Uranium roll front & molybdenum roll front hosted in Dakota Sandstone (Turkey Creek Road roadcut, Dakota Hogback, near Denver, Colorado, USA) 2

            Uranium roll front & molybdenum roll front in sandstone in the Cretaceous of Colorado, USA.

This is an example of a uranium-molybdenum roll front deposit, located at the Turkey Creek Watergap southeast of the town of Morrison, Colorado.  It is hosted in sandstones of the J Sandstone of the South Platte Formation (Dakota Group, Lower Cretaceous).  The uranium is ultimately coming from nearby pegmatitic granites.  At the ~upper right is a yellowish-cored, black-rimmed structure (see close-ups elsewhere in the Turkey Creek Watergap photo album).  That's a uranium roll front.  The black rim is composed of uraninite (UO2 - uranium dioxide).  The surrounding outcrop at this site has abundant yellowish and yellow-brown staining - some of that is native sulfur (S) and some is disseminated iron oxide.  I have not heard or read any specific information regarding the mineral identity of the yellowish core of the uranium roll front shown here (I've been told that carnotite is not present at this site, but tyuyamunite is).

Off to the right of this photo is a uranium-mineralized fault zone.  Uranium compounds are relatively mobile and move through permeable rocks while dissolved in fluids.  Groundwater has moved through the fault, picked up dissolved uranium compounds, and moved through adjacent porous sandstones.  Uraninite then precipitated around a tongue of groundwater, resulting in the roll front seen above.  Uranium mining has occurred on both sides of the Turkey Creek Watergap and targeted uraninite in the fault zone.

Here are some scintillometer readings that I observed being taken from this site, starting from the parking spot along the road, up to the black uraninite rim of the roll front: 900 counts per minute (cpm), 1500 cpm, 1600 cpm, 8000 cpm, 10,000 cpm (the maximum readout for the instrument used).  Other equipment brought here previously has recorded 33,000 cpm radiation from this roll front.

A molybdenum roll front is also present at ~lower left.  It is bluish-gray in color with molybdenite (MoS2 - molybdenum sulfide) and "moly blue", a nickname for ilsemannite (Mo3O8·nH2O - hydrous molybdenum oxide).

Pyrite-rich zones are common in the sandstones here, often closely associated with bright yellow-colored native sulfur (S).

This outcrop is also a site of hydrocarbon seepage - crude oil has emerged from several areas in the sandstone, resulting in dark staining and buildups of tar/asphalt.  The nearby fault zone contains uraniniferous asphalt.  Just down the road (Turkey Creek Road) is a former small oil field - the Johnson # 1 well and the Great Basin # 1 well produced crude oil from the Dakota Sandstone, which occurs at about 5000 feet depth, compared with it being at the surface at the outcrop seen here.

Locality: roadcut along the southern side of Turkey Creek Road through Turkey Creek Watergap, ~2.9 km southeast of the town of Morrison, Jefferson County, north-central Colorado, USA (39° 38' 05.67" North latitude, 105° 10' 07.44" West longitude)

Some rights reserved

Taken on: July 26, 2007

Tags:

molybdenum

uraninite

roll

front

deposit

Dakota

Sandstone

South

Platte

Formation

Cretaceous

Turkey

Creek

Hogback

Morrison

Denver

Colorado « less

Sets appears in: • Radioactive Rocks, Minerals, Fossils • Colorado Rocks, Minerals, Fossils more » • Dakota Sandstone (Cretaceous; western USA) • Turkey Creek Watergap (southeast of Morrison, Colorado, USA) « less

Stats: 527 views

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