Continuing on with more on the Anaconda system of technical control of mining discussed in Part I, particularly the Anaconda mapping method.
In Part I, we had a look at the Anaconda technical control system for engineering and geology and how it was implemented at the Cannon Mine. Much has been made of the Anaconda mapping method in our industry. It is part of a comprehensive system of technical support that was first developed in the Butte, Montana mining camp. The mapping method was developed by David Brunton and Horace Winchell for Anaconda (Amalgamated) in the late 1890’s and carried on with success by Reno Sales during the “Wars of the Copper Kings” in the early 1900’s. It has been mistaken by many geologists as a paradigm for mine geology control. It is an important component of the system discussed in Part I. In various forms it was disseminated to other Anaconda mines that I personally know of; e.g., Yerington, and Park City. Experienced Anaconda production geologists that I worked with like W. J. Garmoe, Chief Geologist at Park City and Carr Fork, pretty much mapped with three colored pencils: 1) Black for contacts, joints, notes and to emphasize structure; 2) Blue for faults; and 3) Red for “mineral”. Bracketed side notes were placed outside the drift face, ribs or dig face. The geologist made his own accurate survey in a way that could be adjusted to final engineering survey later. The map product clearly displayed the location of lithology breaks, strength of mineralization and faulting, all without clutter. The system addressed the mapping of veins and faults perfectly, and could be applied to other types of deposits as well. That is the original Anaconda mapping method.
As a new breed of research-oriented geologists rose within the ranks in the 1960’s and 1970’s, the system was modified and expanded, formalized in a memo issued in 1966 by Anaconda’s J. P. Hunt (Diamond Drill Sections and Detailed Pit and Tunnel Mapping, 1966). Much more emphasis was placed on mineral species and alteration, requiring the mapper to carry a quiver of more than a dozen numbered color pencils to represent all of the different features, and a specially modified clipboard attachment to hold all of them. These modifications were an adaptation that followed the increased exploitation of porphyry and skarn deposits by bulk methods. Much was being learned about these systems and their genesis; a few companies like Anaconda even had research labs that were cooking up theoretical magmas in pressure bombs.
The memo in question comprised 12 pages of instructions, descriptions, drafted maps, lists of abbreviations and symbols, and the required color schemes for lithology, texture, alteration, structure, copper mineral ratios, and placement of notes. It was a cumbersome system that required much more time to implement, and great skill to depict in a way that was presentable. The best practitioners were like 19th century portrait artists, capturing every detail. Some of the logs and maps reminded one of the pointillisme master Seurat’s A Sunday on La Grande Jatte.
Done well, form would emerge from the mass of lines, dots and dashes on the maps, reproducing the textures and mineral distribution of the rock; something like a modern hyperspectral scan.
I was a latecomer to Anaconda with a lowly Master’s Degree. In my first assignment, I was trained by the ‘Berkeley boys’ in the enhanced Anaconda system. We logged miles of porphyry and skarn core, and mapped benches in the pits. Not being an artist, it took me a long time to approach any sort of mastery. I would expend a lot of effort afterwards to extract the information I needed for compilation maps and sections.
All of the projects got this treatment which was feasible at the languid pace of exploration that characterized the aging U.S.-based mining companies in the 1970’s. Apart from Pumpkin Hollow, an aeromag discovery, the conceptual successes made by Anaconda’s western office were actually based on structural interpretations, not petrology. From the operations perspective, the geologists were of little daily relevance to the Yerington mine and the geologists’ focus was finding a new one. The mining proceeded on blast hole information and there was no formal grade control program of which I am aware. Yerington was a good mine and didn’t need much tending once the footprint was established. Sporadic mapping was done and occasionally there might be a consultation on a specific operational issue.
Fortunately, I made a move to the Carr Fork Mine at the pre-production stage where W.J. (Jim) Garmoe was the Chief Geologist. In a couple of sessions underground with Jim, I learned the old Anaconda system and why it was so practical for operations geology. The main idea is to graphically emphasize, or weight structure and mineralization so that you can see where the ore is on your map from across the width of a big conference table. We mapped structure first with a single pencil based on a quick assessment made by stepping along the length of the tape hung on the wall or between survey spads in the back. A thin blue line denoted a weak fault; a thick line denoted a strong one. We then went over the stronger structures with a sharp black pencil to make them stand out from the rest. With this simple system, one could see where the mapper thought the most movement occurred; e.g., on the footwall slip, or on Fault A instead of minor Fault B. This was done with mineralization, too. First the red dots, dashes or lines for veins, then black pencil for emphasis, as warranted. Blue, black, red. Where’s the main fault on the map? Look for a fat blue line. Where’s the mineral? Look for the strong red.
The field sheets shown here are the best examples of this system that I can provide. The first is a bit of quick mapping in a 400 year-old Mexican mine made by me long after my best days underground were behind me.
The map is not drafted, it’s just as it was when I came out of the mine. It’s easy to see the trace of the main structure and the mineralization. There are plenty of structural measurements without a lot of clutter.
The second example is taken from a folio of field sheets for five mining levels of the Oro Cruz Mine that I made 25 years ago and still have in my files. For some reason I didn’t put them in the project file drawer at work. That’s a good thing because the mine, exploiting an odd thrust-hosted deposit, is now closed, and in the U.S. data from old mines is regularly landfilled. The particular example below shows a rib sketch of the thrust zone with a bit of extra orange for intrusives and for quartz to distinguish it from pyrite mineralization. It was hot in that mine and you had to keep from wetting the paper.
It’s plain to see the mineralized zone from, more than anything, the controlling faults.
The final example is a black-and-white copy of a sheet from mapping of a haulage level of the Dean Mine, NV. Salt Lake Blue was the paper of choice in the day, a high-rag content, quality paper somewhat resistant to water. The originals are probably in some landfill library.
Despite the lack of color, it isn’t too hard to see where the structure and mineral occurs and how it pinches and swells. The drift mapping in these examples was done at chest level. Note that each map session’s advance and date is shown in the margins. The scale is shown, and the author.
Geologists trained at Butte learned a standard lettering style that was very elegant. I didn’t have the benefit of that training and Garmoe didn’t think it was especially important. I would never have endured the arduous apprenticeship of Butte and the rigid way of thinking it seemed to produce in some of the ‘survivors’. But I could recognize the work of any Butte-trained geologist (e.g., Dick Miller, Bill Payne) or engineer like Jim Knowlson. It was marvelous. Unfortunately, I have to mostly use the past tense these days. These field notes were transferred to posting sheets which in turn were used as the basis of interpretative maps.
Returning to the Carr Fork story, Jim Garmoe, like some others in Anaconda, had a keen eye for his objective—mine ore, avoid waste. The amount of biotite or sericite didn’t much matter. I blended that basic method with the more elegant, new Anaconda system ingrained in me at Yerington, but I made sure I could see the faults and the copper ore on my Carr Fork maps. And what, in the end, was critical to being able to mine the Carr Fork skarns? I can tell you from the hard lessons of my three years in that mine until it closed prematurely that closure wasn’t due to the amount or type of different minerals shown by colored pencils. Carr Fork failed because of a set of abundant, steep northeast faults and dikes which chopped up that orebody like celery in a vegan restaurant, plus some terrific construction and engineering gaffes. Those faults, well-known to geologists in the historical mines above the new orebody were not taken into account when the new Anaconda crop drilled a literal handful of vertical holes into the skarns and published a reserve based on those amounting to tens of millions of tons of continuous skarn ore. The logs made of the drill holes were very pretty, full-dress Anaconda mapping system style. The headquarters view of the extension of skarn mineralization in the Bingham Syncline to 1500 m below the surface was of a continuous folded sheet—no matter that underground mining in the 1930’s just above the new reserve failed due to the numerous faults and a barren dike that followed the ore lenses. A 90-year old geologist from that earlier era told me all about their woes with that deposit at his home in Salt Lake City in 1982. The new Carr Fork mine was going to be the flagship of the resuscitated Anaconda (and even be the first metric mine in the U.S.!). Those Anaconda exploration geologists were seldom seen as the production date approached, and then never seen again once we were in production, having gone on to fame and fortune at academic institutions while we stayed to try to make something of the mess.
I remember Garmoe and I standing over a longitudinal section made from level maps marveling over how that 30m-thick “orebody” really comprised a couple of variable-thickness lenses, one in the footwall and one in the hanging wall of the Yampa Limestone, separated by internal waste. The limestone contacts with barren quartzites had moved like piano keys in a jazz bar, one block up, another down. Drawpoints designed from the reserves were found to be in the middle of the ore, or 5 m above, or below ore, seldom in the right spot. The displacements and incorrect characterizations of the orebody stratigraphy were so significant that more dense information from later definition drilling could not mitigate the flaws in the original mine design. All that mattered for that mine was the dike and the network of weighted blue lines (northeast faults), and what they did to the black lines (contacts) and red zones (ore) on the map. Not the mineral zoning, the textures or metal ratios. Alteration and other overlays were not useful to guide production.
But for those who still wish to know more about the enhanced (i.e., academic) version of the Anaconda system, there’s a good unpublished summary of the method authored by M. Einaudi in 1997 and available with a web search. One of the application examples given in that booklet is the Pancho porphyry gold (Cu) deposit in the Maricunga belt, illustrating results of field work by another able geologist. Figure 7 in that booklet shows mapping of quartz veinlets that purportedly define the orebody. In detail, they don’t. The only predictor of gold in the Maricunga porphyries is gold itself. No team of geologists working in that entire Belt has been able to apply Anaconda mapping methods to metal grades in a manner useful for either gold or copper resource estimation, or production. I’ve had a go at estimating resources and monitoring grade control on fully seven porphyry gold deposits in the Maricunga, including the most recent Pancho resource, thus I’m not speculating about ore controls. And, while all of the detail is interesting and advisable at the early exploration stage when you have to milk information from every drill hole, it is only tangentially useful for exploration of concealed orebodies because; e.g., the quartz veins and potassic alteration associated with the metals are proximal indicators.
In summary, it is arguably good to know as much as possible about a district and its orebodies, and to give bright, curious scientists an opportunity to have a detailed look at anything and everything. The idea in logging and mapping is to observe and record the facts, and that is fundamental to the Anaconda mapping system. Referring only to the group, and not individuals, production geologists tend to have tunnel vision. This isn’t good always good because data should also be collected in order to test hypotheses and solve problems; tunnel vision in all aspects of a job is a dead-end. Thus, there is a compromise, or a dichotomy in operations. But in a production setting you can’t have the whole team running around mapping biotite and quartz vein densities, spending all day in a single heading or the core shack while there are many other things that need doing. The original Anaconda mapping system, with local minor variation, is a practical shorthand tool for following and predicting ore lenses controlled by lithology, faulting and folding. We can put our large quiver of colored pencils and alteration overlays away for all but special studies, or for consultants. Daily, we can make our necessary notes working with the lean, focused and time-tested system developed 125 years ago, and get on with the many other tasks involved in providing geology inputs to resource estimates and mine operations.
Well, I will do so, at least. Actually, I prefer my tablet for mapping these days—rather than draw geology, I can trace on top of the imaged geology and make notes. I can still annotate and trace over the image with black, blue and red virtual pencils. Anaconda method v. 2022, low-emissions and sustainable (no paper). 😝
