نتایج جستجو برای: crustal contamination

تعداد نتایج: 61183  

2015
James B. Chapman Mihai N. Ducea Peter G. DeCelles Lucia Profeta

Global compilations indicate that the geochemistry of arc magmatism is sensitive to Moho depth. Magmatic products are prevalent throughout the history of Cordilleran orogenesis and can be employed to constrain the timing of changes in crustal thickness as well as the magnitude of those changes. We investigate temporal variations in crustal thickness in the United States Cordillera using Sr/Y fr...

2008
Arun Srivastava Sandeep Gupta V. K. Jain

Source apportionment of total suspended particulate matter (TSPM) and associated heavy metals has been carried out for the city of Delhi using the Chemical Mass Balance Model, Version 8 (CMB8), as well as principle component analysis (PCA) of SPSS (Varimax Rotated Factor Matrix method) in coarseand fine-size mode. Urban particles were collected using a five-stage impactor at six sites in the wi...

2001
M. Brown

Crustally-derived granites may be generated in a variety of tectonic settings, but whatever the ultimate causse of heating crustal thickening, crustal extension, enhanced heat flux from the mantle, or magmatic advection by mantle-derived melts crustal melting likely occurs in a dynamic environment. Under these conditions deviatoric stress acting on an anisotropic crustal source region will lead...

2007
Xisheng Xu Suzanne Y. O’Reilly Xiaolei Wang Zhenyu He

U–Pb dating and Hf-isotope data from detrital zircons have been used to analyse the crustal evolution of the eastern and western arts of the Cathaysia Block in SE China. Zircons from the Oujiang River in eastern Cathaysia indicate that the basement is ominantly Paleoproterozoic (1850–1870 Ma, 2100–2400 Ma) in age with minor Archean components; it was extensively reworked n Jurassic–Cretaceous t...

2004
Mark A. Wieczorek Maria T. Zuber

[1] The average crustal thickness of the southern highlands of Mars was investigated by calculating geoid-to-topography ratios (GTRs) and interpreting these in terms of an Airy compensation model appropriate for a spherical planet. We show that (1) if GTRs were interpreted in terms of a Cartesian model, the recovered crustal thickness would be underestimated by a few tens of kilometers, and (2)...

2003
Anne M. Johansen Michael R. Hoffmann

[1] Ambient aerosol samples were collected over the Arabian Sea during the month of March of 1997, aboard the German R/V Sonne, as part of the German Joint Global Ocean Flux Study (JGOFS) project. This is the third study in a series of analogous measurements taken over the Arabian Sea during different seasons of the monsoon. Dichotomous high-volume collector samples were analyzed for ferrous ir...

2007
D. V. Helmberger X. J. Song L. Zhu

We construct a two-dimensional velocity section sampling the Mojave crustal block in southern California by modeling shear wave (SH) seismograms. Our approach uses individual generalized rays computed from a layered model. The model is divided into blocks with variable velocity perturbations uch that ray responses are allowed to shift relative to each other to maximize synthetic waveform fits t...

2010
Kelly H. Liu Stephen S. Gao

[1] The Hoggar swell in Algeria is one of the significant massifs of northwest Africa. The paucity of high‐ resolution geophysical studies of the crust and mantle beneath the massifs is mostly responsible for the heated debates about the depth of the source region of the Cenozoic volcanism and the closely related uncertainty about the mechanism that formed and maintains the high elevation of th...

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