Project of the Week: Tenoriba Gold-Silver Project, Mexico

2nd December 2020

Featured Image:
Gold nuggets panned at Mammoth’s Tenoriba Property, Mexico. Weight of 29.42g. Sourced: Mammoth website
Mammoth Resources (TSX-V:MTH) is a precious metals exploration company currently focussed on the exploration of their Tenoriba Gold-Silver Project in Chihuahua State, northern Mexico (Figure 1). Mammoth signed an agreement to option Tenoriba to Centerra Gold in December 2018. In September 2020 after 21 months at Tenoriba, Centerra informed Mammoth that they were ceasing all activities in Mexico, a decision that was irrespective of the potential of any of their projects, including Tenoriba. As a result of Centerra’s departure, 100% interest in Tenoriba was returned to Mammoth, a unique opportunity for a small cap junior company. The Company is also searching for opportunities to option other exploration projects in the Americas, but today we’ll be talking about Tenoriba. I spoke to Thomas Atkins (President, CEO & Director) to learn more about the geology and history of Tenoriba and Mammoth’s upcoming exploration plans for the project.

Mammoth’s Tenoriba property is comprised of 4 contiguous claims amounting to 5,333 ha (13 km along strike by 4 km wide) in the heart of the prolific Sierra Madre Precious Metal Belt (Figure 1). This area is a particularly attractive mining jurisdiction in Mexico and if you want to understand comparative geological potential you can look at multi-million ounce gold-silver operations such as the >4Moz Mulatos Gold Mine (Alamos Gold) and the now depleted 2.5M oz El Sauzal Mine (Goldcorp - now Newmont, after takeover of Goldcorp), both located within the Sierra Madre belt near Tenoriba.

Figure 1. The location of the Tenoriba project in Chihuahua State, northern Mexico. Stars on the inset show the location of Tenoriba relative to other deposits of the region.

Tenoriba is prospective for epithermal gold-silver mineralisation and many occurrences of features common to High Sulphidation systems, similar to the aforementioned Mulatos and El Sauzal deposits, including outcrops of vuggy silica (Figure 2), are observed throughout the 5 km trend of ubiquitous gold-silver mineralization most significantly explored at Tenoriba. A trend which remains open along strike. Additional features of these High Sulphidation systems common at Tenoriba, include: highly argillic (silica) altered felsic volcanics, elevated levels (elevated but not at a concentration of any environmental concern) of common trace minerals (antimony, mercury, arsenic and occasionally copper) and epithermal alteration clays (dickite, kaolinite and occasionally pyrophyllite). Further evidence of a robust mineralizing system includes completely silicified host rocks, and breccias which are illustrative of at least two significant epithermal events, if not more.

Figure 2. Vuggy silica at Tenoriba illustrative of a classic High Sulphidation epithermal mineralised system.

In addition to their own data, which we’ll get onto in a minute, Mammoth has access to drill core and data from a prior optioner, Masuparia Gold Corp. (“Masuparia”), which held the project in 2007-08. They however dropped their option following the Global Financial Crisis in October 2008. Between 2007-08 Masuparia spent approximately $2m on exploration which included stream sediment sampling, collection of 2,600 soil samples along a systematic grid covering a 5 km strike length, mapping and collection of hundreds of chip samples. The results of this work led to their drilling 15 diamond drill holes for a total of ~2,500 metres. Highlight intervals from this 2008 drill program include: 1.90m @ 45.90 g/t Au, 9.40m @ 1.37 g/t Au and 34.40m @ 1.03 g/t Au (@ 62m, 135m, and 110m depth, respectively). Mammoth optioned the property in 2012 from the original owners, a couple of Mexican prospectors, and soon thereafter consolidated the historic data identifying a 5x3km (15km2) roughly E-W striking mineralized trend over which gold-silver can be ubiquitously sampled. Highest metal assays observed are 74 g/t Au and 62 g/t Ag.

It should also be noted that Mammoth did some preliminary metallurgical testing at Tenoriba on core samples from the 2008 drilling. Under a microscope gold occurs as free gold or on the perimeter of sulphide grains or along fractures. Bottle roll tests of core collected from different drill holes, at varying depths and grades yielded 100% recovery of gold within 24 hours to 60 metres depth and mid 60 – 70% recoveries to depths as great as 130 metres. These results could bode well for a low capital and operating cost, open pit, heap leach mining and gold recovery operation at Tenoriba. Under such scenario (which has been employed at Mulatos since the inception of mining), because of the relatively low capital and operating costs compared to underground mining, cut-off grades in resource and reserve studies for such mines are commonly as low as 0.2 - 0.3 g/t Au, at Au prices of ~US$1,500/oz.

So, how does Mammoth intend to define gold (and silver) resources at Tenoriba?

Mammoth now owns 100% of Tenoriba* and has, over the past 8 years**, performed a number of surface programs to enhance their understanding of the system and prepare the project for drilling. Exploration activities included: detailed mapping (over 5 km of the trend) and sampling (as much as 7 km along trend) by both chips and channels, and an Induced Polarisation-Magnetometer (IP-Mag) geophysical survey, which covered half of the 15km2 soil geochemical footprint of interest (Figure 3). In the case of channel sampling this totalled ~150m in 14 channels cut within the largest outcrops along trend for a combined chip-channel total of more than 700 samples. In 2017-18 Mammoth carried out an 11-hole diamond drill program totalling 2,705m sporadically testing targets in 3 areas over a 4 km strike length. Highlight intervals from this drilling include: 5.5m @ 5.0 g/t Au, 5.9m @ 3.5 g/t Au and 126.8m @ 0.52 g/t Au, including 25.0m @ 1.2 g/t Au. It was all of these attributes which led to Tenoriba being an attractive property for Centerra to option, their seeing the potential for Tenoriba to host a multi-million-ounce precious metal deposit, with which a company of their size would benefit.

Figure 3. Composite location map - geology, chip-channel samples, geophysics and drill locations.

The size of the panned nuggets (Figure 4) is indicative of robust mineralisation, and as Thomas says, “there’s lots of gold on the property and it didn’t fall from the sky, so it has to be at depth somewhere on the property”.

Figure 4. Gold nuggets panned below the El Moreno area at Tenoriba.

At the current time, Mammoth is focussed on establishing a confident geological model for the mineralised system in preparation for a substantial drill program in early 2021. As part of this program, they’ve engaged the services of a highly qualified PhD geologist with extensive experience and knowledge of epithermal precious metal systems. This independent consultant is reviewing all historical data, outcrop and core at site to confirm that geological features at Tenoriba are High Sulphidation in nature, and where in this system are some of the most prospective areas for further exploration. Separately, Mammoth is also advancing 3D modelling of prior 2D geophysical results and will include all surface and drill data to better understand trends and controls to the mineralization sampled on surface and intersected in drilling in this 3D model.  With the completion of the 3D modelling, Mammoth plans to do infill IP-Mag geophysics to cover the remaining 50% of the property not covered by the initial survey. Thomas believes that having a good sense of the distribution and controls to mineralisation is key to being cost efficient when it comes to planning subsequent drilling. It’s for this reason Mammoth has decided to advance these activities prior to their intended program to aggressively drill test Tenoriba in the new year with up to 50 drill locations for up to 7,500 metres. A drill permit was submitted by Centerra for 139 diamond drill hole locations  over an area of 2.25km x 1.25km and Mammoth is awaiting this permit approval.

The 15km2 area of interest remains open along strike and this is where Thomas cites additional excitement about Tenoriba. It’s evident that Tenoriba is a large property with a large footprint of mineralisation. At this stage identifying the first of what could be numerous areas of concentrated gold-silver mineralisation at Tenoriba is key to unlocking additional mineral potential elsewhere, which may just be the lay of the land for Mammoth. The property is large and as you move westwards a ~700m drop in elevation occurs, taking you deeper into the potential porphyry gold-copper source of these High Sulphidation systems. This isn’t confirmed, but higher temperature alteration mineral assemblages sampled from 2018 drilling in the area, plus a good interval of copper mineralisation; 7.2m @ 3.59% copper, may be suggestive of this potential.

So, to sum up: large property, highly prospective, numerous discoveries, great high-grade intervals and long moderate grade intervals, size potential, and most importantly, gold and silver. Thomas is hoping to issues news on project developments over the coming weeks and months prior to an announcement of the commencement of drilling in early 2021. So, much to look forward to from Mammoth.

All the best,


All information within the above article is sourced from the Mammoth Resources website and personal communications with Thomas Atkins (CEO, Mammoth Resources)

* subject to a 2% NSR which can be acquired anytime 2 years into commercial production for US$1.5m

** there were 3 years during this period when, due to the weakness in the gold price and challenges to raising capital, Mammoth performed no work at Tenoriba

Further Information

Technical report, 2017 diamond drilling - here

Geophysical survey report 2014 - here

Mammoth on Mines and Money 5 @ 5 - here

Posted in Project of the Week

Esme Whitehouse View posts by Esme Whitehouse

BSc Geology at the University of Brighton and MSc Exploration Geology at Camborne School of Mines. Now working as a junior geologist alongside in West Africa with Origin Exploration.