10 ledges were mined historically at an average grade of 8.38 g/t Au within a block of ground measuring 4 km long by 2.4 km deep and 1.5 km wide
Black Hills of South Dakota:
World’s Largest BIF Gold Province
Homestake is the archetype for iron formation-hosted orogenic gold mineralization globally
During its 125-yr mine life, Homestake produced >42 million ounces of gold from 152 Mt of ore @ 8.38 g/t Au with a further 20 million ounces in resources written off at the time of mine closure in 2001
The mine closed due to low gold prices and the need for costly upgraded infrastructure; it did not run out of mineralization
Homestake remains the second-largest producing district in the United States after the Carlin Trend in Nevada and rivals the Carlin Trend in richness for number of gold ounces contained per square kilometer
The Homestake Mine near Lead, South Dakota was North America’s largest and deepest gold mine and at one point in its history produced 10% of the world’s annual gold output
Ore bodies in the Homestake Mine consisting of mineralized quartz-carbonate-sulfide veins and sulfide replacement ore in the Homestake iron formation cluster to the axes of synclinal fold structures called “ledges”
Several of these ledges reached spectacular size. The Main Ledge produced 07 million ounces of gold from 74 Mt of ore while 9 Ledge produced 9.5 million ounces from 36 Mt
A further 20+ fold structures were tested through diamond drilling, producing numerous additional mineralized intercepts outside of the known resource
In fact the full extent of the Homestake gold system has never been determined along strike or down-plunge and remains open in most directions!
Quantifying The Remaining Potential Of The Black Hills Belt
An Immature Search Space = Major Discovery Potential
The world’s major orogenic gold provinces contain clusters of deposits with consistent and predictable size distributions
We are on the hunt for MISSING GIANTS
Not only are there more total ounces to find, they will be contained in MUCH larger deposits.
Mineral Mountain judges the Black Hills to be the World’s Last Great Unexplored Orogenic Gold Province.
Rochford District Overview
The geology of the Rochford District is remarkably similar to that of the Homestake District, with gold mineralization hosted as structurally controlled ore bodies within multiply deformed carbonate-silicate facies iron formation metamorphosed to upper greenschist to lower-mid amphibolite grades. There are around ten small historic gold producers dating to the 1880’s-1930’s and dozens of significant prospects and gold anomalies (all in iron formation) over a 75 km2 area that has seen comparatively little exploration, and is essentially virgin in the subsurface despite the fact it is just 25 km south of the Homestake Mine, which produced in excess of 42 million ounces of gold.
Rochford District Potential
Mineral Mountain Resources has assembled the largest land package ever held by a single explorer in the district (7,500 acres) and by far the most comprehensive integrated data package. Recently Mineral Mountain has flown district-wide airborne magnetics, EM, and radiometrics in addition to compiling an extensive database of stream sediment, rock chip, forest mull and soil geochemical samples. Geologic reappraisal of the district and integration of these newly acquired multidisciplinary datasets into a robust exploration model has set the stage for successful exploration for the first time in the district’s history.
Numerous opportunities in the Rochford District to explore historic high-grade gold producers and follow-up historic significant gold intersections in structurally thickened synclinal fold hinges in the Rochford Iron Formation
Mineral Mountain’s exploration strategy and drilling approach is based on the conceptual models for BIF-hosted gold mineralization in the Black Hills that have been proven successful at Homestake, one of the world’s largest individual gold deposits.
The Homestake “ledge-type” gold targets are a regionally persistent style of gold mineralization that is the product of a common mineralizing event during orogenic deformation. Mineralized ledges are controlled by the intersection of subvertical brittle-ductile deformation zones with chemically reactive iron formation in structurally thickened folds.
Although many of the original Homestake Mine ledges were large and high-grade, they represent challenging exploration targets that require a systematic exploration methodology adopted by Mineral Mountain
Target the intersection of major through-going subregional deformation zones with structurally thickened iron formation in fold axes
Rank targets using cutting edge techniques, including major cation geochemistry of hydrothermal chlorite, multi-element stable isotope geochemistry and LA-ICP-MS analyses of trace elements within sulfides to establish which structurally prepared sites have the requisite connectivity to fertile gold reservoirs and hydrothermal fluid pathways to form a significant gold system
Vector toward ore during early-stage drilling using increasing abundance of late-stage quartz veining with thick hydrothermal chlorite vein selvages, increasing coarse late-stage arsenopyrite, increased gold concentrations, and systematic structural changes indicating proximity to large-volume ore centroids
Follow-up significant (~gram to multi-gram) Au intersections with closer-spaced (50-100m step-out) drilling.
There are a number of favorable exploration opportunities in Rochford District that have never been systematically followed up, but are the focus of Mineral Mountain Resources. Exploration in the late 19th and early 20th centuries identified small gold resources at many properties on the surface that remain open to expansion in all directions. Each opportunity has early-stage gold intersections equal to, or better than, those that Homestake Mining Co. followed-up to make important new discoveries at the Homestake Mine.
Standby Trend:
- Historic recovered production grade of 12 g/t Au to depth of 130 meters, high grade surface grab samples up to 38 g/t Au and drill intersections in and around the Standby Mine by Getty Minerals, Homestake and others (BLG-UG3 – 19m @ 4.61 g/t Au and SM87-3A – 3.05m @ 10.29 g/t Au) up to 1500 m down-plunge from Standby Mine workings
Cochrane Trend:
- Non NI43-101 Compliant inferred resource of 268,000 oz @ 6.34 g/t Au to a depth of only 165 meters below surface in 12,536 meters of drilling across 65 drill holes. Excellent surface gold grades including common grab samples in excess of 30 g/t Au and trench values ranging up to 7.6 m @ 9.02 g/t Au
South Standby Trend:
- A deep trunk hole with two splays in the Bloody Gulch area drilled south of Standby by Western Mining intersected 15m @ 1.19 g/t Au and 1.35m @ 1.17 g/t Au within a broader interval of weakly anomalous Au in quartz-veined, chlorite-quartz-pyrrhotite altered iron formation. Free gold can be panned from soils and numerous small prospect pits in the vicinity.
Lookout Mine Trend:
- Two drill holes down-plunge from the Lookout Mine (RV-95-1 – 58m @ 4.22 g/t Au within a broader interval of 1.65m @ 2.06 g/t Au; RV-95-2 intersected 1.4m @ 4.92 g/t Au within a broader 6-m zone with arsenopyrite and well-developed chlorite selvages on quartz veins.
These examples illustrate target trends in the Rochford District that link surficial gold anomalies to down-plunge historical gold drill intersections, often only to depths of a few hundred meters below surface in a few drill holes. The deepest drilling in the district in the Standby Mine Trend demonstrates sufficient space between known intersections to eventually define a multi-million ounce Homestake-style ore ledge.
Historical Reasons Why Sufficient Follow-up Exploration Was Not Completed in the Rochford District
The majority of historic exploration in the district was conducted during the 1980’s at a time when traditional syngenetic exhalative models for BIF-hosted gold mineralization were the existing paradigm and the modern understanding of these deposits was in an embryonic stage. This greatly hindered the technical understanding of BIF-hosted gold deposits. Detailed geologic reappraisals of the Homestake deposit by HMC personnel from 1983-1993 shifted the emphasis from syngenetic to epigenetic models, which occurred in parallel with a series of important gold discoveries for HMC within the Homestake Mine environment.
HMC conducted exploration for new gold reserves in the Black Hills from 1983-1995, although the majority of their effort was spent in the Homestake District. Homestake possessed a high level of IP over BIF-hosted deposits and they spent their exploration dollars primarily in only one place outside the Homestake District, the Rochford District because they understood the immense potential of the district. Most of their attention was directed to Mineral Mountain’s Standby Mine.
Homestake appreciated that exploration for these targets required perseverance, and they had not finished Rochford exploration by the time of their exit, which occurred due to external factors such as a low gold price and increasing production costs at the mine.
Getty Minerals ceased successful exploration at the Cochrane Mine due to the termination of the exploration division through corporate restructuring. Subsequently Newmont dropped Cochrane area exploration in the 1990s, despite encouraging drilling results, because they did not have a sufficient land position down-plunge on the Cochrane Mine Trend. They could see that the primary mineralization was plunging to the south onto ground that Mineral Mountain now controls.
WMC left the joint venture with Homestake in 1995 because of a need to fund their BIF program in Nunavut, resulting in the discovery of the 6.8 Moz Meliadine gold deposits (2014 indicated + inferred resources, AgnicoEagle), by adopting a similar targeting strategy developed originally for Rochford exploration.
