TWO different spinels, analyses of which are given, occur in the layered ultramafic rocks at Dawros. Chrome spinel occurs both as gravity-stratified cumulates and as complex orbs, while an Al-rich spinel is both in rocks of the main Dawros magmatic sequence and in an association with an aluminous bronzite, which may originate by recrystallization. It is concluded that while the chrome spinel is...

Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is essential to develop genetic models that can be used for exploration purposes. Here we ...

Porphyry deposits, our main source of copper and of significant amounts of Mo, Re and Au, form at convergent margins in association with intermediate-felsic magmas. Although it is accepted that copper is transported and precipitated by fluids released by these magmas, the magmatic processes leading to the formation of economic deposits remain elusive. Here we perform Monte Carlo petrological an...

Eruption forecasting is a major goal in volcanology. Logically, but unfortunately, forecasting hazards related to non-magmatic unrest is too often overshadowed by eruption forecasting, although many volcanoes often pass through states of non-eruptive and non-magmatic unrest for various and prolonged periods of time. Volcanic hazards related to non-magmatic unrest can be highly violent and/or de...

Chemical and isotope data were obtained for the active gas and noble gas of inclusion fluids in coarse-grained samples of magmatic-hydrothermal and magmatic-steam alunite from well-studied deposits (Marysvale, Utah; Tambo, Chile; Tapajós, Brazil; Cactus, California; Pierina, Peru), most of which are discussed in this Volume. Primary fluid inclusions in the alunite typically are less than 0.2 Am...

The magmatic-hydrothermal evolution of porphyry-style mineralization in the shallow crust that is linked to magmatic processes at depth has been extensively studied using bulksample isotopic analysis combined with relative timing constraints. However, a lack of evaluation of the fluid evolution process against an absolute time frame limits further understanding of the ore-forming process. Here,...

Subduction-related magmatic arcs represent immense accumulations of intermediate, calc-alkaline igneous rocks and are considered the main factories of continental crust on Earth. Estimating the pace at which these giant volumes of magmatic rock were added to the crust and the mechanisms responsible for magmatic addition are fundamental issues for the disciplines of igneous petrology and contine...

The carbon isotope content of dissolved inorganic carbon was measured for large cold springs in the central Oregon Cascades. Low 14C activities in some of the springs are interpreted to result from the dissolution of diffuse emissions of magmatic CO2, even though volcanic activity has not occurred in this area for more than 1300 yr. On the basis of dissolved magmatic carbon concentrations in th...

Introduction: Magmatic inclusions in Martian meteorites contain some hydrous minerals such as kaersutites [e.g., 1-2]. The characteristic of Martian kaersutites is their water-poor [3] and Ti-rich (~10 wt%) compositions. The presence of kaersutite gives evidence that Martian parent magma contained water. In fact, several attempts have been performed to estimate the water content in Martian magm...

N2/Ar and Ar/He relationships: Fluid inclusion magmatic gases are measured using quadrupole mass spectrometers and the data is compared to measurements of volcanic gas analyses. Data reported by Giggenbach from active volcanoes give N2/Ar ratios in the general range of 100 to 1000 whereas corresponding Ar/He ratios vary from 100 to 2. Plotted on a Ar/He vs. N2/Ar diagram the data defines a fiel...