Journal ArticleDOI
Preservation of ancient and fertile lithospheric mantle beneath the southwestern United States.
Cin-Ty A. Lee,Cin-Ty A. Lee,Qing-Zhu Yin,Roberta L. Rudnick,Roberta L. Rudnick,Stein B. Jacobsen +5 more
TLDR
It is suggested that depleted mantle is intrinsically less dense than fertile mantle (due to iron having been lost when melt was extracted from the rock), which allows the depleted mantle to form a thicker thermal boundary layer between the deep convecting mantle and the crust, thus reducing tectonic activity at the surface.Abstract:
Stable continental regions, free from tectonic activity, are generally found only within ancient cratons—the centres of continents which formed in the Archaean era, 4.0–2.5 Gyr ago. But in the Cordilleran mountain belt of western North America some younger (middle Proterozoic) regions have remained stable, whereas some older (late Archaean) regions have been tectonically disturbed, suggesting that age alone does not determine lithospheric strength and crustal stability. Here we report rhenium–osmium isotope and mineral compositions of peridotite xenoliths from two regions of the Cordilleran mountain belt. We found that the younger, undeformed Colorado plateau is underlain by lithospheric mantle that is 'depleted' (deficient in minerals extracted by partial melting of the rock), whereas the older (Archaean), yet deformed, southern Basin and Range province is underlain by 'fertile' lithospheric mantle (not depleted by melt extraction). We suggest that the apparent relationship between composition and lithospheric strength, inferred from different degrees of crustal deformation, occurs because depleted mantle is intrinsically less dense than fertile mantle (due to iron having been lost when melt was extracted from the rock). This allows the depleted mantle to form a thicker thermal boundary layer between the deep convecting mantle and the crust, thus reducing tectonic activity at the surface. The inference that not all Archaean crust developed a strong and thick thermal boundary layer leads to the possibility that such ancient crust may have been overlooked because of its intensive reworking or lost from the geological record owing to preferential recycling.read more
Citations
More filters
Journal ArticleDOI
Lithospheric mantle duplex beneath the central Mojave Desert revealed by xenoliths from Dish Hill, California
TL;DR: In this paper, the authors used ultramafic xenoliths hosted in Plio-Pleistocene cinder cones to assess the relevance of this process to the evolution and composition of continental lithosphere.
Journal ArticleDOI
Crustal growth and tectonic evolution of the Mojave crustal province: Insights from hafnium isotope systematics in zircons
TL;DR: In this paper, U-Pb ages and Hf isotopic ratios in zircons from Proterozoic basement and three siliciciclastic cover sequences in southern California provide important insights into the formation of the southern Mojave crustal province and its incorporation into southwestern Laurentia.
Journal ArticleDOI
Origins of cratonic mantle discontinuities: A view from petrology, geochemistry and thermodynamic models
TL;DR: In this article, the authors integrate current knowledge on the physical properties, chemical composition, mineralogy and fabric of cratonic mantle with experimental and thermodynamic constraints on the formation and migration of melts, both below and within cratononic lithosphere, in order to find petrologically viable explanations for mid-lithospheric discontinuities.
Journal ArticleDOI
Buoyancy of the continental upper mantle
TL;DR: In this paper, the authors calculated normative densities for a "low-temperature" garnet and spinel peridotite xenolith suite using Mg# and showed that most of the peridots are positively buoyant with respect to the mantle at their temperatures and pressures of equilibration.
Journal ArticleDOI
Garnetite Xenoliths and Mantle-Water Interactions Below the Colorado Plateau, Southwestern United States
Douglas Smith,William L. Griffin +1 more
TL;DR: Garnetite xenoliths from ultramafic diatremes in northeastern Arizona provide insights into hydration and metasomatism in the mantle as discussed by the authors, and they contain more than 95% garnet, some of which has complex compositional zonation related to growth in fractures within grains.
References
More filters
Journal ArticleDOI
The composition of the Earth
William F. McDonough,Shen-Su Sun +1 more
TL;DR: In this paper, the authors compared the relative abundances of the refractory elements in carbonaceous, ordinary, and enstatite chondritic meteorites and found that the most consistent composition of the Earth's core is derived from the seismic profile and its interpretation, compared with primitive meteorites, and chemical and petrological models of peridotite-basalt melting relationships.
Journal ArticleDOI
Geothermobarometry in Four-phase Lherzolites II. New Thermobarometers, and Practical Assessment of Existing Thermobarometers
Gerhard P. Brey,T. Köhler +1 more
Journal ArticleDOI
Composition and development of the continental tectosphere
TL;DR: In this article, the Wilson cycle is used to balance the tectosphere by depleting the continental upper mantle in a basalt-like component, which stabilizes the old continental nuclei against convective disruption.
Journal ArticleDOI
Os, Sr, Nd, and Pb isotope systematics of southern African peridotite xenoliths: Implications for the chemical evolution of subcontinental mantle
TL;DR: Isotope analyses of Os, Sr, Nd, and Pb elements were caried out on twelve peridotite xenoliths from the Jagersfontein, Letseng-la-terae, Thaba Patsoa, Mothae, and Premier kimberlites of southern Africa, to investigate the timing and the nature of melt extraction from the continental lithosphere and its relation to the continent formation and stabilization.
Journal ArticleDOI
Proterozoic crustal history of the western United States as determined by neodymium isotopic mapping
TL;DR: In this article, three age provinces have been delineated, each generally northeast-southwest trending, having decreasing crystallization ages and increasing initial e nd values with increasing distance southeastward from the Archean craton.