Tuesday, February 27, 2018

The (XRD) Results Are In!


Huzzah! The XRD results are in!

If it weren't for my e-mail exchange with Mark at the beginning of the month, some of the mineral assemblages would have certainly confused me.

Recall: I divided my samples into four categories
  • Solid - in tact, relatively hard crystalline diapir material
  • Intermediate - softer diapir material, can be crumbly
  • Crusty - very friable, vuggy material found on diapir surfaces, often adjacent to intermediate rock
  • Surficial - salts precipitating on soils and rocks downstream of salt diapirs
My hypothesis was that the "solid" diapir samples would be composed of anhydrite, the "crusty" samples would be gypsum (anhydrite that has been aqueously altered), that the "intermediate" would be... maybe both? Given the strong gypsum/anhydrite signatures of secondary salts in the ASTER TIR data, I hypothesized that the surficial salt would be gypsum with halite (after identifying some secondary halite in the field).

Let's start simple.

Here are what some of the XRD analyses show:
  • Solid samples - Anhydrite + Gypsum (more anhydrite than gypsum)
  • Intermediate - Gypsum
  • Crusty - Gypsum, sometimes with traces of quartz or calcite
At first glance, these results are fairly close to the hypothesis, although I had thought the solid samples would be anhydrite only.

A few of the solid samples, though, were not anhydrite. One was calcite (i.e. limestone) with secondary gypsum, and another was dolomite with secondary gypsum, trace quartz and other minerals. This is not alarming. The literature describes the diapirs containing "subordinate limestone, [and] rare dolostone," (Harrison and Jackson 2014). In hindsight, these two rock samples look more like a carbonate than anhydrite or gypsum, but no better "solid" rock exposures were present at these outcrops (Whitsunday Bay Diapir, Strand Diapir).

What surprised me more, though, are the compositions of the surficial salts. 

These samples proved very diverse. Often, they include traces of non-salt minerals (i.e. quartz, clays) but these are extremely likely to be contamination from the soil. It was difficult to scoop up bits of precipitated salt without getting a little dirt or sand mixed in too. So it is not surprising to see common sediments. However, the compositions of the salts were very varied, with:
  • Pure halite
  • Gypsum with mirabilite and dolomite
  • Gypsum with thenardite
To be honest, if it weren't for the e-mail exchanges with Mark, I would not have even thought of checking for thenardite or mirabilite. These minerals are Na2SO4 and Na2SO4·10H2O respectively. Nesse (2012) explains that thenardite can be found in saline lake evaporite deposits, and can be found as an efflorescence on soil. I had to look up what efflorescence means, but it effectively describes the means by which our secondary surficial salts are precipitating on soils and rocks on Axel Heiberg Island. It makes sense that mirability, the hydrated form of thenardite, would be found in the similar settings. Now, unlike halite, thenardite does not have an isometric crystal structure - it is orthorhombic. The implications of this are that thenardite would have spectral absorption bands. I think I should look them up, and see if they are similar to gypsum or not - will thenardite salts be disguised as gypsum in our spectral images? Or can we use different spectral bands to isolate thenardite secondary salts from gypsum secondary salts? Future work will tell, but for now I'm just going to work on finishing my thesis.

P.S. One final highlight -



I have been told that this is exceedingly uncommon. Nesse (2012) says that some samples of halite may be fluorescent (anyone have a UV light?) but that does not necessarily explain how the white powder would turn into a dark grey powder permanently after being run through the XRD machine. Maybe the halite contains radiation-sensitive impurities? Maybe I shouldn't have been licking it in the field?  Who knows. I'm definitely curious, and the XRD technician is also interested in investigating this phenomenon. 



Harrison, J.C., and Jackson, M.P.A. 2014. Exposed evaporite diapirs and minibasins above a canopy                  in central Sverdrup Basin, Axel Heiberg Island, Arctic Canada. Basin Research, 26: 567–                    596. doi:10.1111/bre.12037.

Nesse, W.D. 2012. Introduction to Mineralogy: Second Edition. Oxford University Press, New York.

Tuesday, February 6, 2018

Some salty waters: Thenardite, halite, and gypsum


In my drafts and writing revisions, I noticed that I had a few missing pieces of information.

To clarify a few questions I had regarding the chemistry of perennial springs on Axel Heiberg Island, I reached out to Mark Fox-Powell, who joined us in the field last year. Mark is a post-doctoral research fellow at the University of St. Andrews, with a background in microbiology. His current research is in astrobiology, with emphasis on geochemistry of natural waters.

On our trip, Mark sampled the water and precipitates in and around perennial springs. He is using these samples to analyse their water chemistry, and to produce visible and shortwave infrared spectra of the precipitates. Existing spectral databases of hydrated sulphate and chloride salts are derived from pure minerals produced in controlled laboratory conditions. By using the salts from perennial springs, his team will be able to measure the spectral signatures of impure, naturally occurring salts.

The ultimate goal is to use terrestrial salts as an analogue for "non-icy" materials on Jupiter's moon, Europa. Europa is an ocean world. Its surface is a shell of ice of unknown thickness, over an ocean thought to have the potential to support life. For this reason, Europa is the target of the next NASA flagship mission Europa Clipper which will launch in the early to mid 2020s, and will carry instruments to image its surface at higher resolution. While still unknown, the non-icy materials identified on Europa are hypothesized to be salt precipitates - by understanding the spectral properties of naturally occurring terrestrial salts under Arctic and European conditions, we may be able to better constrain which salts are occurring on Europa. By gaining insight into what chemical materials are present in Europa's waters, astrobiologists will have a better understanding of what kind of life could potentially inhabit these oceans.

So, what did Mark and the team at St. Andrew's find?

We visited three perennial springs during our 2017 Axel Heiberg Island field season. These were Lost Hammer Spring (north of Wolf Diapir), Stolz Springs (emerging from Stolz Diapir), and Colour Peak Springs (southern base of Colour Peak).

Aerial view of Lost Hammer Spring, north and downstream of Wolf Diapir. 

The main vent of Lost Hammer Spring is a >1 m high accumulation of mirabilite and thernardite. Halite precipitates in the surrounding white areas. There is evidence of seasonal layering within the vent.
Lost Hammer Spring has been previously studied by Western alumni Melissa Battler (2013). The water chemistry analysis falls in line with these data, with the spring water being dominated by sodium and chloride. Interestingly, it has the highest sulphate concentration of the springs we visited. Some of these sulphates are precipitating as mirabilite (Na2SO. 4· 10H2O) or thernardite (Na2SO4)  rather than gypsum (CaSO. 4· 2H2O) or anhydrite (CaSO. 4), though. I'm planning on looking into sodium sulphates to see if they have similar or different spectral signatures than their calcium sulphate counterparts.

Segment of the very extensive perennial springs emerging from Stolz Diapir. According to Mark's analysis, the white minerals are dominated by halite and hydrohalite, whereas the darker, greyish minerals are predominantly mirabilite and thernardite
Stolz Springs has the highest concentration of chloride in its waters. This makes sense, given that Stolz Diapir has an outcrop exposure of halite at surface. Different parts of the spring deposits are dominated by halite, and others mirability/thernardite.

Perennial spring at the base of Colour Peak. The dark terraces are calcite+gypsum spring precipitates. The white minerals are halite forming at the edges of the springs.

Colour Peak has multiple spring outlets, which have appear to have lower chloride concentrations than the other sites. The dark terraces are only present at Colour Springs, and are made up of a combination of calcite and gypsum. There are also halite crystals precipitating on the soils adjacent to the terraces. If the terraces contain gypsum, then they certainly are contributing to the strong gypsum signature in our ASTER TIR images downslope of Colour Peak. The streams are very smooth compared to Colour Peak itself, which fits our hypothesis and radar observations!

One of the main takeaways here is that there are certainly more sodium-sulphates around Lost Hammer and Stolz springs than I thought.

Digging through some literature, Howari (2004) writes that thenardite has absorption features at 1.5, 2.0, and 2.3 µm due to the inclusion of water molecules. The latter two are very similar to the absorption features in gypsum at 1.9 and 2.2 µm. Similarly, although crystalline halite does not produce any notable spectral signatures, when aqueous it can also absorb at 2.0 µm from trapped water. Similarly, Howari et al. (2002) write that the SWIR signatures of thenardite can obscure that of gypsum when both are present in soils. This implies that thenardite, halite, and gypsum might look similar in our visible-near infrared and short-wave infrared and composite images. 

Stuff to consider.

I'm going to get back to writing.

Battler, M.M., Osinski, G.R., and Banerjee, N.R. 2013. Mineralogy of saline perennial cold springs on Axel Heiberg Island, Nunavut, Canada and implications for spring deposits on Mars. Icarus, 224: 364–381. doi:10.1016/j.icarus.2012.08.031.

Fox-Powell, M.G., Osinski, G.R., Gunn, M., Applin, D., Cloutis, E., and Cousins, C.R. 2018. Low-Temperature Hydrated Salts on Axel Heiberg Island, Arctic Canada, as an Analogue for Europa. In 49th Lunar and Planetary Science Conference. Lunar and Planetary Institute, Houston. p. Abstract #2564. Available from http://www.lpi.usra.edu/meetings/lpsc2018/pdf/2564.pdf.

Howari, F.M., Goodell, P.C., and Miyamoto, S. 2002. Spectral properties of salt crusts formed on saline soils. Journal of Environmental Quality, 31: 1453–1461. American Society of Agronomy, Crop Science Society of America, Soil Science Society.

Howari, F.M. 2004. Chemical and Environmental Implications of Visible and Near-Infrared Spectral Features of Salt Crusts Formed from Different Brines. Annali di chimica, 94: 315–323. Wiley Online Library.

Tuesday, January 23, 2018

New Year - The Final Countdown

This semester is the final push to graduate on time.

No pressure.

I need to have my thesis ready to submit to my committee by March 12th.

So far I have drafts up to my results section. I'll be submitted monograph style as opposed to manuscript style. I hope I'll be able to put together a manuscript together afterwards.

I've crushed an adequate selection of samples and submitted them for XRD analysis. I tried to represent a range of diapirs, and rock textures at the different sites.  These include crystalline diapir material which is soft but has high toughness (scratches easily, but does not break easily), a friable "crust" which is very vuggy, and an intermediate rock which has varying degrees of friability, but is not vuggy, and surficial salts that crystallized on the surface of non-diagenetically related rocks and soils. The crust rock is frequently found in association with the intermediate rocks, suggesting that these samples represent different degrees of weathering.

Crystalline Rock

Crusty Rock, containing vugs and botryoidal crystal growths
Surficial Salts - Rock was found at the edge of a stream bed
with white salt minerals encrusting it.

"Intermediate" Rock - Friable, but lacking the vugs and
microcrystalline structure of the crust

In choosing samples in the field, and in the lab, I ran into a few difficulties.

One, is that not every sample type (i.e. crystalline, crust, intermediate, surficial) were present at each site.  This would be scientifically interesting.  However, it is possible that each type were present at each site, but I either:

1. Didn't sample them
2. Didn't see them
3. Didn't adequately define the types

I am mostly able to rule out #1, because I established early-on what I wanted to sample to gain a representative rock selection. However, at a few sites (like Whitsunday Bay Diapir, at which the helicopter landed in two places and we jumped out to go grab some rocks while it was still running) it is entirely possible I just didn't have enough time to search thoroughly. The absence of evidence isn't evidence of absence. Third, by its own definition, the intermediate rock has variable degrees of friability, and is often found in close associate with both crystalline and the crust rock. I separated it out to see if we can learn anything about the nature of weathering. As such, there is wiggle-room in determining which category some of the samples best fit.

Another problem is that it was terribly challenging to sample the surficial sediments. The best sample I was able to prepare for XRD required me to scrape off a sufficient amount of salt minerals off of a few pebbles I collected from a stream. The worst samples were where I found the salt precipitating on sand, and scooped up the salt and sand together. As a result, I only submitted a couple for XRD that I thought might provide reliable results, so data in this type may be lacking.

I should get some of the results back this week. It will be cool to see how the diapirs are weathering between anhydrite and gypsum, and how that is affecting their surface textures. 

Monday, November 6, 2017

New RADARSAT-2 images! Looking good!

Good news,

Earlier this year, Catherine and I submitted a SOAR-E proposal to acquire new RADARSAT-2 images of salt diapirs. Our original intent was to get images of halite salt diapirs in Iran to compare with our anhydrite diapirs on Axel Heiberg Island. However, we weren't able to get an images over that target site, and we needed to rethink our plan of attack. Instead, we submitted a request for four additional images over Axel Heiberg Island. One of these was over Stolz diapir, where we found halite in the field.  Of our four requests, only two were granted due to RADARSAT-2 targeting conflicts. Fortunately, Stolz diapir was one of them! The other image we received is a bit north of Expedition diapir, which will provide insight into some of the discrepancies between the ASTER TIR predictions and the Harrison and Jackson field mapping.

Like with previous images, I extracted the circularly polarized data in PolSARPro, and produced terrain corrected circular polarization ratio images in SNAP.  I'm pleased to say that they look great!

Here they are:

Images acquired Sept. 26, 2017 over Stolz and Whitsunday Bay diapirs.
Above, annotated HH-Intensity image. Below, CPR image. 
This site was our first priority for the SOAR-E proposal, so I'm pleased it was one of the 2/4 we received. We visited Stolz and Whitsunday Bay diapirs during the 2017 field season, and samples were collected at each. Stolz diapir is where we collected samples from a halite outcrop, and has the extensive perennial springs deposits at its base. The CPR-bright spot between Stolz and Whitsunday Bay diapir to the slight west corresponds with a salt diapir we passed in the helicopter traverse between sites - I'm not sure if it has a name.

Images acquired Sept 30th, 2017. Above, annotated HH-Intensity image showing where Harrison and Jackson (2014) 
mapped salt diapirs, in contrast to where we observed salt signatures in the ASTER TIR images. 

This site was targeted in attempts to discern the discrepancy between mapping methods. This area is subject to significant glacial coverage over the northern half, and it is likely that glacial coverage obscured the TIR signature over Expedition and Thompson diapirs. We also now have repeat coverage over Colour Diapir, which is one of the sites visited during the 2017 field season. I'm not convinced it extends as far to the west as Harrison and Jackson show. I'll need to recheck our field images.

Now here is what they look like with the 2016 images:

The Arctic DEM supports the hypothesis that the northern half of the Sept 30th image is obscured by glacial coverage

Notably, look at Whitsunday Bay diapir - it is REALLY bright in the radar image. It jumps out way more than the other diapirs. I thought for a moment that could be from early snowfall, but note that there doesn't appear to be much snow over the glacier to the west. I'll consult Landsat images shortly.

The new data is quite promising, too! Previously, the average CPR value (per pixel) over salt diapirs and secondary salts were 0.40 and 0.26 respectively. Now, once we include the new data, the average values are 0.52 for the diapirs and 0.23 for secondary salts. I'm really pleased that the new data has increased the spread between the diapirs and secondary salt deposits.

Now, on to writing, writing writing! And some XRD. But mostly writing.

RADARSAT-2 Data and Products (c) MacDonald, Dettwiler and Associates, Ltd. (year of acquisition) - All Rights Reserved. RADARSAT is an official trademark of the Canadian Space Agency.

Harrison, J.C., Jackson, M.P.A., 2014. Tectonostratigraphy and allochthonous salt tectonics of Axel Heiberg Island , central Sverdrup Basin , Arctic Canada. doi:10.4095/293840

Tuesday, October 24, 2017

International Astronautical Congress


I've returned after spending some time Down Under!

This dish is 70 m across, and received the
final data from Cassini
I am very fortunate to have received a grant to attend the Space Generation Congress (SGC) and 2017 International Astronautical Congress (IAC) in Adelaide, Australia. The grant was a Student Participation Initiative from the Canadian Space Agency. I love them so much.

Before arriving in Adelaide, I took a little detour into Canberra. SGC had organized an optional tour of the Canberra Deep Space Communication Complex. I knew very little about the Deep Space Network (DSN) prior to the tour, and didn't even know this site existed beforehand. The extent of my past knowledge sometimes Cassini data were lost if it was "raining in Madrid".  Now I know that the NASA operates the DSN out of three facilities: Canberra, Madrid, and Goldstone (California).

I was amazed to see the satellite dish that downlinked the final data from Cassini only days after the her final maneuver. There were also dishes that were actively downlinking from MRO and MSL while we were visiting – I thought that was really cool and inspiring. My first project in planetary geology used Magellan images of Venus, and I learned that 98% of Magellan data were downlinked in Canberra. I would like to be involved with planetary mission work in the future, so understanding the data downlink process is useful to understanding the data limitations faced by scientists in this field.

The Deep Space Communications Complex is located between
granitic foothills southwest of Canberra
       The SGC was an new experience for me. Instead of being a standard conference, we chose focus groups to address pressing issues in space exploration. Having a geology background, I picked the "Space Diplomacy" group, as the emphasis was on space resource mining. It was the first time I’ve been at an conference in which I've been the only geoscientist present. This was cool, because I was able to provide real-world examples of terrestrial resource extracting to the discussion. It was great for me to meet people from business, engineering and law who are all interested in space-related topics. These are aspects of the space industry that I have had little to no contact with in my studies, but I think might be important to know about for future career plans. SGC also hosted a cultural night, which was also a great opportunity to meet other delegates and learn about their countries’ backgrounds and interests in space exploration. Naturally, I was thrilled that the South Korean delegates performed "Gangnam Style". We, as Canadians, brought maple cookies, maple candies, and coffee crisps to share.
Matt, one of my group mates, sketches a flowchart showing
the influences of international policy on industrial liability
and accountability.

The SGC international night was at the Adelaide
Zoo. This woman is holding a bilby.
I do love any reason to dress up nice.

Moving on to IAC. I absolutely loved the international networking opportunities and having a chance to see what space agencies around the world are working on. The heads of agencies plenary session was particularly great for this because they provided an overview of the priorities and future goals of each country. ESA gave a plenary session about setting up Moon/Mars Villages, and the vast range of challenges associated with manned planetary exploration. I found this session interesting because many of the infrastructural problems associated with constructing Moon/Mars Villages and in accessing Space Resources are relevant to planetary geology.
In the exhibit hall I learned a lot about the activities of the Japanese Aerospace Exploration Agency (JAXA), Korean Aerospace Research Institute (KARI), and ESA through the various displays and presentations. For example, the JAXA booth hosted presentations on the status of Hayabusa-2, its target, asteroid 162173 Ryugu, and what they learned from Hayabusa-1. Mentioned in a previous post, I worked at the Pheasant Memorial Laboratory in 2015 which was privileged to obtain some of the samples from the first Hayabusa mission, so I was curious about the fate of samples from the next mission. The KARI booth hosted a cultural event where they provided beverages and Korean snacks while talking about their recent innovations in satellite technology. I was delighted that they played K-Pop music videos while esteemed members of the aerospace industry discussed the engineering specifications of the satellites.

I think the girl group on the screen is "Twice" but I decided it wouldn't be a
good use of my time at work to scour their music videos to confirm that.
KARI's booth was beautifully decorated, and displayed some cutting edge tech.
Curiosity's twin hanging out in the
exhibition hall
The CSA sponsored students were invited to take part in events hosted by the International Student Education Board (ISEB). At these activities, we met sponsored students from around the world. I made a bunch of friends among the KARI and JAXA sponsored students, whom I hope to stay in contact with. One of the ISEB networking events took place in the South Australian Museum, coincidentally in the fossil/mineral/meteorite area.  This was fantastic because I was able to apply my geo-knowledge and excitedly chat about minerals to anyone who was interested. 

I admit that there weren’t very many technical sessions relevant to planetary geology.  I attended a few sessions on planetary surface exploration and on remote sensing technologies, but many of the presentations provided information outside of my area of expertise. Most of the technical sessions I attended were aimed at an engineering audience, and even though I want to learn more about the cutting edges of space technologies, this wasn’t the best platform for me to do so.

That being said, I really appreciated the multidisciplinary nature of the conferences. At IAC, I was able to see the diversity of disciplines that contribute to space exploration, from rocket and satellite engineering, space life sciences, government policy, astronomy and astrophysics, Earth observation, communications, business, and public education. I had little experience in many of these fields prior to the congress. I feel that I now have a broader understanding of space-related fields and how they connect with one another, and this will definitely improve my perspective throughout my career. 

At the "Women in Aeronautics" breakfast, the Director General of ESA,
Jan Wörner, spoke about the importance having all types of diversity in a
work place

Thesis update: I'm drying out my samples from our Axel Heiberg Island field trip. Some of the salts and soils are still a bit wet, and need to be a dry powder for doing XRD analysis.

Wednesday, September 6, 2017

Comparisons between features in Yellowstone and on Axel Heiberg Island

Hi hi!
Eclipse, 10:22 MST, I took this
through a telescope

I’m writing to you after a phenomenal family vacation I took with my parents, aunt and uncle down to Idaho and Wyoming. The main destination – the totality zone for the eclipse! The eclipse was indeed a very breathtaking, magical experience, but today I will be writing about some of the geology we saw. While passing through Idaho, we stopped at Craters of the Moon National Monument. We briefly visited with Gavin, Kevin, Raymond, and Mike who were a bit knackered after a day of strenuous fieldwork. I won’t write much more about those lava flows, because Gavin has written about them in stylish detail.After Craters of the Moon, we drove into Wyoming and visited what must be a geological, volcanic mecca – Yellowstone National Park. Now, I could write for pages about the geology of Yellowstone, because it is such an exciting, unique place full of epithermal wonders. For this post, I’m going to focus on two features that seemed to show some parallels to what I saw on Axel Heiberg Island. (But you can see all my photos here!)

First are a lot of ignimbrites around the park, whose violent eruption triggered the massively catastrophic caldera collapse 640,000 years ago. Also known as
ash-flow tuffs, ignimbrites are a type of pyroclastic flow deposits characterized by high abundance of ash-sized (<4 mm) particles and pumice.  The scale of eruption required is enough to partially or fully empty magma chambers. The dramatic exodus of material substantially decreases the internal pressure of the chamber, often resulting in caldera collapse if the chamber roof is no longer sufficiently supported. The top of the magma chamber erupts out and is deposited first, so the ash-flow tuff sequence represents the inverted order of the magma chamber’s internal fractionalization.  The layers in ignimbrites can be divided into pyroclastic flow units from multiple eruptive pulses. A typical ignimbrite sequence contains a basal layer with reverse graded pumice and lithic clasts. Above the basal layer, flow units have density separated clasts: pumice is light and floats to the top, showing reverse grading, whereas denser lithic clasts are normally graded. Ash-flow tuffs thin out and have fewer clasts away from their source. If the flow units cool together, they form a compound cooling unit. Sufficiently hot and thick ignimbrites fuse and solidify from partial or complete welding. Welding occurs when hot, pliable pumice clasts flatten under overburden weight and sinter together, giving them a glassy appearance (Francis and Oppenheimer 2004).
Now you are no doubt wondering what on earth a explosive, caldera-building volcanic unit has anything to do with salt diapirs in the Arctic.  Genetically, nothing. But morphologically? Take a look:
The walls of this river-carved valley are jagged and karstic, looking a lot like what we saw at Stolz and Wolf Diapirs.
This looks a lot like that pseudo-karstic topography we saw in the Axel Heiberg Diapirs. The reason is simple. Ash, like salt, is softer than other types of rock. Therefore, it erodes away more readily than the surrounding units and forms jagged peaks. In fact, because ash-flow deposits are soft the Fremont First Nations used faces of ignimbrite for wall carvings in Utah.  I thought this was neat, and worthy of sharing. I imagine that ignimbrite exposed in valley or canyon walls would look very similar to salt diapirs in synthetic aperture radar, which further demonstrates the need to combine different orbital datasets paint a full picture.
Second are the hot spring travertine deposits, like Mammoth Hot Springs.  The mechanism that forms these deposits in hot springs at Yellowstone is like the perennial cold springs in the Arctic. In Mammoth Springs, geothermally heated ground water passes through limestone via a fault, and leaches out calcium. The calcium-rich water upwells to the surface and deposits calcite in the form of travertine as it cools.  

Mammoth Hot Springs has produced the largest known travertine deposit

Seismic activity alters the spring flow paths, enabling expansive terraces to form 

On Axel Heiberg Island, the waters that form Lost Hammer Spring are thought to be passing through subsurface extents of the Wolf Diapir, thereby passing through halite and anhydrite and leaching out sodium and calcium. Subsequently as the spring flows over, the deposits at Lost Hammer are halite, calcite, gypsum, thenardite and mirabilite (Battler et al. 2013). Despite Mammoth springs being a hydrothermal system, and Lost Hammer Spring being a perennial cold spring, I find it interesting that both sites are formed the same way.
Lost Hammer Spring, seen from above

The edge of Lost Hammer Spring, where salt-rich water has overflown and precipitated

In a week and a half, I’m going to the Space Generation Congress and the International Astronautical Congress in Adelaide, Australia! If I find some downtime, I’ll try to provide some short updates here, but I’ll definitely be tweeting about the conferences!
Battler, M.M., Osinski, G.R., and Banerjee, N.R. 2013. Mineralogy of saline perennial cold spring on Axel Heiberg Island, Nunavut, Canada and implications for spring deposits on Mars. Icarus 224: 364–381. doi:10.1016/j.icarus.2012.08.031.
Francis, P. Oppenheimer, C., 2004. Volcanoes Second Edition. Oxford University Press.

Tuesday, August 8, 2017

Axel Heiberg Adventures Part II

                Hello, hello, and welcome to Part II of our Axel Heiberg field adventures! As mentioned last post, we moved campsites about half-way through the trip. The plan was to move from Lost Hammer Spring to South Fjord Diapir. South Fjord is the largest salt dome on the island at a monstrous 5 km diameter! We were to make the move in three trips by helicopter. Oz and I would go first with our personal tents and some other essential gear, the helicopter would return and pick up a net load (literally, in a hanging net) of other gear including the fat bikes, and then on the third trip would bring Mike and Mark with the communal tent and the remaining gear. So Oz and I took off, needing to scout for a place to land that would be safe, accessible, and geologically interesting. But in a 5 km-wide mountain of continually rising and crumbling salt, what could not be interesting?

Until we got there.


That’s, um.  Hmm.

Well, at least we can confirm South Fjord Diapir has rough surfaces.
There is too much snow! We can’t possibly land here! Oz is shocked – it is mid-July and South Fjord Diapir is a winter-wonderland. He said that he visited this site in late June some-years ago, and there was nowhere near this much snow. This has some interesting implications for remote sensing work. Snow and ice can heavily influence radar response – what if South Fjord dome was blanketed in snow when our radar images were taken? I resolve to check Landsat images taken around the dates our radar images have been taken. I have done this since returning – it does look like one of our six images might be affected – perhaps I should mask out the ice and snow and redo the radar zonal statistics extraction!

What do we do? We flew around the dome for a bit, taking pictures while deciding where our backup camp will be. Remember that helicopter time is a valuable resource, so we need to decide quickly. Oz asks if there is a diapir near the end of Strand Fjord. I recall that there is, but I don’t know the distance to it. As we begin to fly over there, I pull out the field laptop that I had in my backpack. I’ll admit, I felt pretty cool flying in a helicopter while measuring distances in ArcGIS to make quick decisions where to land. I determine that Strand Diapir is approximately 6 km from the shoreline, and we deem this close enough to hike to.  We’re off to land in Strand Fjord!

And oh, what a beautiful campsite it was!

Icebergs in the Fjord, a low fog is rolling through. The dark rock unit is an folded igneous sill.
The brown rock is gullied the surface has undergone solifluction.
Strand Fjord, near our campsite.
The sandy banks have compositional layering.
I honestly think this is the most wonderful place I’ve ever camped. We had glaciers and ice bergs and beautiful sharp mountains with intense solifluction. It was beautiful. I did some soil sampling between our camp and the Fjord on one of our off days. 
Again, we saw patches of precipitated salts. Interestingly, these salts tended to be concentrated along the rims of wet/dry sand boundaries. The whole fjord area shows up in the TIR images as having VERY STRONG gypsum/anhydrite signatures, all deriving from the nearby Strand Diapir. Mike, Mark and I went on a hike to visit the northern half of the diapir exposure one day. 

The inland-area of the Fjord appears to be a glacially carved U-shaped valley, so Strand Diapir is split into two main outcrops across the valley. The salts in Strand Diapir are also interacting with some volcanic intrusions, causing some beautiful iron staining.

Behind me is the glacier that carved the U-shaped valley and provides the meltwater for the river.

The brilliant colours are from oxidation reactions between igneous rocks and the diapir.
The igneous rocks provide the metals, the anhydrite provides sulphur.
A reoccurring theme, the outcrops show some exposures of intact rock salt, but the majority of the surface has weathered into the highly vuggy gypsum crust that is characteristic of the Axel Heiberg Island anhydrite diapirs. Part way up the valley wall, the anhydrite is interbedded with what I think is limestone. I haven’t exampled the sample yet, but the dark colour and texture looks like a carbonate and past literature states that limestone is commonly interbedded with the Otto Fjord Formation salts. On a regional scale, the diapir material is stratigraphically overlying the orange stained unit, which I think is a volcanic sill, and has since undergone synclinal folding.

Flying in a helicopter never gets old
Something that I really appreciated this trip was being able to finally investigate the mystery of the radar-dark bright region, mapped as Isachsen Formation (quartz sandstone with some igneous intrusions). As a weather front was rolling in, our helicopter pilot asked if we wanted to make any last quick visits. I gave him the coordinates at the centre of the feature – the peak of a broad mountain range. He looked westward, and observed that that was where the storm was the thickest, and he wouldn’t be able to land there. Nonetheless, we headed that way along the coast, wary of the thick clouds in the distance. The very peaks were shrouded in clouds, but he asked if seeing the sides were enough. Elated to be there, I said yes, and to my delight we made a full perimeter tour around the feature before heading back to the safety of our campsite. Many photos were taken, and the verdict is that these slopes are COVERED in cobble-sized talus that would effectively scatter RADARSAT-2’s 5.6 cm radar beams. Since these are also high elevation peaks, snow and ice is admittedly also a possibility. I’m going to check the Landsat images soon to investigate. Sadly because we couldn’t land I wasn’t able to sample, or get good scaled photos. -sobs-
In addition to the fist-sized rocks everywhere,
take a moment to appreciate that sweet folding.
Travertine terraces from perennial spring from Colour Peak
Finally, one of the highlights of the trip was scaling the 550 m Colour Peak. Colour Peak has been part of the epitome for my thesis, showing that salt diapirs are radar-rough, whereas the materials that erode off of them and reprecipitate elsewhere are radar-smooth. Mark and Mike spent the day sampling the calcite-rich perennial springs effusing from the base of the mountain. The springs are building terraces of black travertine – the type of calcite that precipitates from cold water springs. 1-3 mm cubic halite crystals lined the edges of the streams. Mike founds some really cool crystals in a small cave – the sample he gave me is decorating my coffee table as I write this. The smell of H2S was pungent, and I found myself craving egg salad whilst down there. 
Oz and I, however, journeyed up to climb the massive diapir.  The best exposures of salt textures were at the top, with the flanks being either covered in soil, talus, or completely weathered and crusty outcrop.  The ascent was tough.  The diapir is steep sided covered in poorly sorted colluvium. The skree contains sand to boulder-sized rocks. We also found some palm-sized fragments of clear selenite crystals amongst the soil patches. I think the anhydrite colluvium and gypsum-rich soil is enough to product the spectral signature seen in the ASTER TIR image downslope of Colour Peak without us needed to appeal to the perennial spring. Because much of the slope material was unconsolidated, our feet were prone to slipping down as we moved upwards. I’m very fortunate that Dr. Osinski is an experienced climber, and I was able to follow where his footsteps packed down the debris.  Frequently we would take a step on what seemed to be solid ground, only to have our foot punch through the weathered gypsum crust into a 20 cm deep vug.  
Rough, steep, the return of slightly karst-y topography.

Close to the summit are outcrops of solid anhydrite or gypsum. Unlike at Wolf Diapir, where the solid salt was powdery and friable, here the salt is crystalline.  Erosional processes are carving the solid salt into points like the rillenkarren seen on halite diapirs and in karstic carbonates. The rillenkarren are smooth at the mm scale, but undulate at the cm scale and would appear rough at C and L-Band SAR. 
Rippled rillenkarren textures on crystalline anhydrite sample.

The sharp, solid salt looks beautiful up close.  Of course, nothing compares to the stunning, beautiful view from the summit!


An excellent view across Expedition Fjord,
            and the travertine perennial spring down below


The rocks up here are mostly blocky, partially weathered, and the ground is covered in colluvium. Once again we are able to confirm that salt diapirs are rough on the ground, not just in radar.

Very blocky, rough, and sadly too unstable and dangerous to venture farther.
You can see where Colour Diapir ends, and the adjacent mountain begins
based on surface texture alone. 
  Any discussion of Colour Peak would be incomplete without explaining how it got its name. The colluvium also includes rubble and gravel of angular igneous lithologies, including what is ostensibly dacite and diorite. Some of the volcanic material is oxidizing to form gossans. The gossans are dazzling zones of vivid orange, yellow, and brown alteration. These are found in close association with diapirs on Axel Heiberg Island, including North Agate Fjord and Junction Diapir where basaltic intrusions from the Isachsen Formation are altering to form copper and iron sulphides and secondary copper sulphates (Williamson 2011). The calcium sulphates in the diapir provide the sulphur for these alterations to occur. Remember, we saw this same alteration at Strand Diapir!  We collected some samples of yellow rhombohedral crystals have been taken to the lab to for analysis

The journey home was bittersweet. I’m going to miss this place.

And such concludes my 2017 Axel Heiberg adventure.
Elise xx