Piles of Sand

Am I doing any work or just exploring the city? What have I been up to in the lab?  I'm so glad you asked, and I have an answer for you this week.  Prepare yourself- this is a (lengthy) science update post!

I am now officially one month into my time here in Boston.  Besides adjusting to life as a grad. student, life in a new city, and my two classes for the semester (geochemistry and a mathematical modeling course), I have plenty of ambitious research goals for the semester.  In fact, I have at least four projects that I am supposed to be starting or working on at some point in the next couple months.  I have a feeling you'll hear about them over the coming months..or years.

But before I can produce large amounts of relevant data in the lab, I am currently in that joyous stage of being the newbie, the trainee, the person who has no idea how to do most of the routine procedures in my new lab and has to ask someone for help every time I come up against the next step.  Clearly there are some benefits to that situation (like being limited in what labs I have been trained in so therefore feeling no guilt at not spending every waking moment in the lab or the constant learning of new and exciting things) as well as drawbacks (like not being even remotely self-sufficient and making slow research progress).  I have been assured by my adviser that it could take me a good year to two years until I can confidently handle any and all of the research tasks expected of me- so I suppose I am doing well for a month in. It's all about perspective.

That being said, I am happy to share with you what I have accomplished this month in the lab.  Really, it all centers on making piles of sand.

Glen Clova, Scotland

The first of my four projects involves sand collected from a river flowing through Glen Clova, Scotland.  Glen Clova is a famous glacially-carved, U-shaped valley and is part of the type locality for the Barrovian metamorphic sequence.  I visited in June and collected the sample, along with my adviser and field assistant.  (If you missed my post on summer fieldwork and want to see more details on my trip to Scotland or pictures, check it out here.)  The current goal for the sample is to separate out the mineral garnet and attempt to establish an age for individual garnet grains.  This sample will be a part of the method development for my dissertation.  My overall PhD project is focused on developing a system for dating detrital (eroded and then redeposited elsewhere) garnets, which has essentially never been done and would open a whole new tool for geochronology.

The first step is taking my bucket of sand and separating out the grains of garnet from the overwhelming amounts of quartz, feldspar, and other minerals present.  While you could theoretically just sit there with tweezers and hunt through the bucket, that would be terrible and not very efficient.  Therefore, we can use properties of the minerals to separate them into different "piles."  Many geologists (and most prospectors) have gone through a similar series of steps as a part of the basic sample preparation that is my current lab activity.

The first step is to send the sand through sieves with different size mesh screens.  This divides the grains into piles with similar grain sizes.  This is important not only for later mineral separation steps, but allows me to gain an idea of the grain size distribution for garnet in this sample.  Since I am developing a new method that uses a single grain of garnet at a time, I would ideally like to find the largest grains that exist to start with, before working down to smaller grains.  Also, since my samples have much larger grains than what my lab is used to working with (finely crushed "pure" garnets), I got to determine that we need some sieves with larger mesh sizes and order them.  Thus, my first contribution to making my lab more versatile! Hooray!

Once the grains are separated by size, I have been using a Frantz electromagnetic separator to divide the grains based on magnetic susceptibility.  Most mineral grains are magnetic to at least a small degree, especially if you use a big enough electromagnet and set it appropriately.  The differences in magnetic susceptibility between minerals of different types allow sand to be separated into piles based on the degree of magnetism.

The Frantz I've been using the past couple weeks

Here's how it works:

1. Clean the machine thoroughly.  (You definitely don't want grains from the previous user's sample contaminating your sample!)
2. Turn on the magnet and set the desired level of magnetism.  Since I'm aiming for garnet, I usually start with a high setting to eliminate the least magnetic minerals and work my way towards gradually eliminating more magnetic minerals.  People who want to separate out other minerals may approach it differently.
3. Load whatever sample you wish to separate into the glass container that will feed the grains into the machine.  Usually you want to use a hand magnet on this sample before you load it, because that will remove one mineral (magnetite) that is the most magnetic and keep very magnetic grains from sticking to the magnet.
4. You can control how quickly the glass feeder container and a tray between the two portions of the electromagnet vibrate to control how quickly grains move through the magnet.  Grains fall out of the feeder (ideally basically one grain at a time so they don't influence one another) and move down a tray between the electromagnet.  The tray is tilted so that by gravity, grains prefer to move down the side away from the operator.  However, grains that are more magnetic than the magnet's current setting will be pulled up to the portion of the track closer to the operator.  The grains are then separated into two containers at the other end- the closer one being more magnetic and the one further away less magnetic.
5. Since I want garnet I continually rerun the pile collected in the container closest to me at a lower magnetic setting so that it is separated into two new piles.  This continues until I have one or two piles that have a larger proportion of garnet than any of the other piles.

Some people use heavy liquids or water tables to separate minerals by density and to reduce the amount of time required and increase the efficiency of the Frantz.  We have been discussing having me implement these strategies in our lab eventually, especially since I may have to separate relatively large amounts of sand.  We shall see what the future holds.

I also got to make another contribution to improving my lab's efficiency by constructing a "backboard" to keep my grains from bouncing out of the Frantz as they dropped out of the feeder.  Evidently the combination of larger grain size plus an old Frantz model leads to quite a few grains trying to jump ship before they head down the tray- regardless of how high or low the vibration of the feeder and tray is set.  I improvised a shield from weighing paper and label stickers- nothing like scientific McGuyvering.

That pretty much sums up month one in the lab.  So far it has been basic sample processing (all of which I actually did once upon a time as an undergrad. for a term project) but at least it's progress!  I'll share the next step for these piles of sand in an upcoming post.

The Prologue: Scotland Fieldwork

In keeping with my first post, my PhD adventure not only requires an introduction but has a prologue as well.  In mid-June I participated in a week of Scottish fieldwork, which technically means that before my move to Boston I have already completed my first week as a PhD student!  I traveled to Scotland along with my new adviser (Dr. Ethan Baxter) and a field assistant to collect the rock samples I will use to start my PhD project.  I have more stories than I could possibly share here, so I'll try to focus on the highlights of my very first PhD adventure but consider yourself warned- this won't be a short post!

Tues.\Wed. June 14\15

• Starting on Tuesday, I flew from Indianapolis to Detroit and boarded my next flight from Detroit to Amsterdam.  I arrived in Amsterdam at 9:30AM local time on Wednesday morning, where I met up with Ethan and our field assistant before continuing on to Edinburgh, Scotland.
• Once on the ground in Scotland we picked up our rental car (complete with the driver's side on the right, the gear box to the driver's left, and stick shift) and drove to St. Andrews, where we spent the remainder of the day at the University of St. Andrews.  We met wonderful colleagues in the geology department, nailed down plans for where we planned to sample each day, and Ethan gave an impromptu talk for a portion of their dept. on what we hope to accomplish with the detrital garnet project I am undertaking.

Thurs. June 16

• This was our first day of actual fieldwork.  We spent the majority of the day working near Stonehaven and Cowie along the coast of the North Sea. 

North Sea coastal scenery near Cowie, Scotland

• The tide was out when we arrived, so we started on the exposed rocks and moved closer to the cliffs and further north throughout the early afternoon, scouting for the coarsest grained samples we could collect to give us a shot at decent-sized detrital garnet grains.  We collected the first two samples (coarse sandstone) of my PhD project along the coast that morning and afternoon!  I also got to see chlorite-grade metamorphic units that are part of the Dalradian classic Barrovian sequence (which only means something to the geologists reading this who know the Barrovian sequence was first worked out in Scotland) and ruins in the distance that were used for filming a portion of Mel Gibson's Macbeth.
• In the evening we did a bit of "geotourism" by visiting Glen Clova.  Glen Clova is a big U-shaped glacial valley carved through Barrovian sequence metamorphic rocks.  While we were there we collected a bucket of sediment out of the river running through the bottom of the valley that will be one of the first samples I work on starting in September.  We also saw the most spectacular rainbow I have EVER seen.  It stretched from one side of the valley to the other and was fully doubled for a while!  

Glen Clova rainbow

Fri. June 17

"Magic" Blue Door

• We were joined in the field by Dr. Ruth Robinson (University of St. Andrews) and one of her students for fieldwork at Glen Esk, along the River North Esk.  To get to our field site we had to pass through the "magic blue door" (an access door in a stone wall that provided access to a trail along the river).
• We worked our way along the river, collecting two samples from coarse sandstone lenses amidst conglomerate with fist-sized clasts.  As we worked, we occasionally saw a salmon or two as they jumped and ran up the river!

River North Esk

Arbroath "Smokies"

• After we finished at Glen Esk, we visited more cliffs along the coast near Arbroath to see the Old Red Sandstone unit.  We also stopped in Arbroath to sample their famous "smokies"- otherwise known as whole smoked haddock.  You buy the fish gutted, smoked, and whole then crack them open and remove the spine before eating the meat out of the skin.  It was REALLY good!
• That night we stayed in a castle.  Named Barony Castle, the castle has been converted to a very nice hotel.  To make the deal even sweeter, the castle has a 3D concrete topographic map of Scotland on the grounds to commemorate a map built by Polish soldiers who used the castle as a barracks during World War II.       

Barony Castle near Peebles, Scotland

Sat. June 18

• The rainy weather of Scotland finally caught up with us.  Saturday consisted of several stops at outcrops and quite a bit of driving.
• Our first planned stop was to sample a garnetiferous layer mentioned in a published paper describing the rocks of the area by Walton.  The second planned stop was to scout for a location to replicate samples taken by Graham Oliver that were described as containing plenty of detrital garnet.  Both of them were classic outcrop stops.
• The best stop of the day was unplanned.  We stopped just past the town of Lendalfoot in a parking lot to look at the maps and climbed down to large boulders along the coast.  We ended up getting to check out some awesome ultramafic boulders that are a part of the Ballantrae ophiolite sequence.  They contain lots of epidote and serpentine and extensive veination.  

Ultramafic boulder on the beach with veination

• That night for dinner we ate authentic fish and chips that we got from a carryout "fish bar" and ate sitting on benches in the square!

Sun. June 19

view from Ballantrae sample site

• In the morning we did the actual sampling at the second site we had scouted the day before.  It is a classic roadcut exposed along the road above Loch Ryan.
• In the afternoon we went inland to collect some bonus samples not directly related to my detrital project.  The Ballantrae Ophiolite sequence has a metamorphic sole, which contains garnet-bearing amphibolite and pyroxenite formed as the hot oceanic slab was emplaced.  We hoped to collect samples of both that contain garnets large enough to be dated by the traditional garnet method in use at BU.  We succeeded in collecting the samples and this will probably be the first side project that I will begin work on in September!  There is only one date for the metamorphic sole that is often cited, and adding a garnet date will help better constrain the age of the unit.
• The samples of the Ballantrae metamorphic sole required us to climb up a hill in a sheep pasture to get to exposed rock units.  The scenery was beautiful and we finally got to see a large garnet (1.8 cm x1.4 cm). 

Mon. June 20

St. Andrews Cathedral ruins

•  This was our last full day in Scotland, and we spent it in St. Andrews once again.  In the morning we prepared, labeled, sorted, and packed all our samples to be shipped back to the United States.  We ended up with three wood crates weighing a total of 66kg (145.5 lbs)!  
• After we packed up all the samples and wrapped up all of our work, we got to spend the rest of the day as tourists in St. Andrews!  We saw ruins of the St. Andrews cathedral and castle, the 18th hole of the Old Course (the birthplace of golf), more of the University of St. Andrews' campus, and even ate lunch at a restaurant Prince William and Kate once frequented as students. :-)

18th hole of the Old Course- Golf's Birthplace!

Tues. June 21

• We had to say goodbye to Scotland!  I flew from Edinburgh to Amsterdam and from Amsterdam to Boston.
• Going through customs at Boston, I got the privilege of going through the "agricultural customs line," (thanks to my traipsing through both cow and sheep pastures) where the customs agent checked the bottom of my boots for animal poop!  I also had another customs agent who barely believed that I was working while I was abroad.  :-)
• I got weather delayed in Boston for 4+ hours, but I finally made it home safe and sound just before 2AM Wed. morning!

I would say week one as a PhD student went pretty well.

Goodbye Scotland! (River South Esk, Glen Clova)