نتایج جستجو برای: mafic rocks
تعداد نتایج: 23127 فیلتر نتایج به سال:
Melting of mafic veins in a marble-cake mantle may play an important role in generating isotopic and chemical heterogeneities in mid-ocean ridge and ocean island basalts. Mafic veins have lower solidi than mantle peridotite and will be preferentially sampled during partial melting, particularly at low melt fractions. However, the abundance of mafic components in the mantle or their role during ...
In the Palaeoproterozoic Nagssugtoqidian orogen of West Greenland reworked Archaean and juvenile Proterozoic orthogneisses occur side by side and are difficult to differentiate in the field. Archaean gneisses have tonalitic to trondhjemitic compositions with relatively low Al2O3 and Sr, and may have been derived from magmas formed by melting of basaltic or amphibolitic rocks at moderate pressur...
Introduction: Several types of magnesian highlands rocks occur in the lunar samples including the mafic Mg-suite rocks, magnesian feldpathic granulites, and magnesian anorthosites. Some mafic magnesian rocks are easily accommodated into the magma ocean model, as large variations in Mg/Fe are expected as the magma ocean crystallizes, forming source regions for magnesian melts. The origin of othe...
Introduction: The lower crust of the Moon remains a critical unknown for models of lunar compositional mass balance and for models of petrogenesis of lunar rock types. Key questions addressed here are (1) how mafic are the rocks of the lower crust and (2) are they ferroan or magnesian? Answers to these questions bear on the concentration and distribution of radiogenic heat-producing elements an...
The alpha proton x-ray spectrometer (APXS) on board the rover of the Mars Pathfinder mission measured the chemical composition of six soils and five rocks at the Ares Vallis landing site. The soil analyses show similarity to those determined by the Viking missions. The analyzed rocks were partially covered by dust but otherwise compositionally similar to each other. They are unexpectedly high i...
The Xade Complex is an unexposed Y-shaped body, approximately 100 km long and 25km wide, located close to the western margin of the Kaapvaal craton in Botswana. The Complex is characterized by large coincident magnetic and gravity anomalies. It is completely covered by varying thicknesses of Kalahari sediments as well as by Karoo strata, which means that detailed analysis of high resolution air...
Introduction: Shocked rocks are known from various planetary bodies of the solar system including Earth, Moon, Mars, and several types of asteroids. It was first recognized on Earth that stages of progressive shock metamorphism can be defined [1,2,3,4] and this concept was later on confirmed for lunar rocks [5] and meteorites [6,7,8]. Initiated by the IUGS “Subcommission on the Classification o...
Mineral chemistry of micas from the subduction-related mafic and felsic alkaline rocks of the Kaleybar alkali-gabbro and the Bozqush nepheline syenite was determined. The micas generally occur as large poikilitic grains with Fe-Ti oxides and mafic minerals and give the rocks a spotted texture. Micas in the alkali-gabbro sometimes display a distinct lamination. Based on the International Mineral...
One of the characteristic features of Ordovician tectonism in the east Lachlan Fold Belt is the occurrence of calcalkaline to shoshonitic basalts, which have been recognised as part of an intraoceanic arc environment (Glen et al. 1998), consistent with early tectonic interpretations (Oversby 1971; Scheibner 1973). Aside from typical traceelement abundances of intraoceanic arcs, critical evidenc...
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