[1] We argue that by fracturing rock, not by raising it relative to base level, tectonics plays its most important role in causing rapid incision of valleys and rapid erosion of hillslopes. Tectonic deformation riddles the upper crust with fractures, which not only provide avenues for water flow and thus promote weathering and further disintegration of rock but also fragment bedrock into debris...

The titanium concentrations of 484 zircons with U-Pb ages of *1 Ma to 4.4 Ga were measured by ion microprobe. Samples come from 45 different igneous rocks (365 zircons), as well as zircon megacrysts (84) from kimberlite, Early Archean detrital zircons (32), and zircon reference materials (3). Samples were chosen to represent a large range of igneous rock compositions. Most of the zircons contai...

Magma genesis, migration, and eruption have played prominent roles in the chemical differentiation of the Earth. Plate tectonics has provided the framework of tectonic environments for different suites of igneous rocks and the dynamic mechanisms for moving masses of rock into melting regions. Petrology is rooted in geophysics. Petrological and geophysical processes are calibrated by the phase e...

The Etive igneous complex has intruded into Dalradian and Moine meta-sedimentary rocks in Devonian. Main rock types of the complex are granodiorite, monzodiorite, monzogranite, granite and diorite. Geochemical studies show that the magmas were of high K calc-alkaline, I-type and metaluminous nature. Application of discriminant diagrams to the Etive rocks indicates a possible within-plate tecton...

Geochemical signatures throughout the layered Earth require significant mass transfer through the lower crust, yet geological pathways are under-recognized. Elongate bodies of basic to ultrabasic rocks are ubiquitous in exposures of the lower crust. Ultrabasic hornblendite bodies hosted within granulite facies gabbroic gneiss of the Pembroke Valley, Fiordland, New Zealand, are typical occurrenc...