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tholeiite Line breaks: tho¦lei|ite
Pronunciation: /ˈθəʊlɪʌɪt/

Definition of tholeiite in English:


[mass noun] Geology
A basaltic rock containing augite and a calcium-poor pyroxene (pigeonite or hypersthene), and with a higher silica content than an alkali basalt.
Example sentences
  • Trace element data and isotopic analysis demonstrate that the arc is composed of islandarc tholeiite and ocean-island basalts and calc-alkaline arc-type extrusive rocks.
  • Except for its lower degree of partial melting (hence, a higher content of volatile matter), alkali basalt is thought to have an origin similar to that of tholeiite.
  • In the Pechenga-Varzuga volcanosedimentary belt, alkali basalts eruptions about 2.2 Ga in age gradually gave way to tholeiite pillow lavas, Fe-picrite flows and Ti-rich basalts with ages around 1.98 Ga.


Pronunciation: /ˌθəʊlɪˈɪtɪk/
Example sentences
  • In the Canaries, the lavas are much more compositionally varied in each of these stages, ranging from tholeiitic basalts to phonolites and trachytes.
  • A tholeiitic suite of dolerite dykes in the southwestern Borrowdale Volcanic Group is a separate, later magmatic event.
  • The Whin Sill complex is a large tholeiitic quartz dolerite intrusion in northern England.


Mid 19th century: from Tholei, the name of a village (now Tholey) in the Saarland, Germany, + -ite1.

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