GeoSphere

GeoSphere

Cruisin’ for Deep Sea Vents

My friend John Jamieson, who is now a prof in the geology department at Memorial University in Newfoundland and Canada Research Chair in marine geology and is also a former GeoSphere guest poster is currently on a research cruise near Fiji. John researches deep sea vents, aka. black smokers/seafloor massive sulphide deposits that are exhaling super heated water at tectonic plate boundaries around the world. These vents are modern analogues of the conditions in which volcanogenic massive sulphide deposits form, which are major sources of iron, copper, lead and zinc around the world.

Watch the really cool video below to learn all about the cruise and why we care about black smokers and mapping the ocean floor.

While you’re at it, check out some of the other awesome videos from the Schmidt Institute for Ocean Science!

 

Blast from the Past: It’s all about scales

It has often been said that geology is the study of scales. Time scales, large scales, small scales and many others. Indeed, one of the most crucial parts of any photo or map is the scale. Furthermore, geologic concepts can be applied from the planet scale to the atomic scale and every size in between. What confuses most people though is not only do we work in terms of huge size/magnitude variations but we also work with huge temporal variations. Processes that can take billions of years to nanoseconds all have their place in geology. Perhaps this is part of what makes it such a fascinating science?

Anyway, I thought it might be fun to share a few variations in scale that I have noticed recently.

A large hoodoo in Dinosaur Provincial Park, Alberta. I would say it is around 5m high and the rock on top is at least 5m across if not larger. (Photo: Matt Herod)

Some smaller hoodoos also located in Dinosaur Provincial Park, Alberta. I woudl say these ones are about 50cm high. By the way, the round object between the two hoodoos at the back is a dinosaur vertabrae. Likely a Hadrosaur. (Photo: Matt Herod)

Some really small hoodoos. I found these on a recent recon trip to a sand pit north of Ottawa near Cantley, Quebec. (Photo: Matt Herod)

Pretty cool eh?! People generally think of hoodoos as big spectacular structures that look like they are performing an incredible act of balance. Hoodoos form through erosive processes on the soft sediment underlying a large rock. They can be formed by wind, rain, or freeze-thaw cycles that erode the soft sediment below the boulder. However, eventually the sediment directly beneath the rock/pebble is protected from above preserving the hoodoo.

Here is another example of how scale has nothing to do with process. What I mean by this is that the same process that forms large features is also capable of forming small ones, like the hoodoos above.

A medium size rat-tail at Cantley Quarry, Quebec. It is probably around 8m long and the rock in the front is about 1m. That is my co-TA, Brett, for scale. (Photo: Matt Herod)

This monster rat-tail is over 50m long! You can see the xenolith in the front where the rusty discolouration is. There is also a smaller rat-tail in the foreground. (Photo: Matt Herod)

A “micro” rat-tail. This tiny one is only a few cm’s long but it still has the same basic structure: comet shaped with an obstacle in the front. Although, in this case the obstacle is a mineral grain and not a gneiss boulder.

Okay, so hoodoos are not the only erosional feature than can be formed at a variety of scales. However, I think these rat-tails are even more impressive than the hoodoos. Rat tails are glacial erosion features that form underneath a glacier by vast, fast flowing rivers of glacial meltwater actually eroding the rocks and forming these streamlined features. The dominant bedrock in the area is a soft marble that contains xenoliths of hard Grenville gneiss. The gneiss acts as a barrier to the meltwater forcing it to flow around it. This protects the marble directly behind the xenolith and forms the rat-tail.

Scales don’t just vary in erosion features though. There are lots of other great examples of scale variation throughout geology.

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Massive selenite crystals in the famous “cave of crystals” in Naica, Chihuahua, Mexico with a person for scale. (Image: Wikipedia)

Gypsum (Var.: Gypsum) Locality: Red River Floodway, Winnipeg, Manitoba, Canada (Source)

The gypsum crystals of the crystal cave were formed by heated groundwater that was evidently extremely saturated with respect to gypsum. I haven’t done the calculations about how insanely over saturated this water must have been to precipitate crystals this large, but maybe if I’m bored one day I’ll try it out. The chemical formula of gypsum is CaSO4 – 2 H2O. The water filled the cave and the crystals were able to precipitate around 500,000 years ago. The dating method used was U-Th disequilibrium dating.

I have a funny anecdote about the picture of the cave above. I remember when news of the cave hit the media. I was taking advanced mineralogy at the time and someone brought that picture in to show our prof and get his reaction. His first reaction, before doing any research, was that the picture was photoshopped and the cave did not exist. It just goes to show that a) this cave is incredible and b) it is possible to fool mineralogists sometimes.

Small fold in meta-sedimentary rock of the Pinnacle Formation in Sutton, Quebec. (Photo: Matt Herod)

Photo of yours truly demonstrating the curvature of this fold which is also in the Pinnacle Fm. in Sutton, Quebec (Photo: not Matt Herod, but with my camera)

Google Maps image of the Rideau Lakes area north of Kingston, Ontario. Notice the kilometre scale folding in the area and how the lakes conform to the structural geology of the area.

As you can see the study of geology is really all about scale. Every major geologic discovery is required to have context in terms of either the geologic time scale or size. I have given some examples of how size can vary regardless of process. If you have any examples  of scales in geology I would love to hear about it. Please post in the comments below. If your example is in picture form I would be happy to add them to this post.

Thanks for reading! FYI, this post was originally published back in 2012.

Matt

Geology Photo of the Week #52 – Looking from the past to the future

This weeks photo is a beautiful yet sad reminder that Arctic research and work is still a dangerous undertaking just as it was for the early Arctic explorers.

The following text is by Vladislav Petrusvich: Canadian research icebreaker CCGS Amundsen by Beechey Island in 2013 after tragic event when a researcher (Klaus Hocheim), captain and a helicopter pilot were killed in a tragic helicopter crash during scientific cruise. Beechey Island is related to ill-fated Franklin expedition that overwintered at the island. The shot is made through the remaining wall of a supply depot used by the search parties looking for disappeared Franklin expedition in 19th century.

Beechey Island is located in the Northwest Passage and was named after the artist on board Capt. William Perry’s Arctic exploration in 1819. Beechey Island was next visited by the Franklin expedition in 1845 as Sir John Franklin’s first winter encampment aboard the HMS Erebus (discovered in 2014) and Terror (not yet found). Recent archaeological investigations by Parks Canada have found three mummufied bodies that had died of lung disease and lead poisoning, which appeared to be from the lead solder used in the canning of food although it now appears that the lead may be from the water distillation system on the ships.

Photo of the Week #51

I’m getting back in the bog saddle. After a brief hiatus as I was adjusting to the life of a real, productive member of the PGS (post grad school) world I am good to go for blogging again. Enjoy the photo of the week!

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Sphalerite’s “Transformer” by Dmitry Tonkacheev, IGEM RAS, Moscow, Russian Federation

The text that follows is a technical description of the photo by the photographer, Dmitry Tonkacheev.

Presented intergrowths of the infinite number of dark-brown sphalerite’s and arborescent crystals of gold were synthesized using gas transport method at 850 centigrade degree during 20 days by Dmitry Chareev from the Institute of Experimental Mineralogy RAS in Chernogolovka city, Moscow Region while we were working on the project of Russian Scientific Fund in the Institute of Ore Geology, Petrology Mineralogy and Geochemistry RAS.
The main aim of this project was the determination of the maximum possible concentration and chemical state of some trace elements in the most abundant sulfides, synthesized using different techniques, including in ZnS. We obtained crystals of Fe-bearing sphalerite with simultaneous incorporation of Cd, Mn, In, Se and Au. The concentration of gold reaches 3,000 ppm (0.3 wt.%). This is amazing for natural sphalerite. The next goal was in-depth-study of the influence of the presence of Se, In, Fe, Mn on Au concentration and also lattice parameter in ZnS. In this connection in the furnace-charge of Fe-bearing sphalerite, different admixtures were added in different combinations or severally.

According to LA-ICP-MS data Fe did not encourage Au annexation (73±1 ppm). The bulk of Au wire “boards” on the dark-brown phase surface in the form of fascination crystals (usually arborescent). Some of them looks like a weapon from the “Transformers” arsenal or parts of his armor. Also bright diamond luster of this creature makes our “Knight” even more ultra-modern.

Militiamen’s profile was confirmed by twisted skeletal crystal on the transformer’s head. It looks like ostrich plumage or horn, which were the main attribute in the plate armor of ancient warriors and indicated about their noble birth. Truly, it is a king of all sulfides. The good news for us is the fact, that the coarsening of this bellicose subject is approximately 1-2 mm.

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