Earths Deep Mantle

This book presents the first overview of the composition and structure of the Earth’s lower mantle. The first part focuses on the study of lower-mantle minerals, identified as inclusions in diamonds from different regions of the world. Three associations are established among the lower-mantle minerals: ultramafic, mafic, and carbonatic. The carbonatic association is of particular interest because it characterizes the media of natural diamond formation. In turn, the second part analyzes the structure of the lower mantle, revealing its heterogeneous composition. It is based on the results of experiments demonstrating phase transitions in lower-mantle minerals, and on seismological data. Deep-seated earthquakes point to the presence within the lower mantle of numerous seismic boundaries caused by mineral structure transitions. In closing, the last part of the book compares observed data with experimental data, highlighting several discrepancies that indicate Earth may have a more complex planetary history than previously assumed, and examining its primarily non-chondritic composition.

Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 160. Understanding the inner workings of our planet and its relationship to processes closer to the surface remains a frontier in the geosciences. Manmade probes barely reach ˜10 km depth and volcanism rarely brings up samples from deeper than ˜150 km. These distances are dwarfed by Earth's dimensions, and our knowledge of the deeper realms is pieced together from a range of surface observables, meteorite and solar atmosphere analyses, experimental and theoretical mineral physics and rock mechanics, and computer simulations. A major unresolved issue concerns the nature of mantle convection, the slow (1-5 cm/year) solid-state stirring that helps cool the planet by transporting radiogenic and primordial heat from Earth's interior to its surface. Expanding our knowledge here requires input from a range of geoscience disciplines, including seismology, geodynamics, mineral physics, and mantle petrology and chemistry. At the same time, with better data sets and faster computers, seismologists are producing more detailed models of 3-D variations in the propagation speed of different types of seismic waves; new instrumentation and access to state-of-the-art community facilities such as synchrotrons have enabled mineral physicists to measure rock and mineral properties at ever larger pressures and temperatures; new generations of mass spectrometers are allowing geo-chemists to quantify minute concentrations of diagnostic isotopes; and with supercomputers geodynamicists are making increasingly realistic simulations of dynamic processes at conditions not attainable in analogue experiments. But many questions persist. What causes the lateral variations in seismic wavespeed that we can image with mounting accuracy? How reliable are extrapolations of laboratory measurements on simple materials over many orders of magnitude of pressure and temperature? What are the effects of volatiles and minor elements on rock and mineral properties under extreme physical conditions? Can ab initio calculations help us understand material behavior in conditions that are still out of reach of laboratory measurement? What was the early evolution of our planet and to what extent does it still influence present-day dynamics? And how well do we know such first-order issues as the average bulk composition of Earth?

This book highlights and discusses recent developments that have contributed to an improved understanding of observed mantle heterogeneities and their relation to the thermo-chemical state of Earth's mantle, which ultimately holds the key to unlocking the secrets of the evolution of our planet. This series of topical reviews and original contributions address 4 themes. Theme 1 covers topics in geophysics, including global and regional seismic tomography, electrical conductivity and seismic imaging of mantle discontinuities and heterogeneities in the upper mantle, transition zone and lower mantle. Theme 2 addresses geochemical views of the mantle including lithospheric evolution from analysis of mantle xenoliths, composition of the deep Earth and the effect of water on subduction-zone processes. Theme 3 discusses geodynamical perspectives on the global thermo-chemical structure of the deep mantle. Theme 4 covers application of mineral physics data and phase equilibrium computations to infer the regional-scale thermo-chemical structure of the mantle.

A multidisciplinary perspective on the dynamic processes occurring in Earth's mantle The convective motion of material in Earth's mantle, powered by heat from the deep interior of our planet, drives plate tectonics at the surface, generating earthquakes and volcanic activity. It shapes our familiar surface landscapes, and also stabilizes the oceans and atmosphere on geologic timescales. Mantle Convection and Surface Expressions brings together perspectives from observational geophysics, numerical modelling, geochemistry, and mineral physics to build a holistic picture of the deep Earth. It explores the dynamic processes occurring in the mantle as well as the associated heat and material cycles. Volume highlights include: Perspectives from different scientific disciplines with an emphasis on exploring synergies Current state of the mantle, its physical properties, compositional structure, and dynamic evolution Transport of heat and material through the mantle as constrained by geophysical observations, geochemical data and geodynamic model predictions Surface expressions of mantle dynamics and its control on planetary evolution and habitability The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.

Deep Earth: Physics and Chemistry of the Lower Mantle and Core highlights recent advances and the latest views of the deep Earth from theoretical, experimental, and observational approaches and offers insight into future research directions on the deep Earth. In recent years, we have just reached a stage where we can perform measurements at the conditions of the center part of the Earth using state-of-the-art techniques, and many reports on the physical and chemical properties of the deep Earth have come out very recently. Novel theoretical models have been complementary to this breakthrough. These new inputs enable us to compare directly with results of precise geophysical and geochemical observations. This volume highlights the recent significant advancements in our understanding of the deep Earth that have occurred as a result, including contributions from mineral/rock physics, geophysics, and geochemistry that relate to the topics of: I. Thermal structure of the lower mantle and core II. Structure, anisotropy, and plasticity of deep Earth materials III. Physical properties of the deep interior IV. Chemistry and phase relations in the lower mantle and core V. Volatiles in the deep Earth The volume will be a valuable resource for researchers and students who study the Earth's interior. The topics of this volume are multidisciplinary, and therefore will be useful to students from a wide variety of fields in the Earth Sciences.

Deep Earth: Physics and Chemistry of the Lower Mantle and Core highlights recent advances and the latest views of the deep Earth from theoretical, experimental, and observational approaches and offers insight into future research directions on the deep Earth. In recent years, we have just reached a stage where we can perform measurements at the conditions of the center part of the Earth using state-of-the-art techniques, and many reports on the physical and chemical properties of the deep Earth have come out very recently. Novel theoretical models have been complementary to this breakthrough. These new inputs enable us to compare directly with results of precise geophysical and geochemical observations. This volume highlights the recent significant advancements in our understanding of the deep Earth that have occurred as a result, including contributions from mineral/rock physics, geophysics, and geochemistry that relate to the topics of: I. Thermal structure of the lower mantle and core II. Structure, anisotropy, and plasticity of deep Earth materials III. Physical properties of the deep interior IV. Chemistry and phase relations in the lower mantle and core V. Volatiles in the deep Earth The volume will be a valuable resource for researchers and students who study the Earth's interior. The topics of this volume are multidisciplinary, and therefore will be useful to students from a wide variety of fields in the Earth Sciences.

Plate tectonics can drift continents and push up mountains, but what drives the plates? This is an insider’s account of how we answered questions posed over two centuries ago, and completed geology’s quest for a driving mechanism. Forging through confusing evidence, apparent contradictions and raging debates we arrived at not one but two mechanisms: sinking plates and rising plumes.

A technique for visualizing Earth's subsurface at high resolution Hidden out of sight in Earth’s subsurface are a range of geophysical structures, processes, and material movements. Muography is a passive and non-destructive remote sensing technique that visualizes the internal structure of solid geological structures at high resolution, similar in process to X-ray radiography of human bodies. Muography: Exploring Earth's Subsurface with Elementary Particles explores the application of this imaging technique in the geosciences and how it can complement conventional geophysical observations. Volume highlights include: Principles of muography and pioneering works in the field Different approaches for muographic image processing Observing volcanic structures and activity with muography Using muography for geophysical exploration and mining engineering Potential environmental applications of muography Latest technological developments in muography The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.