Abstracts 2010

January Technical Presentation
Geology and Evaluation of the Bear Lodge Rare-Earths Project, Wyoming
Don Ranta and Jim Clark
Rare Element Resources Ltd.

The Bear Lodge Mountains of northeastern Wyoming are composed of the upper levels of a mineralized Tertiary alkaline-igneous complex that is a component of the Black Hills Uplift of western South Dakota and northeastern Wyoming. The Bear Lodge alkaline intrusions with associated breccia bodies have domed the surrounding Paleozoic and Mesozoic sedimentary rocks in the early Tertiary (approximately 38-50 Ma). A few large Precambrian granite exposures are found within the complex and host some of the gold mineralization. The alkaline complex has surface dimensions of approximately 2.8 by 6 miles elongate in a northwesterly orientation, with a number of small intrusive outliers cutting older sedimentary rocks beyond the alkaline complex.

Gold: Gold mineralization occurs extensively in the Bear Lodge intrusive complex in known near-surface low-grade deposits and possibly in high-grade vein-type occurrences at depth. The alkaline complex shares many attributes with the more deeply eroded Cripple Creek complex in Colorado and has significant potential to host minable gold deposits. Newmont is Rare Element's partner in advancing the gold exploration program and is in the process of earning a 65% J.V. interest.

Rare Earths: Rare-earth-element (REE) mineralization occurs in the north-central core of the Bear Lodge alkaline system and is surrounded by the gold deposits and occurrences. Rare-earths mineralization is hosted by a heterolithic diatreme breccia, multiple intrusions of phonolite, trachyte, and other alkaline igneous rocks, and a variety of associated breccias. Most rare-earths mineralization is located in higher-grade carbonatite dikes or their near-surface oxidized equivalents within or adjacent to the Bull Hill diatreme, and the REE-bearing dikes are contained within a large zones of low-grade REE stockwork.

The US Geological Survey studied the Bear Lodge Mountains (M.H. Staatz, 1983, USGS Professional Paper 1049-D) and estimated that it contains one of the largest occurrences of disseminated REE in North America. The USGS made this statement partly based on the work of the US Bureau of Mines, which had drilled 10 widely spaced holes and had access to drill-hole information from several mining companies. The USBM estimated a large tonnage of low-grade REE mineralization in the Bull Hill area. Virtually all of the significant REE occurrences in the Bear Lodge area are controlled by Rare Element's claims.

A NI 43-101-compliant inferred mineral resource was estimated within the dikes for three mineralogical zones - oxide, transitional, and unoxidized. The total inferred resource of the Bull Hill deposit is 9.8 million tons averaging 4.1% rare-earth oxide (REO). The near-surface part of the deposit is the oxide zone that has 4.5 million tons at 4.3% REO and comprises nearly half of the total resource. The 2009 drilling program has expanded this resource, with a focus on the oxide zone, and assays are being received. Bear Lodge mineralization in carbonatites is weighted typically toward the light rare-earth elements: cerium is most abundant, followed by lanthanum, neodymium, praseodymium, and samarium.

Rare Element's focus is on the oxide portion of the rare-earth resource because the oxide mineralization has responded best to metallurgical treatment. A combination of a loose and friable character of the FMR material and the fine-grained nature of the REE minerals allows a unique metallurgical pre-concentration method of crushing (- ยจ "), scrubbing, and screening to get 90% recovery of the REE with a 13% REO grade in the minus 25 micron (-500 mesh) fraction. Further testwork may provide methodology to upgrade an REE concentrate to 40% or more REO, before extraction and separation of the individual rare-earth elements. Engineering studies have begun for a Scoping Study of the project.

February Technical Presentation
Lithium One: A Two-Pronged Approach to Developing New Lithium Supply in Canada and Argentina
Iain Scarr, Vice President- Development, Lithium One, Inc.

The next new mines to supply the world's growing need for lithium will look similar to existing operations. To be competitive, they will share four key attributes: a quality resource, predictable and manageable production costs, a location in a stable, mining-friendly jurisdiction, and amenability to existing, proven technology.

Lithium One is pursuing the best "end member" projects that draw on existing technologies for lithium extraction from an Atacama-type brine and a high-grade spodumene deposit. Both projects are on track for development in the key time window for the blossoming automotive lithium battery industry.

The Sal de Vida Project in mining-friendly northwest Argentina is progressing towards a high-quality brine resource. It adjoins FMC's low-impurity resource at Salar del Hombre Muerto. The lithium and potassium grades of the brine are high and preliminary tests of the chemistry have also been favorable.

The James Bay Project in Quebec is a high-grade spodumene-bearing pegmatite deposit that occurs at the surface adjacent to water, power, and a paved highway. The project is bolstered by its high grade and location in one of the leading mining jurisdictions in the world. The deposit has been extensively drilled and metallurgical testing is underway.

March Technical Presentation
How do you know you are in a world class Ni camp?
Steve Beresford Global Project Generation Manager - Nickel MMG

The last decade has seen a shift from empirical to whole mineral systems approaches to exploration targeting. This change has been necessitated by a shift to under cover exploration and the need to improve decision making in areas of greater empirical uncertainity. A balanced predictive and detective approach to targeting is thus a prerequisite for exploration.

The shift in approach has seen considerable improvements in global to cratonic scale targeting for Ni-Cu-PGE deposits. This step change in predictive ideas has largely been led by GEMOC and WMC Resources. However a gap in targeting still exists between the cratonic scale and the prospect scale, a scale currently filled by potential field structural interpretation and precompetitive geochemical techniques eg till, stream sediments, lake and heavy mineral techniques and the developing field of hydrogeochemistry.

World class deposits are known to represent the manifestation of large mineral systems with significant greater crustal scale footprints than the deposit itself. The focus of this presentation is on defining the regional to camp scale footprint of world class Ni-Cu-PGE camps.

Intrusive breccia in varied-textured sulfide matrix, The ovoid, Voisey's Bay.

April Technical Presentation
From Volcanic Ash? or from Granite?
Robert E. Melin

The Gas Hills district in central Wyoming has produced around 90 million pounds of U308. Deposits mined were in arkose beds in an alluvium apron about 20 miles across named the Puddle Springs Member of the Wind River Formation of Lower Eocene age. In the west half of the district the Puddle Springs fanned out onto a plain cut onto Cretaceous shale and bounded on the east and south by cuestas of Mesozoic and Paleozoic formations. The arkose unit is as much as 300 feet thick. In the middle of the arkose, between the Central and West Gas Hills, is the Dry Coyote Conglomerate. It is largely altered, and uranium deposits are above, below and lateral to it.

Geologists have proposed five ways for uranium to reach the deposits. Four of the ways involve moving uranium from Sweetwater granite to the deposits; and one way involves leaching it from volcanic ash and moving it to the deposits. The volcanic ash proposal supposes that Gas Hills uranium came from volcanic ash beds of Eocene, Oligocene, Miocene and Pliocene age that totaled about 2000 feet thick before late Pliocene erosion. Volcanic ash came from a long-lived hot spot, a super-volcano we call Yellowstone. Rain water leached uranium from each newly fallen ash bed and carried it down to gravels which guided uranium-bearing water to the deposits.

The first way for getting uranium from Archean granite to the Gas Hills is that the granite eroded and became arkosic gravel in the Puddle Springs member. Ground water leached uranium from the arkose and carried it through the arkose to the deposits. Second, Robert Guilinger of Union Carbide in 1963 told of a highly radioactive cobble in core from an arkose bed in the West Gas Hills. It contained uraninite veinlets with secondary quartz in granitoid rock that had a "cataclastic texture" with "extreme shearing." He supposed that it came to Wind River arkose from a uraninite vein in the Granite Mountains.

Third, USGS geologists Rosholt and Bartel in 1969 deduced from uranium and lead isotope analyses that an absolutely colossal amount of uranium had been extracted from Archean granite. Uranium went away, and tell-tale uranogenic lead was left behind. Other workers later added that uranium was removed from granite across fifty miles of exposure and to depths of at least 1550 feet, the maximum depth cored to date in the Sweetwater batholith. Rosholt and Bartel thought the "most feasible" time for removal of uranium was Tertiary, and that rain water did it. Fourth, USGS geologists Stuckless and Peterman in 1977 and Stuckless and Miesch in 1981 wrote that crystallization of granite took place under conditions of high water content and high oxygen content. Water and oxygen are vital in ISR systems, and they were on hand to mobilize uranium from hot, newly emplaced granite in Archean time. Stuckless and Nkomo in 1978 supposed that mid-Proterozoic metamorphic heat drove as much as 45% of the uranium from Archean granite into "crystalline rocks farther north." Stuckless in 1979 added that uranium deposits could form "at any time following early Precambrian."

I choose to believe that Archean or older uraniferous terranes were granitized about 2600 Ma to make Sweetwater granite. Oxygen and water in the granite helped to move uranium from hot, newly emplaced granite into uraninite veins in crystalline rocks to the north. Uranogenic lead was left behind in the granite we walk on. The Laramide orogeny unearthed many uraninite vein clusters, and detritus from one was soon reconstituted as the Gas Hills uranium district. Guilinger told of a piece from one of the veins.

May Technical Presentation
Evolving Gold Corp. - Exploring for Covered Gold Targets,
South Carlin Trend, Nevada
Robert Barker, CEO, Evolving Gold Corporation

In late November of 2007, Evolving Gold Corporation signed an agreement with various subsidiaries of Newmont Mining Corporation covering four exploration areas in the Carlin Trend in Nevada. One of the four areas is southwest of the town of Carlin, about half way between the Gold Quarry deposit to the north and the Rain deposit to the south. We refer to this area as the Carlin Project. This exploration area covers a portion of the Humboldt gravity high, which Evolving Gold interprets as an indication that favorable Lower Plate host rocks can be intersected by drilling at reasonable depths. Drilling on the Carlin Project was delayed until the summer of 2009, when Evolving Gold drilled pa series of reverse circulation precollars. Core drilling was initiated on precollar CAR-002 in June, 2009.

By July, 2009, core drilling on CAR-002 had intersected what was interpreted as favorable Lower Plate units, and the company reported encouraging fine-grained, sooty pyrite, decalcification, and abundant visual evidence of favorable trace elements, including realgar, orpiment, stibnite and barite. Hole CAR-002 was terminated at 4,983 feet. This was the first drill hole to penetrate the full thickness of favorable Lower Plate host rocks in this part of the Carlin Trend. In September Evolving Gold reported three zones of highly anomalous gold values:

115 ft at 0.035 opt Au, starting at 2,815 ft, including 5 ft at 0.347 opt Au
35 ft at 0.029 opt Au, starting at 3,000 ft, including 5 ft at 0.107 opt Au
75 ft at 0.032 opt Au, starting at 4,660 ft, including 35 ft at 0.052 opt Au

Trace element values locally reached high values of >10,000 ppm As, 8,320 ppm Sb, and 20 ppm Hg, along with high values in Ba. This drill hole demonstrated the target area hosted thick zones of gold mineralization, with the potential to attain grades approaching economic values exploited elsewhere in the underground operations in the Carlin Trend. Evolving Gold interpreted these drill results as extremely encouraging.

After completing two shorter core holes in precollars CAR-003 and CAR-004, a second deep core hole was initiated at CAR-007. This hole was completed to a depth of 4,307 feet, at a location approximately 2,000 feet to the northwest of CAR-002. This major offset was driven by moving higher on the large scale gravity high, and locating the drill rig near a small, isolated dimple in the broad gravity feature. Hole CAR-007 intersected stratigraphy similar to that intersected in CAR-002, but at a somewhat shallower depth, and CAR-007 also intersected three main zones of gold mineralization. Though detailed biostratigraphic studies are still underway, Evolving Gold interprets these intervals to be, from the highest to the lowest, Webb equivalent (which hosts the Rain deposit to the south), Popovich (which hosts much of the gold mineralization in the northern Carlin Trend), and Roberts Mountain equivalent (which hosts gold mineralization at Jerrit Canyon). The highest grades encountered in CAR-007 include:

60 ft at 0.340 opt Au, starting at 3,045 ft

35 ft at 0.216 opt Au, starting at 3,020 ft, including 10 ft at 0.677 opt Au

15 ft at 0.905 opt Au, starting at 3,090 ft, including 5 ft at 1.69 opt Au

CAR-007 ended in extensive solution breccia, with open vugs lined with quartz crystals. CAR-007 demonstrates the potential to define a major, high grade gold deposit at depth in a previously under-explored portion of the highly productive Carlin Trend.

Maness International Geological (MIG) FontTc
Lindsey V. Maness, Jr., Geologist
Golden, CO
lvmaness@Comcast.net Web-Site: http://www.China-Resources.net

The Maness International Geological (MIG) FontTMc (2006-2010, all rights reserved), comprises an unique set of letters, numbers, symbols, characters and glyphs, generated to provide geologists and others in the earth sciences with an unified, unambiguous means of recording, reporting and displaying, including on maps and through standard data-base and GIS software, geological, geophysical, geochemical, geomorphic, geographic, environmental and other information in most of the widely-used Latin-Greek-Cyrillic alphabets. A far more extensive than previously available set of geological symbols and letters is provided. In addition, the Chinese phonetic Bo-Po-Mo-Fe font is included: Chinese Wade-Giles and Pin-Yin are fully enabled through the Latin fonts. Others are in-process. Finally, any client can suggest changes or additions to the MIG Font TMc, all of which suggestions will be received with gratitude and sincerely evaluated for possible incorporation herein. Purchasers of any Version before 3.00 (e.g., v. 1.01) receive free upgrades up to and including to Version 3.00.

The sole holder of the intellectual property rights to the MIG FontTMc, Lindsey V. Maness, Jr., is solely responsible for any errors.

September 2010 Technical Presentation
Exploration, Development and Mining of Roll-front Uranium Deposits
by In-situ Recovery (isr)
Cal VanHolland and Sam Talbott
Ur-Energy USA

The presentation will offer an overview of sedimentary uranium geology from exploration through the restoration stages of In-situ Recovery (ISR) mining, focusing on roll-front type uranium deposits.

The discussion will begin with a description of the general characteristics of roll-front deposits, including aqueous geochemistry, required geologic conditions, deposit formation, deposit geometry and mineralogy. General exploration methodologies from grass-roots through discovery will be reviewed, including drilling and geophysical logging techniques and evaluation.

Development activities required to bring a deposit from the discovery phase into the mining stage will be summarized. This will include a brief summation of permitting, economic and geological requirements, ore deposit delineation drilling, chemical disequilibrium and PFN logging, and resource estimation.

Presentation of the In-situ recovery (ISR) technique of mining uranium deposits will incorporate mining geochemistry, production well patterns, production monitoring, and processing to yellowcake.

Finally, post-production restoration and reclamation methods will be summarized with reference to restoration geochemistry and regulatory requirements.

October Technical Presentation
The Aynak Copper Tender and Afghanistan's Mineral Wealth
A Fair, Transparent and Successful Venture in Afghanistan
William J. Crowl, Vice President, Mining Sector, Gustavson Associates
Mark N. Semenoff, Legal Advisor, Semenoff LLC
Simon D. Handelsman, Ph.D., P. Eng., Financial Advisor

The Aynak copper deposit, located 35 km south of Kabul, Afghanistan in the northern portion of Logar Province, was the first mineral resource to be tendered through international competitive bidding in Afghanistan's history. Aynak is one of several prospective resource areas under state control and identified as possible national development opportunities. The second such tender, for the Hajigak iron ore deposit, is set to kick off this Fall. Recent announcements about the value of the mineral wealth of Afghanistan have increased interest in this isolated, war-torn country. Terms like "combat geologist" have been used recently to describe US Government-backed prospectors involved with locating and quantifying Afghanistan's riches.

The Aynak name is used broadly to describe a sediment-hosted, copper-mineralized body contained within a small 5x4 km land parcel, and consisting of a Central & Western zone, together with the Darband and Jawkhar copper prospects, along strike to the east and south respectively. Small-scale copper production at Aynak dates back 2,000 years, but recent exploration interest began in 1973-1974 when Soviet and Afghan geologists conducted prospecting and geological mapping. Based on favorable early findings, the Soviet Geological Mission "Technoexport" conducted a systematic exploration program of Aynak in two main phases.

Gustavson Associates was the Transaction Advisor to the Afghan Ministry of Mines, responsible for the entire Tender process. The Tender kicked off in late 2006 with a Request for Expressions of Interest. Following an internationally vetted, transparent bidding process, a winning bidder was selected from the 5 bids submitted. A Mining Contract was negotiated with MCC (a joint venture between China Metallurgical Corp and Jiangxi Copper). Negotiations of ancillary agreements for security, water, power, other minerals and a railway followed and were recently completed. MCC plans to build a complex consisting of a 50ktpd open pit and underground mine and concentrator, a 200ktpy copper smelter and refinery, a 400MW coal fired power plant (including the coal mine and transmission lines) and a railway (if feasible). Total capital cost of the facilities, less the railway, is estimated to be between $2 and $3 billion US dollars. MCC has committed to adherence to the World Bank Equator Principles, the Guidelines for Health and Safety and the relocation and resettlement guidelines.

November 1, 2010 Technical Presentation
The Case for the Mantle-Epithermal Connection in Western USA
Jim Saunders (Auburn University)
Matt Brueseke (Kansas State University)

The mantle is generally enriched in such elements as the precious metals, PGE's, copper, nickel, etc., relative to continental crust. But what makes the mantle "ripe" for producing ore deposits in some places but not others? One setting that is very conducive for production of porphyry and/or epithermal ores is the mantle above a subduction zone. This has been known from the beginning of the general acceptance of the theory of plate tectonics, but details are still coming to light. Recent research by Jeremy Richards and Graham Begg emphasize the role that subduction plays in making the overlying lithospheric mantle "fertile" for generating magmas that lead (eventually) to the formation of shallow porphyry and epithermal ores in the overlying crust. Richards has documented this process (in Geology, May 2009) and calls it "post-subduction" orogenesis. Begg and his former colleagues and Western Mining in Australia began using the "mantle preparation" concept in exploration a decade ago, and recognized that preservation of the fertile lithospheric mantle wedge was also important. In short, preservation means keeping "dead" asthenospheric mantle from assimilating the fertile lithospheric mantle. And perhaps the best way to do this is where there was "flat" (low-angle) subduction such as the Andes today, or more to the point for this talk, Laramide subduction in western USA during the Mesozoic. In this talk we use the Begg-Richards concepts of subduction and mantle preparation/ protection and apply them to western USA epithermal ore formation during last ~70 Ma. More specifically, we summarize our recent research on metal(loid) volatility as it relates to cycling of the elements up from the subducted slab, upward into the "fertile" mantle, and ultimately into the shallow crust. In addition, we also discuss how "our" most famous mantle plume, the Yellowstone Hotpsot, was able to tap the post-Laramide fertile lithospheric mantle and produce some pretty spectacular bonanza epithermal ores (Sleeper, Midas, National, etc.) in the northern Great Basin. Oddly, that mantle plume-epithermal connection appears to have been very short-lived (~1-2 Ma), which may also be the result of metal volatility.

If one looks at the geographic distribution of <75 Ma epithermal ores (those mined for Hg-Au-Ag) in western USA (fig. 1), there is a distinct west-to-east geographic zonation of ores rich in Hg, then Se, then Te. This geographic zonation parallels the relative volatility of the elements, Hg>Se>Te and also depth to the Farallon plate during the Laramide "mantle preparation" event. We propose that metal and metalloid volatility is important during the progressive heating of the subducted slab, and is part of the mantle preparation that previously has been thought of mainly in release of volatile "gases" such as CO2 and water and perhaps alkalis. Perhaps it is difficult to envision gold, silver, and copper as volatile elements, but they are. For example, laser-ablation ICP-MS of fluid inclusion studies (Heinrich et al., 1999, Geology) show that gold and copper are concentrated in low density, more volatile fluids that separate from hypersaline fluids in the porphyry environment. Even more to the point, heating of meteorites in a vacuum leads to gold release at relatively low temperatures (<300oC) compared to many other elements.

So if one accepts that the release of volatile metals and metalloids is part of the subduction-related mantle preparation process, what can we infer about Cretaceous and younger ore ore-forming processes in western USA? First, it is clear that partial melting in the previously prepared mantle in the latter stages of subduction can tap volatile metal(loids) in the mantle and lead to formation of porphyry and associated epithermal ores (e.g. ores in the Colorado Mineral Belt, Arizona Cu-porphyry province, Butte, etc). But as Richards describes, it is "post-subduction" where the ore-forming action starts in earnest. Eocene bonanza epithermal ores in the Republic, Washington district are triggered by rifting (resulting in the Republic Graben, and also the Wenatchee district), which apparently imitated partial melting in mantle and subsequent magma rising through crust aided by rift structures. Eocene magmatism (~40 Ma) led to the major porphyry deposits and associated gold skarns and Bingham and Battle Mountain Nevada, and also apparently the "distal skarns" that we have always called "Carlin-Type Deposits." Continued magmatism related to subduction and slab-roll back, coupled with Basin and Range-style extension also to lead to extensive magma emplacement and locally caldera formation throughout the Great Basin and Rockies (e.g. Rio Grande Rift, Southern Rocky Mountains volcanic field) producing numerous major mineral deposits including epithermal ores, diatreme Au-Te ores (perhaps they are epithermal too) such as Cripple Creek and Ortiz (NM), and of course the Climax-Type Mo deposits in Colorado and in the Great Basin. In the mid-Miocene, bimodal volcanism related to the initial emergence of the Yellowstone Hotspot in the northern Great Basin triggered a flare-up of epithermal mineralization for a brief period of time (Silver City, ID, Sleeper, National, Midas, Ivanhoe, Mule Canyon, etc.). Lastly, western USA epithermal mineralization continues evidently to almost the present time with young epithermal deposits like Florida Canyon (NV) and McLaughlin (CA). In conclusion, it appears to us that the mantle under western USA is still fertile and apparently has not quit producing epithermal ores.

Distribution of Hg deposits (not all are actually epithermal), and Se- and Te-rich Au-Ag epithermal ores in the western USA.

Diagrammatic cross-section of the mantle preparation process during the Laramide Orogeny as a function of progressive deepening of the subducted slab. Both figures are from Saunders and Brueseke (in prep.)

December Technical Presentation
Sediment-hosted Zn-Pb deposits: a two billion year history of tectonics, evaporites and the opening and closing of ocean basins
David L. Leach
Scientist Emeritus, US Geological Survey

This presentation provides new insights into the fundamental controls that an evolving Earth had on the genesis and preservation of sediment-hosted Pb-Zn deposits. The uneven distributions of these deposits in time will be discussed within a context of evolving tectonic and geochemical environments to better understand when and where these deposits formed in the crust.

Sediment-hosted Pb-Zn deposits can be divided into two major sub-types. The first sub-type is clastic-dominated lead-zinc (CD Pb-Zn) ores, which are hosted in shale, sandstone, siltstone, or mixed clastic rocks, or occur as carbonate replacement, within a clastic-dominated sedimentary rock sequence. This sub-type includes deposits that have been traditionally referred to as sedimentary exhalative (SEDEX) deposits. The CD Pb-Zn deposits occur in passive margins, back-arc and continental rifts, and sag basin, which are tectonic settings that, in some cases, are transitional into one another. The second sub-type of sediment-hosted Pb-Zn deposits is the Mississippi Valley-type (MVT Pb-Zn) that occurs in platform carbonate sequences, typically in a passive margin tectonic setting.

The formation of MVT and CD Zn-Pb deposits are considered in a framework of the Wilson Cycle of ocean basins. Clastic Dominated Zn-Pb deposits formed mainly in sedimentary sequences of ancient passive margins during the opening of ocean basins. The inevitable closure of the ocean basins results in the destruction, or metamorphism and deformation of the passive margin deposits. Mississippi Valley-type deposits formed in the carbonate platform sequence during collision or soon after plate convergence ceased. The contrasting in tectonic setting of these deposits determines the tectonic recycling and preservation of the ores. CD deposits are less likely to be preserved relative to MVT deposits.

Considering that the redox state of sulfur is one of the major controls on the extraction, transport, and deposition of Pb and Zn at shallow crustal sites, sediment-hosted Pb-Zn ores can be considered a special rock type that recorded the oxygenation of Earth's hydrosphere. The emergence of CD and MVT deposits in the rock record between 2.02 Ga, the age of the earliest known deposit of these ores, and 1.85-1.58 Ga, a major period of CD Pb-Zn mineralization in Australia and India, corresponds to a time after the Great Oxygenation Event (GOE) that occurred at ca 2.4 to 1.8 Ga. Contributing to the abundance of CD deposits at ca 1.85-1.58 Ga was the following: a) enhanced oxidation of sulfides in the crust that provided sulfate to the hydrosphere and Pb and Zn to sediments; b) development of major redox and compositional gradients in the oceans; c) first formation of significant sulfate-bearing evaporites; d) formation of red beds and oxidized aquifers, possibly containing easily extractable Pb and Zn; e) evolution of sulfate-reducing bacteria; and f) formation of large and long-lived basins on stable cratons.

Although MVT and CD deposits appeared for the first time in Earth history at 2.02 Ga, only CD deposits were important repositories for Pb and Zn in sediments between the GOE, until after the second oxidation of the atmosphere in the late Neoproterozic. Increased oxygenation of the oceans following the second oxidation event led to an abundance of evaporites, resulting in oxidized brines, and a dramatic increase in the volume of coarse-grained and permeable carbonates of the Paleozoic carbonate platforms, which host many of the great MVT deposits. The MVT deposits reached their maximum abundance during the final assembly of Pangea from Devonian into the Carboniferous. Following the breakup of Pangea, a new era of MVT ores began with the onset of the assembly of the Amasia supercontinent.