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narrower basalt original original
narrower basalt original
definition Fine-grained or porphyritic igneous rock with less than 20 percent quartz, and less than 10 percent feldspathoid minerals, in which the ratio of plagioclase to total feldspar is greater 0.65. Typically composed of calcic plagioclase and clinopyroxene; phenocrysts typically include one or more of calcic plagioclase, clinopyroxene, orthopyroxene, and olivine. Includes rocks defined modally in QAPF fields 9 and 10 or chemically in TAS field B as basalt. Basalt and andesite are distinguished chemically based on silica content, with basalt defined to contain less than 52 weight percent silica. If chemical data are not available, the color index is used to distinguish the categories, with basalt defined to contain greater than 35 percent mafic minerals by volume or greater than 40 percent mafic minerals by weight. more like this
leuco-basalt more like this
mela-andesite more like this
picrite more like this
picrobasalt more like this
narrower original
broader basalt original original
broader basalt original
source after LeMaitre et al. 2002 more like this
Resource original
Concept original
in scheme simplelithology original
is primary topic of basalt