Geophysical Surveying At The Blackhawk Silver Mining District Exceeds Expectations
SIERRA BLANCA, TX - Texas Mineral Resources Corp. (TMRC), reported that analysis of Time Domain Electro-Magnetic (TDEM) surveying of high-grade silver veins in the Black Hawk District, Grant County, New Mexico has yielded extremely encouraging results.
The Black Hawk District, located near Silver City in southwestern New Mexico, is well known for the occurrence of well-defined high-grade bodies of native silver, containing significant amounts of U.S. Government-designated critical minerals: nickel, cobalt, and arsenic as well as uranium. Within these mineralized lenses, silver grades as high as 20% have been reported in the past.
These extremely high grades are in keeping with the historical records of production from this unique geologic type of deposit, which include well known districts like Cobalt, Ontario; Port Radium, NWT; Anneberg and Freiberg, Saxony; and Jachymov in the Czech Republic, all of which were prolific silver districts. The Black Hawk District was active in the 1884-1894 period during which time the Black Hawk and the Alhambra mines accounted for most of the production. Owing to their small size, these extremely high-grade ore shoots have been proven almost impossible to locate by traditional geologically targeted diamond drill holes.
As a result of the high concentrations of native silver in the core zones of the ore shoots, it was postulated that they would be electrically conductive. Three types of electric conductors are common in nature: massive metal or metallic minerals, graphite and saline water. With graphite and saline water unlikely to be present in the rocks underlying the Black Hawk District, the deposit is a prime candidate for an exploration method detecting massive metal and metallic minerals.
TMRC engaged Zonge Intl. to assess the Black Hawk District using its Time Domain Electro Magnetic (TDEM) surveying process. “A non-invasive method conducted on the surface of the deposit, TDEM allows a more focused and efficient approach to traditional drilling, by providing a map of subsurface targets before a single hole has been sunk,” said Dan Gorksi, CEO.
Two scoping level geophysical studies were conducted in late 2021 and early 2022 under the guidance of Thomas Weis, consulting geophysicist, Computational Geosciences Inc. and Zonge International. Zonge’s NANOTEM process, a variant of conventional time domain electromagnetic surveying, is used to locate metallic objects such as pipes, tanks and unexploded ordnance, and effectively locates small electrically conducting bodies at shallow depths. Transmission loops were modified to increase depth capability without unduly degrading the definition. In practice TDEM surveying is accomplished by laying out loops of wire on the ground surface, switching on and off a relatively strong electric current and recording the electro-magnetic effects induced in electrical conductors in the subsurface. A survey covering an aggregate 18 acres and consisting of 24 overlapping current loops was designed and carried out in February 2022. The field collection of these data is in process but is a relatively straightforward procedure. Analysis of these data is key and requires significant computer time per current loop.
Previously reported that the analysis of three of these loops, covering approximately ten percent of the area surveyed, had identified three strong anomalies worthy of being designated drill targets. Analysis now has been completed on another six loops. An additional four are currently undergoing analysis and an additional eleven loops remain to be processed. Within the nine loops thus far analyzed, thirteen strong and relatively deep conductive anomalies have been identified, with another four possible anomalies lying slightly outside the boundaries of the current loops. Data is being reliably captured to a depth of one hundred to one hundred twenty feet.
“Results of this stage of analysis have exceeded our expectations,” said Gorski. “We had expected to define anomalies within the trend of the known Alhambra vein and, indeed, the survey had been designed along these expectations, and four of these anomalies were within this trend. The unexpected result was that a total of thirteen large and deep reaching anomalies were found within an approximately nine-acre area. Although nine of these anomalies lie to the east of the Alhambra vein, these linear features conform to the trends of known carbonate veins in the immediate area. The fact that these targets are within one hundred and twenty feet of the surface insures that the intensity of drilling necessary to outline these features can be practically carried out.”
The next stage of work is to refine the geophysical procedure to improve the definition of the individual anomalies both laterally and to depth to better guide drilling. Drilling will commence immediately upon completion of the next phase of geophysics and the acquisition of the necessary permits. Subject to these steps, TMRC expects to commence drilling in March or April 2023.