Tuff Schist

The adventures of an unstable geologist

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The Amazon River Flows Backwards, And Now Scientists Have Figured Out Why | IFLScience

(Source: thisoddlittleworld)

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pearl-nautilus:

Parkinsonia Dorsetensis Ammonite - Middle JurassicThis specimen has been polished to show ‘suture’ lines, frilled edges of the septa which separate the chambers.source:

pearl-nautilus:

Parkinsonia Dorsetensis Ammonite - Middle Jurassic

This specimen has been polished to show ‘suture’ lines, frilled edges of the septa which separate the chambers.

source:

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earthstory:

The Rama Schist

This is another part of the complex of twisted, bent, metamorphosed, nearly 2 billion year old rocks that sit at the bottom of the Grand Canyon and make up some of the oldest, deepest rocks exposed anywhere in the western U.S.

The other parts of the schist we’ve seen, the Vishnu Schist and the Brahma Schist, look a lot like metamorphosed parts of the ocean, metamorphosed sedimentary rocks and metamorphosed basaltic rocks. Those sit in contact with granites that look like an island arc that slammed into North America about 1.7 billion years ago.

These rocks fit into that same story. The Rama schist is a third component in the mixture of schists; more felsic, quartz and plagioclase rich metamorphosed rocks.

These rocks have the chemistry of volcanic rocks erupted close to the Earth’s surface, as happens often in island arcs. The rocks may have been faulted or moved around prior to running into the growing continent, but they were pulled into the same mountain building and metamorphic event as the surrounding sediments and basalts.

These rocks were probably volcaniclastic before they were metamorphosed, produced by explosive volcanic eruptions. Some of the layering is even maintained in the second image. Based on those details, the protolith of these rocks (what they were before metamorphism) was probably a tuff. 

In other words, it would be fully accurate to call this rock a tuff schist. You’re welcome.

-JBB

Image credit: Tisha Irwin (with permission, taken on sample on GC National Park Rim Trail) https://www.flickr.com/photos/tishairwin/14491015401
Visit her page: http://www.photonsandplutons.com/
Also used: Ilg et al., GSA Bulletin, 1996http://gsabulletin.gsapubs.org/content/108/9/1149.short
Previous articles: 
https://www.facebook.com/photo.php?fbid=71718732167564https%3A%2F%2Fwww.facebook.com%2Fphoto.php%3Ffbid%3D717596974968016
https://www.facebook.com/photo.php?fbid=718487278212319
https://www.facebook.com/TheEarthStory/posts/718917208169326

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wouldirunoff:

Someone from the department just emailed me this. Bowen was a really important geologist, for some context. (link to more in depth explanation of why Bowen was important)
This is so beautiful. 
these guys were pals, so this is all kidding around or whatever, but it’s still beautiful
Excerpt from the link above: “Some readers may also recall the delightful discussion on the origin of granites in which Bowen described the metasomatizers as the “soaks” who had to have their liquor in lavish quantities whereas the pontiffs, the magmatists, handled their liquor like gentlemen, taking it or leaving it as the occasion indicates.”

wouldirunoff:

Someone from the department just emailed me this. Bowen was a really important geologist, for some context. (link to more in depth explanation of why Bowen was important)

This is so beautiful. 

these guys were pals, so this is all kidding around or whatever, but it’s still beautiful

Excerpt from the link above: “Some readers may also recall the delightful discussion on the origin of granites in which Bowen described the metasomatizers as the “soaks” who had to have their liquor in lavish quantities whereas the pontiffs, the magmatists, handled their liquor like gentlemen, taking it or leaving it as the occasion indicates.”