Abstract - Blue Sky Uranium

Draft Paper to be Submitted to the IAEA for Publication
A newly-discovered “surficial-type” uranium-vanadium district
in the Eastern Cenozoic “Bajos Basin” of Rio Negro Province (Patagonia), Argentina
By: Ronald McMillan, Jorge Berizzo, David Terry, Bruce Smith, Daniel Bussandri and Hugo Caranza;
Blue Sky Uranium Resources Corp., Vancouver, Canada
Abstract
In 2006, Blue Sky Uranium Corporation (“Blue Sky” and Minera Cielo Azul S.A. in Argentina)
initiated a uranium exploration program in the Patagonia Region of Argentina. Car-borne reconnaissance
in eastern Rio Negro resulted in the discovery of carnotite mineralization at Santa Barbara in a road cut
on Highway #66 – the first documented uranium occurrence in the Rio Negro Province. In 2007, Blue Sky
completed 7,071 line km of airborne radiometric surveying over a portion of the “Bajos Basin” and
identified two significant anomalies – one over the Santa Barbara occurrence and a second over the Anit
occurrence. Subsequently in 2010, Blue Sky completed a second survey totalling 22,214 line km – this
resulted in the discovery of the Ivana occurrence – other anomalies are being evaluated.
The three currently-known areas of mineralization (Santa Barbara, Anit and Ivana) are all hosted
in unconsolidated clastic sedimentary strata – possibly of late Tertiary or Pleistocene age. The three
uranium occurrences occur in slightly elevated areas in sediments. The current geological environment
of the “Bajos Basin” is that of an enclosed internal drainage system in an area of ephemeral streams and
playa lakes. Elevations in the area range from approximately 50 m below sea level to 250 m above sea
level.
The Santa Barbara occurrence is hosted in grits and pebble conglomerate – the host strata
appear to reflect a flood-plain environment. To date carnotite is the only documented uranium mineral.
Three northeast-trending subparallel airborne radiometric anomalies (respectively 12, 6 and 5 km in
length) have been detected above flat-topped low mesas which have been eroded in the current
physiographic regime. Limited hand auguring has outlined a 0.5 to 1.0 m thick near-surface mineralized
horizon ranging up to 600 ppm U (0.071% U3O8).
The Anit occurrence has been the focus of most of the exploration work to date. Again
carnotite is the uranium mineral. Trenching and aircore drilling have outlined a mineralized fluviatile
channel 6 km long, an average of 1.97 m thick and 40 to 480 m wide (approximately 1 km2 in area) at an
average grade of 337 ppm U (0.04 % U3O8) and 594 ppm V. Like the Santa Barbara occurrence, Anit is
partially eroded.
The recently-discovered Ivana occurrence again contains carnotite hosted in fine well-layered
claystone and fine sand likely belonging the Middle Miocene Bajo del Gualicho Formation. The
environment at Ivana appears to be a low-energy flood-plain or lacustrine (playa) environment. Minor
preliminary pitting and the airborne radiometric survey suggest mineralization could extend over an
area of approximately 25 km2, with hand pits exposing uranium values of up to 575 ppm U (0.068 %
U3O8) across 3 metres.
Blue Sky’s work to date has confirmed a district-scale uranium discovery in the Rio Negro
Province of Argentina. The environment shows many similarities to the geological setting of several
important “surficial-type” deposits in Western Australia and Namibia - however there are several
significant differences.
List of Figures
Figure 1 - Location Map “Bajos” Uranium Project - Rio Negro Province.
Figure 2 - Geological Map of Rio Negro showing the area of Blue Sky Uranium’s tenures
in the “Bajos Basin”.
Figure 3 - Santa Barbara Airborne Uranium Channel Contours from Airborne Petroleum
Geophysics Pte Ltd.
Figure 4 - Anit Airborne Uranium Channel Contours from Airborne Petroleum
Geophysics Pte Ltd.
Figure 5 - Ivana Airborne Uranium Channel Contours from Airborne Petroleum
Geophysics Pte Ltd.
Figure 6 - Anit occurrence as outlined by aircore drill holes.
Figure 7 - Anit occurrence as outlined by Excavator Pits.
List of Tables
Table 1 - Generalized Stratigraphic Column
Table 2 - Upgrading Flowsheet at 0.2 mm Split (Furfaro, 2010)
List of Photographs
Photo 1 - Dr Jorge Berizzo above a pit with yellow carnotite at the discovery location at the
Santa Barbara occurrence on Hwy #66.
Photo 2 - Daniel Bussandri in prospect pit with high-grade carnotite mineralization at the Anit
occurrence.
Photo 3 - Trench through high-grade mineralization at the Anit occurrence.
Photo 4 - Trench 5 Anit occurrence - High-grade carnotite on crossbeds in pebble conglomerate.
Photo 5- Trench 5 Anit occurrence - Top, carnotite on petrified wood; Lower left, carnotite
disseminated in matrix of pebble conglomerate – Lower centre and right, coarse
gypsum rosettes.
Photo 6 - Carnotite coating pebble adjacent to coarse gypsum (white) at the Anit occurrence.
Photo 7 - Ivana 1 Cateo – Uranium showing a few metres below the crest of a mesa flanking
Laguna Tres Picos (one of the salars in the “Bajos”area).
Introduction (ownership, acknowledgements and location)
The “Bajos” Uranium Project is currently owned by Blue Sky Uranium Corporation (“Blue Sky”)
and/or subsidiaries (100% owned).
The authors would like to acknowledge the contribution of Mr. Diego Charchaflie in the early
stages of the project. Mr. Sean Hurd, our president, has been involved since the inception of the project
– he has been strongly supportive and has contributed several innovative ideas. Mr. J. Grosso and Carlos
D`Amico contributed to various legal and socio-economic aspects of the project. Ms. Maria Ledezma
Negron, the company solicitor, negotiated several legal hurdles. Dr. Gilles Arseneau of SRK Consulting
provided suggestions regarding the calculation of a mineral resource. Finally AREVA, in particular Mr.
Roland Sol, have made numerous technical contributions to the project.
In general, Argentina is a grossly underexplored country with very high potential for discovery
for uranium. Mining companies avoided exploration activity in during the two previous uranium
“booms” - after World War 2 and in the 1970’s. Most of the exploration and mining during these periods
was done by the Comisión Nacional de Energía Atómica (CNEA). Despite this, Argentina has a long
history of nuclear power generation and uranium mining. Argentina has three nuclear reactors: one
CANDU (600 Mw), one Siemens (300 Mw) and a third Siemens (600 Mw) is set to go into service in the
next few months. A fourth argentine-designed reactor (CAREN, 100 Mw) is under construction. Small
research reactors have been built in Argentina - one of these reactors is working in Australia and
another is located at the Atomic Energy Centre Bariloche (El Centro Atómico Bariloche or CAB) in Rio
Negro Province. There are three past-producing uranium mines in Argentina, but no mines are currently
in production. Uranium fuel is currently imported.
Infrastructure in the “Bajos Basin” area is excellent. The city of Neuquen (population 270,000)
is located 100 km northwest of the Santa Barbara property. Neuquen has a major airport and is an
important supply centre for the nearby oil and gas industry. Villa Regina (population 25,000) is 50 km
north of Santa Barbara. Villa Regina is the centre of a lush orchard and market garden industry adjacent
to the Rio Negro River, a large river which is sourced in the Andes Mountains and which flows into the
Atlantic Ocean north of the properties. The village of Valcheta (population 3,500) is located 70 km south
of the Ivana property.
A network of secondary and tertiary gravel roads connect the three uranium prospects. Several
high voltage transmission lines cross the properties, bringing power to coastal areas from dams in the
Andes. Although reasonably close to infrastructure, the uranium occurrences are located in a relatively
flat region with a very low population density. Rainfall is approximately 300 mm per year. Topography in
the “Bajos Basin” is subdued with relief generally less than 200 metres – it is an area of internal drainage
and salars with elevations ranging from approximately 50 metres below sea level to 250 metres. The
climate is arid with scrub vegetation. Scattered subsistence farms raise cattle, sheep and goats. Wildlife
includes guanaco (a type of llama), foxes, hares and rheas.
Figure 1 - Location Map “Bajos” Uranium Project - Rio Negro Province.
Blue Sky Exploration Work
In 2006, Blue Sky initiated a uranium exploration program in the Patagonia Region of
Argentina. Initially Dr. Jorge Armando Berizzo conducted car-borne reconnaissance in both western and
eastern Rio Negro. The program was designed to investigate continental sedimentary strata similar to
the Lower Cretaceous Chubut Group, the host rocks in the Cerro Solo uranium district in adjacent
Chubut Province. Reconnaissance was undertaken on secondary (mainly gravel) roads and tracks
utilizing a Saphymo SRAT – SPP2 scintillometer. The survey located several small uranium occurrences in
western Rio Negro which were ultimately designated to a low priority. Exploration in the eastern part of
the Rio Negro “Bajos Basin” targeted Upper Cretaceous units of continental epiclastic “red-bed” strata
of the Bajo de la Carpa and Anacleto formations as well as Cenozoic continental and marine strata which
included acid tuffaceous units as “source rocks” for uranium. On December 4, carnotite was discovered
at Santa Barbara in a road cut on Highway #66, and since the discovery took place the 4th of December
it was named “Santa Bárbara”. The Santa Barbara occurrence is associated with a Plio-Pleistocene fluvial
paleochannel overlying Upper Cretaceous clastic sediments.
Figure 2 - Geological Map of Rio Negro showing the area of Blue Sky Uranium’s tenures in “Bajos Basin”.
In August of 2007, Blue Sky contracted New Sense Geophysics Ltd of Toronto to complete an
airborne radiometric and total field magnetic survey over several areas in eastern and western Rio
Negro Province. The survey covered 2,385 km2 (a total of 14,689 line km at line spacings of 400 m and
1 km). Of this, 7,071 line km covered parts of the eastern “Bajos” Basin and identified two significant
anomalies – one over the Santa Barbara occurrence and a second over the Anit occurrence. The Anit
anomaly is 2 km wide and 14 km long. Subsequently in 2010, Blue Sky contracted Airborne Petroleum
Geophysics (Asia Pacific) Pty Ltd for a second survey totalling 22,214 line km (1 km spaced lines)
covering a total of 20,921 km2 – this survey discovered the Ivana occurrence. Other anomalies detected
in the surveys are under investigation.
Blue Sky has maintained a crew for ground follow-up which has totalled up to 10 geologists,
technicians and field assistants. In the most promising areas, surface radiometric surveys were
undertaken on 100 m spaced lines with readings at a spacing of 25 m (a total of 77,549 readings). At
both the Anit and Santa Barbara targets Blue Sky utilized electronic ionization cells obtained from Rad
Elec Inc. to measure radon flux over several days – a total of 1,230 stations were surveyed. Most of
physical testing was undertaken on the Anit project where 210 aircore holes were drilled (a total of
5,040 meters). Subsequently 310 excavator pits were completed – pits reached a maximum depth of 6
metres. In addition, 1.5 km of backhoe trenching crosscut the mineralization. More than 11,265 samples
have been collected (5,093 samples from drill holes, 4,976 from pits, 871 from trenches and 325 from
outcrops). At the recently-discovered Ivana target, a total of 17 hand pits have been completed within
an area of 28 km2.
Table 1 - Generalized Stratigraphic Column
QUATERNARY
PLEISTOCENE
RENTERIA FM
PLIOCENE
EL CUY LAVAS
MIOCENE
CHINCHINALES FM
OLIGOCENE
SOMUN CURA FM
PALEOCENE
ARROYO BARBUDO
FM
RENTERIA FM
BAJO DEL
GUALICHO FM
TERTIARY
ANACLETO FM
UPPER
CRETACEOUS
BAJO DE LA CARPA
FM
NEUQUEN
GROUP
MIDDLE
LOWER
UPPER
JURASSIC
MIDDLE
LOWER
PUESTO IRIS FM
MARIFIL
VOLCANIC
COMPLEX
UPPER
TRIASSIC
MIDDLE
LOWER
CUROCO VOLCANOPLUTONIC COMPLEX
TRENETA
COMPLEX
PERMIAN
DEVONIAN
SIERRA GRANDE FM
SILURIAN
ORDOVICIAN
UPPER
PUNTA SIERRA FM
PROTEROZOIC
UPPER
YAMINUE COMPLEX
NAHUEL NIYEU
FM
SIERRA BLANCA
DE LA TOTORA
FM
Photo 1 - Dr Jorge Berizzo above a pit with yellow carnotite at the discovery location at the Santa
Barbara Occurrence on Hwy #66.
Figure 3 - Santa Barbara Airborne Uranium Channel Contours from Airborne Petroleum Geophysics
Pty Ltd.
Figure 4 - Anit Airborne Uranium Channel Contours from Airborne Petroleum Geophysics Pte Ltd.
Figure 5 - Ivana Airborne Uranium Channel Contours from Airborne Petroleum Geophysics Pte Ltd.
Regional Geology
The eastern Cenozoic “Bajos Basin” of Rio Negro Province is located north and northeast of the
Nordpatagonian Massif. Several distinctive physiographic units characterize the area: (a) Basaltic
tablelands at the northern foothills of the Massif, (b) Mesa-type units underlain by Upper Cretaceous
clastic sediments, (c) Lower to Upper Cenozoic clastic sediments in the central and northern parts of the
area and (d) Alluvial plains drained by ephemeral rivers which flow from southwest to northeast into
“Bajos” and terminate in numerous shallow saline lakes (salars). The Cenozoic host rocks to the uranium
occurrences are clearly related to this arid landscape which consists of mesas, alluvial plains and basins
which are commonly occupied by permanent saline lagoons. Alluvial, colluvial and mass-wasting
deposits have accumulated where arroyos have eroded the soft sediments.
In the southern portion of the Rio Negro “Bajos Basin” bedrock lithologies include
metamorphic, igneous and sedimentary rocks ranging in age from Upper Proterozoic to Recent. The
oldest bedrock unit is the Yaminué Complex composed of gneisses, schists and granitic rocks that lie in
tectonic contact with the Nahuel Niyeu Formation. The Nahuel Niyeu Formation comprises low-grade
metasedimentary strata of Upper Proterozoic age. Upper Ordovician granitic rocks intrude the older
rocks. Siluro-Devonian marine sedimentary rocks unconformably overlie the metamorphic rocks.
Igneous rocks associated with Gondwana magmatism intrude the metamorphic basement and are
widespread at the northern part of the Nordpatagonian Massif. Andesites, rhyolitic tuffs, dacitic
ignimbrites and acid intrusive rocks of the Triassic Treneta volcano-plutonic complex unconformably
overlie and intrude the older igneous and metamorphic rocks. Continental sedimentary deposits of
Upper Triassic-Lower Jurassic age rest unconformably on the Triassic volcanic rocks. These strata, In
turn, are unconfomably overlain by the Marifil Volcanic Complex (dacites, rhyodacitic and rhyolitic
ignimbrites, lavas and tuffs) of Lower to Middle Jurassic age.
The western portion of the Rio Negro “Bajos Basin” is underlain by the Permian to Middle
Triassic Curacó Volcanic-Plutonic Complex. Lithologies include tonalites, granodiorites, granites and acid
volcanic rocks crosscut by northeast-trending vertical dykes of spessartitic lamprophyres and tonalitic
and dioritic porphyries. On its north contact the Curacó Complex abuts Upper Cretaceous-Tertiary
sediments in an east-west trending fault contact. The Curacó Complex extends southward to the
foothills of the Nordpatagonian Massif where it is called the La Esperanza Volcanic-Plutonic Complex.
Upper Cretaceous continental epiclastic sediments of the Neuquén Group (Rio Colorado subgroup) unconformably overlie the above rocks. Two units, the Bajo de la Carpa Formation (Santonian)
and Anacleto Formation (Lower Campanian) are sedimentary red-bed units. These units underlie the
Santa Barbara and Anit paleochannels.
The Huantraical tectonic event (about 75 my) resulted in an erosional unconformity affecting
the Upper Cretaceous red-beds. Subsequently continental and marine strata of the Malargüe Group
(itself subdivided into the Upper Cretaceous Allen and Jagüel Formations and the Paleocene Roca
Formation) were deposited on the Upper Cretaceous strata. The Arroyo Barbudo Formation records an
extensive marine transgression at the Cretaceous-Tertiary boundary and consists of pelites, fine
sandstones, marls, siltstones, and limestones. During Oligocene time the Somún Curá Formation records
extrusive extrusion of olivine basalts - small outcrops are present in the southern part of the “Bajos”
area. This extrusive event at approximately 36 Ma possibly coincides with deformation of the Neuquén
and Malargüe Groups following the regression of the Paleocene sea.
Continental epiclastic and pyroclastic rocks of the Upper Oligocene-Middle Miocene
Chichinales Formation were then deposited in the north-central part of the basin. Contemporaneously
in the north-eastern portion of the basin, continental marine sediments (carbonates, tuffaceous
sandstones, coquinas, pelites and tuffs) of the Bajo del Gualicho Formation accumulated. The midMiocene marine transgression resulted from the inversion of the regional paleoslope caused by the rise
of the Andes Mountains and attendant subsidence in the “Bajos” area.
Unconformably overlying the Chichinales Formation, the Upper Miocene Sierra Blanca de la
Totora Formation contains epiclastic, pyroclastic and chemical sediments (carbonates) of continental
origin. It in turn is conformably overlain by the Upper Miocene El Palo Formation composed of coarse
sandstones and tuffs of continental-fluvial origin. Subsequently, Lower Pliocene olivine-bearing basaltic
“El Cuy” lavas record extrusive volcanism. Plio-Pleistocene Rentería Formation clastic sediments succeed
the basaltic volcanism.
During the Pleistocene Period there was erosion as well as deposition of alluvial sediments and
formation of several Quaternary terraces associated with the Limay, Rio Negro and Cullén Leufú Rivers.
During Late Pleistocene extensive pediment surfaces were developed. Holocene deposits consist of
lacustrine sediments as well as sand dunes, alluvial and colluvial accumulations and present-day alluvial
fans.
Regional Structure
The most important structure, as far as the development of the “Bajos Basin”, and the
environment associated with the uranium mineralizing event, is the NW-SE trending normal fault which
links all of the most important “Bajos” (Los Menucos, Trapalcó, Salitral Negro, Ojo de Agua and del
Gualicho). This fault defines the north-eastern limit of the Nordpatagonian Massif and the area of
subsidence of the Rio Colorado Basin.
A second important regional structure is the Rio Negro Fault which trends at 0800 and is also
the structure controlling the course of the Rio Negro River.
The Curaco Heights is underlain by the Triassic Treneta volcano-plutonic complex that forms
the western limit of the Eastern Cenozoic Rio Negro Basin. The northern limit of the Curaco Heights is
controlled by an ENE-WSW fault that is coincident with the course of El Salado Creek. The southern limit
is believed to be controlled by an ENE-WSW fault which controls the course of El Loro Creek. Another
important regional fault is associated with the Cabeza de Potro Valley and trends NE–SW.
Property Geology
The Santa Barbara occurrence is hosted by a Mesozoic to Quaternary sedimentary sequence
overlying the Triassic Treneta volcanic-intrusive complex. Outcrops are scarce in an area of low relief,
and stratigraphy can only be seen is stream (arroyo) cuts. The Cretaceous sedimentary sequence begins
with Santonian-age Bajo de la Carpa Formation continental sediments composed of fine to
conglomeratic sandstones intercalated with green clay and lenses of gypsum and petrified (silicified)
wood. Pebbles in the conglomeratic sandstones range up to about 1 cm. These sediments are in turn
covered by continental tuffs with clay interlayers of the Oligocene-Miocene Chichinales Formation.
Upper Tertiary and Quaternary Photoau basalts commonly cap mesas. Quaternary and Recent
sediments cover all the “Bajos”. The host Bajo de la Carpa Formation strata appear to reflect a floodplain environment of moderate to low energy.
The geological environment at Anit is similar to Santa Barbara, with outcrops of Cretaceous
sediments of the Bajo de la Carpa Formation covered by younger sediments and soils. In contrast to
Santa Barbara, mineralization is hosted in these younger sediments that consist of cross-bedded gravels
and sands with abundant petrified logs, some of which reach several metres in length. Locally the
conglomeratic and/or sandy host rocks are stained with brown iron oxides. The conglomerates are
coarser than the pebbly sandstones at Santa Barbara with quartz pebbles up to 2 cm in diameter. The
environment appears to be that of a high-energy fluviatile paleochannel.
At both Santa Barbara and Anit, the fluviatile channel systems overlie green clay units that predate the uraniferous clastic sediments. The green clay layers vary in thickness between 1 and 20 m and
are believed to be post-Cretaceous and to occupy depressions (or a valley) above the Cretaceous
sediments. Based on a preliminary palynology study by Davis (2010), the gravels and sands have a late
Paleogene or Pleistocene age. They are topographically a few metres higher than the current arroyos.
The environment at the recently-discovered Ivana occurrence contrasts with Santa Barbara
and Anit. The oldest units in the area are marine sediments of the Upper Cretaceous-Lower Paleocene
Arroyo Barbudo Formation. The Arroyo Barbudo Formation consists of a Lower Member (Aguada de
Cecilio - Maastrichtian Age) with claystones and limestones capped by a layer of coquina and an Upper
Member (El Fuerte-Danian Age) with calcareous sandstones and coquina. These are overlain by
sandstones and tuffaceous and coquinal sandstones of the Eocene-Miocene Gran Bajo del Gualicho
Formation, which is in turn overlain by sandstones and conglomerates of the Pliocene Rio Negro
Formation. Pleistocene and Holocene sediments complete the sequence. Uranium mineralization is
hosted in fine sandstones interbedded with white clays with small fragments of plant leaves and stems
tentatively believed to correspond to the Gran Bajo del Gualicho Formation.
Mineral Occurrences
To date, carnotite K2(UO2)2(VO4)2·3H2O, a uranyl vanadate, is the only visually recognized
uranium mineral. It is possible that other uranium minerals such as tyuyamunite Ca(VO4)2(UO2)2·8H20
could be present because no comprehensive mineralogical studies have been undertaken. No clear
correlation has been recognized between the uranium mineralization and any specific lithology.
Mineralization occurs in all sedimentary rocks (conglomerates, sandstones and claystones) and recent
sediments (gravels, sands, clays and soils). Petrified wood is present at both Santa Barbara and Anit, but
has not been found at Ivana. Gypsum (CaSO4.2H2O) is abundant at Anit and closely associated with the
carnotite. AMMTEC Ltd (2010) also reported bassanite (2CaSO4.H2O) in Anit samples. Gypsum is also
important but less conspicuous at Santa Barbara and Ivana. Calcrete, while locally present, is relatively
scarce in all three occurrences.
At Santa Barbara, Blue Sky has completed airborne and ground radiometric and radon surveys
which have outlined three parallel radiometric anomalies measuring 11 km, 6.5 km and 5 km in length
and up to 1.5 km in width. The anomalies reflect a near-surface horizon of uranium mineralization in
poorly consolidated Cretaceous sediments. Thirty-five hand-augured holes have been drilled to a depth
of 2-3 m at Santa Barbara and have outlined mineralization between 0.5-1.0 m in thickness at a depth of
0.5-1.5 m below the surface. Hand pits exposed mineralization of up to 0.035 % U over 1 meter.
Figure 6 - Anit occurrence as outlined by aircore drill holes.
Figure 7 - Anit occurrence as outlined by Excavator Pits.
Photo 2 - Daniel Bussandri in prospect pit with high-grade carnotite mineralization at the
Anit occurrence.
Photo 3 - Trench through high-grade mineralization at the Anit occurrence.
Photo 4 - Trench 5 Anit occurrence - High-grade carnotite on crossbeds in pebble conglomerate.
Photo 5 - Trench 5 Anit occurrence - Top, carnotite on petrified wood; Lower left, carnotite disseminated
in matrix of pebble conglomerate – Lower centre and right, coarse gypsum rosettes.
Photo 6 – Carnotite coating pebble adjacent to coarse gypsum (white) at the Anit occurrence.
The Anit occurrence is located 60 km southeast of Santa Barbara. Mineralization at Anit is
hosted by gravels in a linear fluviatile channel. The occurrence has been tested with 210 aircore holes (a
total of 5,040 m). Unfortunately the friable carnotite mineralization was pulverized during drilling and
significant quantities were lost in the exhaust from the cyclone recovery system. Blue Sky subsequently
completed and sampled a total of 310 excavator pits of up to 6 m depth. The pits were dug with a CAT
320 L Excavator and tested the occurrence along north-south lines. At Anit Central, lines were spaced at
spaced 400 m, with pits generally spaced at 40 m on the lines. At Anit West lines were spaced at 200 m
with pits at 40 m. This work has produced more reliable samples and has documented a channel-shaped
mineralized zone more than 6 km long with a higher-grade and thicker central core. The mineralization
is an average of 1.97 metres thick, but it ranges up to 6 metres in thickness. The mineralized
paleochannel ranges in width from 40 to 480 m and covers a linear-lenticular area of approximately
1 km2. Overall the mineralized pits (103 pits with greater than 50 ppm U over 1m) average 0.04 % U3O8
(338 ppm U) and 594 ppm vanadium. Vertical channel samples were collected over 0.50 m intervals
down 3 walls of each pit and combined into one sample of approximately 5 kg. The north wall of each pit
was mapped to facilitate correlation of individual units between pits.
Photo 7 - Ivana 1 Cateo – Uranium showing a few metres below the crest of a mesa flanking Laguna Tres
Picos (one of the salars in the “Bajos”area).
The Ivana occurrence is located 40 km southeast of Anit in the Bajo de Valcheta area.
Preliminary reconnaissance (ground scintillometer prospecting and 17 hand pits) has been undertaken
within an anomalous area of approximately 25 km2. The best pit returned 575 ppm U (0.068 % U3O8)
over a width of 3 metres. No silicified petrified wood has been found at Ivana – however plant remains
as well as pelecypods are present. The environment at Ivana is strikingly different from Santa Barbara
and Anit – Ivana is located near the terminus of a closed sedimentary sub-basin that is approximately 40
km wide. The basin drains rhyolitic volcanics with high background uranium values.
Metallurgical Testing
Independent Metallurgical Operations Ltd (IMO) prepared a “Sighter Metallurgical Testwork
Report (November 2010)” on metallurgical testing of mineralized samples from for the Anit occurrence.
This work demonstrated that most of the mineralized material from the Anit occurrence can be
significantly upgraded by simple and inexpensive wet screening to remove coarse pebbles that contain
little or no uranium mineralization and producing relatively high-grade concentrates. An example from
the 0.2 mm split is presented below in Table 2.
Table 2 - Upgrading Flowsheet at 0.2 mm Split (Furfaro, 2010)
The results are preliminary and based on seven selected samples of the main uraniummineralized lithologies at Anit – the study was designed only as a guide to future detailed metallurgical
investigations.
Discussion and Conclusions
1 - Classification
Overall, the environment in the “Bajos” region shows many similarities to that which hosts
important “surficial-type deposits” in Western Australia and Namibia – however there are significant
differences. Firstly, the carnotite mineralization and host sediments in the “Bajos” region are underlain
by Mesozoic clastic sedimentary rocks and not by Precambrian “basement”. Secondly, the fossils present
in the host sediments suggest an arid but not a desert environment. Thirdly, the host sediments (and
probably the uranium mineralization) appear to range from Miocene to possibly Pleistocene in Age
based on preliminary palynological studies, whereas the Australian and Namibian deposits are younger.
The above features of the “Bajos” occurrences, and particularly their paucity of calcrete, are
major departures from the model described by the Cuney and Kyser (2008) in their classification of
calcrete-hosted uranium deposits. At Santa Barbara and Anit, the host fluvial sediments are poorly
consolidated sands and gravels associated with gypcrete and show similarities to the Tubas Deposit in
Namibia (Pagel, 1984) and to the Laguna Salada Deposit in neighbouring Chubut Province (Rodrigo et al,
1984).
2 - Genesis
Genetically, the uranium mineralization appears to have been deposited under semi-arid
conditions by groundwater. Most of the Cenozoic formations in the Eastern Cenozoic Basin contained
acid tuffs, whose aggregate thickness reached more than 200 metres – during devitrification and
weathering these could have constituted a huge source of uranium in groundwater. Airborne
radiometric surveys also point to sources for the uranium up-slope to the west, where highly uraniumanomalous felsic rocks outcrop. The Permo-Triassic Curacó plutonic-volcanic complex outcrops 40 km
west of Santa Barbara. The Triassic-Jurassic Treneta Complex (rhyolitic and leucocratic intrusive rocks) is
highly uranium-anomalous and outcrops the same distance west-southwest of Anit. Rhyolitic
ignimbrites and associated felsic extrusive rocks of the Jurassic Marifil Volcanic Complex outcrop
adjacent to and up-slope from Bajo de Valcheta where the Ivana occurrence is located.
Although there are no obvious local mafic or ultramafic rocks which might constitute a source
for the vanadium, there are several episodes of basaltic volcanism in the stratigraphic record.
Throughout the area, black magnetite-rich heavy mineral accumulations are common in arroyos and
sheet wash areas. At the time of the formation of the Anit and Santa Barbara fluviatile channels,
magnetite likely accumulated with other heavy minerals. The magnetite could have oxidized during the
prolonged weathering interval associated with the silicification of the petrified wood. The released
vanadium might have combined with dissolved uranium carried in the silica-rich groundwater to
precipitate carnotite.
3 - Economic Potential
Finally, the Metallurgical work by Independent Metallurgical Operations Ltd demonstrated that
most of the mineralized material from the Anit occurrence can be significantly upgraded by wet
screening to remove unmineralized coarse pebbles. Upgrading has the potential to significantly reduce
processing and transportation costs making the development of several satellite deposits utilizing one
central operating facility economically attractive. This simple beneficiation process resulted in a grade
that is comparable or exceeds the head grade of geologically similar deposits in Africa and Australia.
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