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A variety of basalt which is saturated or slightly oversaturated in silica with respect to alkalis. A silica-oversaturated (quartz-normative) basalt, characterized by the presence of low-calcium pyroxenes (orthopyroxene and/or pigeonite) in addition to clinopyroxene and calcic plagioclase. Olivine may be present in the mode, but neither olivine nor nepheline appear in the norm
Classification of Tholeiitic basaltHide
Sub-divisions of Tholeiitic basaltHide
Mineralogy of Tholeiitic basaltHide
Essential minerals - these are minerals that are required within the classification of this rock:
|Calcic plagioclase||A petrological term for plagioclase series feldspars dominant in calcium.|
|Olivine||Equivalent to Fayalite-Forsterite Series; usually a more or less Fe-bearing forsterite.|
|Pyroxene||A petrological term for Pyroxene Group.|
Non-essential minerals - these minerals are common, sometimes major components, but are not always present:
Phanerozoic : 66.8 ± 0.3 Ma to 1.2 ± 0.1 Ma - based on 5 recorded ages.