Results 321 to 330 of about 776,982 (368)

Sedimentary Rocks and Crustal Evolution: Tectonic Setting and Secular Trends

The Journal of geology, 1991
A significant change in the composition of turbidites deposited at active tectonic settings is seen at the Archean/post-Archean transition. In comparison to post-Archean active margin turbidites, Archean greenstone turbidites exhibit more uniform Th/Sc ...
S. McLennan, S. Taylor
semanticscholar   +1 more source

Mantle Convection for Geologists

, 2011
1. Introduction 2. Context 3. Why moving plates? 4. Solid, yielding mantle 5. Convection 6. The plate mode of convection 7. The plume mode of convection 8. Perspective 9. Evolution and tectonics 10. Mantle chemical evolution 11.
G. Davies
semanticscholar   +1 more source

The Late Cretaceous Impact of the Trindade Mantle Plume: Evidence from Large-volume, Mafic, Potassic Magmatism in SE Brazil

, 1995
S. A. GIBSON*, R. N. THOMPSON, O. H. LEONARDOS, A. P. DICKIN AND J. G. MITCHELL 'DEPARTMENT OF GEOLOGICAL SCIENCES, UNIVERSITY OF DURHAM, SOUTH ROAD, DURHAM DHi 3LE, UK "DEPARTMENTO DE GEOQUIMICA E RECURSOS MINERAIS, INSTITUTO DE GEOCIENCIAS ...
S. Gibson, R. Thompson, O. Leonardos, A. Dickin, J. G. Mitchell   +4 more
semanticscholar   +1 more source

Secular Variation in Economic Geology

, 2010
The temporal pattern of ore deposits on a constantly evolving Earth reflects the complex interplay between the evolving global tectonic regime, episodic mantle plume events, overall changes in global heat flow, atmospheric and oceanic redox states, and ...
R. Goldfarb, D. Bradley, D. Leach
semanticscholar   +1 more source

Phase Transformations and Differentiation in Subducted Lithosphere: Implications for Mantle Dynamics, Basalt Petrogenesis, and Crustal Evolution

The Journal of geology, 1982
Mantle pyrolite differentiates at mid-oceanic ridges to form a layered lithosphere consisting of a basaltic crust, immediately underlain by harzburgite and further underlain by pyrolite which has experienced depletion only of highly incompatible elements
A. .. Ringwood
semanticscholar   +1 more source

The Deep Roots of Geology: Tectonic History of Australia as expressed by Mantle Anisotropy 

2022
<p>Australia is an old stable continent with a rich geological history. Limitations in sub-surface seismic imaging below the Moho, however, mean that is unclear to what extent, and to what depth, this rich geological history is expressed in the mantle. Studies of seismic anisotropy, which reflect past/present mantle deformation, can offer
openaire   +1 more source

Mantle fluids in the San Andreas fault system

, 1997
Fluids associated with the San Andreas and companion faults in central and south-central California have high3He/4He ratios. The lack of correlation between helium isotopes and fluid chemistry or local geology requires that fluids enter the fault system ...
B. Kennedy, Y. Kharaka, W. Evans, A. Ellwood, D. DePaolo, J. J. Thordsen, G. Ambats, R. Mariner   +7 more
semanticscholar   +1 more source

Volcanic Arc Magmas: Implications of a Melting-Mixing Model for Element Recycling in the Crust-Upper Mantle System

The Journal of geology, 1980
A multicomponent melting-mixing model for the origin of volcanic arc basalt magmas implies signifi cant recycling of K, Rb, Ba, and other elements in the crust-upper mantel system.
R. Kay
semanticscholar   +1 more source

Upper-mantle origin of the Yellowstone hotspot

, 2002
Fundamental features of the geology and tectonic setting of the northeast-propagating Yellowstone hotspot are not explained by a simple deep-mantle plume hypothesis and, within that framework, must be attributed to coincidence or be explained by ...
R. L. Christiansen, G. Foulger, J. R. Evans   +2 more
semanticscholar   +1 more source

A Review of the geology and tectonics of the Kohistan island arc, north Pakistan

, 2010
This paper summarizes some 30 years of more intense recent work and almost 100 years of geological observations in Kohistan. The paper is divided into two section: an earlier factual-based section with minimal interpretation, and a later section ...
M. Petterson
semanticscholar   +1 more source