Talk:Bowen's reaction series

comment and suggestion

The Text diagram of the Bowen Series does not render correctly in Google Chrome on OS X 10.9.2 Dspencer (talk) 00:27, 6 March 2014 (UTC)

Bowen's reaction series was described by Pentii Eskola as the most important theorem in igneous petrology published during the first half of the 20th Century. I've also read a remark by a recipient of the AGU's Bowen award that the reaction series is just a mnemonic device for undergraduates. Assuming the first is correct, should it be expanded. Its importance, for example, lay in disproving the eutectic theory of petrogenesis. In this, each coarse igneous rock had its own primary magma. Bowen's reaction series, by substitution the observed peritectic relations of magma & mineral, reduces the primary magmas to one. Arguments over it were arguments about its application, not about the theorem. Should this entry be extended substantually? Should major attacks on it be discussed & shown to be probable errors of application rather than flaws in the (thermodynamic) theory? Geologist 01:02, 5 April 2007 (UTC)

short answer, yes the article should be expanded. I don't know how valuable the "anti" arguements would be however, as you suggest they mostly not about the theory.

The following explains why I think this should be a major article.

First, this article illustrates to me some problems that appear when writing an encyclopedia. Who is our audience? Should we promulgate information widely accepted by textbooks, though specialists consider it wrong? Should the length of an article correspond to it's importance.

"Bowen's Reaction Series" could become a very long article, for it could easily include the early history of petrology, then much of 20th Century igneous petrology. That's how important this one theorem, and Bowen's book 'Evolution of the Igneous Rocks' was to petrology. One could present an initial section that offers the series as a summary of Bowen's laboratory experiments on a synthetic basalt. (The hydrous minerals in it, however, were not seen in experiments until methods improved.) His experiments proved that a mineral doesn't always just grow after it first crystallizes, but can dissolve while a different mineral suddenly appears & grows. As one can see from the diagram, extracting crystals at different temperatures can create gabbros, diorites, granodiorites, and granites. This fact, later explained by thermodynamics, revolutionized petrology.

A history section could follow that illustrates the importance to petrology of being able to explain how one primary magma can create plutons of varied compositions. Basalt was long believed sedimentary. Eventually, geological travels revealed volcanos in Italy; ancient volcanos in Southern France with basalt appearing to have flowed from these; various igneous rocks in Iceland that were capable of forming by the mixing of two or three 'primary' magmas. Vogt's pioneering experiments & knowledge of eutectics led him to the conclusion that compositionally varied plutons had first melted at eutectics, where a primary liquid of at constant composition will continue to form as more heat is added. Until Bowen's reaction series proved the existence of another genesis, the question that dominated igneous petrology was how many primary magmas there were. Petrologists mixed them, as was done in Iceland.

Then Bowen proved all could have come from one primary magma. The proof was the experimental existence of the two columns of the 'reaction series' (though the bottom was 'fudged'). One could draw horizontal rows that showed the crystals formed gabbro during one temperature interval, then reacted with the liquid and formed diorite instead. That a mineral could react and not appear in the final rock was revolutionary. In addition, Bowen's 'mercury' experimental method transformed experimental petrology, his use of flawless thermodynamic reasoning is essential today, his application of the van Laar equation for mixtures in drawing phase diagrams was before its time, but later became an essential tool in petrology, metallurgy, glass science, & materials science.

Bowen's thermodynamic evaluation and consequent dismissal of many popular petrogenetic theories made him hated in his day; and his field test of the 'reaction series' (using ancient volcanic islands off Scotland to illustate that basalt could create tiny quantities of granite) was twisted such that it confuses petrologists even today. The reaction series (a theorem) used synthetic, oxygen-rich basalts to offer 'proof by interpretation' (the only known technique for proving existence) of the possibility of creating a variety of common igneous rocks from one primary magma.

Many irrelevant facts were used, for years, to attack Bowen's ideas and even attack the value of laboratory experiments to petrology. Finally, Bowen's noting that the residual liquid (at the bottom of his diagram) is depleted in iron incensed a previous experimentalist at the laboratory. (Had he interpreted Bowen's theorem differently, he would have discovered the importance of 'indifferent thermodynamic states' in altering the differentiation paths of basalts.) However, because his field evidence contradicted his interpretation of Bowen's theorem (the one common in texts today), he used this enrichment in iron to continually attack, in print, all of Bowen's work. The iron enrichment proved to be caused by a depletion of iron in the initial magma. His & others arguments I called an 'incorrect application' of Bowen's theorem; but they are possibly believed by some today to present a counterexample that disproves (if one missreads Popper a bit) Bowen's reaction series.

There are, in fact, an indefinite number of reaction series, each differing in the composition of the original magma. The existence of only one is sufficient to prove an existence theorem. 'Bowen's reaction series' is not an ordered sequence of mineral pairs, it is a graphical proof of the one thermodynamic theorem that founds modern igneous petrology.

Above I explain why I believe this article should be of greater importance and should be expanded. The 'anti' arguments are actually important, for many geologists think Bowen's reaction series is a summary of some lab experiments on an artificial rock; some think of it as a failed attempt to explain the origin of continents some still think it has been disproved by Fenner's counterexample (or the great viscosities exhibited by some magmas). There is an entire monograph on Bowen's reaction series by David A. Young, published in 1998 by the Mineralogical Society of America, which I have not read.

Though I have no access to this book, many do. The first sentence of the Wikipedia's article now reads: 'Within the field of geology, Bowen's reaction series is the work of the petrologist, Norman L. Bowen who was able to explain why certain types of minerals tend to be found together while others are almost never associated with one another.' This sentence seems 'in apropos' of Bowen's reaction series. Though one could today view it that way, no one in Bowen's time did; and many theorems in metamorphic petrology, as old as the reaction series, are more appropriate in explaining this observation.

Because of these facts, I believe Bowen's reaction series should be a major article. It could use more work. Geologist (talk) 06:01, 21 December 2007 (UTC)

Does 'Bowen's Reaction Series' describe relative rates of weathering?

Is there a good reference for this? Beaches in Hawaii are made of olivine. It's not at all clear that rate of weathering and 'distance from equilbrium' are related. It's not clear that rate of crystallization and 'distance from equilibrium are related'. I'm sure you can quote many references to this 'fact' (for I have seen many), but none I have read prove it or even use as an argument any observation or fact.

To the contrary is C.N. Hinshelwood's remark in Chapter 18 of his 1951 book The Structure of Physical Chemistry : ' ... The activation energy always represents energy absorbed, whether the total energy change in the reaction is positive, negative, or zero. For this reason there can be no general relation between rate of reaction and equilibrium constant, and the early attempts to exloit the equation reaction rate = affinity / chemical resistance would be meaningless, even if a more precise definition could be given of chemical resistance.' Geologist 01:02, 5 April 2007 (UTC)

There was an early article by someone whose name began with a 'G' :-) who used the incorrect conclusion that distance from equilibrium was related to reaction rate to interpret Bowen's Reaction Series in terms of weathering. I don't believe anyone believes the conclusions of this paper today. Early in the 20th Century, Fritz Haber eventually received the Nobel Prize for his application of chemical theory to the manufacture of ammonia. Though the ammonia-producing reaction is exothermic, Haber increased the temperature. Thermodynamics correctly predicted less ammonia by doing this: but it greatly increased the rate of its production.

Bowen wasn't interested in weathering; and even if your observations prove true (which I'm afraid they won't), Bowen's Reaction Series is an applied thermodynamic theorem (involving peritectic reactions). No theory that I know relates 'distance from equilibrium' and 'rate of reaction'. Geologist (talk) 06:14, 21 December 2007 (UTC)