Thomas Gold (1920–2004)

I’ve had this book sitting on the “to be read” stack (now expanded to four stacks, due to ceiling height) for a long time and finally got around to reading it. This turned out to be embarrassing, since I had formed an incorrect conclusion about what author Thomas Gold was proposing, based on the book title. I had been under the impression that Gold’s hypothesis involved biotic oil, but that the oil formed at much greater depths and in a wider variety of rocks than conventional wisdom allowed. Popular news reports didn’t do too much to disabuse me; it was actually reading Gold’s work that did it.


There have been abiotic oil theories floating around long before Gold, but Gold was the first scientist of sufficient stature to persuade anybody to take him even slightly seriously. Since Gold was also something of a polymath, he had the debate advantage that he could pull in knowledge from disparate fields and thereby confound anyone of a narrower view; talking astrophysics to petroleum geologists, geology to biologists, and molecular biology to astrophysicists. This must have lead to considerable frustration in his opponents; they knew he was wrong but couldn’t go far enough outside their own fields to remove all doubt.


Gold proposed that there were huge amounts of primordial carbon in the deep crust and upper mantle, where they had condensed directly for solar nebula material. He cited the type of meteorite called “carbonaceous chrondites” as evidence that there was a lot of carbon floating around in space as Earth was forming.


This has been proposed before, but always foundered on the observation that petroleum bears unarguable biological signatures: it is enriched in C12 at the expense of C13, and crude oil favors alkanes with an even number of carbon atoms (the C12 enrichment occurs because complicated multistep biological reactions favor light molecules; even-number alkanes are favored because acetyl coenzyme A transfers carbon as acetyl groups). Anyway, Gold explained this by allowing that petroleum was biotic, but it was the result of biological processing of primordial methane gas by barophile and thermophile microorganisms living at depth.


Gold had a number of evidentiary trains. The one that attracted the most attention was the claim that petroleum reservoirs spontaneously refill (which they apparently do, in some cases and to a relatively small extent). Gold suggested this was evidence of petroleum upwelling from below. A second argument was based on isotopic ratios in crack-filling carbonate grains. The claim here was that these carbonates did not derive from atmospheric carbon dioxide but from upwelling methane reacting with oxides in the surrounding rock. Presumably this hypothetical methane had not been bacterially processed yet and therefore had different isotope ratios. The third argument was based on helium abundance in petroleum areas. Gold argued that helium could only come from deep crustal or mantle racks, and that its presence in petroleum fields was evidence that deep rock in the area still had sufficient pore space to allow it to upwell. And if helium could do it, methane could too.


Gold attracted sufficient attention to get funding for a test boring in Swedish basement rock. The scientific press reported this project as unsuccessful – traces of hydrocarbons were found but they could be attributed to drilling fluid. Gold countered by saying the project used only water-based drilling fluid, that various hydrocarbon gases (up to pentane) had been found all the way to the bottom of the boring, and that the boring had yielded 60 kilos of a black, malodorous substance which Gold claimed was magnetite mixed with light hydrocarbons. You would think sample care would be ultra important in a project like this, but somehow only a very small sample of this material was retained and there wasn’t enough for reanalysis by other labs.


Thus the Swedish experiment gave interesting results but not nearly enough to confirm Gold’s ideas. Up to this point the book is interesting reading; Gold’s a good explainer and I regret he never wrote any other “popular” works. Unfortunately, the last couple chapters become increasingly woowoo. Gold exhibits one of the failures of many pet theorists; he tries to use it to explain everything – the origin of diamonds (from pressurized methane) and earthquakes (from upwelling hydrocarbons). He’s on increasingly shaky ground (no pun intended, but I’ll take credit for it anyway) as he gets further away from the aspects of geology he originally investigated.


To be fair to Gold, some of his critics got carried away as well. I remember reading an article dismissing Gold because even if petroleum reservoirs were refilling, they weren’t doing it fast enough to make any difference in world oil production. This misinterprets one of Gold’s arguments; reservoir refilling is one of the things he considers evidence for hydrocarbon upwelling from depth. However, the main point of Gold’s abiotic oil suggestion is that oil should be recoverable anywhere, not just the sedimentary traps where it’s searched for now. Thus the refilling of existing reservoirs is of minor importance to oil recovery; according to Gold, there should be abundant oil under (for example, the Canadian Shield).


Worth reading, to be prepared to discuss Gold if nothing else.… (more)