tholeiite

Pleistocene basalt and tholeiite is found in the Penghu Islands.

The rock on the island is volcanic tholeiite andesite, and volcanic explosive fragments.

The tholeiite contains plagioclase and pyroxene.

Also dykes of augite syenite, picrite and tholeiite dolerite were intruded.

The chemical compostition of these basalts can vary from tholeiite to alkali basalt within the same island group, but is never calc-alkaline.

Flood basalts have tholeiite and olivine compositions (according to the classification of Yoder and Tilley).

On the southern part of the Central Plateau, there are olivine melilite nephelinite, olivine nephelinite, quartz tholeiite lava flows.

This was followed later in the Neoproterozoic on the eastern side of the island with beds of diamictite, dolomite, mudstone, tholeiite, and picrite interleaved with conglomerate.

The International Union of Geological Sciences recommends that tholeiitic basalt be used in preference to the term "tholeiite" (Le Maitre and others, 2002).

The Rajmahal volcanics predominantly comprises of tholeiitic basalt, quratz tholeiite, olivine tholeiite and alkali basalt.

Komatiitic magmas are considered to be a source for spatially associated tholeiite basalts based on a study linking the two rock types in the Karelian greenstone belt of northwest Russia.

The Harzburg gabbro-norite intrusion forms part of this complex, but has a primary chemistry similar to an island-arc tholeiite, although it shows the effects of large scale assimilation of crustal rocks.

It has greater than 17% alumina (AlO) and is intermediate in composition between tholeiite and alkali basalt; the relatively alumina-rich composition is based on rocks without phenocrysts of plagioclase.

The basaltic sills of similar age (near 200 Ma, or earliest Jurassic) and composition (intermediate-Ti quartz tholeiite) which occur across the vast Amazon River basin of Brazil were linked to the province in 1999 .

Isotopic ratios of noble gases, such as He/He, are also of great value: for instance, ratios for basalts range from 6 to 10 for mid-ocean ridge tholeiite (normalized to atmospheric values), but to 15-24+ for ocean island basalts thought to be derived from mantle plumes.