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
Re–Os isotope systematics of Archean chromitites from the Chimalpahad Anorthosite Complex, south-east India: Implications for mantle extraction processes
TL;DR: The Chimalpahad Anorthosite Complex is located within the Archean Peninsular Gneissic Complex in the SE Indian shield as mentioned in this paper, which contains layers of chromitites and associated websterites and anorthosites.
Journal ArticleDOI
Hard-cored continents
TL;DR: Each continent contains pockets of ancient crust that appear to have been unaffected by tectonic forces since they formed billions of years ago, according to scientists.
Journal ArticleDOI
Geochemical study of Cenozoic mafic volcanism in the west-central Great Basin, western Nevada, and the Ancestral Cascades Arc, California
TL;DR: In this paper, a transect across the west-central Great Basin (GB) in Nevada to the Ancestral Cascade Arc (ACA) in the northern Sierra Nevada, California (∼39°-40° latitude) was sampled along a traning across the Eocene to Mio-Pliocene volcanic rocks.
Journal ArticleDOI
Decoupled water and iron enrichments in the cratonic mantle: A study on peridotite xenoliths from Tok, SE Siberian Craton
TL;DR: In this paper, the authors used polarized Fourier transform infrared spectroscopy (FTIR) to obtain water content in olivine, orthopyroxene (Opx), and clinopyroxenes (Cpx) of 14 Tok xenoliths.
Journal ArticleDOI
Late‐Cretaceous construction of the mantle lithosphere beneath the central California coast revealed by Crystal Knob xenoliths
TL;DR: In this article, the authors examined six peridotite samples ranging from fertile lherzolites to harzburgite residues and concluded that the mantle lithosphere beneath the central California coast was emplaced after Cretaceous flat slab subduction and records a thermal signature of Neogene subduction of the Pacific‐Farallon ridge.
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.