projects > regalo uranium property
Pacific Bay's 100% owned Regalo uranium property is located in the Patagonia Region of southern Argentina approximately 70 kilometers southwest of Pan American Silver's world class Navidad silver-lead project. The Regalo property lies to the north-west of the Cerro Solo uranium mine (estimated to hold 10.3 million pounds of uranium) which is the subject of increasing international interest. The Regalo was originally explored for gold from 2004 to 2005 and hosts widespread epithermal- style alteration (learn more about the gold exploration below). In June 2005, Pacific Bay discovered an outcrop sample assaying 205 ppm uranium on the Regalo property and initiated further activities for its uranium potential. In 2007, Pacific Bay initiated a 400,000 KM airborne radiometric and magnetic survey at Regalo (cost, approx $400K by paid for by previous partner Aquiline). Completed in 2008, the survey identified numerous priority uranium targets.
Regalo's "Arroyo Pajaritos Uranium Prospect"
Located within the San Jorge Basin, the Regalo Property hosts rocks of the Arroyo del Pajarito member of the Los Adobes formation which contains the most significant uranium deposits in the region. The 205 ppm uranium finding on the Regalo property prompted Pacific Bay to file for additional claims to expand the Regalo Project to the north and east to cover and protect three known uranium prospects, known as Arroyo Pajaritos (See Regalo Uranium Prospects image). The Regalo Project claims were originally filed for gold and completely surround a government-owned uranium occurrence (known as Torre 610 Claims) uncovered during construction of the high voltage power line through the area in the 1980's. During the 2005 field season, Pacific Bay geologists saw indications of a classic roll-front type uranium system in volcaniclastic sediments of Cretaceous age. A rock sample of an approximately 30 cm thick, gray-brown coloured, reduced siltstone layer exposed in a cliff outcrop at Arroyo Pajaritos. Beyond initial prospecting, this showing is unexplored.
"Arroyo Pajaritos Uranium Prospect" - Possible Roll Front Uranium Deposit
Roll-front uranium deposits are formed where groundwater in permeable sandstone or conglomerate encounters the interface between oxidizing and reducing conditions. Uranium in solution is precipitated at the interface, often forming a crescent-shaped roll-front ore body.
Reference: Heylmun, Edgar B., 2003, Roll-Front Uranium Deposits: ICMJ's Prospecting and Mining Journal, October, 2003. http://www.icmj2.com/03Oct/03OctFeature.htm
Over the years, the reduction front will migrate in the direction of groundwater flow, thus creating an ore body that may extend for hundreds of feet. The crescent tips will often string-out and create tabular blanket deposits which may contain black and yellow uranium oxides. Oxidized zones are often distinctive features of uranium deposits, as shown on the illustration. Some deposits can be found just by noting the colors that are usually present. However, the deposits are usually found with radiation detectors long before other details are noted. Exceptions could be where uraninite or coffinite is so newly-formed that radioactive daughter products have not yet formed. These non-radioactive uranium deposits have to be discovered by means of chemical analyses. There are a lot of uranium deposits that are tabular and are not roll-fronts. Such beds often adjoin organic mudstones or shales, or occur where there are organic trash pockets in the sandstones. The rich deposits at Lisbon, Utah, and Grants, New Mexico, are tabular.
Arroyo Pajaritos Uranium Prospect - A Closer Look
In the image below, the yellow colour anomaly in the normally red Cretaceous sandstones marks a zone with elevated background radiation and is typical of roll-front uranium deposits. The 205 ppm uranium sample was taken form the cliff just out of sight to the left.
The yellow colours in the redbed sandstone and conglomerate sequence associated with the roll-front type uranium mineralization can be seen in the background in the following photo.
The following is a view of strongly radioactive siltstone layer exposed along cliff at Arroyo Pajaritos. A sample collected here assayed 205 ppm U (0.48 lbs/t U3O 8) in a zone approximately 0.5 m thick. The siltstone layer contains a small amount of carbonaceous plant debris and is up to 1.5 m thick. It is bounded above and below by coarse channel sandstones and conglomerates of the Lower Cretaceous Pajaritos Member of the Los Adobes Formation which is the basal member of the Lower to Middle Cretaceous age Chubut Group.
Here is the Arroyo Pajaritos uranium prospect, looking north, with yellowish color anomaly visible in redbed sandstones and conglomerates in the background.
Torre 610 Claims
The following is a view of the Cretaceous-age sedimentary basin on the 23 km2 government "Torre 610" claim which sits in the middle of Pacific Bay's 10 km X 10 km Regalo III claim. Uranium mineralization in this area is hosted in low-energy, continental-fluvial sandstones and siltstones overlying the basal conglomerates of the Pajaritos member of the Los Adobes Formation. The sedimentary units are deformed into an anticline-syncline pair by drag folding in the hanging wall of the main NW trending fault. The Regalo gold anomalies are in the older Jurassic age rocks in the footwall of this regional fault to the west.
Below is a view from the Regalo III claim looking west/north to the "Torre 610" claim. Uranium was uncovered here in the 1980's during construction of the dual high tension powerlines supplying an aluminium smelter on the coast from a hydroelectric project in the cordilleran Lake District. The basalt tower in the background is the "Gorro Frigio" named for the hat worn by the freed Roman slaves and copied from the French Revolution onto the Argentine national shield. The Tehuenche indians believed this to be the medicine bag of the sorcerer Yastekt.
Below is a close -up of yellow autinite in roadcut on the "Torre 610". Epigenetic uranium mineralization in this area is hosted in low -energy, continental-fluvial sandstones and siltstones overlying the basal conglomerates of the Pajaritos member of the Los Adobes Formation. Regionally, this basin that hosts the Cerro Solo uranium deposit is characterized by epigenetic mineralization found at several stratigraphic levels.
Regalo's Gold Potential
The Regalo property lies in the arid, windswept extra-Andean Patagonian steppes in an area of subdued topography and poor outcrop that was not thoroughly prospected during the mining exploration boom of the 1990's when companies focused instead on the better outcrops in the Andean cordillera and foothills to the west. The Navidad silver-lead deposit 70 kms north of the Regalo property led explorers to stake favourable Upper Jurassic to Cretaceous calcareous clastic and volcaniclastic rocks similar to those hosting the Navidad mineralization along, crustal-scale, northwest trending, structural zones. The Regalo property encompasses one of the strongest multi-sample gold anomalies in the regional stream sediment database.
Pacific Bay began reconnaissance of the Regalo property in January, 2004, and quickly followed up on very encouraging gold values in dry-wash silt samples with a second field campaign in February-March, 2004. During the 2005 summer field program, it was discovered that Regalo hosts widespread epithermal- style alteration of host rock limestones, calcareous clastic sediments and volcaniclastic units. The hydrothermal alteration of these sediments and volcanics takes the form of widespread replacements of favourable stratigraphic horizons by chalcedony, jasperoid, "silicrete" or "ferricrete" in some of the gold anomaly areas, and by strong argillic (clay) alteration in others. Pathfinder elements such as arsenic, lead, copper and molybdenum are present at weakly anomalous levels in some of the hard, resistant rocks at the surface, but it is believed that the bedrock source of the strong gold anomalies tends to recede in outcrop and lies beneath soil cover.
Project History
The project began with exploration on the original "Regalo" claim, or cateo covering an area of 10,000 hectares (38.6 square miles). It quickly became apparent to Pacific Bay that potential gold mineralization extended to the north, and early in 2004 the "Regalo II cateo" was staked immediately to the north covering another 10,000 hectares (38.6 square miles). Work during the 2004-2005 austral summer field season has led Pacific Bay to file for an additional 7,670.8 hectare (29.6 square mile) cateo over an area immediately to the east of the Regalo and Regalo II cateos. Approval of this "Regalo III" cateo is expected to be received from Chubut province in due course. All properties requested to date become part of the Regalo project under the option agreement's perimeter clause.
Fall 2004 Exploration
Pacific Bay's geological team carried out its first phase field program during the austral spring months of October and November, 2004.
Over 1,600 samples were taken, and the majority of these were soils collected on widely spaced grids with lines 200 m (656 ft) apart with 50 m (165 ft) sample spacing along the lines. Four main areas were tested, the Discovery Zone, the Jasperoid Zone, the Yastekt - West Valley Zone and the Yastekt South Zone. Although each area appears to have a somewhat different geological character, each returned substantial areas of strong gold soil anomalies of 100 ppb Au and above. Significantly, the highly anomalous gold values are not isolated occurrences, but rather appear in long strings over hundreds of meters along contiguous lines within each of the soil grids, over terrain with no outcropping rock exposures.
Discovered - 2005
In the Yastekt South Zone, the strong gold anomalies are consistent over almost one square kilometre. The Yastekt South anomaly comprises 98 soil analyses that average 299 parts per billion gold. Normal, "background" gold values in the area are less than 5 parts per billion. Two of the 98 soil analyses returned values in excess of 3 grams per tonne gold, which, if removed from total, result in an average across the approximately one kilometre square zone of 236 parts per billion gold, which is considered to be very anomalous.
Preliminary indications are that several localities are now ready for trenching and test pitting to define targets for drilling.
All technical work on the Regalo property to date has been done by Dr. Richard Culbert, P.Eng. who is an arms-length, independent Senior Consulting Geologist to Pacific Bay Minerals and Qualified Person under Canadian National Instrument 43-101.