Most people don't know what I'm doing, mostly because when people ask me, I give the shortest answer possible to avoid boring them. Not that I think it's boring, no way. It's just that if you're not into geology and all the lingo, things can get pretty confusing and convoluted pretty fast, which leads to boredom. Anyway, I figure if I type it, you can skip over it without worrying about being polite and trying/pretending to listen/understand.
For starters:
This is zebra dolomite. It's pretty obvious where the name came from. However, despite their optical differences, the black and white layers are indeed the same mineral, dolomite (CaMg(CO3)2).
This is a close-up image of the black dolomite. It was taken with an SEM (scanning electron microscope) and the entire image is maybe one millimeter across. There's lots of stuff in the black dolomite that's not dolomite. All those white spots are different minerals, like quartz, feldspar, rutile, anhydrite, apatite, and a bunch of others. Those minerals are detrital, which means that as the black dolomite was forming by precipitating from seawater, a bunch of other little particles were carried by rivers and streams into the ocean and they fell out into the newly precipitated black dolomite.
This is a photomicrograph (that's some of our fancy lingo) of the white dolomite. Most of the white spots on here are dust or scratches, not so much other minerals. So, the white dolomite has virtually no detritus in it. Here's why I think that is: The black dolomite is primary and the white dolomite secondary. So we had a block of solid black (it's actually dark grey) dolomite that was then altered by some sort of fluid. As a part of my thesis, I'm trying to determine the hydrothermal fluid that altered and recrystallized the black dolomite into the white.
These are tiny little nanocrystals of apatite. They fill fractures throughout the black dolomite and are also found along the border between the white and black dolomite. There are two hypotheses I'm examining so far as where the apatite came from in the dolomite. The first is that it's detrital, the second is that it precipitated in cracks when there was just the black dolomite, and the third (whoops, guess there are three) is that they crystallized from the same fluid that altered the dark dolomite to the white. I hope it's three, personally, because if that's the case, then I could get an age at which the black dolomite was altered.
This is just a little tiny inclusion in the black. It's rutile (TiO2), a mineral that is commonly used as a pigment in paints and makeup. The flaky stuff to either side is some kind of clay.I haven't explained too much about my thesis yet, I guess. Just showing off some cool pictures. So what I'm doing boils down to a couple main objectives. 1) I want to compile a detailed microscopic study of the dolomite and its inclusions using x-ray crystallography, scanning electron microscopy, and transmission electron microscopy (the TEM is a cool cool microscope- its resolution is so high that you can see planes of atoms). 2) Look at the difference between the zebra dolomite in my localities compared to other locations throughout the Basin and Range and the world. That's something that I forgot to mention. There are lots of zebra dolomites, all over the world and others in Utah, however, other zebra dolomites are associated with precious or heavy metal ore deposits (Pb, Zn, Au, Ag) or oil and the ones I'm studying are not. So hopefully, someday, I will know why. 3) Interpret the data in terms of an origin of the fluid that altered the black dolomite. So far, with other zebra dolomites, this hasn't really been done. It's generally agreed that their origin is hydrothermal, however, there is a lot of disagreement as to what the source fluid could be. Figuring out an origin, or at least constraining one, will be hard, especially if isotopic data is ambiguous.
That took a long time. And it's just a very rough idea what I'm doing. The details get even more boring. To other people, not me. I love this stuff.
PS- Mike and I are moving!! To a house!!




