Simple Lithology


broader fine grained igneous rock
narrower andesite
intermediate composition igneous rock
narrower andesite
definition Fine-grained igneous rock with less than 20 percent quartz and less than 10 percent feldspathoid minerals in the QAPF fraction, in which the ratio of plagioclase to total feldspar is greater 0.65. Includes rocks defined modally in QAPF fields 9 and 10 or chemically in TAS field O2 as andesite. Basalt and andesite, which share the same QAPF fields, 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. Typically consists of plagioclase (frequently zoned from labradorite to oligoclase), pyroxene, hornblende and/or biotite. Fine grained equivalent of dioritic rock. more like this
basaltic andesite more like this
leuco-basalt more like this
mela-andesite more like this
note Note the mela-andesite and leuco-basalt categories are not recommended in this system. If chemical analytical data are available to constrain the silica content, the basalt or andesite category should be used. more like this
source after LeMaitre et al. 2002 more like this
in scheme simplelithology
is primary topic of andesite
narrower boninite
broader andesite