نتایج جستجو برای: basaltic
تعداد نتایج: 2375 فیلتر نتایج به سال:
Despite the abundant evidence for the enrichment of phosphorus during the petrogenesis of natural ferro-basalts, the effect of phosphorus on the physical properties of these melts is poorly understood. The effects of phosphorus on the viscosity, density and redox ratio of a ferro-basaltic melt have been determined experimentally. The viscosity measurements were obtained using the concentric cyl...
Water-rock interactions within the seafloor are responsible for significant energy and solute fluxes between basaltic oceanic crust and the overlying ocean. Permeability is the primary hydrologic property controlling the form, intensity, and duration of seafloor fluid circulation, but after several decades of characterizing shallow oceanic basement, we are still learning how permeability is cre...
The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represe...
The Isua greenstone belt (Fig. 1) contains the oldest known, relatively well preserved, metavolcanic and metasedimentary rocks on Earth. The rocks are all deformed and many were substantially altered by metasomatism, but both the deformation and metasomatism were heterogeneous. Transitional stages can be seen from relatively well preserved primary volcanic and sedimentary structures to schists ...
We review petrologic evidence that the acapulcoites and lodranites formed by < 1 ~01% to probably >20 ~01% whole rock partial melting of a chondritic precursor material. At low degrees of partial melting, only Fe,Ni-FeS cotectic melting occurred. Migration distances for partial melts were short, resulting in the formation of acapulcoites with essentially chondritic troilite and plagioclase cont...
Article history: Basaltic magmatism is a co Received 31 July 2008 Received in revised form 21 November 2008 Accepted 9 December 2008 Available online 30 January 2009
The Rare Earth Elements (REEs) have been widely used to investigate marine biogeochemical processes as well as the sources and mixing of water masses. However, there are still important uncertainties about the global aqueous REE cycle with respect to the contributions of highly reactive basaltic minerals originating from volcanic islands and the role of Submarine Groundwater Discharge (SGD). He...
Introduction: Recently, a lot of basaltic shergottites have been found from the desert areas in northern Africa and Middle East Asia. Most of them contain large olivine grains that are not present in the previously known basaltic shergottites (except for EETA79001). These olivine grains are mostly Mg-rich, but they show different mineralogical features in each meteorite. Dar al Gani 476 and its...
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