January 2012 Technical Presentation
Magnetic and Gravity Datasets: Mapping Tools for Exploration Under Cover
Helen Williams, Senior Geophysicist, MMG

One of the most pressing challenges society currently faces is the ever-increasing demand for resources fuelled by population growth and development of the third world. As such, it is with some irony that those of us in exploration also head towards the realisation that the potential for discovery of large ore deposits outcropping at the surface of the Earth has become vastly diminished.

The world's next big discoveries are unlikely to be poking out of the ground but more probably exist in a search space that is decidedly more difficult to explore because we are largely blind to it. As a matter of urgency, we need to become more clever about the way we investigate geology, structure and mineralisation not only under cover but at depths we haven't traditionally been comfortable exploring to.

Potential field (e.g. magnetic and gravity) datasets provide a powerful means of investigating the subsurface in three dimensions from the continent/lithosphere-scale to the local-scale, often providing key insights into lithology, structure and tectonic history of an area - all crucial elements in providing a context for economic mineralisation.

High-resolution magnetic and gravity datasets are relatively cheap (or in some cases free) to acquire (particularly in North America and Australia) and yet are severely underutilized as a resource in both industry and academia. These data can be used to interpolate between isolated locations of geological information (e.g. drillholes, seismic sections, structure and geology in outcrop) and integrate well with other forms of spatial data to unravel a three dimensional geological history of an area. Hence magnetic and gravity data can aid an understanding of an area from a regional project generation perspective right through to the targeting stages of a campaign.

As technology advances and our software and hardware capabilities increase, 2D/3D quantitative and qualitative analysis of magnetic and gravity data is becoming ever more exciting. Progress in processing, imaging, modeling and interpretation methodologies of these data have been competing well to match the superior advancement in acquisition technologies achieved over the last century. The result is not only a greater resolution in datasets acquired but a near proportional increase in the amount of geological information that can be gleaned from them. The applications of gravity and magnetic data in exploration are wide-ranging in terms of commodities and deposit styles.

This presentation will include case studies and examples from North America and Australia to illustrate the enormous value that gravity and magnetic data can bring to exploration by aiding a better understanding of a given area at a number of scales.


February 6, 2012 Technical Presentation
We've Always Preferred Lucky Geologists to Good Ones
Peter Maciulaitis

In 1982, Franco Nevada Mining Corporation Ltd. (FNMC) was created by Seymour Schulich to test the entrepreneurial skills of young metals analyst Pierre Lassonde. FNMC went public in 1983, raising $2M Cn selling shares at $0.35 Cn. FNMC listed on the Toronto Stock Exchange. Over the next 20 years, FNMC grew into the world's 5th largest gold mining company as measured by market capitalization. In 2003, FNMC merged with Newmont Mining, making Newmont the largest gold mining company in the world. Pierre Lassonde became Newmont's president. FNMC had operated with a very small staff of employees and consultants.

Initially, FNMC attempted to achieve cash flow by finding, then mining a gold deposit. Attempts to develop reserves at an inactive gold mine and later by drilling a low-grade gold resource both failed. In 1986, two consulting geologists alerted Lassonde that the underlying royalty on the Goldstrike property was for sale. Located along the Nevada's Carlin Trend, Goldstrike was producing only 42,000 ounces of gold per year. FNMC quickly acquired the royalty gaining instant cash flow without a discovery or mining. A few months later American Barrick Resources Corp. purchased the Goldstrike operations. Goldstrike was on the road to becoming the largest gold mine in US history.

In 1985, FNMC began grassroots exploration utilizing a consulting geologist, adding a second consultant in 1987. As royalty income quickly increased, FNMC feared being classed a passive foreign investment company (PFIC). To avoid becoming a PFIC, gain exploration exposure, and obtain mining intelligence, FNMC and a sister company, Euro-Nevada Mining Corporation Ltd., provided these geologists with a budget of $600K-$1M Cn/year. In 1993-1994, the unthinkable occurred. A high-grade vein gold deposit was discovered, helping double the value of the companies.


March 12, 2012 Technical Presentation
The Wyoming Uranium Province -
A Case Study on the Origin of Sandstone Uranium Deposits
W. William Boberg

The Wyoming uranium province is a major uranium province with occurrences in nearly all rock units exposed in the region. Approximately 91,000 tonnes (t) of U3O8 have been produced since the early 1950s and approximately 165,000 t U3O8 "forward-cost reserves" are recognized in the region with significant uranium having been mined from geologic units of various ages from Cretaceous to Oligocene. Many technical studies from the 1950's through the 1980's make the province a good case study on the origin of sandstone uranium deposits.

The observation that the major uranium deposits within Cenozoic sedimentary rocks are generally in clusters that surround the Precambrian core complexes of central Wyoming suggests that the origin of the Wyoming uranium province most likely started during the Archean with the formation of granitic and metamorphic rocks of the Granite Mountains of central Wyoming. The major deposits in the Wyoming uranium province occur as roll fronts in fluvial sedimentary units of both Paleocene and Eocene age, whereas other economic deposits in the province occur in Cretaceous sedimentary rocks and brecciated rocks of Precambrian age. Regardless of the age or type of host rock, it is likely that many of the deposits have a common genesis.

Crustal deformation initiated during the Laramide orogeny and throughout the early Tertiary resulted in the creation of major basins containing significant volumes of Tertiary sediments adjacent to the Precambrian core complexes. Extensive physical and chemical weathering of the Precambrian cores of the uplifts took place during early Tertiary due to the subtropical climate with high rainfall. Studies demonstrate that the central Wyoming Precambrian granitic rocks lost 50 to 75% of their uranium content during the Laramide events.

Volcanism in the western United States, starting in middle to late Eocene, affected the Wyoming region, followed by extensive periods of volcanism from various centers that continued sporadically through the Pliocene and into the Quaternary. Extensive deposition of thick rhyolitic tuff sequences were deposited throughout the region over a span of more than 45 million years. Uranium-rich weathered debris from the Precambrian highlands was included in thick beds of tuffaceous sediments deposited in the basins. Uranium was readily leached from these ash-fall tuff sequences by the dissolution of the glassy ash.

Uranium enriched surficial water which leached uranium from the ash fall tuffs and deeply weathered Precambrian rocks was the ore-forming fluid for the roll fronts and related deposits. The Wyoming uranium province had the benefit of having had those two major sources of uranium available to create deposits in the sandstones of the region. Once in solution, the uranium was transported in surficial waters along paleodrainage systems that shifted across the landscape in response to various regional and local tectonic events. Where the paleodrainage systems encountered groundwater recharge areas along their flow path the uranium enriched water recharged the ground water below the paleodrainage systems. Favorable locations for the deposition of uranium deposits were permeable rocks capable of transmitting significant quantities of the ground water.

The oxidizing, uranium enriched groundwater moved into porous and permeable sandstones in the subsurface, sometimes traveling greater than 10 kilometers downdip before reducing conditions caused the uranium to precipitate. Organic carbon buried with the original sediments or the leakage of hydrocarbons into the sediments from below created the reducing conditions which resulted in the precipitation of the uranium in the sandstone host rocks. Acid neutralization of the uranium enriched waters in carbonate karst regions resulted in the precipitation of uranium minerals in caverns and karst breccia pipes.

Exploration methods, primarily drilling and geophysical logging of drill holes, using these concepts of the origin of these deposits, have been very successful at discovering new deposits in the Wyoming region.


April 2, 2012 Technical Presentation
The Nature and Significance of High-Grade Metamorphism and Intense Deformation on the Izok VHMS Alteration Halo and Deposit
By Robert M. Nowak

Exploration for volcanic-hosted massive sulfide (VHMS) deposits is challenging in metamorphosed and deformed terrains especially as the shape and mineralogy of hydrothermal alteration halos enveloping mineralization may be cryptic. My research aimed to determine the effects of high-grade metamorphism and intense deformation on the mineralogy, textures, and geochemistry of altered metarhyolite in the footwall to the Izok VHMS deposit, Nunavut, Canada.

This study found consistent patterns in metamorphic mineral assemblages and geochemistry occur within the footwall on the scale of the footwall, but also zoning on more complicated, centimeter to meter scales. On the footwall scale, assemblages in footwall metarhyolite distal to the massive sulfide are dominated by quartz, muscovite, and albitic feldspar. Locally, primary volcanic textures such as breccias, are preserved. Closer to mineralized zones the quartz-muscovite schist contains prominent muscovite-plagioclase nodules, and closer still the appearance of sillimanite-muscovite nodules. The most proximal domains of footwall metarhyolite consist of garnet-biotite- and cordierite-biotite+/-garnet- dominated assemblages.

Systematic geochemical analysis revealed that Zr/TiO2 ratios of footwall metarhyolites are distinct from other lithologies analyzed (meta-andesite and metagabbro). Similar Zr/TiO2 values down-hole through the footwall and linear variations in Zr vs. Ti diagrams indicates that these elements were relatively immobile during pre-metamorphic hydrothermal alteration, and therefore are useful to correlate metamorphosed equivalents of primary rock types in this setting. Other bulk-compositions and compositional variations are consistent with those preserved in relatively pristine VHMS alteration halos elsewhere. For example, bulk-rock compositions richer in K occur in areas distal to the massive sulfide lens, consistent with a sericite-altered rhyolite protolith common in outer domains of deposits. Enrichment in Fe, Mg, and Mn in more proximal domains is consistent with the chlorite-altered rhyolite protoliths that occur in the most altered domains of VHMS deposits. The link between pre- and post-metamorphic bulk-rock compositions is also supported by the presence of primary hydrothermal textures (i.e., bladed textures (now defined by chlorite)) along sulfide-vein margins, which appear to have survived intense ductile deformation.

Textural analysis of sulfide-bearing domains underlying the deposit also suggests that only minor remobilization occurred. Therefore, modification related to amphibolite-facies metamorphism (P˜3.6 kbar, T˜450°C) of the footwall to the Izok deposit is interpreted as having a minor effect on rock compositions. Therefore, the metamorphic mineral assemblages present in similar metamorphosed VHMS deposits can be used as exploration indicators. However, the geometry of ore zones, alteration domains, and modified sulfide textures, suggests that it is deformation and not metamorphism that has had the most significant effect on the deposit character. More research is therefore suggested to enhance our understanding on the interplay between deformation and the primary deposit geometry.


May 14, 2012 Technical Presentation
Rare Earth Element Associations within Hydrothermal Uraninite
Ores from the Schwartzwalder Mine, Golden, Colorado, USA
By Jim A. Paschis, Consulting Geologist
Boulder, Colorado, jimpaschis@yahoo.com

The Schwartzwalder Mine was the largest hydrothermal uraninite vein deposit mined in the USA. A range of uraninite ore grades from the mine were analyzed using semi-quantitative mass spectroscopy and chemical assay1. The naturally-occurring rare earth elements of the lanthanide series contained in a four-suite sampling of ores were recently reviewed. Low and high grade ores from the mine showed negative and positive enrichment below and above crustal abundance, respectively. The highest grade ore had enrichments ranging from ~5 (cerium) to ~60 (thulium) times for 14 specific elements in the series. The lowest grade ore showed depletions of ~6 (lanthanum) to ~1.1 times for many elements in the series while samarium, europium, and thulium were slightly elevated above crustal abundance. The apparent depletion of many lanthanide series elements from lower grade ore suggests they were mobilized from and deposited at higher grade uraninite ore locations. The chemical refining of the mine's uraninite ores to the end product "yellow cake" means that significant amounts of rare earth elements may reside within mill impoundments.

Rare Earth Element#105#37#9#74Crustal abundance2 _ppm_Enrichment factor
factor (ppm, s-q ms)492, 00022900082201440U 2 .9
Lanthanum30070107398
Cerium3001003030665
Praseodynium10070779.211
Neodymium700100103041.517
Samarium30030310743
Europium1003013250
Gadolinium30070736.248
Terbium3010<111.225
Dysprosium10030135.219
Holmium7010<1<11.354
Erbium10070133.529
Thulium3010110.560
Ytterbium10030333.231
Lutetium103<1<10.520
September 12 Technical Presentation
A Comprehensive Geologic Analysis of the Aggeneys-Gamsberg BHT District, South Africa
Craig R. McClung, Ph.D., Consulting Geologist
Lone Tree, Colorado, crmcclung@juno.com

Representing a world-class district, the Aggeneys-Gamsberg district is regarded as typical examples of Broken Hill-type (BHT) mineralization. Located approximately 750 km north-northeast of Cape Town, in the Northern Cape Province of South Africa, the Aggeneys-Gamsberg district covers approximately 250 km2 of semi-arid desert. Composed of five major stratabound, polymetallic massive sulfide deposits (Swartberg, Broken Hill, Broken Hill Deeps, Big Syncline and Gamsberg), the Aggeneys-Gamsberg district had an initial estimated combined grade and tonnage of 505 Mt @ 4.18% Zn, 1.40% Pb, 0.18 % Cu and 18.2 g/t Ag, as well as minor amounts of Au and an estimated 6 Mt of barite from the Gamsberg deposit.

The BHT deposits of the Aggeneys-Gamsberg district are hosted by multiply deformed and metamorphosed, amphibolite-facies rocks of the Mesoproterozoic Bushmanland Group; a thin, less than 1 km thick, multiply deformed and metamorphosed, rootless succession of shallow, continental margin volcano-sedimentary rocks (McClung, 2006) belonging to the central Namaqua Metamorphic Province (NMP; Joubert, 1974). The NMP represents a crescent-shaped mobile belt outcropping throughout northwestern South Africa and southern Namibia, which experienced intense polyphase deformation combined with high-T/low-P metamorphism (Joubert, 1971; Lipson, 1978) during the Mesoproterozoic Namaquan Orogeny.

Bodies of base-metal sulfides are restricted to the chemogenic sediments of the Kouboom Subgroup, where they are hosted by an oxide-/silicate-facies iron formation at the Swartberg, Broken Hill and Broken Hill Deeps deposits, but by calc-silicate-rich pelitic schist at the Gamsberg and Big Syncline deposits. Whereas the western Pb- and Cu-rich deposits (i.e. Swartberg, Broken Hill and Broken Hill Deeps) comprise stacked massive/bedded to brecciated, stratiform lenses of magnetite/sulfide with a Fe-Pb-Mn-Zn-Cu-Ba +/- Cd-Co-Bi-Sb-Ag-(Au)-rich metal assemblage enveloped by a complex group of "skarn-type" minerals, toward the east the Zn/Pb and Zn/Cu ratios increase, culminating in the very large, Zn-Ba-rich Gamsberg deposit (265 Mt at 6.1% Zn and 0.3% Pb and +6 Mt of BaSO4). The Gamsberg deposit is confined to a single, large sheath-fold that forms a steep-sided inselberg with disseminated to massive, stratabound to locally stratiform bodies of Fe-Zn +/- Mn sulfides and oxides hosted by a lower mineralized calc-silicate-rich pelitic schist and upper mineralized amphibolite/calc-silicate gneiss, enveloped by a complex assemblage of ``skarn-type'' minerals. Bedded barite is most prominent at the Gamsberg deposit, where it forms a massive bed and occupies a stratigraphic position immediately overlying ore-equivalent calc-silicate-rich schists in the upper portion of the Gams Formation.


September 12 Technical Presentation
Kamoa Copper Deposit
Danielle Schmandt

The Kamoa copper deposit is located in the Katanga Province of the southern Democratic Republic of Congo outside of the area previously considered prospective for large copper deposits. With a 1 % Cu cut-off, the hypogene ore zone of Kamoa spans over 81 km2 varying in thickness from 2 to 15 meters and is currently laterally unconstrained. The deposit is hosted at the stratigraphic contact between hematitic and locally pyritic Mwashya Subgroup sandstones and overlying fine-grained pyritic diamictites of the Grand Conglomérat Subgroup. The Mwashya sandstones appear to have been deposited in a fluvial to marginal marine environment. The Grand Conglomérat diamictite contains glacially-derived mass transport and sediment gravity flow deposits. The unit appears to have been deposited in an active, locally anoxic marine environment. The contact between the Mwashya and Grand Conglomérat units represents a major change in depositional style and probably was a period of rapid subsidence or sea level rise. The majority of the Kamoa orebody occurs within the lowermost portion of the Grand Conglomérat Subgroup which contains siltstones with high concentrations of diagenetic framboidal and later cubic pyrite that may be indicative of early hydrothermal activity. Later hydrothermal alteration mineral assemblages within the Grand Conglomérat are stratigraphically zoned changing from a potassic alteration and silicification assemblage in the lowermost stratigraphic units to a dominantly magnesian alteration assemblage higher in the stratigraphy. Carbonate mineralogy in this same interval changes upward from ankerite to calcite. Ore stage sulfide minerals are zoned vertically away from the Mwashya-Grand Conglomérat contact changing from chalcocite to bornite to chalcopyrite to pyrite with increased stratigraphic height. Hydrothermal alteration and sulfide minerals occur as fine-grained disseminations within the diamictite matrix that probably represent replaced diagenetic pyrite as well as coarse-grained rims on diamictite clasts. These rims are vertically oriented and tapered, often contain euhedral mineral grains of both alteration minerals and, within the ore zone, sulfide minerals; the rims are best developed in the lowermost stratigraphic units and gradually lessen in size, vertical elongation, and abundance up stratigraphic section. Sulfur isotope studies indicate the majority of the sulfur in the copper sulfides was derived from earlier formed diagenetic iron sulfide. Fluid inclusion analysis indicate that the ore forming fluid was saline, ~23-26 wt% NaCl wt eq., and had homogenization temperatures (Th) ranging from 210 to 240o C.


November 12 Technical Presentation
History and Exploration at the Magma Mine, Superior, Arizona
And Discovery of the Magma (Resolution) Porphyry
Alex Paul

The Magma Mine at Superior, Arizona has produced over 25 million tons of high grade (5% Cu) ore yielding some 2.5 billion pounds of copper. Silver discoveries in 1875 led to the creation of the Pioneer mining district. Although the Magma vein outcrop was discovered at this time, development and production did not commence until 1911 when Boyce Thompson created the Magma Mining Company and started to pursue the rich copper vein. Aggressive exploration kept the mine in production for eighty-five years with only brief shutdowns during economic depressions.

Early mine development and production concentrated on the Magma Vein following its lead to depth and eastward under the post-mineral Apache Leap volcanic tuff. Mine production prior to 1960 focused on the Magma Vein. In 1949 massive carbonate replacement orebodies were discovered east of the vein stopes. Between 1949 and 1960 production gradually shifted from the veins to the massive replacement ores. District wide exploration between 1970 and 1982 pursued targets south of the Magma vein and the known replacement deposits. Due to depressed copper prices the mine shutdown for a brief time in 1982.

When the mine reopened in 1990, exploration for additional high grade copper resources was continued to the south of the existing mine. During the course of exploration drilling between 1992 and 1998 a porphyry system was identified some 2 km south of the historic mine. Drilling indicated a mineralized deposit at least 750m long by 250m wide by 300m high with hypogene copper mineralization grading >1% Cu.

Several factors contributed to the discovery of the porphyry system. The size, tenor and style of mineralization along the Magma Vein and its proximity to the porphyry deposits at Ray and Pinto Valley had long suggested that the district might host a hidden porphyry deposit. Support from the operating mine and the recognition of key porphyry elements by mine staff geologists aided in development of a geologic model from limited drill data. Persistence in acquiring data regarding the porphyry allowed development of this concept while attending to the business of sustaining ongoing underground mining operations. Importantly, an open-minded management provided support for pursuing possibilities beyond the narrow scope of extending the life of the selective high grade mine.


December 2 Technical Presentation

The Sheep Creek Cu-Co deposit is a chalcopyrite-rich deposit hosted within and around locally cobaltiferous massive pyrite horizons of the Newland Formation on the northern edge of the Mesoproterozoic Helena embayment, Belt-Purcell basin near White Sulphur Springs, Montana. Drilling by Cominco American from the 1970's to 1993 intercepted two main laterally extensive mineralized horizons, the lower and upper sulfide zones, which are comprised of fine-grained, bedded semi-massive to massive pyrite that are underlain and interbedded with intrabasinal debris flow deposits. The interfingering of debris flow deposits and pyrite, rapid lateral facies changes, and light sulfur isotopic signature of the fine-grained pyrite support synsedimentary to early diagenetic pyrite growth as stratiform sheet-like bodies. These sheets formed within multiple sub-basins related to embayment development.

The lower sulfide zone contains alteration minerals including dolomite, coarse pyrite-marcasite, and quartz. Isotopic signatures of hydrothermal dolomite (δ13C from -6.2 to -0.8 mil) are interpreted to reflect incorporation of isotopically light organic carbon during diagenesis. Later pyrite and marcasite have similar to heavier δ34S values compared to fine-grained pyrite, recording growth under closed-system conditions after burial. The isotopic values of massive and vein barite that encapsulates fine-grained pyrite in the upper sulfide zone suggest that the barite formed from cold methane seeps. Paragenetically late chalcopyrite (and tennantite in the upper sulfide zone) replaces dolomite, fine-grained pyrite, and barite with the highest copper grades commonly associated with intense silicification. It also occurs in dolomite and/or quartz veins within and below the lower sulfide zone. Both fine-grained pyrite and thermochemical sulfate reduction (TSR)-induced barite dissolution provided important sources of sulfur for the distinctly isotopically light (-7.8 to 6.6 mil) chalcopyrite.

The Sheep Creek deposit shares geological and structural similarities with synsedimentary/diagenetic Zn-Pb and late diagenetic/epigenetic Cu deposits in the Belt-Purcell and northern Australian Proterozoic sedimentary basins (e.g. Mt. Isa basin; Fig. 1). Collectively, these deposits share relatively similar host rocks and the presence of faults that allowed for ore-fluid transmission and focusing, although apparent timing of fluid flow and processes of metal trapping differ among the deposits. The synsedimentary pyrite (+/-barite) at Sheep Creek records mineralization that involved reduced, low temperature, and hence Zn-Pb-poor fluids. Copper mineralization involved higher temperature hydrothermal fluids. These fluids overprinted the earlier Zn-Pb-poor, pyrite- and barite-rich strata that provided important sources of sulfur during the mineralizing process.

Graham, G.E., 2012, Geologic and stable isotope investigations of the Sheep Creek Cu- (Co-Ag) deposit and comparison to other sediment-hosted basemetal deposits in Mesoproterozoic basins: Unpublished Ph.D. thesis, Golden, Colorado, Colorado School of Mines, 137 p.

Lydon, J. W., 2007, Geology and metallogeny of the Belt-Purcell Basin, in Goodfellow, W. D., ed., Mineral Deposits of Canada: A Synthesis of Major Deposit-Types, District Metallogeny, the Evolution of Geological Provinces, and Exploration Methods, Special Publication No. 5, Geological Association of Canada, Mineral Deposits Division, p. 581-607.

Polito, P.A., Kyser, T. K., Southgate, P. N., and Jackson, M. J., 2006b, Sandstone diagenesis in the Mount Isa basin: an isotopic and fluid inclusion perspective in relationship to district-wide Zn, Pb, and Cu mineralization: Economic Geology, v. 101, p. 1159 - 1188.