Hi EZ,
Probably the most important paper ever published on porphyry deposits was done by Don Singer in 2008 (or 2009?). He studied the characteristics of almost every porphyry deposit on the planet and provided the findings to not only his colleagues in the profession but also to us investors that would like to capitalize on this knowledge. Here is a link:
https://pubs.usgs.gov/of/2008/1155/
I think that Perez’s assertion that there were two porphyries present has pretty well been borne out. The Singer paper tells us why. The presence of a Cu-Mo (type 21a) porphyry at the ADL is beyond compelling. This is due to the ridge crest sampling program orchestrated by Auryn. Recall that it revealed a massive area (3,600 meters in the N to S direction and 1,200 meters in the E to W direction) showing copper and moly anomalies RIGHT AT SURFACE and in intrusive breccias present there. These breccias bore high levels of tourmaline. Gold with the grades we’re seeing at the ADL mesothermal vein deposit are seldomly associated, spatially or temporally, with type 21a Cu-Mo deposits. In isolated porphyries, you tend to get one or the other, moly or gold, but you rarely get both. In fact, moly is pretty much ONLY mined in porphyry environments.
Next you need to overlay the C.S. Perez hyperspectral satellite imaging survey showing a 7 Km swath of “about a dozen” intrusives oriented in a SW to NE direction across the plateau and its southern downslopes. At the ADL, these “intrusives” include what clearly appear to be an ultra-rich mesothermal vein system, porphyries, skarns, breccias, mantos, etc. What all of these structures have in common, now we’re thinking on a “District” scale, is the same gigantic magma chamber (sometimes two magma chambers that are linked). The gold and copper/silver/moly bearing hydrothermal fluids and gases all came out of the same magma chamber. After the formative process is completed over tens of millions of years, the relict magma chamber and the area immediately above its former roof/carapace is referred to as a “porphyry”.
The more likely source for gold grades as insanely high as is found at the ADL is a Cu-Au (type 20c) porphyry. Keep in mind that some mesothermal deposits are of a metasomatic origin or associated with plutonic rock. When the Auryn geoscientists did the Re/Os dating study and found that the ore was about 91 million years old (Cretaceous) in origin matching the age of the Andacollo Cu-Au porphyry to its north near La Serena, immediately the Andacollo Mining District became the most likely template for the ADL Mining District’s deposits. The same basic rock formations underly both although they go by different names i.e. the Veta Negra and Las Chilcas formations. At the Andacollo deposit, abnormally high-grade gold tends to radiate out in a 5 Km radius from the centrally located porphyry. Sound familiar? So, I would definitely count on 2 separate porphyries (or porphyry-skarn complexes) at the ADL. Maurizio told us very clearly at the Las Vegas “informational meeting” that the porphyry areas are way too big for Auryn to take on solo. Back then, Freeport McMoRan, gave Maurizio permission to use their name as being a party of interest to the porphyry areas. He also mentioned that there were two mega-majors “even bigger than Freeport” that were interested. He couldn’t give us their name.
We need to keep in mind that were dealing with the ADL “Mining District”. The development of the various ADL deposits has occurred over time which typically involves many “phases”. Vein deposits, as well as skarns, breccias, mantos, etc., typically occur in conjunction with porphyries often above and lateral to the porphyry. Sometimes the porphyry and the adnexal structures can be linked temporally and/or spatially to each other but sometimes not. Sillitoe and his colleagues are still fighting over whether or not the Andacollo Mine is spatially or temporally linked to the underlying magma chamber. These adnexal structures are “related”. Recall the PR from management noting that the Merlin 1 Vein over at the Caren Mine was “related” to the Don Luis 1 Vein.
What we need to keep in mind is that due to the “related” nature of these various deposits, interested majors are definitely going to take notice of the grades being realized in the vein complexes even though they might be more interested in the adnexal structures especially the porphyry in the case of the mega-majors. We investors are not going to see the majors dive into the Medinah or Auryn markets just because of these insanely high grades. I would assume (but cannot confirm) that negotiations behind the scenes got accelerated coincident to these high-grade revelations. This is especially true with the recent price performances of copper and moly. We are living in a time period in which there have not been any major discoveries made for quite some time and the MR/MR on the balance sheets of the majors is getting pretty skinny.
We’re all obviously excited about the grades being found in the vein complexes around the Don Luis and other nearby veins. Keep in mind though that the mere presence of these super rich veins is highly suggestive and corroborative of the presence of all of these various other adnexal structures that also are derived from the same magma chambers and that all might be of a high-grade nature. It’s a “system”. Soon we’ll get a view of the cash flow that will emanate out of the development of the various vein complexes. I don’t sense that any of the various prognostications are even close to reality. I’d suggest trusting management and starting with the initial 40 tpd projection based pretty much on one or let’s say 1.5 working faces since management did say that this projection initially couldn’t be achieved until the new “Fortuna Adit” got to one of its various targets. This took longer than anticipated. Keep in mind that these projections are based on Santiago being in full quarantine status and the supply chains being somewhat hamstrung. Part of the purpose of the adit is to increase the number of “working faces” for the miners to go after at the same time. I think a more accurate way to gauge production is to multiply 40 tpd times the number of working faces in play at any given time. Back when the Caren Mine/Merlin 1 Vein system was the primary target for production, Maurizio anticipated somewhere around 6 working faces where simultaneous blasting and mucking would occur. The mining process is somewhat straight forward in one sense. You drill holes in the working face with a jackleg percussion hammer. You stuff the holes with explosives (often ANFO). You yell out the customary “fire in the hole”. You blast and let the dust settle and then you “muck” (scoop up) the ore and deliver it to the adit opening. The key is to get a lot of “working faces” going at the same time.
