Homestake Paleoplacer Property

> 1973 Homestake Mining Co. – Ross R. Grunwald Technical Report (provided courtesy of the Homestake Adams Research and Cultural Center at Deadwood, South Dakota).

 


After Caddey and others, 1991

The first significant Black Hills gold event occurred approximately 1.74 billion years ago with the deposition of more than 40 million (recovered) ounces of gold in the Homestake iron-formation. From the time of iron-formation gold deposition, Proterozoic erosion removed approximately 30,000 feet of rock from the earth’s crust and exposed the Homestake lode to an erosional event that distributed more than 10 million ounces of gold into drainages on the regolith surface forming very high-grade gold paleoplacer deposits. The Homestake Paleoplacer deposit is characterized by gold bearing quartz pebble conglomerates, similar to the Jacobina conglomerate gold deposits of Bahia, Brazil, that were deposited to the north and away from the elevated exposure of the mineralized Homestake iron-formation source lode. Multi-ounce per ton gold grades were historically not uncommon to these deposits, principally because the source gold lode was up graded by lateritic weathering processes prior to erosion and distribution of the gold into the ancient paleochannels. At 560 million years ago the Cambrian seas advanced depositing marine sediments that eventually covered the primordial Black Hills highlands and sealed the paleoplacer deposits under cover.

Dakota Territory’s Paleoplacer Property encompasses 224.4 mineral acres located approximately one mile north of the Homestake Lode source. Tertiary-age rhyolite intrusive rocks dominate the outcrop on the property, along with limited outcrops of Cambrian Deadwood formation contained within the rhyolite intrusive. The rhyolite is in the form of a sill/laccolith 50 to 500 feet thick that overlies the basal quartz pebble conglomerate units of Deadwood formation and the extensions of gold bearing paleoplacers sourcing from the Homestake lode at the Open Cut. 
 

After Caddey and others, 1991
 

Between 1875 and 1920, approximately 1.5 million ounces of gold were realized from the modern placers and a string of mines that produced high-grade ores from the Homestake Paleoplacer, including the Baltimore & Deadwood, Esmeralda, Hidden Treasure, Pinney, Omega, Deadwood-Terra, Hawkeye-Pluma, Gentle Annie, Monitor, Gustin, Minerva and Deadbroke Mines.

Dakota Territory’s Paleoplacer Property includes the past producing Gustin, Minerva and Deadbroke Mines, which were the last three mines on the channel and are located furthest to the north at the point where the channel disappears under the cover of the younger Cambrian sedimentary and Tertiary igneous rocks. The Deadbroke Mine began operations in the earliest days of the 1870’s Black Hills Gold Rush and continued to produce gold through the 1920’s by underground room and pillar methods at depths ranging from 100 to 200 feet below surface.


Deadbroke Mine Sample Data provided courtesy of Deadwood History, Adams Museum Collection and the Homestake Adams Research and Cultural Center at Deadwood, South Dakota.

In 1973, Homestake Mining Company entered into a mining lease on the Deadbroke Property based on interest generated by a report authored by Homestake Geologist, Ross R. Grunwald and entitled “Ore Potential of The Deadbroke Mine and Other Northern Black Hills Conglomerate Ores”. In 1974, Homestake dewatered the Deadbroke Mine and conducted a comprehensive mine mapping and sampling program. A total of 214 channel samples were collected by Homestake Geologists from the perimeter of accessible stope and development headings, as well as from pillars left in stopes. The average gold value for the 214 channel samples taken was 0.074 ounces per ton taken over an average sample length of 6.0 feet. Remnant pillar sample values were considerably higher at an average gold grade of 0.126 ounces per ton, including a peak gold sample value of 0.750 ounces per ton taken from the back of a stope at the south end of the mine workings. The higher sample values obtained from pillars near the center of the production headings is indicative of a higher grade core ore body surrounded by a halo of lower grade mineralization that was apparently marginal at the $20.67 per ounce gold prices that prevailed while the Deadbroke Mine was in operation.

In the 1980’s, Homestake Mining Company drilled at least 23 drill holes exploring for the extension of the paleochannel north of the Deadbroke Mine. The program discovered significant gold mineralization at a distance approximately 1,800 feet north of the Deadbroke Mine on the northward projection of the channel trend.

With the extensive historic data now available, Dakota Territory has commissioned Brian Leslie Cole of Vineland, Ontario, Canada to prepare an independent Preliminary Technical Assessment Report in the form of National Instrument 43-101 on the Property.

In addition, Dakota Territory intends to conduct its first drill program on the Paleoplacer Property during the summer of 2014. The drill program has been designed to:

  • Test the extent and grade of gold mineralization surrounding the Deadbroke Mine workings.
  • Test the extent and grade of gold mineralization surrounding the Gustin and Minerva Mine workings that were not sampled by Homestake in the 1970’s.
  • Test the extension of the higher grade core mineralization of the channel from the Deadbroke Mine northward 1,800 feet to the discovery indicated by Homestake Mining Company’s historic drill programs of the late 1980’s.
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