Austria Conference-07 kh-iaea-mongolian rift basins-2012

Uranium Prospectivity of Mongolian Basins
Kristl Hoksbergen 1, Enkhbayasgalan Dugerjav 2,
Munkhbold Nayam-Ochir 2
1Cameco Corporation, 2 Cameco Mongolia

29, May, 2012

Key Messages
● Mongolia has a complex structural past, with Jurassic and
Cretaceous tectonism creating many extensional rift basins
along the main Mongolian lineament;
● These extensional basins contain many uranium occurrences
as well as deposits containing a combined total of over 25,000
tonnes U;
● Uraniferous basins consist of the same elements many of the
unexplored basins contain;
● The Tamsag basin in Mongolia covers an area of over 48,000
km2;
● Sediments of the Tamsag are highly prospective for the
formation of sandstone hosted uranium deposits;
● Mongolia is highly unexplored, and contains many basins
prospective for sandstone hosted uranium.

IAEA Technical Meeting: The Origin of Sandstone Uranium Deposits:
Slide 2
A Global Prospective -May 29th, 2012

Sandstone Deposits of the World

-Coordinates taken from the IAEA Database

Slide 3

Location Map

Slide 4

Sandstone Uranium in Mongolia

2,460 tonnes U
3,039 tonnes U

3,000 tonnes U

9,800 tonnes U

-Tonneage taken from the IAEA database

Slide 5

Palinspastic Reconstruction

Modified from Ito et al, 2006

Slide 6

Tectonic Terranes of Mongolia

Main Mongolian Lineament

-Modified after Badarch et al, 2002

Slide 7

Mongolian Meso and Cenozoic Basins

Slide 8

Basin Development in Mongolia

Modified from Traynor and Slayden, 1995

Slide 9

Extensional vs Contractional Basins
Kazakhstan

-Modified from Yazikov, 1996

Both Figures Diagrammatic - Not to scale

Karoo (Selous) Basin Tanzania

-Modified from Catuneanu, 2005

Slide 10

Rift Sedimentary Environments


Slide 11

Rift Basin Stratigraphy- An Example


Slide 12

The development of a uranium bearing
Mongolian rift basin

Slide 13

Initiation of Jurassic rifting

Slide 14

Deposition of Jurassic volcanoclastics and
mafic extrusives

Slide 15

Lower Cretaceous rifting and syn-rift
sedimentation of coal bearing lacustrine and
fluvial sediments

Slide 16

Rifting ceases at the end of the Lower
Cretaceous. Deposition of post-rift Upper
Cretaceous red beds and fluvial sediments,
minor fault reversal

Slide 17

Deposition of Cenozoic alluvial deposits and
prominent basin inversion

Slide 18

Location of sandstone-hosted uranium
deposits

Structural

Roll Front
Basal
Channel

Slide 19

Basin Focus: Tamsag Basin

Tamsag Basin

LEGEND

Slide 20

Basin Focus: Tamsag Basin

Modified from Davaa, 2010

Slide 21

W-E Property Interpreted Basin Section
CMK-140
CMK-144
CMK-141

CMK-145

CMK-146
Alluvium

K1 Sediments

1 km

Slide 22

W-E Property Cross-Section from Drilling
CMK-140

CMK-144

CMK-143

CMK-141

CMK-145

CMK-146
10 m
1 km

Slide 23

Requirements for Uranium Deposition
Source Transport Trap

Uraniferous Rocks; -Fluid Conduit; Reducing Agent;
- “Hot” Granites -Porous/permeable sands: -Organic trash
-Volcaniclastics -Braided/Meandering -Pyrite
-Alluvial Fans -H2S/Hydrocarbons
-Deep seated structures

Slide 24

Conclusions
● Large sandstone hosted uranium systems are
usually found in contractional basins (foreland
basins);
● Rift basins typically develop as a series of sub-
basins, are more compartmentalized, and produce
more closed depositional systems;
● However, rift basins are capable of hosting
economic deposits, including the Karoo Basin of
Africa, and several basins in Mongolia;
● Mongolian Cretaceous basins contain suitable
uranium source rocks, host stratigraphy and
efficient mineralization traps;
● Mongolia contains many aerially extensive rift
basins that are relatively unexplored.

Slide 25

Austria Conference-07 kh-iaea-mongolian rift basins-2012

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