BGS Rock Classification Scheme

Metabasalt, alkali

Code	MBAALK
Description	Metabasalt, alkali
Qualifiers	alkali
Definition	Meta-igneous rock, field identifiable alkali-basalt protolith. Fine-grained, av. <0.25mm normal crystalline extrus/intrus rock; CI >35 vol% >40 wt%; qtz <20% or feldspath <10% of QAPF, felds >65% plag; TAS SiO2 45-52wt%, (97%<48.5). CIPW norm with nephel.
Linked data	http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/MBAALK

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CAVEAT

"Thumbnail" definitions attached to some of the table entries are an interim attempt to provide simple short descriptions of the "unqualified" rock types presented within the BGS Rock Classification Scheme. Every effort has been made to ensure accuracy and consistency but minor contradictions or omissions might be present. The BGS welcomes any feedback pointing out such minor imperfections and/or providing constructive comment and suggestions for improvement of the definitions. In the first instance such feedback should be directed to Dr Tim McCormick.