Explosive eruptions involve mainly silicic magmas in which sulfur solubility and diffusivity are low. This inhibits sulfur exsolution during magma uprise as compared to more mafic magmas such as basalts. Silicic magmas can nevertheless liberate large quantities of sulfur as shown by the monitoring of SO2 in recent explosive silicic eruptions in arc settings, which invariably have displayed an e...

The ~1.08 Ga anorogenic, A-type Pikes Peak batholith (Front Range, central Colorado) is dominated by coarsegrained, biotite±amphibole syenogranites and minor monzogranites, collectively referred to as Pikes Peak granite (PPG). The batholith is also host to numerous small, late-stage plutons that have been subdivided into two groups (e.g. Wobus, 1976. Studies in Colorado Field Geology, Colorado ...

Abstract All models of the magmatic and plate tectonic processes that create continental crust predict presence a mafic lower crust. Earlier proposed crustal doubling in Tibet Himalayas by underthrusting Indian requires layer with high seismic P-wave velocity ( V p > 7.0 km/s) above Moho. Our new data demonstrates some thickest on Earth middle Lhasa Terrane has exceptionally low < 6.7 thr...

The composition of the crust is one most uncertain and controversial components continental estimates due to (1) limited direct access (2) inconsistent indirect assessments. Here we show that by combining high-resolution shear velocity (Vs) models with newly measured ratio compressional wave (Vp) Vs, or Vp/Vs ratio, for crystalline crust, a 3-D (SiO2 wt%) model can be derived uncertainty estima...

Collisional orogens commonly include mono-metamorphic and poly-metamorphic units, their different evolution can be difficult to recognize reconcile. The Theodul Glacier Unit (TGU) in the Western Alps consists of an association metasedimentary metamafic rocks embedded within Zermatt-Saas tectonic unit. In spite recent petrological studies, it remains unclear whether these underwent one or multip...

O'Neil et al. (Reports, 26 September 2008, p. 1828) presented neodymium-142 data for rocks from northern Quebec, Canada, and suggested that these rocks may represent the oldest preserved crustal section on Earth. We argue that the age of the rocks is based on a spurious correlation between rocks that are probably not co-genetic and negative (142)Nd anomalies that may be the result of an analyti...

Introduction: Preliminary investigations by these authors concerning the comparison and contrast of characteristics associated with terrestrial layered mafic intrusives (LMI's) and Venusian coronae indicate some similarities in morphology and possibly origin. Our premise is that coronae, and processes related to their formation, may not be unique to Venus and that mantle plumes could have been ...