Assembly, configuration, and break-up history of Rodinia: A synthesis

Basaltic volcanism 'samples' the Earth's mantle to great depths, because solid-state convection transports deep material into the (shallow) melting region. The isotopic and trace-element chemistry of these basalts shows that the mantle contains several isotopically and chemically distinct components, which reflect its global evolution. This evolution is characterized by upper-mantle depletion of many trace elements, possible replenishment from the deeper, less depleted mantle, and the recycling of oceanic crust and lithosphere, but of only small amounts of continental material.

Mantle geochemistry: the message from oceanic volcanism

This book is a tutorial written by researchers and developers behind the FEniCS Project and explores an advanced, expressive approach to the development of mathematical software. The presentation spans mathematical background, software design and the use of FEniCS in applications. Theoretical aspects are complemented with computer code which is available as free/open source software. The book begins with a special introductory tutorial for beginners. Followingare chapters in Part I addressing fundamental aspects of the approach to automating the creation of finite element solvers. Chapters in Part II address the design and implementation of the FEnicS software. Chapters in Part III present the application of FEniCS to a wide range of applications, including fluid flow, solid mechanics, electromagnetics and geophysics.

Automated Solution of Differential Equations by the Finite Element Method: The FEniCS Book

The Visual Display of Quantitative Information

[1] The Solonker suture records the termination of the central Asian Orogenic Belt (CAOB). However, tectonic development of the Solonker suture is poorly understood. We report new field data for the Ondor Sum melange in the Ulan valley, and present a new evaluation of the orogenic belt extending from the southern Mongolia cratonic boundary to the north China craton within the context of a new geological framework and tectonic model, which incorporates relevant data from the literature. The southern accretionary zone between the north China craton and the Solonker suture is characterized by the Mid-Ordovician-Early Silurian Ulan island arc-Ondor Sum subduction-accretion complex and the Bainaimiao arc. This zone was consolidated by the Carboniferous-Permian when it evolved into an Andean-type magmatic margin above a south dipping subduction zone. The northern accretionary zone north of the Solonker suture extends southward from a Devonian to Carboniferous active continental margin, through the Hegenshan ophiolite-arc accretionary complex to the Late Carboniferous Baolidao arc associated with some accreted Precambrian blocks. This northern zone had consolidated by the Permian when it developed into an Andean-type magmatic margin above a north dipping subduction zone. Final subduction of the central Asian ocean caused the two opposing active continental margins to collide, leading to formation of the Solonker suture in the end-Permian. Predominant northward subduction during final formation of the suture gave rise in the upper northern plate to a large-scale, postcollisional, south directed thrust and fold belt in the Triassic-Jurassic. In summary, the CAOB underwent three final stages of tectonic development: early Japanese-type accretion, Andean-type magmatism, and Himalayan-type collision.

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Accretion leading to collision and the Permian Solonker suture, Inner Mongolia, China: Termination of the central Asian orogenic belt

A boundary between compositionally distinct regions at a depth of about 1600 kilometers may explain the seismological observations pertaining to Earth's lower mantle, produce the isotopic signatures of mid-ocean ridge basalts and oceanic island basalts, and reconcile the discrepancy between the observed heat flux and the heat production of the mid-ocean ridge basalt source region. Numerical models of thermochemical convection imply that a layer of material that is intrinsically about 4 percent more dense than the overlying mantle is dynamically stable. Because the deep layer is hot, its net density is only slightly greater than adiabatic and its surface develops substantial topography.

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Compositional stratification in the deep mantle

The D″ Discontinuity and its Implications

Ultralow Velocity Zone at the Core-Mantle Boundary

The "ophiolite conundrum" describes the conflict in many ophiolite complexes between (1) structural and stratigraphic evidence for seafloor spreading in a non-island-arc environment and (2) geochemical evidence for derivation of magmas from highly depleted mantle similar to that found at present over subduction zones ("supra-subduction zone" settings). Tethyan ophiolites provide many excellent examples of the conundrum. These complexes crop out in four major belts from the western Mediterranean to the Himalaya. Many bodies display a complete ophiolite sequence (e.g., Troodos, Cyprus, and Semail, Oman), whereas others display only a partial sequence, characteristically with lavas and/or sedimentary rocks overlying serpentinized peridotite (e.g., western Mediterranean complexes, parts of Kizildag, Turkey). Chemical compositions of the lavas in these ophiolites range from standard E-MORBs (enriched mid-oceanic-ridge basalts) to highly depleted magmas (e.g., low in Nb, Ta, Ti, and some other trace elements), reminiscent of modern volcanic-arc and backarc basin (supra-subduction zone) settings. Geologic or stratigraphic evidence for any extensive arc edifice is generally lacking, and most complexes are overlain by pelagic sedimentary rocks. Modern mid-ocean ridges show compositional variations reflecting incomplete mixing of mantle components. Some mid-oceanic ridge lavas display trace element signatures (i.e., incompatible element enrichment) unlike those of MORB affinity but reminiscent of the supra-subduction zone field. These data and a new model for a two-layer mantle of depleted material in the upper 1500 km and denser, enriched mantle below suggest a resolution of the ophiolite conundrum. In this model, the composition of mantle tapped by oceanic spreading centers for the past 1100 m.y. is nonuniform or "historically contingent," i.e., it depends upon the prior history of spreading and subduction. Spreading-center magma compositions may have varied just as the patterns of continental assembly and fragmentation have altered the tectonic arrangement of Earth's surface.

Louise H. Kellogg

Papers

Compositional stratification in the deep mantle

The D″ Discontinuity and its Implications

Ultralow Velocity Zone at the Core-Mantle Boundary

Tethyan ophiolites, mantle convection, and tectonic historical contingency: A resolution of the ophiolite conundrum

The role of plumes in mantle helium fluxes