just testing

I think I now have Facebook set up to display my LiveJournal posts as "notes" in Facebook. This is just a test to see if it works, and how it shows up. There will be a real post later. Really.

just testing

I think I now have Facebook set up to display my LiveJournal posts as "notes" in Facebook. This is just a test to see if it works, and how it shows up. There will be a real post later. Really.

this could make a difference

Ever since I first started obtaining estimates of temperature of formation for the first growth of my garnets my advisor has been expressing some minor concern that the numbers sounded a bit low. You see, garnets tend to have obvious growth-zoning profiles if the record of their change in composition is preserved, but tend to approach homogeneous patterns when heated to high enough temperatures to permit "diffusion". The number which tends to get bandied about as hot enough to permit diffusion in garnet is 650 degrees C. My samples, which have cores which are homogeneous and zoned rims, kept giving me estimates in the low 500's C for the garnet cores, and slightly lower temperatures (but higher pressures) for the garnet rims. This had us wondering if A) the estimates are wrong B) if they are correct, the cores did form at the low temperature, then got heated enough to do the diffusion, but for some reason didn't grow any new garnet, and then dropped temperature again before raising pressure and growing the last bit of garnet or C) something we hadn't thought of yet.

Today I re-read the paper that is normally cited as the source for the 650 C and higher = diffusion in garnet. Looking at it closely, it clearly states that diffusion may well happen in garnet at lower temperatures if they remain at those temperatures for sufficiently long enough. This has me wondering if, perhaps, my garnets did start growing down in the low 500 C range, then the rock sat there, cooling, but ever so slowly and slightly, for long enough for diffusion to happen and make them mostly, but not quite, homogeneous, followed by a quick increase in pressure which caused the zoned rims to grow over the older cores. This is certainly an easier to imagine scenario than the one mentioned in the list above. I've sent my advisor an e-mail asking his thoughts on the subject, but it is well after business hours, so he won't see it till tomorrow.

In addition to the above thoughts, I've done a bit more editing on the thesis--I think I may have finally deleted the last of the no-longer needed paragraphs that were written before I got the modelling to work for that last bunch of samples. After the deletions and today's additions, the thesis is now 322 words and one figure longer than it was yesterday, and chapter two is once again over 20,000 words total. I *think* I've got it far enough along to give back to my advisor for comment while I go on to the edits for the other chapters, but since he won't see it till tomorrow anyway, I may as well wait, read it over again in the morning, and see what he says in reply to today's e-mail. There is still ever so much to do, but I think I can see the end from here. Kind of like the way one can almost see the Rockies from the Mississippi.

this could make a difference

Ever since I first started obtaining estimates of temperature of formation for the first growth of my garnets my advisor has been expressing some minor concern that the numbers sounded a bit low. You see, garnets tend to have obvious growth-zoning profiles if the record of their change in composition is preserved, but tend to approach homogeneous patterns when heated to high enough temperatures to permit "diffusion". The number which tends to get bandied about as hot enough to permit diffusion in garnet is 650 degrees C. My samples, which have cores which are homogeneous and zoned rims, kept giving me estimates in the low 500's C for the garnet cores, and slightly lower temperatures (but higher pressures) for the garnet rims. This had us wondering if A) the estimates are wrong B) if they are correct, the cores did form at the low temperature, then got heated enough to do the diffusion, but for some reason didn't grow any new garnet, and then dropped temperature again before raising pressure and growing the last bit of garnet or C) something we hadn't thought of yet.

Today I re-read the paper that is normally cited as the source for the 650 C and higher = diffusion in garnet. Looking at it closely, it clearly states that diffusion may well happen in garnet at lower temperatures if they remain at those temperatures for sufficiently long enough. This has me wondering if, perhaps, my garnets did start growing down in the low 500 C range, then the rock sat there, cooling, but ever so slowly and slightly, for long enough for diffusion to happen and make them mostly, but not quite, homogeneous, followed by a quick increase in pressure which caused the zoned rims to grow over the older cores. This is certainly an easier to imagine scenario than the one mentioned in the list above. I've sent my advisor an e-mail asking his thoughts on the subject, but it is well after business hours, so he won't see it till tomorrow.

In addition to the above thoughts, I've done a bit more editing on the thesis--I think I may have finally deleted the last of the no-longer needed paragraphs that were written before I got the modelling to work for that last bunch of samples. After the deletions and today's additions, the thesis is now 322 words and one figure longer than it was yesterday, and chapter two is once again over 20,000 words total. I *think* I've got it far enough along to give back to my advisor for comment while I go on to the edits for the other chapters, but since he won't see it till tomorrow anyway, I may as well wait, read it over again in the morning, and see what he says in reply to today's e-mail. There is still ever so much to do, but I think I can see the end from here. Kind of like the way one can almost see the Rockies from the Mississippi.