CHARNOCKITE

 

Charnockites are rather peculiar rocks - they consist of an unusual mix of minerals, principally quartz, feldspar, and pyroxene.  Charnockites can be coarsely crystalline-textured or foliated.  Some are high-grade metamorphic rocks, while others are intrusive igneous rocks, but all are quartzo-feldspathic with pyroxene. (more info.)

 

The feldspar component of charnockite characteristically ÒglimmersÓ when tilted in the light (see especially the large lower feldspar crystal in the photo of ÒVerde Butterfly GraniteÓ below).

 


 

Ubatuba Granite from near the town of Ubatuba in southeastern Brazil.  This late Neoproterozoic to Cambrian (~650-500 million years) charnockite has large, dark-greenish feldspars, black pyroxene, and some quartz.

 


 

Verde Butterfly Granite - garnetiferous charnockite (a.k.a. hypersthene monzogranite) from the Precambrian of southeastern Brazil.  It formed during the late Neoproterozoic to Cambrian (~650-500 million years ago).  The rock is dominated by feldspar (greenish), pyroxene (black), quartz, and garnet (very deep red).

 


 

Seaweed Green Granite (a.k.a. Pocono Green Granite, Pine Green Granite) - a garnetiferous charnockite from the Precambrian of Orissa State, Eastern Ghats Orogenic Belt, eastern India.  The very dark red garnet component of this rock is mostly mixed with black pyroxene patches.  The black pyroxene areas are generally elongated, and aligned more or less parallel throughout the rock (foliated texture).

 


 

Nara Brown Granite (a.k.a. Nara Granite, Caledonia Granite, Caledonia Nara Brown Granite, Caledonia Nara Granite) - this has the appearance of an ordinary porphyritic granite with K-feldspar phenocrysts, but petrologic and regional geologic work shows that it is a charnockite (a porphyritic farsundite or porphyritic quartz mangerite, to be more specific).

Geologic Unit & Age: Rivire-ˆ-Pierre Plutonic Suite, Grenville Orogeny metamorphism, late Mesoproterozoic, ~1.1 Ga.

Locality: quarry north of town of Rivire-ˆ-Pierre, Portneuf County, southern Quebec, southeastern Canada.

 


 

 

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