Marysvale Project

The uranium mineralization in the Marysvale Project area formed approximately 19 Million years ago when rhyolite magma began intruding the uranium-enriched rocks underlying the area. The pressure from the magma caused above rocks to fracture and the heat from the magma fuelled a hydrothermal system with fluids enriched in uranium and molybdenum. These fluids filled fractures creating the uranium and molybdenum bearing veins, such as the ones mined in the Central Mining Area in the 50’s and 60’s. Since the time of their formation, the uranium bearing veins have been subject to leaching processes caused by ground and meteoric water. These processes have transported part of the uranium from the veins and deposited it in horizontal pods at groundwater level. The exploration targets at Marysvale thus include both primary uranium ore (in the veins) and secondary uranium ore (in horizontal pods). For a more detailed description of the property geology please see below.

	Figure A: Intruding magma caused faulting and fractures in above bedrock.
	Figure B: Uranium was deposited in faults and cracks by a hydrothermal system fuelled by the upwelling magma

The Marysvale property occurs within the Marysvale volcanic field, one of the largest Tertiary volcanic fields in the western USA. There are two main intervals of volcanic activity in the Marysvale field separated by an erosional unconformity; the intervals are distinguished by a shift in composition related to the changing nature of the North American plate margin to the west.

The volcanic rocks were erupted through and onto an older sequence of Mesozoic to Lower Cenozoic sediments which outcrop to the west, but are not exposed in the vicinity of the property. These sedimentary rocks are represented by a 1,800 m section of quartzites, shales and limestones exposed on Deer Trail Mountain about 9 km southwest of the property.

The older and more voluminous volcanic interval in the Marysvale field is represented by the Bullion Canyon Volcanic Series, which erupted from multiple vents over the period 35 to 22 Ma. The series is characterized by intermediate calc-alkaline rocks, dominated by dacitic and rhyodacitic lava flows and ash-flow tuffs, estimated to aggregate a total of 600 to 900 m in thickness.

The Monroe Peak caldera is the largest caldera in the Marysvale field, measuring about 18 km from north to south, and 26 km from east to west. The caldera formed with the eruption of an estimated 208 cubic kilometres of rhyodacitic ash-flow tuff about 23 Ma, and the intracaldera rocks were then intruded about 21-22 Ma by masses of quartz monzonite and granite that represent shallow cupolas derived from a deep source batholith. These intrusives drove hydrothermal systems that have pervasively altered the intracaldera rocks. The 22 Ma “Central intrusive” quartz monzonite is one of these intrusives. It is the host rock for the majority of uranium production recorded from the Marysvale area. Several replacement alunite deposits have a genetic association with the Central intrusive.

An erosional surface developed on the Bullion Canyon volcanics prior to eruption of the Mount Belknap Volcanic Series, beginning about 21 Ma. At this time, the North American plate margin to the west shifted from a subduction margin to a transform regime. The Mount Belknap rocks are alkali rhyolite flows and tuffs with the largest individual units reaching 450 m in thickness. They were erupted from two sources, an eastern, and a western source area. The eastern source area erupted within the Monroe Peak caldera, and migrated across the caldera rim to the southwest over time.

Steven et al. (1981) demonstrate that large volumes of Mount Belknap rocks have been leached of 20 to 25 % of their original uranium content by devitrification of volcanic glass, and conclude that the Mount Belknap and younger rhyolites are the source of all significant uranium mineralization in the Marysvale area.

Siltstone, sandstone and conglomerate of the Miocene Sevier River Formation were deposited in area basins and grabens, and alluvial fan and flood-plain deposits of Quaternary age are found on present-day valley floors.

Two styles of faults occur in the Marysvale area: steep faults of variable orientations associated with intrusion and collapse of magma chambers, and north-northeast- and north-northwest-trending faults related to basin and range extension.

Most of the 1.4 million pounds of U3O8 production recorded from the Henry Mining District has come from the Central Mining Area, within one mile west of and adjacent to the Property. The production came from steep magmatic-hydrothermal veins that cut the “Central intrusive” quartz monzonite, and younger fine-grained granite. These veins continue upwards into horizontal veins contained within an overlying rhyolite flow unit of the Mount Belknap Series. Production was also derived from the flat veins.

In general, veins are genetically associated with an unexposed rhyolitic stock of the Mount Belknap Series, dated at about 18 Ma, which intruded the Central intrusive below the lower limit of underground workings and drilling. Emplacement and subsequent collapse of the stock fractured the overlying roof rocks, allowing hydrothermal fluids to precipitate uranium-bearing quartz-fluorite veins in the resultant open-space fractures.

The uranium veins show a close spatial relationship to distinctive, glassy rhyolitic dikes that contain anomalous molybdenum and uranium. Dike material forms the matrix of a vertical pipe of breccia that manifests the abrupt pressure release that allowed the roof blocks to settle. The relative competence of the Central intrusive quartz monzonite allowed it to hold open fractures and localize the uranium mineralization. USGS geologists have postulated that the uranium-bearing veins are the near-surface expression of a Climax-type molybdenum porphyry deposit at depth.

The property sits at the intersection of the eastern source area for Mount Belknap volcanics, and the Monroe Peak caldera. Surface exposures on the property are dominated by rhyodacitic lava flows of the Monroe Peak intracaldera sequence, with subordinate volumes of tuffaceous sandstone and airfall tuff. The volcanic units are horizontal or inclined at low angles to the east. Rhyolite domes and plugs of the Mount Belknap Series intrude the flows. Hydrothermal alteration is widespread, and resistant knobs of siliceous sinter occur at the sites of former hot springs. In places, silicic and advanced argillic alteration has obliterated primary textures.

The Central intrusion, a 22 Ma intracaldera quartz monzonite, outcrops along the western side of the property. Several hydrothermal deposits of replacement alunite on the property are genetically associated with the Central intrusive. These include the Mary's Lamb and the Al-Kee-Mee deposits.

The property is cut by northeast- and northwest-trending faults that are related to basin and range extension. Late hydrothermal alteration may have been localized along some of these faults.

Uranium occurs as supergene mineralization in strongly clay-altered rhyolitic volcanics. Secondary uranium minerals are found at several locations on the surface.