projects > cerro solo uranium play
Pacific Bay has two properties in the Patagonia region of southern Argentina: Cerro Solo claims and Regalo property. PacBay's Cerro Solo claims lie to the east of the Cerro Solo uranium mine (estimated to hold 10.3 million pounds of uranium) which is the subject of increasing international interest. The Cerro Solo claims include 3 contiguous uranium exploration concessions totaling 300 square kilometres (115 square miles) were acquired based on favorable geology and proximity to the Cerro Solo, Cerro Condor and Los Adobes uranium deposits. In April/May of 2006, Mega Uranium (MGA.TSX) conducted a reconnaissance RC drilling programme next to PacBay's claims to investigate the projected extension of the mineralized zone eastwards from the Cerro Solo uranium deposit. The programme, comprising 26 widely spaced holes of 42-144 metre depths, included intersections of 2m @ 0.11% U3O8 and 1m @ 0.21% U3O8. Mega intends to conduct detailed drilling programmes in the vicinity of both these intersections. In April 2007, Pacbay optioned the Cerro Solo claims to Argentinean explorer Portal Resources. Portal can earn a 60% interest by spending a total of $1.2M over 4 years.
Regalo's "Arroyo Pajaritos Uranium Prospect"
In June 2005 the Company announced an outcrop sample assaying 205 ppm uranium on our Regalo property. This finding prompted PacBay 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, PacBay 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. PacBay plans to kick-start exploration on the Regalo Uranium prospects in the near future.
"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.
