William F McDonough

University of Maryland, College Park | UMD, UMCP, University of Maryland College Park · Department of Geology

The composition of the bulk silicate Earth (BSE) is the product of planetary accretion, core differentiation and Moon formation. By establishing the composition of the BSE, one can determine the composition of the bulk Earth and by subtraction, calculate the core’s composition. The BSE represents the bulk Earth minus the core, which in today’s term...

Mesosiderites are an amalgamation of crustal silicates and molten metal, and their formational history is not well understood. It is widely believed that redox reactions occurred in the mesosiderites during metal–silicate mixing. Previous studies evaluated redox reactions by studying the silicates within mesosiderites, but little attention has been...

Minerals are solid state nuclear track detectors - nuclear recoils in a mineral leave latent damage to the crystal structure. Depending on the mineral and its temperature, the damage features are retained in the material from minutes (in low-melting point materials such as salts at a few hundred degrees C) to timescales much larger than the 4.5 Gyr...

The earth's surface heat flux is 46$\pm$3 TW (terrawatts, 10$^{12}$ watts). Although many assume we know the earth's abundance and distribution of radioactive heat producing elements (i.e., U, Th, and K), estimates for the mantle's heat production varying by an order of magnitude and recent particle physics findings challenge our dominant paradigm....

Earth's internal heat drives its dynamic engine, causing mantle convection, plate tectonics, and the geodynamo. These renewing and protective processes, which make Earth habitable, are fueled by primordial and radiogenic heat. For the past two decades, particle physicists have measured the flux of geoneutrinos, electron antineutrinos emitted during...

This study provides a global assessment of the abundance of the major oxides in the deep continental crust. The combination of geochemistry and seismology better constrains the composition of the middle and lower continental crust better than either discipline can achieve alone. The inaccessible nature of the deep crust (typically >15 km) forces re...

Ungrouped iron meteorites Tishomingo, Willow Grove, and Chinga, and group IVB iron meteorites, are Ni-rich. Similarities include enrichments of 10-100 × CI for some refractory siderophile elements, and equivalent depletions in more volatile siderophile elements. Superimposed on the overall enrichment/depletion trend, certain siderophile elements (P...

Debate abounds regarding the composition of the deep (middle + lower) continental crust. Exhumed medium‐ and high‐grade metamorphic rocks, which range in composition from mafic to felsic, provide information about the bulk composition of the deep crust. This study presents a global compilation of geochemical data on amphibolite (n = 6,500), granuli...

Observation of anti-neutrinos emitted from radioactive isotopes inside Earth(geo-neutrinos) brings direct information on the Earth’s chemical composition and its heat balance, which strongly relate to the Earth’s dynamics. To date, two experiments (KamLAND and Borexino) have measured geo-neutrinos and constrained the range of acceptable models for...

Terrestrial planets (Mercury, Venus, Earth, and Mars) are differentiated into three layers: a metallic core, a silicate shell (mantle and crust), and a volatile envelope of gases, ices, and, for the Earth, liquid water. Each layer has different dominant elements (e.g., increasing iron content with depth and increasing oxygen content to the surface)...

Chondrites are sediments of materials left over from the earliest stage of the solar system history. Based on their undifferentiated nature and less fractionated chemical compositions, chondrites are widely considered to represent the unprocessed building blocks of the terrestrial planets and their embryos. Models of chemical composition of the ter...

Trace elements, distinguished by their low abundances (parts per million by weight (ppmw)), track local, regional, and planetary-scale processes in samples sourced from throughout the solar system. Such analyses of lunar samples have provided insights on its surface rocks and interpretations of its deep interior. However, returned samples, sourced...

Composition of terrestrial planets records planetary accretion, core-mantle and crust-mantle differentiation, and surface processes. Here we compare the compositional models of Earth and Mars to reveal their characteristics and formation processes. Earth and Mars are equally enriched in refractory elements (1.9 × CI), although Earth is more volatil...

Potassium (K) informs on the radiogenic heat production, atmospheric composition, and volatile element depletion of the Earth and other planetary systems. Constraints on the abundance of K in the Earth, Moon, and other rocky bodies have historically hinged on K/U values measured in planetary materials, particularly comparisons of the continental cr...

Chondrites are undifferentiated sediments of materials left over from the earliest stage of the solar system history, and are widely considered to represent the unprocessed building blocks of the terrestrial planets. Compositional models of the planets generally find chondritic relative abundances of refractory lithophile elements (RLE) in the bulk...

Noble gas plasmas are commonly used as ion and excitation sources in inductively coupled plasma (ICP) optical emission and mass spectrometry for organic and inorganic chemical analysis. However, the high power (∼kW) and voluminous gas flow rate (∼15 L min⁻¹) of commercial plasmas limit their potential deployment in remote terrestrial and planetary...

Chondrites, the building blocks of the terrestrial planets, have mass and atomic proportions of oxygen, iron, magnesium, and silicon totaling ≥90% and variable Mg/Si (∼25%), Fe/Si (factor of ≥2), and Fe/O (factor of ≥3). The Earth and terrestrial planets (Mercury, Venus, and Mars) are differentiated into three layers: a metallic core, a silicate sh...

We report the Earth's rate of radiogenic heat production and (anti)neutrino luminosity from geologically relevant short‐lived radionuclides (SLR) and long‐lived radionuclides (LLR) using decay constants from the geological community, updated nuclear physics parameters, and calculations of the β spectra. We track the time evolution of the radiogenic...

Terrestrial planets provide Solar System insights into the evolution of accretion, core-mantle and crust-mantle differentiation, and surface processes. The Earth and Mars have equal enrichment in refractory elements (1.9 × CI), although the Earth is more volatile-depleted and less oxidized than Mars. Their chemical compositions were established by...

The composition of the lower continental crust is well studied but poorly understood because of the difficulty of sampling large portions of it. Petrological and geochemical analyses of this deepest portion of the continental crust are limited to the study of high‐grade metamorphic lithologies, such as granulite. In situ lower crustal studies requi...

Debate continues on the amount and distribution of radioactive heat producing elements (i.e., U, Th, and K) in the Earth, with estimates for mantle heat production varying by an order of magnitude. Constraints on the bulk‐silicate Earth's (BSE) radiogenic power also places constraints on overall BSE composition. Geoneutrino detection is a direct me...

Comparing compositional models of the terrestrial planets provides insights into physicochemical processes that produced planet-scale similarities and differences. The widely accepted compositional model for Mars assumes Mn and more refractory elements are in CI chondrite proportions in the planet, including Fe, Mg, and Si, which along with O make...

Comparing compositional models of the terrestrial planets provides insights into physicochemical processes that produced planet-scale similarities and differences. The widely accepted compositional model for Mars assumes Mn and more refractory elements are in CI chondrite proportions in the planet, including Fe, Mg, and Si, which along with O make...

SNOLAB is one of the deepest underground laboratory in the world with an overburden of 2092 m. The SNO+ detector is designed to achieve several fundamental physics goals as a low-background experiment, particularly measuring the Earth’s geoneutrino flux. Here we evaluate the effect of the 2 km overburden on the predicted crustal geoneutrino signal...

The Earth, a hybrid engine, is powered by two main sources of energy: residual primordial energy, evolved from accretion and core separation, and heat from radioactive decay. Radiogenic heat production in the Earth comes principally from ⁴⁰K, ²³²Th, ²³⁸U, and ²³⁵U (i.e., 99.5% in total) and a lesser amount from ⁸⁷Rb and ¹⁴⁷Sm (i.e., 0.5%). The Eart...

We report the Earth's rate of radiogenic heat production and (anti)neutrino luminosity from geologically relevant short-lived radionuclides (SLR) and long-lived radionuclides (LLR) using decay constants from the geological community, updated nuclear physics parameters, and calculations of the beta spectra. We carefully account for all branches in K...

Debate continues on the amount and distribution of radioactive heat producing elements (i.e., U, Th, and K) in the Earth, with estimates for mantle heat production varying by an order of magnitude. Constraints on the bulk-silicate Earth's (BSE) radiogenic power also places constraints on overall BSE composition. Geoneutrino detection is a direct me...

The link between the Milton pallasite and the South Byron Trio irons is examined through metallography and metallogaphic cooling rates; major, minor, and trace element compositions of metal; inclusion mineralogy and mineral compositions; and oxygen isotopic compositions. The metallic hosts of these Ni-rich meteorites (18.2–20.3 wt% Ni) are dominate...

Chondrites are undifferentiated sediments of material left over from the earliest solar system and are widely considered as representatives of the unprocessed building blocks of the terrestrial planets. The chondrites, along with processed igneous meteorites, have been divided into two broad categories based upon their isotopic signatures; these ha...

Models that envisage successful subduction channel transport of upper crustal materials below 300 km depth, past a critical phase transition in buoyant crustal lithologies, are capable of accumulating and assembling these materials into so-called "second continents" that are gravitationally stabilized at the base of the Transition Zone, at some 600...

This report highlights two different types of cross-talk in the photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube detector has 24 $8 \times 8$-anode Photonis MCP-PMTs Planacon XP85012, totalling 1536 individual pixels viewing the 2-liter cube of plastic scintillator.

This report highlights two different types of cross-talk in the photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube detector has 24 8 × 8-anode Photonis MCP-PMT Planacon XP85012, totalling 1536 individual pixels viewing the 2-liter cube of plastic scintillator.

SNOLAB is one of the deepest underground laboratories in the world with an overburden of 2092 m. The SNO+ detector is designed to achieve several fundamental physics goals as a low-background experiment, particularly measuring the Earth's geoneutrino flux. Here we evaluate the effect of the 2 km overburden on the predicted crustal geoneutrino signa...

Refractory lithophile element ratios of enstatite chondrite components are variable, suggesting chemical fractionations in a reduced nebula condition.

Radioactive decay of potassium (K), thorium (Th), and uranium (U) power the Earth's engine, with variations in 232Th/238U recording planetary differentiation, atmospheric oxidation, and biologically mediated processes. We report several thousand $^{232}$Th/$^{238}$U ($\kappa$) and time-integrated Pb isotopic ($\kappa$$_{Pb}$) values and assess thei...

Regional characterization of the continental crust has classically been performed through either geologic mapping, geochemical sampling, or geophysical surveys. Rarely are these techniques fully integrated, due to limits of data coverage, quality, and/or incompatible datasets. We combine geologic observations, geochemical sampling, and geophysical...

Regional characterization of the continental crust has classically been performed through either geologic mapping, geochemical sampling, or geophysical surveys. Rarely are these techniques fully integrated, due to limits of data coverage, quality, and/or incompatible datasets. We combine geologic observations, geochemical sampling, and geophysical...

We present a new approach for evaluating existing crustal models using ambient noise datasets and its associated uncertainties. We use a transdimensional hierarchical Bayesian inversion (THBI) approach to invert ambient noise surface wave phase dispersion maps for Love and Rayleigh waves using measurements obtained from Ekstrom (2014). Spatiospectr...

The China Jinping Underground Laboratory (CJPL), which has the lowest cosmic-ray muon flux and the lowest reactor neutrino flux of any laboratory, is ideal to carry out low-energy neutrino experiments. With two detectors and a total fiducial mass of 2000 tons for solar neutrino physics (equivalently, 3000 tons for geo-neutrino and supernova neutrin...

Lower crustal recycling depletes the continental crust of Eu and Sr and returns Eu and Sr enriched materials into the man- tle (e.g., Tang et al., 2015, Geology). To test the hypothesis that the MORB source mantle balances the Eu and Sr deficits in the continental crust, we carried out high precision Eu/Eu* and Sr/Sr* measurement for 72 MORB glasse...

Rare earth elements such as neodymium and samarium are ideal for probing the neutron environment that spent nuclear fuels are exposed to in nuclear reactors. The large number of stable isotopes can provide distinct isotopic signatures for differentiating the source material for nuclear forensic investigations. The rare-earth elements were isolated...

The Earth's engine is driven by unknown proportions of primordial energy and heat produced in radioactive decay. Unfortunately, competing models of Earth's composition reveal an order of magnitude uncertainty in the amount of radiogenic power driving mantle dynamics. Recent measurements of the Earth's flux of geoneutrinos, electron antineutrinos fr...

Panamá Viejo, founded in 1519 by the Spanish explorer Pedrarias Dávila, was the first permanent European settlement on the Pacific Ocean, and became a city, by royal decree, in 1521. Shortly after its creation, the city became an important base for trade with Spain. In 1671, the English pirate Henry Morgan waged an attack on Panamá Viejo, which res...

In the heart of the Creighton Mine near Sudbury (Canada), the SNO+ detector is foreseen to observe almost in equal proportion electron antineutrinos produced by U and Th in the Earth and by nuclear reactors. SNO+ will be the first long baseline experiment to measure a reactor signal dominated by CANDU cores (~55% of the total reactor signal), which...

Seismic tomography models reveal two large low shear velocity provinces (LLSVPs) that identify large-scale variations in temperature and composition in the deep mantle. Other characteristics include elevated density, elevated bulk sound speed, and sharp boundaries. We show that properties of LLSVPs can be explained by the presence of small quantiti...