spent the day in class
May. 1st, 2008 10:04 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
kareinaToday I attended day one of a Short Course sponsored by CODES : Thermodynamic Modelling Workshop
The course was primarily aimed at modeling for hydrothermal alteration in ore deposit systems, and my project has *nothing* to do with ore deposits of any sort, but my project does focus on thermodynamic modeling of metamorphic rocks (working out what temperature and pressure could have been responsible for the growth of the minerals which are present in the rock based on their compostions), so I went in hopes of picking up a useful tidbit or two. Indeed there were
Perhaps because he knew that there was a metamorphic petrologist in the room, one of the presenters commented early in the day how important he feels Ph is for chemical reactions. He stated that metamorphic petrologists tend to think in terms of pressure and temperature, and they see muscovite as an indicator of low temperature conditions, but he sees it as being formed by a Ph driven reaction, particularly the reaction wherein muscovite transforms to paragonite (or vice versa). This comment got me to thinking (again) about some of the reactions in my rocks. The program I am using to do my modeling, Perplex, is convinced that for a number of my samples the mineral paragonite should be present at the temperatures and pressures at which my garnet cores were forming. However, paragonite has not been reported for these rocks, and I have not seen any evidence of it in these samples. There are any number of possible reasons for this (assuming that the program is right about that in the first place, which is not, necessarily, a safe assumption). It could be that it *was* present when the garnets first started growing, but at some later time it completely reacted out and, perhaps it became the albite, which is present in many of these samples. Or perhaps at the time the garnets started growing the rock had a different chemical composition than it does now, and there was never any paragonite--perhaps fluids moved through these rocks at some time after the first growth of garnet, and picked up some elements and dropped off others, resulting in enough of a change in the total rock composition as to fool the program as to what minerals could have been present back then.
Needless to say, I am going to have to check a variety of things to see if either of these are more likely for these rocks, or if there is some other explanation. It seems like every day my "to-do" list for this project just gets longer and longer!
The other useful thing I got from the workshop is how phase diagrams are constructed from chemical reactions. Now, I've seen explanations of this in text books, but somehow, having it done in a lecture, and then having the exercise to work, wherein we calculated each step necessary, starting with balanced chemical equations, made it ever so much more clear. Yes, I've got that nifty program to create them for me, but understanding what steps it is doing behind the scenes is a goodness!
However, despite finding useful stuff in today's class, after discussing it with the instructor, I shall not attend the second and third days (which are far more focused on the ore deposit stuff), but will stay home and work on my own project!
The course was primarily aimed at modeling for hydrothermal alteration in ore deposit systems, and my project has *nothing* to do with ore deposits of any sort, but my project does focus on thermodynamic modeling of metamorphic rocks (working out what temperature and pressure could have been responsible for the growth of the minerals which are present in the rock based on their compostions), so I went in hopes of picking up a useful tidbit or two. Indeed there were
Perhaps because he knew that there was a metamorphic petrologist in the room, one of the presenters commented early in the day how important he feels Ph is for chemical reactions. He stated that metamorphic petrologists tend to think in terms of pressure and temperature, and they see muscovite as an indicator of low temperature conditions, but he sees it as being formed by a Ph driven reaction, particularly the reaction wherein muscovite transforms to paragonite (or vice versa). This comment got me to thinking (again) about some of the reactions in my rocks. The program I am using to do my modeling, Perplex, is convinced that for a number of my samples the mineral paragonite should be present at the temperatures and pressures at which my garnet cores were forming. However, paragonite has not been reported for these rocks, and I have not seen any evidence of it in these samples. There are any number of possible reasons for this (assuming that the program is right about that in the first place, which is not, necessarily, a safe assumption). It could be that it *was* present when the garnets first started growing, but at some later time it completely reacted out and, perhaps it became the albite, which is present in many of these samples. Or perhaps at the time the garnets started growing the rock had a different chemical composition than it does now, and there was never any paragonite--perhaps fluids moved through these rocks at some time after the first growth of garnet, and picked up some elements and dropped off others, resulting in enough of a change in the total rock composition as to fool the program as to what minerals could have been present back then.
Needless to say, I am going to have to check a variety of things to see if either of these are more likely for these rocks, or if there is some other explanation. It seems like every day my "to-do" list for this project just gets longer and longer!
The other useful thing I got from the workshop is how phase diagrams are constructed from chemical reactions. Now, I've seen explanations of this in text books, but somehow, having it done in a lecture, and then having the exercise to work, wherein we calculated each step necessary, starting with balanced chemical equations, made it ever so much more clear. Yes, I've got that nifty program to create them for me, but understanding what steps it is doing behind the scenes is a goodness!
However, despite finding useful stuff in today's class, after discussing it with the instructor, I shall not attend the second and third days (which are far more focused on the ore deposit stuff), but will stay home and work on my own project!