What is a picrite in geology ?

Picrite : definition

Streckeisen diagrams (or QAPF diagrams) - Classification of plutonic and volcanic rocks
A picrite is an ultrabasic volcanic rock of black color, with a microlitic or doleritic texture, characterized by a great abundance of olivine (from 30 to 50%) and titaniferous augite (about 30%), with as accessory minerals : brown amphibole , labrador-bytownite, biotite or phlogopite, and sometimes analcime. These rocks usually belong to ultrabasic complexes, or form veins in other basic rocks.

Picrite can belong to the alkaline series but also to the tholeiitic. It is distinguished from basalts by the abundance of olivine.
Picrite - © plugon.us - rocks767

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