During Cenozoic time, the Colorado Plateau was raised about 2 km above sea level. The most-recent and best-documented uplift of the plateau (;1 km) has been concentrated at its southwest margin between 6 and 1 Ma, whereas the eastern Colorado Plateau may have been at high elevations since Eocene time. To better understand the recent tectonic activity at the southwest margin of the Colorado Plat...

We report here the results of a petrographic and geochemical study of remarkably well-preserved kimberlites from the Kangamiut region in Greenland. The samples contain between 5 and 45% of olivine in the form of rounded “nodules”, each 1 to 5 mm in diameter. Most originally were single crystals but many consist of polycrystalline, monomineralic aggregates. Olivine compositions vary widely from ...

The effects of lateral variations in lithospheric thickness and mantle viscosity on surface motions in Laurentia are investigated using the Finite Element method. Both a simple axisymmetric ice model and a more realistic ice deglaciation model (ICE4G) are used to investigate the effects of lateral heterogeneity. Beside the laterally homogeneous reference model, six laterally heterogeneous model...

Here we report the first set of thallium (Tl) isotope data in alkaline rocks from North China Craton to constrain nature recycled materials metasomatized subcontinental lithospheric mantle. Samples Hekanzi and Saima complexes display Tl compositions (ε205Tl) identical present-day upper mantle continental crust, suggesting that neither low-temperature altered oceanic crust nor pelagic sediments ...

Several recent inversion studies have clearly indicated the lack of resolving power of the normal mode data set and the possible trade-offs among the various parameters. These studies have also shown that the final model is as dependent on the starting model as on the data set. It is therefore important to incorporate body wave data into any inversion scheme not only to gain resolution but also...

A mass imbalance exists in Earth for Nb, Ta, and possibly Ti: continental crust and depleted mantle both have subchondritic Nb/Ta, Nb/La, and Ti/Zr, which requires the existence of an additional reservoir with superchondritic ratios, such as refractory eclogite produced by slab melting. Trace element compositions of minerals in xenolithic eclogites derived from cratonic lithospheric mantle show...

This thesis consists of three papers examining problems related to the crustal structure, isostasy and subsidence history of aseismic ridges and mid-plate island chains. Analysis of gravity and bathymetry data across the Ninetyeast and eastern Walvis Ridges indicates these features are locally compensated by an overthickening of the oceanic crust. Maximum crustal thicknesses are 15-30 km. The w...