[1] Flow of the mid-crust in the Tibetan Plateau may strongly influence the patterns of deformation and topography within this area. This flow requires the lowercrust to have low viscosity and so quantifying this viscosity may be used to test the idea of channel flow. An application of Bayesian methods to geologic and geodetic data from north central Tibet yields lower-crustal viscosities (assu...

a r t i c l e i n f o Keywords: Lithium isotopes A-type granite Mafic enclave Continental crust Lithium concentrations and isotopic compositions of 39 A-type granites and mafic enclaves from 11 plutons in Northeast China and the North China craton are used to constrain their genesis and to characterize further the average composition of the continental crust. Lithium concentrations (2.8 to 80 p...

S U M M A R Y Rayleigh wave phase velocity maps in southern Africa are obtained at periods from 6 to 40 s using seismic ambient noise tomography applied to data from the Southern Africa Seismic Experiment (SASE) deployed between 1997 and 1999. These phase velocity maps are combined with those from 45 to 143 s period which were determined previously using a two-planewave method by Li & Burke. In...

3.18.3 CHARACTERISTICS OF ARC MAGMAS 7 3.18.3.1 Comparison with MORBs 7 3.18.3.1.1 Major elements 7 3.18.3.1.2 We are cautious about fractionation correction of major elements 9 3.18.3.1.3 Distinctive, primitive andesites 11 3.18.3.1.4 Major elements in calc-alkaline batholiths 11 3.18.3.2 Major and Trace-Element Characteristics of Primitive Arc Magmas 18 3.18.3.2.1 Primitive basalts predominat...

In some places, there is strong evidence that the lower continental crust has flowed so as to smooth out variations in crustal thickness caused by differential crustal extension or shortening. In order to better understand the processes involved, we investigate the behavior of a fluid layer over a fluid half-space to see how such a system responds to the deformation of its upper and lower bound...

The impact of mechanical layering and the strength of the Indian lower crust on the dynamics of the modern India-Asia collisional system are studied using 3-D thermomechanical modeling. The model includes an Indian oceanic domain, Indian continental domain, and an Asian continental domain. Each domain consists of four layers: upper/lower crust, and upper/lower lithospheric mantle. The Tarim and...

[1] We report some of the first noble gas data for in situ lower oceanic crust and shallow mantle. From a suite of gabbros and peridotites recovered from the Atlantis Bank oceanic core complex on the Southwest Indian Ridge, we measured He, Ne, Ar, Kr and Xe concentrations as well as He/He and Ar/Ar ratios, there by documenting the noble gas content and signature of oceanic lithosphere. Except f...

In the southern Tibetan plateau, which is considered to be the ongoing India–Eurasia continental collision zone, tracing of the Indian crustal front beneath Tibet is still controversial. We conducted deep subsurface electrical modeling in southern Tibet and discuss the geometry of the front of the Indian crust. Three areas along the Yarlung-Zangbo river zone for which previous magnetotelluric (...