Journal ArticleDOI
Thermal regime of the southern Basin and Range Provincec 1. Heat flow data from Arizona and the Mojave Desert of California and Nevada
John H. Sass,Arthur H. Lachenbruch,S. P. Galanis,Paul Morgan,Susan S. Priest,T. H. Moses,Robert J. Munroe +6 more
TLDR
In this article, heat flow in the Salton Trough and its neighboring ranges, the Death Valley fault zone and its southward extension along the eastern boundary of the Mojave block, and zones of shallow depth l <10 kmr to the Curie isotherm were inferred from aerornagnetic data.Abstract:
With about 150 new heat flow values, more than 200 values of heat flow are now available from the crystalline terranes of southern California, the Basin and Range Province of Arizona, and Paleozoic sedimentary rocks of the southwestern Colorado Plateau lCPr. Heat flow ranges from about 5 mW m−2 on the CP near Flagstaff, Arizona, to more than 150 mW m−2 in the crystalline rocks bordering the Salton Trough in SE California. The heat flow pattern within this region is complex, although it correlates with regional physiographic and tectonic features. Unlike the adjacent Sierra Nevada Batholith where heat flow is a linear function of nearhsurface radiogenic heat production, no statistically significant correlation exists between heat flow and heat production in the study area, possibly because of its complex tectonic history, involving lateral movement of basement terranes, and relatively young heat sources and sinks of different strengths, ages, and durations. Contemporary and Neogene extensional tectonism appears to be responsible for the very high heat flow l>100 mW m−2r associated with the Salton Trough and its neighboring ranges, the Death Valley fault zone and its southward extension along the eastern boundary of the Mojave block, and zones of shallow depth l<10 kmr to the Curie isotherm las inferred from aerornagnetic datar in west central Arizona. Low l<60 mW m−2r heat flow in the Peninsular Ranges and eastern Transverse Ranges of California may be caused by downward advection associated with subduction and compressional tectonics. Relatively low heat flow l67±4 mW m−2r is also associated with the main trend of metamorphic core complexes in Arizona, and the outcropping rocks in the core complexes have a low radioactive heat production l1.3±0.3 μW m−3r compared to the other crystalline rocks in the region l2.1±0.2 μW m−3r.read more
Citations
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Lateral variation in upper mantle viscosity: role of water
TL;DR: In this paper, geochemical data on the water contents of western US lavas and mantle xenoliths, compared these data to water solubility in olivine, and calculate the corresponding effective viscosity of olivines, the major constituent of the upper mantle, using a power law creep rheological model.
Journal ArticleDOI
Water contents in mantle xenoliths from the Colorado Plateau and vicinity: Implications for the mantle rheology and hydration-induced thinning of continental lithosphere
Abstract: [1] Nominally anhydrous minerals (e.g., olivine, clinopyroxene, and orthopyroxene) in peridotite xenoliths collected from the Colorado Plateau and southern Basin and Range in western North America were systematically analyzed by Fourier transform infrared spectroscopy for water contents. Measured water contents range from 2 to 45 ppm for olivine, from 53 to 402 ppm for orthopyroxene, and from 171 to 957 ppm for clinopyroxene. The Colorado Plateau has the highest water contents (up to 45 ppm H2O in olivine, 402 ppm H2O in orthopyroxene, and 957 ppm H2O in clinopyroxene), while San Carlos in the southern Basin and Range has the lowest water contents (up to 4 ppm H2O in olivine, 82 ppm H2O in orthopyroxene, and 178 ppm H2O in clinopyroxene). With the exception of San Carlos, the olivine and pyroxenes from all other localities (Dish Hill, Grand Canyon, and Navajo) have water contents close to or higher than that inferred for the fertile asthenospheric mantle. We interpret the high water contents measured here to have been introduced into the base of the lithospheric mantle by rehydration associated with the subduction of the Farallon plate beneath North America during the early Cenozoic. Application of an updated flow law for dislocation creep of wet olivine to lithospheric mantle conditions beneath the Colorado Plateau predicts that for a given background shear stress, hydration alone can result in approximately 1 order of magnitude drop in the effective viscosity at the base of the lithosphere. If viscosity alone is used to distinguish the lithosphere from underlying asthenosphere, this suggests that hydration could have resulted in more than 10 km of lithospheric thinning. Viscosity reduction and lithospheric thinning of even larger extents (up to ∼100 km) are predicted when thicker lithosphere (such as Archean cratons) and larger water contents (up to water-saturated conditions) are considered. If our interpretations are correct, the implications of our study go beyond western North America and hint at a possible way of recycling continental mantle, including cratonic mantle, back into the convecting mantle.
Journal ArticleDOI
Mobility of continental mantle: Evidence from postseismic geodetic observations following the 1992 Landers earthquake
TL;DR: In this article, a combination of Global Positioning System (GPS) and Synthetic Aperture Radar (InSAR) data collected during a ∼3-year epoch following the 1992 Landers earthquake was used to investigate postseismic mechanisms responsible for the high transient velocities.
Journal ArticleDOI
Heat flow in the Indian shield
Sukanta Roy,R.U.M. Rao +1 more
TL;DR: In this article, new heat flow values have been determined for the Indian shield, including 28 from the Archaean Dharwar craton, one from the Proterozoic Cuddapah basin of southern India, four from the southern part of the Aravalli mobile belt of northwestern India, and 37 from the Cretaceous-Eocene Deccan Volcanic Province (DVP) of central India.
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
TL;DR: 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.
References
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Journal ArticleDOI
Heat flow and energetics of the San Andreas Fault Zone
TL;DR: In this article, the authors show that there is no evidence for local factional heating of the main fault trace at any latitude over a 1000 km length from Cape Mendocino to San Bernardino, and average heat flow is high (∼2 HFU, ∼80 mW m−2) throughout the 550 km segment of the Coast Ranges that encloses the San Andreas fault zone in central California.
Journal ArticleDOI
Rates of vertical groundwater movement estimated from the Earth's thermal profile
TL;DR: In this article, an analytical solution was developed describing vertical steady flow of groundwater and heat through an isotropic, homogeneous, and fully saturated semiconfining layer, and a type-curve method for estimating groundwater velocities from temperature data was presented.
Journal ArticleDOI
Cordilleran metamorphic core complexes: Cenozoic extensional relics of Mesozoic compression
Peter J. Coney,Tekla A. Harms +1 more
TL;DR: In this article, a model that unifies the age and tectonic significance of the Cordilleran metamorphic core complexes was proposed, which reconciles opposing views of the core complexes and places them in a more comprehensible setting with respect to Mesozoic-Cenozoic thermotectonic history.
Journal ArticleDOI
Evolution of pull‐apart basins and their scale independence
Atilla Aydin,Amos Nur +1 more
TL;DR: In this paper, a simple model suggests that the width of the pull-apart basins is controlled by the initial fault geometry, whereas the length increases with increasing fault displacement, and two possible mechanisms responsible for the increase in width are suggested: coalescence of neighboring rhomb grabens as each graben increases its length and formation of fault strands parallel to the existing ones when large displacements need to be accommodated.
Journal ArticleDOI
Crustal temperature and heat production: Implications of the linear heat‐flow relation
TL;DR: The linear relation between surface heat flow and heat production in plutons is easily explained in terms of an exponential decrease of heat production with depth in the crust as discussed by the authors, which is the only possible explanation, provided that three other assumptions that seem geologically reasonable are made.
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