I’m busy traveling at the moment, so Georneys will continue to be quiet for another couple of weeks. However, I thought that I’d quickly share a picture from my recent flight for this week’s “Monday Geology Picture” post. This picture shows the impressive topography of the Samail Ophiolite, which is located in northern Oman and the United Arab Emirates. An ophiolite is a section of oceanic crust and mantle that has been tectonically emplaced onto land.
Have you ever stayed in a hotel room and packed it to the brim with camping gear and scientific equipment and samples? Then chances are you’re a field geologist!
I took the above picture at a hotel in Muscat, Sultanate of Oman after 4 weeks of fieldwork in the Samail Ophiolite back in 2009. Our hotel room was packed full of camping gear, boxes of rocks and water samples, and various scientific instruments, such as pH meters. My favorite piece of scientific equipment was the light tan plastic box in the foreground on the right-hand side of the picture; that light tan box contained a storage container that was filled with liquid nitrogen in order to keep biological samples cold. We nick-named that storage container “R2 D2”, and we gave it a special place in one of the Land Cruisers. We even buckled it in with a seatbelt to keep it from tipping over!
Does anyone else have similar pictures of hotel rooms containing field gear?
For this week’s Monday Geology Picture, I thought I would share a picture of peridotite in thin section viewed under a microscope. This particular peridotite originates from the Samail Ophiolite, Sultanate of Oman, and is a weakly-deformed harzburgite that is ~40% serpentinized. You can see the fine network of serpentine veins throughout the sample. The brightly-colored patches are olivine and pyroxene minerals. I really enjoy looking at rocks in thin section– rocks can be so beautiful in thin section, particularly when viewed under cross-polarized light.
In other news, the defendable draft of my PhD thesis is due on Friday, so blogging (aside from posting cat pictures on Geokittehs) will continue to be light.
A few weeks ago on Twitter, I expressed amazement that I had accumulated 800 followers. Unfortunately, I neglected to save the series of tweets, but I tweeted something along the lines of: “Wow. 800 followers. I can’t believe so many people are interested in ophiolites and trace fossils.” I tweeted this because ophiolites and trace fossils are the topics I have been blogging about the most in recent months.
In response, a number of my twitter followers assured me that they loved ophiolites and trace fossils. Some people also joked, “We just follow you for Geokittehs.” Then fellow geoblogger Tony Martin suggested that I post an ophiolite and trace fossil mash-up post to see how many twitter followers I would gain. I laughed and said I would do so, but a few weeks have slipped by since I’ve been so busy working on my thesis.
At this moment, I have 981 Twitter followers. That means I’ve accumulated almost 200 new followers in a few weeks! Since I haven’t posted all that much on Georneys, I attribute most of that to my Geokittehs posts :-).
I normally don’t worry too much about how many Twitter followers I have or how much traffic this blog receives. I really enjoy writing Georneys, and if other people enjoy reading Georneys then that’s just icing on the cake for me. However, I do find myself amazed that I have accumulated nearly 1,000 Twitter followers and that so many people read– and sometimes enjoy!– my geological musings. That’s really great. I’m happy that I reach so many people and, in some cases, help them understand geology a little bit better. I also really enjoy and appreciate the interactions I have with other geologists through this blog. Perhaps, then, the more Twitter followers I have, the merrier.
So, I think I will take up Tony’s challenge. Below is a mash-up of pictures of ophiolites and trace fossils. I’ve only visited two ophiolites, and many of the trace fossil pictures are actually just traces, but hopefully this ophiolite and trace fossil mash-up is good enough to gain me some more tweeps. If you appreciate this mash-up, please consider following me on Twitter. My user name is @GeoEvelyn. I’ll check back in a week to see how many twitter followers I’ve gained (or lost) as a result of this mash-up. In any case, enjoy!
Ophiolite:
Trace Fossil:
Ophiolite:
Trace Fossil:
Ophiolite:
Trace Fossil:
Ophiolite:
Trace Fossil:
Ophiolite:
Trace Fossil:
Ophiolite:
Trace Fossil:
Ophiolite:
Trace Fossil:
Cat:
I put the cat photo in for good measure. Cat photos are always good for attracting internet followers.
Today I am going to share some pictures of listwanite (also sometimes spelled listvenite, listvanite, or listwaenite), an unusual rock type that I bet even some of the well-educated geologists who read this blog have never seen or even read about. I don’t even think there’s a wikipedia entry about listwanite. Perhaps I’ll write one after my thesis defense next month.
Listwanite forms when ultramafic rocks (most commonly mantle peridotites) are completely carbonated. The pyroxene and olivine minerals found in peridotite commonly alter to form carbonate and serpentine minerals. However, peridotites are usually not completely carbonated. Rather, they typically contain carbonate veins (primarily magnesite; also calcite, dolomite, and other carbonates). Complete carbonation of peridotite means that every single atom of magnesium and calcium as well as some of the iron atoms has combined with CO2 to form secondary carbonate minerals such a magnesite and calcite. The silica atoms in listwanite are found in quartz. Thus, liswanites consist of quartz (a rusty red color) and carbonate and also sometimes talc and Cr-muscovite (a mineral known as mariposite/fuchsite). Geologists are still studying how listwanites form, but they likely form through the interaction of CO2-rich fluids with peridotites at higher than ambient temperatures up to ~200 degrees Celsius. Structural controls (faults and fractures) permit the percolation of the CO2-rich fluids through peridotite, so the formation of listwanites is generally structurally controlled.
Listwanites are important rocks to study for a number of reasons. First of all, listwanites contain large amounts of CO2 which originated from fluids and which is now stored in solid mineral form. Recently, geologists and other scientists have been investigating the potential of storing CO2 in solid minerals (which are more stable than CO2 stored as a liquid or gas) through carbonation of mafic and ultramafic rocks (see, for example, this Nature Geoscience Progress Article by Matter and Kelemen, 2009). Mafic and ultramafic rocks uptake significant CO2 through their natural alteration processes (that’s what I study for my PhD, so expect more on this in the next year or so as I submit my papers for publication). However, the natural carbonation rates of these rocks are too slow to significantly offset anthropogenic CO2 emissions. Therefore, scientists are currently investigating if it is possible to geoengineer CO2 uptake in mafic and ultramafic rocks so that this CO2 uptake happens more quickly. This could be done, perhaps, by fracturing and heating and injection of CO2-rich fluids. This is already being tested in mafic basalts through the CarbFix Project in Iceland.
However, scientists and engineers still have plenty of work to do in order to figure out the right conditions and protocols for CO2 sequestration in mafic and ultramafic rocks. In order to learn about what conditions lead to complete carbonation of ultramafic rocks, scientists such as Peter Kelemen and Gregory Dipple (and their many grad students and collaborators) are working to learn more about listwanites to see if mother nature can provide some clues.
In addition to the recent interest in listwanites for carbon sequestration efforts, listwanites are also important because they are often associated with economic mineral deposits, particularly gold deposits.
So, now that I’ve explained what listwanites are and why they are important, here are some pictures of listwanites which I observed during my trip to Oman back in January. Listwanites are pretty neat rocks, aren’t they?
Over the past couple of weeks, I posted pictures of pillow basalts and sheeted dikes in the Samail Ophiolite, Oman. To round out the crustal ophiolite sequence, I thought I would post a couple of pictures of mantle peridotite in the Samail Ophiolite. As you can see in the below pictures, mantle peridotite in the Samail Ophiolite is generally highly-weathered and a dullish brown color. Harzburgite tends to be a darker red-brown color while dunite is a lighter tan (or “dun”, hence the name) color.
Last week I posted a picture of pillow basalts in the Samail Ophiolite, Oman. I recently visited Oman for a geology conference, and I was fortunate enough to see pillow basalts and many other wonderful geological sights in the Oman mountains and beyond. When I posted the picture of pillow basalts, geoblogger Ron Schott asked if I also had some pictures of sheeted dikes with chill margins. Good news, Ron. I do! Unfortunately, these aren’t the best pictures since they were taken in near-darkness with a flash. However, you can still see some of the dike features, including some classic chill margins.
For those of you who don’t know why ophiolites and sheeted dikes are really, really neat geologic features, I suggest reading an old post of mine titled O is for Ophiolite.
Here are the sheeted dike pictures:
I’m currently in Oman for a geology conference, so today’s geology picture is one I recently took here in the Samail Ophiolite. The picture shows some weathered and fractured pillow basalts with a pencil for scale. These are not the best-looking pillow basalts in the ophiolite. The freshest ones are found in the Geotimes sequence up in the northern part of the ophiolite whereas these weathered ones are the best ones you can observe close to Muscat, the capital city of Oman. I apologize that this picture is a bit dark. Unfortunately, we arrived at the pillow basalt outcrop just as darkness was falling. So, I took this picture using my camera flash. Still… spectacular, isn’t it? Seafloor pillow basalts on land, in the middle of the desert!
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| Posing with a pseudostalagmite, Oman, January 2009. |
def. Speleothem:
An encompassing term used to describe all types of chemical precipitates that form in caves.
If you’ve ever been in a cave, you’ve probably seen speleothems. Speleothems generally precipitate from groundwater which has percolated through the bedrock surrounding the cave and leached various elements and compounds. When the enriched water reaches the cave, changing conditions (a large open space has very different pressure and temperature than pore spaces in bedrock) allow gases, such as carbon dioxide, to escape from the water. Evaporation can also occur. The changing composition of the water encourages the (usually very, very slow) precipitation of speleothem minerals from cave waters.
Chemically, the speleothems which form in a particular cave are similar in composition. Most caves are formed in limestone, and so the speleothems will generally be formed of calcite, the dominant mineral in limestone. However, depending on how and where the speleothem is precipitated, it can take on a variety of shapes. Scientists and other cave explorers have given different names to these various morphologies. Examples of speleothems are stalactites, stalagmites, flowstones, cave coral, cave drapery, cave curtains, and cave crystals. There are dozens of names for various cave mineral formations, so speleothem is a nice catch-all phrase for geologists to use.
Here is a great picture (from Wikipedia) of some of the most common types of speleothems:
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| Photo by Dave Bunnell of some common speleothems. Taken from Wikipedia here. Click photo to enlarge. |
Most speleothems form over thousands upon thousands of years. Thus, you shouldn’t touch or remove speleothems unless you’re doing so for legitimate science. Even when collecting speleothems for science, one should be conservative. Geologists should take small samples and obtain the necessary permissions. Fortunately, for my own research in Oman I am often able to collect speleothems which have fallen on the ground and are no longer growing.
At the top of this post is a picture of me with a stalagmite in Oman. I didn’t sample this one, but I did sample some of its neighbors. This particular stalagmite isn’t forming in a true cave but rather in an open hallow underneath a layer of rock. Water percolated through the layer of rock and formed speleothems in the hallow underneath. The speleothems I study in Oman are thus really pseudospeleothems– they are not in true caves but rather in little overhangs and hallows.
Now, for those of you who still confuse stalactite and stalagmite, here’s a reminder of something you probably learned in grammar school but may have forgotten by now:
StalaCtites hang tight (or tite) to the Ceiling while stalaGmites grow up from the Ground.
Finally, below are few more pictures of some Omani pseudospeleothems. These pseduospeleothems are forming in overhangs in travertines (carbonate precipitates) which are forming at the surface of the peridotite layer of the ophiolite. Be sure to click on the two panoramas to enlarge them. Note the location of the pseudospeleothem column in the two panoramas. Many pseudospeleothems are located in the overhang around this column. The last picture has my colleague Lisa standing next to this column for scale; this shows the enormous size of the travertine deposit.
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| Travertine pseudospeleothems, Oman, January 2009. |
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| Water dripping from a pseduospeleothem straw, Oman, January 2009. |
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| Panorama of Wadi Sudari Travertine I, Oman, January 2010. |
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| Panorama of Wadi Sudari Travertine II, Oman, January 2010. |
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| Lisa standing next to an enormous column of travertine, Oman, January 2009. |
I am participating in my first Accretionary Wedge- yay! For those of you who don’t know, the Accretionary Wedge is a monthly “geology blog carnival” where geobloggers of all kinds are invited to blog on a theme.
I contemplated participating in the past two Accretionary Wedges, but I’m very busy with my thesis this winter. Therefore, I didn’t quite have enough time and energy to bake something for Accretionary Wedge #30 or to write about something I was surprised to learn for Accretionary Wedge #31. This month’s Accretionary Wedge is easy, though! For Accretionary Wedge #32, I just have to post my favorite geology picture.
One of my favorite geology pictures (I have several- so difficult to chose!) is a picture of my favorite campsite ever. The picture below shows a makeshift campsite just off a road in northern Oman. The beautiful mountain in the background is Jebel Misht, one of several exotic limestones in the middle of the Samail Ophiolite. I was lucky enough to spend a few nights at this campsite in 2009 and 2010 as part of my PhD thesis fieldwork. One of my field sites, located near the small village of Al-Bana and close to the Misht campsite, has been named “Jebel Misht Travertine” by my research group.
Jebel Misht is a popular climbing destination. Making your way up the tall southeast cliff is not an easy task. When a French team of climbers accomplished the first successful ascent of Jebel Misht in 1979, the Sultan of Oman arranged to have the climbers picked up by helicopter from the top of the mountain and whisked off to the palace for a celebration. Jebel Misht means “Comb Mountain” in Arabic. Indeed, the mountain’s majestic cliff resembles a gigantic comb resting peacefully amidst the seafloor rocks of the ophiolite.
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| Jebel Misht campsite, Oman, January 2009. |
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