Kenyte (porphyritic anorthoclase phonolite) (Pleistocene; southern slopes of Mt. Kenya Volcano, south-central Kenya, East African Rift Valley)

            Kenyte from the Pleistocene of Kenya, Africa. (10.2 cm from top to bottom; 4.1 cm at its widest)

Large whitish-grayish crystals = anorthoclase feldspar phenocrysts.
Dark matrix = flow-banded, ~cryptocrystalline material.

This is the second-rarest lava type on Earth.  It is only known from two localities: 1) the extinct Mt. Kenya Volcano in Kenya and 2) the active Mt. Erebus Volcano in Antarctica.  Chemically and texturally, kenytes are porphyritic phonolites (intermediate, alkaline-rich volcanic rocks) dominated by large phenocrysts of anorthoclase feldspar ((K,Na)AlSi3O8).

So why aren’t kenytes just called porphyritic anorthoclase phonolites?  Well, kenytes are different, but a gradational spectrum of lithologies exists between kenyte lavas and porphyritic anorthoclase phonolite lavas.  The intended distinction is in the characteristics of the matrix.  Kenyte matrix is supposed to be glassy-textured or homogeneously cryptocrystalline-textured or composed of devitrified glass.  Kenyte matrix also often shows obvious flow-banding (seen in this sample).

This kenyte is Pleistocene in age, collected from the southern slopes of the Mt. Kenya Volcano, which is an extinct and eroded volcano in south-central Kenya, just next to the East African Rift Valley system.  The volcano was active principally during the Pliocene and Pleistocene.  The summit area of Mt. Kenya consists of majestic-looking, high spires of rock - these rocks are shallow intrusives that filled up the throat of the old volcano.  The eroded slopes of the volcano consist of a variety of extrusive rocks, including trachytes, basalts, phonolites, and kenytes.
---------------
Mostly synthesized from:

Baker (1967) - Geology of the Mount Kenya area.  Geological Survey of Kenya Report 79.  78 pp.  4 pls.  1 map.
 
Price et al. (1985) - Geochemistry of phonolites and trachytes from the summit region of Mt. Kenya.  Contributions to Mineralogy and Petrology 89: 394-409.

Some rights reserved

Taken on: August 25, 2014

Tags:

kenyte

Mt.

Volcano

East

African

Rift

Valley

phonolite

anorthoclase « less

Sets appears in: • Kenya Rocks & Fossils • Phonolite more » • Mt. Kenya Volcano (south-central Kenya, East African Rift Valley) « less

Stats: 2,599 views

go back

close tools panel

Badge creator

Use Flickriver Badge Creator to create a badge linking to your photos, your group or any other Flickriver view.

You can place your badge on your Flickr profile, Blog or Website.

Add to your iGoogle or Netvibes page

Flickriver widget for iGoogle or Netvibes can display almost any Flickriver view - most interesting today, by user, by group, by tag etc. Once added to your personalized homepage, just edit widget settings to select your desired view.

Clickr on one of the buttons below to install:

Embed on your Web site

To embed this view, Copy and Paste the following HTML code:

Black background (preview):

White background (preview):

Firefox and Chrome addons

Adds a 'Flickriver' button to your browser. While viewing any Flickr photos page, click on this button to open the same view on Flickriver.

Install in Firefox
Install in Chrome

Search plugin

Add 'Search on Flickriver' to your browser's search box. Works with Firefox and Internet Explorer. Install search plugin

"View on Flickriver" Greasemonkey script

A Greasemonkey script that adds Flickriver links to various Flickr photo pages - user photos, favorites, pools etc, allowing to quickly open the corresponding Flickriver view.

Also, allows quickly viewing any Flickr photo on black background in large size.

Install "View on Flickriver" script

Bookmarklet

While viewing any Flickr photos page, click on the bookmarklet to open the same view on Flickriver.

To install: drag and drop the following link to your Bookmarks toolbar.
IE users - add the link to your Favorites under the Links folder