Talk:Ore genesis

I have added this Ore Genesis section as a lot of geologists, especially in the U.S., do not study economic geology in depth. That is not to say they are bad, just more popular is the fossils and Yellowstone than in Australia, and more plentiful the employment in environmental geology than minerals than in Australia. I produced this to help out some friends on the livejournal geology community; please join if you wish. All ore deposits are different, each has similarities and differences to all others within the same class. I hope these summaries are somewhat middle-ground with respect to the processes and theories involved. If you disagree, at least do some research first, especially if you are not "authoritative" on these matters.Rolinator 11:30, 23 December 2005 (UTC)

Added some gold references.Rolinator 11:57, 23 December 2005 (UTC)

Decided to rewrite this to emphasise the importance of formation processes as opposed to geological setting. Also added a list of deposit types under the classification subheading, so that we can pehaps get working on describing the features of these deposit types in the future.Rolinator 10:31, 29 December 2005 (UTC)

Excellent page. Well done! —Preceding unsigned comment added by 89.100.130.17 (talk) 18:48, August 24, 2007 (UTC)

Fractional Crystallization

"Fractional Crystallization: separates ore and non-ore minerals according to their crystallization temperature." I'm certainly no expert, but as a chemist I KNOW that FC is NOT just about temperature, especially in geological contexts. The Fractional crystallization (geology) article states that both pressure and compositional changes (i.e. loss or addition of volatiles such as water, O2, and CO2) "can have dramatic effects on magma evolution." The article Igneous differentiation states"The primary cause of change in the composition of a magma is cooling." FC, of course occurs in other geological contexts (i.e. sedimentation), which doesn't necessarily follow that for igneous melts. While I'm at it, this section claims the crystals "may settle". Well. There's 3 possibilities: they are more dense than the surrounding fluid and sink (settle), they are less dense and float (upwards), or the difference in density is insufficient to provide them the opportunity to do either. (The 4th possibility is they re-dissolve). Fractional separation (as contrasted with crystallization) is mostly about a temperature gradient near the solidification temperature of the fluid, and in this case, typically, the pure fluid freezes out at the coldest zone, often without regard for density. In summary, the causes of separation are gradients of pressure and especially temperature, as well as compositional gradients AND changes in all those processes (which may be too abrupt to be considered gradients). Finally the reference given only says FC is one way magnetite forms. The article gives the impression it is the (only) way. (Change to "Some chromite and magnetite minerals form in this way."98.17.181.251 (talk) 05:59, 18 June 2024 (UTC)