منابع مشابه
Preferential low-pH dissolution of pyroxene in plagioclase–pyroxene mixtures: Implications for martian surface materials
Acid weathering of plagioclase–pyroxene mixtures has been investigated with an open system kinetic dissolution model. The modeling reveals that elevated plagioclase/pyroxene ratios observed in some low-albedo martian regions and atmospheric dust could be partially caused by preferential dissolution of pyroxenes at pHs below ∼3–4. Surface materials with smaller grain sizes, affected by lower pH ...
متن کاملPyroxene Europium Valence Oxybarometer. Effects of Pyroxene Composition, Melt Composition and Crystallization Kinetics
Introduction: The behavior of multivalent elements such as iron, chromium, vanadium, and euro-pium in magmatic systems reflects the f O2 of the environment. The oxidation state of these elements will influence the mineral assemblage, crystallization sequence , and element partitioning[1]. The effect of f O2 on the relative proportions of divalent and trivalent Eu has proven to be a useful tool ...
متن کاملModel pyroxenes I: Ideal pyroxene topologies
Ideal pyroxenes are hypothetical structures based on ideal closest-packed arrangements of O anions. They are modeled after observed pyroxene structures and have the general formula M2M1T2O6, where M2 and M1 represent octahedrally coordinated cations, and T represents tetrahedrally coordinated cations. An algorithm has been created to construct all possible ideal pyroxenes based on closest-packe...
متن کاملPyroxene Mineralogies of Near-earth Vestoids
Introduction: For any near-Earth asteroid (NEA) on a possible collision course with Earth, a number of factors must be determined to evaluate the object’s potential hazard. One of these factors is the object’s mineralogy, which can be used to estimate the density and, therefore, the mass of the object. This work discusses how to determine the mineralogies of NEAs that have reflectance spectra s...
متن کاملMantle plumes persevere
A recent census suggests that seamounts1 — typically extinct underwater volcanoes — are numerous. It has been estimated that about 125,000 seamounts with a height of more than one kilometre exist on our ocean floors. Most of these are postulated to form at volcanic hotspots that are the surface expressions of mantle plumes — hot material upwelling from Earth’s interior. Yet, many seamounts do n...
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ژورنال
عنوان ژورنال: Nature
سال: 1975
ISSN: 0028-0836,1476-4687
DOI: 10.1038/254106a0