The case against the syngenetic Volcanogenic Massive Sulfide model—Prologue

This is a prologue to a series of posts that provides a counterpoint view of the syngenetic Volcanogenic Massive Sulfide (VMS) mineralisation model (Jackson, 2017), which is largely accepted as factual by the economic geology community.

But a minority of structural geologists, such as Bruce Hobbs and I, doubt the validity of syngenetic models such as the VMS model.

I’ll give my conclusion up front, which is:

Ancient VMS deposits are epigenetic deposits, just like orogenic gold deposits, and these are part of a spectrum of metalliferous deposits formed in the same open chemical system during deformation

I’ve come to this conclusion after considering the structural geological patterns of VMS deposits that have been effectively ignored or overlooked for decades since the introduction of the syngenetic VMS model. I’ve repeatedly seen the same structural patterns in a variety of metalliferous deposits in hundreds of drilling datasets that I’ve studied over the last 20 years and these patterns clearly indicate that there’s a common link between VMS deposits and orogenic gold deposits.

Before the 1960s, sulfide deposits were thought to be epigenetic in origin, so this idea isn’t new. Despite the countless papers on VMS deposits in the last 60 years, I believe more and more structural evidence will be revealed to turn the tide of opinion, simply because geologists will start to look for the evidence that I describe in these posts. Some of you have already contacted me after the Ore Deposits Hub talk I gave with Bruce Hobbs (Cowan and Hobbs, 2020), saying that you’ve seen some of these patterns before.

I expect almost all of you will disagree with me, because I’m telling you something that goes against conventional wisdom and what you’ve been taught at university. But that’s okay, as I’ve gone through this process before. Nearly 20 years ago, I was telling anyone who would listen that 3D interpolation was the way of the future for geological modelling, but few would take me seriously. In 2020, geologists talk as if implicit geological modelling is just common sense, but the truth is, once upon a time, I was the only person who thought it was common sense. What seemed perfectly logical to me wasn’t logical to the majority of geologists and convincing people took a lot of time and effort. I expect to experience the same opposition but on a much larger scale on the subject of VMS because it is one of the main ore deposit models that almost every geologist takes for granted to be fact.

This time, ironically, I encourage you to not believe me. Instead, I want you to go to the literature and look at your raw data to see if you can spot the anomalies yourself. You may even discover anomalies that I haven’t identified as yet. And that’s ultimately the purpose of this series of posts—for you to learn how to question everything that you read and hear, and instead rely entirely on the observation skills that you were taught as students of geology.

Why publish as LinkedIn posts?

This series of posts are based on new and largely unpublished observations and thoughts of mine. I’m doing this intentionally, prior to submitting manuscripts to journals, so as to:

1. have an online record of my ideas so that they can be searched and so there’s a public record of the dates I stated my ideas.
2. obtain useful feedback to further strengthen my argument for formal publication.
3. get geologists to re-examine their data to see if they can see the features that I describe in my posts.
4. get readers to try and falsify my interpretation.

I hope to reach the wider economic geology community and geologists than those I would normally reach through formal publications so they can start looking for the features that I describe in my posts now, rather than later. This way, as-yet-unidentified convincing examples could be included in formal research papers. I also encourage geologists to try and falsify my theory.

But what is falsification, and why is it so important to the scientific method? I’m glad you asked!

Scientific method embraces falsification, not verification

This series of posts will rely on you knowing the scientific method. I can’t expect everyone to know the scientific method, because it is rarely taught in our undergraduate geology classes, so I’ll take this opportunity to explain it. I strongly believe that any interpretation models presented by scientists should be falsifiable—that is, testable, by practical means.

A way to explain an observation was discussed by Nobel prize-winning physicist Richard Feynman, and I referred to his method in an earlier post as Feynman’s three-step scientific method:

Step 1: Guess (theoretical construct to explain the observation)

Step 2: Compute the consequences of the guess

Step 3: Compare directly to nature/experiment/experience/observation.

All these steps are necessary to test a theory, and theory that can be tested in this way is called a falsifiable theory.

Feynman said that if the predicted consequences (Step 2) made as a result of the initial theoretical construct/guess (Step 1) do not agree with what is observed in nature (Step 3), then the guess is wrong.

‘It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.’ —Richard P. Feynman

Feynman was outlining the principles of falsification, which were introduced by an Austrian philosopher, Karl Popper (Shea, 2016). In 1935, Karl Popper published his groundbreaking book Logik der Forschung (translated to ‘Logic of Research’). More than two decades later, Popper’s book was translated into English and published as The Logic of Scientific Discovery (Popper, 1959). Popper demonstrated that scientific theories are tested by falsification, not verification. He stated that if a theory isn’t falsifiable, it’s pseudoscience not science. For a summary of Popper’s ideas in the context of applied geology, see the article written by geostatisticians, John Vann and Mike Stewart (2011).

Examples of practical falsification

How does Popper’s idea of ‘scientific theories are tested by falsification, not verification’ translate to practice? Let’s say I stated a theory that ‘All cars are red’. This is a falsifiable theory, of course, because you can simply go out to the streets and notice the colour of the cars, and the first car you see that isn’t red would falsify the theory, so the theory of ‘All cars are red’ is considered a scientific theory according to Popper. This example illustrates that a scientific theory need not be sensible—it merely needs to be falsifiable or testable.

Here’s a real example from more than 320 years’ ago, and it’s a story that takes place in Fremantle, Western Australia, where I live. Europeans believed that all swans were white until Dutch explorer Willem de Vlamingh’s expedition observed black swans in the (now) Swan River of Western Australia in January 1697 (Fig 2).

The assumption that ‘all swans are white’ was refuted when a single black swan was observed by one of de Vlamingh’s crew. It required only one counterexample to falsify the accepted consensus, despite the millions of white swans previously observed by Europeans throughout history until that fateful day in 1697 when the first black swan was spotted. The number of observed white swans became irrelevant once the single counterexample was observed because the theory ‘all swans are white’ was falsified. Every time I see a beautiful black swan in the Swan River it reminds me of this important and significant scientific lesson—that a single simple observation can bring down an entire scientific theory that may have lasted for centuries. This is why I have a picture of black swans in my LinkedIn profile page—these swans highlight to me how important observation is, especially for the discipline of geology.

Here’s an example from mathematics. Irrational numbers are real numbers that cannot be expressed as a ratio of two integers. Pythagoras (c. 570 – c. 495 BCE), and his followers (Pythagoreans), believed that all numbers are rational. It only took one example of √2 (square root of 2) to falsify the theory and show that not all real numbers were rational. The discovery of irrational numbers is said to have been shocking to the Pythagoreans, and it is rumoured that the Pythagorean who made this information public was drowned at sea.

Finally, here’s an economic geology example. In the 1980s, economic geologist Prof. Ed Spooner (University of Toronto) argued that the origin of the vein-hosted gold in the various intrusions from Archaean Abitibi belt in Quebec was magmatic. In numerous publications, Spooner listed well-argued geochemical and geological evidence in support of his hypothesis that the gold was magmatic. Spooner’s post-doctoral fellow, Dick Jemielita, who, ironically, was hired to support Spooner’s magmatic fluid research efforts, provided the counterexamples that disproved Spooner’s hypothesis. Jemielita found that the U-Pb dates obtained from rutile from the gold veins post-dated the zircon and titanite ages from several intrusions by nearly 60 million years, and announced this news to the world (Jemielita et al 1989, replicated below in Fig 3).

It was clear the gold was deposited late, well after the consolidation and cooling of the igneous host, thereby falsifying the magmatic fluid hypothesis. What’s remarkable about this particular example is that in contrast to the numerous lengthy articles written on the magmatic origin of gold in the Abitibi by Spooner and students, it took just one short abstract to falsify the well-stated theory (Fig 3), showing that the falsification process can be brief and decisive. No other additional information was required but that was because of the theory of Ed Spooner was well-defined and falsifiable.

All the examples above are of scientific theories that were falsifiable because they predicted specific feature or outcomes that were later proved to be false (Steps 2 and 3 in Feynman’s three-step process). However, vague theories are harder to test (falsify)—the VMS mineralisation model discussed below is such a theory.

Feynman said in his 1964 Cornell University lecture that ‘You cannot prove a vague theory wrong’ (go to 5:10min in the next video).

Feynman was essentially agreeing with Popper (1959) about how vague theories are effectively unfalsifiable because such theories cannot predict what happens next. That is, in Feynman’s three-step process, Step 2 isn’t possible with a vague theory, so the theory remains stuck in Step 1. The theory remains a guess, and nothing more, and these theories are what Karl Popper referred to as pseudoscience.

A theory that is unfalsifiable—the VMS model

Every publication on VMS that I’ve read focuses on gathering evidence to verify the syngenetic VMS theory, but not to falsify it, which is the opposite of what Popper and Feynman both recommended as scientific method. Anyone can gather evidence to support a theory, but I can’t recall a single VMS paper published in the last 60 years that’s tried to falsify the theory itself, or suggested ways to falsify it.

Attempts to falsify the syngenetic VMS theory, by prediction (Step 2 of Feynman’s method) are always countered with exceptions to explain the contradictory geological evidence seen in the field. For example, it’s very common to see massive sulfide veins cross-cutting tectonic schistosity in a VMS deposit (a feature I’ll address in future posts). The very clear relative timing of the cross-cutting of the sulfide emplacement shows it to be epigenetic (syn-deformation) and not syngenetic (synvolcanic). However, VMS proponents will counter with an exception, stating that the sulfides were ‘remobilised’ during deformation, without explaining how this remobilisation occurred (ie. vague theory). Similarly, for the many VMS deposits hosted in fold hinges, VMS proponents counter with another exception and state that the folds must have ‘nucleated’ on pre-existing sulfide deposits, without explaining how this mysterious process takes place (ie. another vague theory).

These exceptions, which are only conjecture, are not backed up with evidence, thus the syngenetic VMS theory of mineralisation remains an unfalsifiable theory. By Popper’s definition (1959), using exceptions to explain away contradictory evidence relegates the VMS theory to pseudoscientific dogma, irrespective of how many papers have been published about this mineralisation model. In other words, the VMS model does not follow the protocol of the scientific method used in other scientific disciplines. The theory remains stuck in Step 1 of Feynman’s three-step scientific method.

Just pause for a moment and think about these exceptions in terms of my earlier proposed theory that ‘All cars are red’. Imagine further that my colleague Bruce also shares this theory, so Bruce and I go out to the road to test the theory. When I see a red car, Bruce counts this as a valid observation in support of his theory, but as soon as I see a car that isn’t red, I would expect the theory to be falsified, but instead, Bruce counters with exceptions, such as

• ‘You don’t have your glasses on so you’re not seeing correctly’, or
• ‘The smog level is really high today, so it’s affecting the way you are seeing colours correctly’, or
• ‘You’re colour blind’.

These exceptions are simply excuses based on unfounded conjecture and nothing more. On other occasions, Bruce might distract me so I miss seeing the cars that aren’t red. Unbelievable as it may seem, these types of distractions litter the published geological literature, which I’ll discuss in this series of posts.

Exceptions and tricks like these do nothing to support the theory; instead, because of these excuses, the theory remains firmly in the pseudoscientific camp.

My counterpoint view of VMS deposits as epigenetic deposits is a falsifiable, and therefore, scientific theory according to Popper (1959). I’ll specify exactly how to falsify this theory in future posts, and I’m interested in how this plays out in real time. Perhaps there are situations in which sulfide mineralisation is clearly synvolcanic, but my intuition is that these will be recently obducted sea floor massive sulfide deposits. I have no issues with the existence of seafloor massive sulfides (SMS) that form proximal to sea floor spreading. However, I don’t believe the ancient massive sulfides categorised as VMS are the deformed equivalent of these modern SMS deposits. I predict that the ancient VMS deposits in Archean fold belts in Australia and Canada are likely to be all epigenetic, and I’ll point out the logic of why I think this in future posts.

I believe that the more people who try to falsify my theory, the better for the theory and for the economic geology community, which is why I’m writing down these thoughts before I submit them for formal publication. If the theory is falsified before publication, I see that as a good thing, because we won’t be wasting the time of the journal editors to even consider my manuscript. If it’s not falsified, then it deserves to be published.

I’ve never been convinced of the VMS model from the day I first heard about it in a talk nearly 30 years’ ago at the University of Toronto where I was a postgraduate student. In the next post, I will share with you what information that I heard that made me immediately be suspicious of the VMS model.

Part 2 of this series of posts on VMS can be found here:

References (most articles available here)

Cowan, E.J and Hobbs, B.E. 2020. How to determine the timing of mineralisation from deposit-scale grade patterns (plus Q&A). Ore Deposit Hub online presentation, 15 July, 2020. Archived at Ore Deposit Hub YouTube channel. https://youtu.be/AMpe5MzxYog

Jackson, A. 2017. ORE DEPOSITS 101 – Part 7 – VMS and Sedex. YouTube video by Sprott Global Resource Investments (SpotEDU YouTube channel).

Jemielita, R.A., Davis, D.W., Krogh, T.E., Spooner, E.T.C. 1989. Chronological constraints on the origin of Archaean lode gold deposits in the southern Superior Province from U-Pb isotopic analyses of hydrothermal rutile and sphene. Geol. Soc. Am., Abstr. with Programs 21:6, pA351.

Popper, K. 1959. The logic of scientific discovery. New York, Harper and Row. 480pp (English translation from the original 1935 publication Logik der Forschung).

Shea, B. 2016. Karl Popper: Philosophy of Science. In Fieser, J. and Dowden, B (Eds) Internet Encyclopedia of Philosophy.

Vann, J. and Stewart, M. 2011. Philosophy of science: a practical tool for applied geologists in the minerals industry. Applied Earth Science (Trans. Inst. Min. Metall. B) 120, 21–30.

Acknowledgements

Mel Hickman and Derek Shaw for providing feedback on early drafts.