The Basin and Range Province of the western United States is one of Earth’s most studied regions of continental rifting, and yet the timing and character of the onset of Cenozoic extension are still controversial. Some structural studies have concluded that extension in the Great Basin part of the Basin and Range Province is as old as 41–37 Ma (Rahl and others, 2002) or 32–30 Ma (e.g., Axen and...

Zircon U-Pb dating is a powerful and widely used geochronologic technique to constrain the timing rates of magmatic high lower-grade metamorphic processes, as well sediment provenance. trace element (TE) compositions also record processes during zircon growth. In this study, laser ablation split-stream (LA-SS)-ICP-MS TE depth-profiling novel two-dimensional mapping techniques are in combination...

tertiary andesitic basalts of the sirjan area, urmieh-dokhtar magmatic arc, iran, contain plagioclase phenocrysts enclosed in a matrix of amphibole, clinopyroxene and rare olivine crystals. textural and compositional evidence suggests two significantly different types of plagioclase phenocrysts occur in the andesitic basalts. the most common type of plagioclase phenocrysts have zoning patterns ...

The Ross orogen of Antarctica is one of Earth’s great Phanerozoic mountain belts. It is thought from igneous geochemistry, deformation patterns, and sedimentation history to be the result of late Neoproterozoic and early Paleozoic plate-margin convergence between paleo-Pacifi c oceanic lithosphere and continental lithosphere represented by the composite East Antarctic shield. Convergence along ...

The total magmatic output in modern arcs, where continental crust is now being formed, is believed to derive from melting of the mantle wedge and is largely basaltic. Globally averaged continental crust, however, has an andesitic bulk composition and is hence too silicic to have been derived directly from the mantle. It is well known that one way this imbalance can be reconciled is if the paren...

The Wadi Dib magmatic complex is the oldest known alkaline ring complex in the Egyptian part of the Pan-African orogenic belt. Rb-Sr isotope data for seven samples suggest a Vendian age of 578=k16 Ma, and a 87Sr/S6Sr initial ratio of 0.7048±0.0010. The igneous complex has a diameter of 2 km and was emplaced within granodioritic Pan-African host rocks at the intersection of two faults. It shows ...

[1] Orogens with multiple (ultra)high-pressure ((U)HP) and (ultra)high-temperature ((U) HT) metamorphic events provide a complex but telling record of oceanic and continental interaction. The Early Paleozoic history of the “Heart of China,” the Qinling orogenic collage, offers snapshots of at least three (U)HP and two (U)HT metamorphic events. The preservation of remnants of both oceanic and co...