneutrinos
• terrestrial heat
ResearchGate has not been able to resolve any references for this publication.