World Library  
Flag as Inappropriate
Email this Article

Augen

Article Id: WHEBN0006400494
Reproduction Date:

Title: Augen  
Author: World Heritage Encyclopedia
Language: English
Subject: Geology of Guernsey, Metamorphic petrology, List of rock textures, Philips and the Monkey Pen, Ultra-high-pressure metamorphism
Collection: Metamorphic Petrology
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Augen

A Gneiss with large eye-shaped feldspars

Augen (from German "eyes") are large, lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. In cross section they have the shape of an eye.

Feldspar, quartz, and garnet are common minerals which form augen.

Augen form in rocks which have undergone metamorphism and shearing. The core of the augen is a porphyroblast or porphyroclast of a hard, resilient mineral such as garnet. The augen grows by crystallisation of a mantle of new mineral around the porphyroblast. The mantle is formed contiguous with the foliation which is imparted upon the rock, and forms a blanket which tapers off from either side of the porphyroblast within the strain shadows.

During shearing, the poprhyroblast may rotate, to form a characteristic augen texture of asymmetric shearing. In this case, the position of the tails is unequal across the foliation, with some augen showing clear drag folding of the mantle into the strain shadow. This derives a form of shear direction information.

A metamorphic rock which is clotted with augen is often called an augen gneiss. A long wall of this augen gneiss can be felt at the Mineral and Lapidary Museum of Western North Carolina.

See also


This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.