Wooster undergraduate researchers will share findings at international conference

August 2nd, 2019

Wooster, OH – Team Geochemistry finished a highly productive summer research season with two conference abstracts that we submitted to the 2019 Fall Meeting of the American Geophysical Union. AGU will be an excellent opportunity for the team to hone their presentation skills, network with potential employers and graduate school advisors, and explore the wide range of disciplines in the geosciences. Read about our work in the abstracts:

Ok and Bræðravirki offer us opportunities to explore past climates and interactions between volcanoes and glaciers, helping us predict what might be in store for Iceland and other ice-covered volcanoes across the world. (Photo Credit: Hannah Grachen)

A Geochemical Study of Bræðravirki Ridge (Western Volcanic Zone, Iceland) Reveals Regional Glaciovolcanic Variations and Complex Tindar Construction 

By Hannah Grachen, Simon Crawford-Muscat, Billy Irving, Meagen Pollock, Benjamin R. Edwards, Shelley A. Judge, Layali Banna, Kendra Devereux, Marisa Schaefer

Summary: As global ice recedes in response to climate change, volcanoes that erupted under the ice are becoming more exposed. We studied one such subglacial volcano in Iceland called Bræðravirki Ridge, and found that Bræðravirki is chemically different from other nearby subglacial volcanoes. We also found that there were several packages of volcanic ash and lava that were erupted at different times. These findings show that subglacial eruptions are complicated, and we might be able to use these types of observations to understand more about the history of volcanoes and glacial ice in an area.

Although tuyas in the Western Volcanic Zone (WVZ) of Iceland have been studied in detail, little work has been done on the numerous smaller tindars there. This study compares Bræðravirki Ridge, a 3-km long tindar on the southeastern flank of Ok shield volcano in the WVZ, to regional tuyas and creates a model for ridge formation based on combined mapping and geochemical analyses. Bræðravirki is dominated by palagonitized lapilli tuff with scattered intrusions, rare exposures of intact pillow lavas, and multiple tuff/lapilli tuff units. Whole rock samples were measured for major and trace elements by XRF and ICP-MS. Mineral compositions were measured by SEM-EDS. Major elements show that Bræðravirki is relatively enriched in SiO2 and depleted in CaO, FeO*, and MgO compared to regional data. Within the ridge, vitric tuff/lapilli tuff units are more evolved (MgO 6.29-6.66 wt.%) than other units (MgO 6.94-7.72 wt.%). Preliminary Rhyolite-MELTS (v. 1.0.1) models are consistent with the two compositional groups being genetically related by 3 kb fractional crystallization of a common parent magma. The MELTS models generate plagioclase (An61 to An70) and two pyroxene (low- and high-Ca) compositions that are observed in the SEM-EDS mineral data. Incompatible trace elements show limited variation between the two compositional groups (Nb/Y 0.37-0.41), suggesting stable melting conditions. We propose a two-stage eruptive model that begins with an explosive phase, followed by a second explosive-effusive phase that forms intrusions and pillows. The second phase is hypothesized to be initiated by a recharge event, emplacing the higher-MgO units. This study demonstrates that small tindars can be constructed through multiple eruptive events that shift in eruptive style and that glaciovolcanic edifices in the same region can have significant compositional differences, possibly providing insights into the understanding of their timing, magmatic history, and paleo-ice conditions.

Microscope photo of one of the granitic rock samples that was classified using the new and old naming systems.

New Igneous Classification System Produces Consistent Rock Names and Illuminates Modal Data

By Hannah Grachen, Anna Cooke, Charley Hankla, Ethan Killian, Cody Park, Layali Banna, Kendra Devereux, Meagen Pollock

Summary: Rock names are useful for understanding what a rock is made of, how it formed, and how it might be useful. For rocks that form from molten magma, the current naming system doesn’t communicate all of the relevant information. Earlier this year, scientists proposed a controversial new naming system to make rock names more meaningful. We tested the new naming system and found that it worked well at the microscopic scale but was more confusing when using the naked eye. We found that the new rock names contained more useful information than the old rock names, and we think that the new system could become the future of rock classification.

In the February 2019 issue of GSA Today, Glazner et al. proposed a new classification system for igneous rocks, citing shortcomings within the standard International Union of Geological Sciences (IUGS) classification system, in use since 1974; chiefly its inability to convey modal data and its arbitrary division of interrelated rocks into disparate types. Their proposed system recognizes rock classifications on ternary diagrams to be “fuzzy” rather than distinct, therefore better representing the continuous nature of rock sequences and lending their system the term “fuzzy classification scheme”. They suggest a system of limited root names combined with modal percentage numbers and significant accessory minerals to provide more informative and straightforward rock names. To test this claim, we have named a suite of six thin sections and hand samples of granitic rocks from Songo Pluton, North Jay Quarry, Mount Waldo, and Deer Isle, using both the IUGS and “fuzzy” classification schemes. We also obtained modes on thin sections through quantitative image analysis using Adobe Illustrator and ImageJ, this being an important step in our process due to the difficulty of differentiating alkali feldspar and plagioclase in our samples. We determined that while the comments on Glazner et al.’s paper are critical, in the tests we performed, some of those criticisms, such as the non-replicability of the proposed system due to interpretive bias, are insubstantial. In thin section, the fuzzy system naming led to more consistent naming results than in hand sample observations, while the opposite was true in hand sample. One of the things we would suggest after conducting our tests is to include boundaries to distinguish the names in a better way. Overall, the proposed system’s ease of data communication is an improvement on the IUGS system that warrants more attention and modification.

Team Geochemistry’s Grand Finale

July 31st, 2019

Wooster, OH – Team Geochemistry wrapped up their grand adventure last week. The summer research experience left us with fond memories of trips to Dickinson College and Iceland, knowledge of lots of new analytical techniques, and many new friendships, not to mention the important findings from a critical field site that we’ll be presenting at the December meeting of AGU. Here are some parting thoughts on our bittersweet ending from guest blogger Kendra Devereux (’21):

After returning from Iceland, team geochemistry has been hard at work prepping their samples. In just two short weeks, all 23 whole rock samples from the field have been cleaned, powdered, sieved and turned into fused glass beads and pressed pellets.

Hannah, Layali, and Kendra spent the first week back from Iceland sieving their powdered samples.

Layali happily sieving!

Hannah happily sieving!

Hannah finished her time for the summer last week and is busy moving to Florida with her family, leaving Layali and Kendra on their own for their last week of work. Layali and Kendra spent this past week making 23 fused glass beads and 23 pressed pellets

Pressed pellets and glass beads are all ready to be analyzed with the XRF next week!

As a celebration of all their hard work, Dr. Pollock, Layali, and Kendra enjoyed “Taste of Wooster” downtown on Thursday night.

A delicious chocolate marshmallow whoopie pie from The Blue Rooster.

After 8 weeks together, team geochemistry have said goodbye until the 2019-2020 school year begins!

Wooster geologists working at site of first glacier memorial in Iceland

July 23rd, 2019

Iceland – Big news this week as researchers dedicate the first-ever monument to Okjökull glacier, memorializing the first Icelandic glacier to lose its glacier status to climate change. Ice loss in Iceland is dramatic; researchers expect all of Iceland’s glaciers to go extinct in the next ~200 years, with drastic changes to Icelandic culture and economy. As the ice retreats and reveals the underlying land, scientists can investigate ancient volcanoes that erupted thousands of years ago under the glacier. Wooster geologists were with a team from Dickinson College on the scene of Ok volcano this summer, exploring a glaciovolcanic ridge that is now exposed on the southeast flank of Ok volcano.

View of Ok shield volcano from the south. Bræðravirki is the glaciovolcanic ridge on the southeast flank of Ok volcano. (Photo Credit: Hannah Grachen)

Another view of Bræðravirki ridge from the east. The summit of Ok volcano is off of the photo to the right. (Photo Credit: Hannah Grachen)

Most of Bræðravirki ridge is made of yellow ash that was erupted explosively and has been consolidated into a rock called tuff. The patterns in the rock tell us about how it formed. (Photo Credit: Hannah Grachen)

The tuff has a distinct yellow color that forms when the volcanic ash reacts with hot water. We also see glassy black rocks in the ash that we think are volcanic bombs, which form when lava is ejected violently during an explosive eruption. (Photo Credit: Hannah Grachen)

The ridge also has irregularly shaped bodies of massive rock. These are light gray and extremely hard, with a unique pattern of cracks that forms as the molten rock cools and solidifies. We think these are fingers of magma that get injected into the growing ash pile. (Photo Credit: Hannah Grachen)

Ok volcano and Bræðravirki ridge give us the opportunity to explore past climates and interactions between volcanoes and glaciers, helping us predict what might be in store for Iceland and other ice-covered volcanoes across the world. (Photo Credit: Hannah Grachen)

Look for us at the December 2019 meeting of the American Geophysical Union in San Francisco, CA (USA), where we will be presenting our findings from Bræðravirki ridge.

Summer undergraduate researchers travel to Iceland to explore volcanoes

July 19th, 2019

Iceland – In our last post, Team Geochemistry was getting ready to head to Iceland for some field work on volcanoes. Our goals were to map and sample volcanoes that erupted under glaciers, which have since retreated, exposing the pillow lavas and ash that formed when lava met ice. We met up with a research team from the Dickinson College Earth Sciences Department, and also brought Dr. Shelley Judge, Wooster’s structural geologist. Together, we collected over 30 samples, took 1000s of photos, flew the drone for 8 hours, and made 100s of structural measurements. Overall, it was a successful and productive field season, with some laughs along the way! Layali Banna, member of Team Geochemistry (and basalt goddess), describes their field experience.

[Guest blogger Layali Banna] Last week, team geochemistry went to Iceland. We met up with some old friends there, but we met some new ones as well. In total there were ten of us and we were ready to take Iceland by storm.

All of us walking along Undirhlíðar (from left to right: Phoebe, Dr. Edwards, Marisa, Dr. Judge, Dr. Pollock, Kendra, Layali and Ethan; Hannah Is behind the camera taking the photo.)

After a long day of flying we decided to mostly take it easy, just doing a short walk around a nearby quarry to learn more about what we will be looking for out in the field.

Dr. Pollock posing for her glamour shot.

The second day was much different though – we spent almost all day out on Hannah’s site collecting samples for her project at Bræðravirki ridge. Divided into two teams, one group walked the ridge collecting samples, while the other group used a drone to map the ridge. This was a prime time up at the ridge since there was no snow cover, unlike past years where the gullies were hidden by snow, allowing us a great look at it without anything in the way.

Kendra smiling with Prestahnúkur in the background, which is a rhyolite volcano.

A gulley on Bræðravirki that was buried in snow during past years was now accessible for sampling.

Our third day in Iceland after that long day in Bræðravirki we spent the morning inside working on our field books and collecting some data, making observations on our samples.

 

Everyone working together to look through all the samples we had collected the day prior.

The latter half of the day we surveyed Undirhlíðar and ended up goofing around a bit at a certain spot called the bowl.

Kendra and Marisa trying to figure out how they are going to climb up the side of the bowl.

After our half day we returned to Undirhlíðar. This time we were split up into three groups all doing different things in separate areas. One group mapped with drones, another analyzed and mapped deformation bands, taking samples and pictures of the bands, and the last group went and took samples for Marisa’s project.

A beautiful, thick, glassy dike found on Undirhlíðar.

Time for a snack break! Marisa is eating a nutritious energy boosting cookie.

Finally, on our last day in Iceland everyone was given a free day to do what they want, exploring some of the natural wonders the island has to offer as well as touring the capital of Iceland, ReykjavÍk.

Hannah finally getting her photo taken instead of her always being the one taking them at Krýsuvík thermal zone.

The group stopped for some famous Icelandic street dogs in ReykjavÍk, Kendra is ready to dig in.

All too soon it was time for us to pack our bags and say goodbye to our friends and Iceland. It was time to head back to Wooster and work on the samples we collected in the lab.

 

High-Temperature Geochemistry in Action

July 18th, 2017

WOOSTER, OH – Over the last couple of weeks, our Keck Geology Team Utah has been hard at work in the College of Wooster Geology labs. We collected a dozen samples from Ice Springs Volcanic Field in the Black Rock Desert, Utah to understand the eruption history and the age of the lava flows.

The first processing step is to powder the sample. Addison Thompson (’20, Pitzer College) uses the rock saw to isolate pieces of fresh rock.

Addison and Madison Rosen (’19, Mt. Holyoke College) use a sledge to break the sawn pieces into smaller bits.

Sam Patzkowsky (’20, Franklin and Marshall) cleans the chips so that we can crush them in the shatterbox.

Emily Randall (’20, College of Wooster) sieves the powder and makes sure all of it is small enough for the next step. We sent some of this powder to the Purdue PRIME Lab, where they’ll measure the abundance of 36Cl in our rocks.

Pa Nhia Moua (’20, Carleton College) pulls samples out of a red-hot oven so that we can measure Loss on Ignition (LOI) to determine how much H2O might be in the samples.

Sam and Addison weigh out accurate amounts of the oxidized sample and flux, which lowers the melting temperature and helps our samples melt so that we can make glass discs.

The samples get melted in the fluxer and poured into molds to make glass discs.

The glass discs are loaded in the XRF and analyzed for their major element chemistry. We use the chemistry along with the data from Purdue and the location and orientation of the sample to calculate an age for the lava flow.

We’re using another method called Varnish MicroLamination (VML) dating to provide an independent estimate of the age of the lava. Desert varnish is a dark coating of clays and iron- and manganese-oxides that accumulates on the surface of samples in arid environments. You may have seen ancient petroglyphs carved into the desert varnish. Researchers use the layering in VML to date pieces of rock art. In order to use the VML method, we have to make ultra-thin slides of our rocks so that we can see through the varnish.

Addison pours epoxy into plastic molds to mount the VML samples.

Pa Nhia has been sanding her VML sample for days to grind it to the correct thickness without grinding away the varnish. It’s dirty, delicate work.

By the end of the week, we should have age estimates for the lava flows and a better idea of the sequence of eruptive events that formed Ice Springs Volcanic Field. Check back later for our GSA abstract!

The conclusion of an excellent field season

June 28th, 2017

Guest Bloggers: Addison Thompson (’20, Pitzer College), Pa Nhia Moua (’20, Carleton College), and Sam Patzkowsky (’20, Franklin and Marshall) write about our last day of field work

6.26.17  Despite the often inhospitable conditions of the Black Rock Desert, the cohesion of team Utah made the scientific process enjoyable.  After the immediate success of the first day, it was given that the group would surpass any benchmark that Dr. Pollock had imagined.  The constant willingness for members to go above and beyond what was necessary to advance the mission in the Black Rock Desert was indicative of the excitement the group derived from the task at hand.

Team Utah with cinder cones in the background.

Although sweating, sore arms, and general discomfort at this point was par for the course, the final day in the field was bitter sweet.  The group ended on a high note, collecting a total of seven samples on the day.  Dr. Pollock said, “finding a suitable piece of pahoehoe is like finding a needle in a haystack”, so the group found two.  In addition to the pahoehoe samples, numerous samples were found that were suitable for Varnish Microlamination testing.  With the day complete, the group left the four cinder cones and their vast, puzzling lava flows in search of petroglyphs that were said to be nearby.  These were never found.  The ride back to camp was quiet, people were either staring out the window at the expansive Utah landscape or with their heads rocked to the side catching some z’s.

Pa Nhia Moua Carleton College ’20 demonstrating proper enthusiasm whilst in the field.

Pa Nhia Moua
Carleton College ’20 Member of Team Keck
As we ventured on our last day in the field, we were determined to make up for our day “off the field”. With pride and gratitude, the team worked hard to use all information we learned on the field to search for suitable samples. Hurrah to Team Utah! The seven samples we collected in one day shows our spirit, our optimism, and our growth of knowledge! And as a plus, a massive lava tube (~15-20 m tall) was discovered, and offered us wonderful protection from the shining rays of the sun. Great job team! Now, may luck and knowledge be with us in the labs!

“I could have sworn we parked the car over there.”

Sam Patzkowsky

Franklin & Marshall College ’20

As our trip in Utah comes to a close, I am flooded with all the unique and rewarding experiences that occurred.  One of these experiences that stuck out to me was from our first day in the field; right after lunch we had split up into groups to try and understand what the heck was going on in the immediate area.  My group consisted of me and Addison Thompson (Pitzer College ’20), and as we trudged off away from the other group, it hit me, I had known this kid for all of three days and suddenly we were thrust into a position to work together to attempt to understand the volcanics of this field, unknowing if we’d have a great dynamic or a poor one.  As this work continued, I knew that even if we had different personalities, geology is a field where people can set aside their differences, whatever they may be, and just nerd-out about rocks.  It is truly a unique field of study and one that I am excited to continue working and studying in.  Oh, and Addison is one heck of a group partner, in case you were wondering.

Emily Randall ’20 the College of Wooster collecting a righteous sample of Pahoehoe with colleagues looking on eagerly.

Our resident photogenic individual, Sam Patzkowsky, Franklin & Marshall ’20 beating the heat with a crispy apple.

Team Utah Takes to the Field

June 26th, 2017

Guest Blogger: Addison Thompson (’20, Pitzer College) writes about our first 3 days of field work.

6.23.17 For the Utah group, the first day in the field was daunting yet rewarding as our intrepid group of young geologists made themselves acquainted with the Ice Springs Volcanic Field.  The Ice Springs Volcanic Field, located in the Black Rock Desert of Utah, is home to many old cinder cone volcanos that currently lay dormant.  In the past the cinder cones were active volcanos, spitting and oozing lava.  The lava flows have since cooled and currently take the form of basaltic rocks spilling out from four primary cinder cones, Miter, Crescent, Pocket and Terrace.

The day began at 7:15am with breakfast, after which foods were divided for lunch, sandwiches were assembled, and packs were equipped and made field ready.  Everything was ready, as was the team and off the Utah group went to the field site, arriving just after 9am.  After days of anticipation, stepping out of the car face to face with what the group had read so many articles and papers about was magical.  In no time, the group  was on their way, climbing up the service road, and eventually up the cinder cone named Miter in order to get a lay of the rocky land.

Team Utah atop the Mitre cinder cone

The terrain comprised uneven, sharp, basaltic rocks and was difficult to traverse, but the group managed.  After climbing Miter, the next move was to follow the presumed Miter lava flow path which eventually emptied into a flat basin, an area interpreted to be where a lava flow once pooled.  A good section of pahoehoe, a ropy formation of a basaltic rock, was quickly identified, and its sample was taken.

Sam Patzkowsky (’20 Franklin and Marshall College and Team Keck member) dislodging a piece of Pahoehoe to be used as a sample.

With the success of the pahoehoe find, it was time for lunch.  Shade was hard to come by, so people did their to take refuge from the incessant beating of the sun.  Water was a must.  After lunch the group split up in the attempt to identify the Mitre/Crescent lava flow boundary, not an easy task.  Regardless of the difficulty, progress was made and we ended the day with promising evidence that could work towards our hypothesis.  After a long first day in the field, morale was high but energy was very low; dinner was a welcomed sight.

6.24.17 Waking up on the second day was a breeze.  The group had a plan in mind and very little was left to chance.  First on the chopping block was a visit to the Carbon-14 dating site followed by accessing the area that is believed to house the Miter/Crescent boundary.  Sadly the Carbon-14 dating site was only accessible by a private road, so that idea was nixed.  Next up was entering the lava flows from the north west side via a rarely traveled dirt access road.  The going was bumpy but eventually the car made it to a suitable stopping point.  The walk to the toes (the extent) of the lava flows was a brief flat jog that took minutes; however, the real challenge began when it became necessary to climb the lava flows in order to press on.   Over the course of the trip, the sharp basaltic rocks have claimed many a causality, so the group favored precision over speed.  In searching for Miter/Crescent boundary evidence, it was impossible to ignore other important geologic occurrences.  One of these interesting being a large boulder, about 8ft. tall, comprised of lava bombs that must have been part of a cinder cone that rode a lava flow to the edge.

Measuring a boulder that was transported to its current location by a lava flow.

This helped give an idea about the power of the flows.  Measurements of the boulder were taken along with photos for reference.

As the group pressed deeper into the flows they began to notice an accumulation of large basaltic slabs sticking out of the ground in all directions and angles.  Dr. Pollock noted that information about these slabs could be important towards our ultimate goal, so slab measurements needed to be taken, twenty in all.  Taking a slab measurement consisted of noting the coordinates of the hunk of rock, its width in centimeters, taking photos of the slab under examination, and lastly noting the size of the vesicles (holes created by the expulsion of gas during the cooling process).

Two members of Team Keck measuring a slab’s width.

The reward was lunch and maybe shade.  Luckily, shade was easier to find than the day before and the group crouched, laid, and sprawled under the angled rocks.  But like all good things, lunch came to an end.  Regardless of the heat, the group was always eager for more field work so they decided to push farther east in search of a boundary that had previously been visible from a birds eye map.  At the boundary, samples were to be taken for geochemistry analysis.  Eventually the boundary was reached and the samples were taken.  After a efficient day in the field it was time to turn around.  Dinner was burgers and everyone went to sleep soon there after.

6.25.17  The third full day in Utah did an excellent of of testing everyones nerves.  A special thanks goes out to Dr. Pollock for her cool disposition in the face of a turbulent situation.  The day began as a normal day does with breakfast, then lunch packing, and finally going over the mission of the day.  The catch was that the back right tire of the car that didn’t want to go along with the plan.  Minutes away from the field site the low tire pressure sign flashed on the dashboard so the group turned around and went to go get air for the noticeably deflated tier.  However the issue was that the tire had a puncture, not that it simply had low pressure.  With the spare now on the car, there was no backup and driving over rocky terrain without a spare tire is a disaster waiting to happen, so the call was made to switch rental cars.  This required Dr. Pollock driving the rental up to the Salt Lake Airport to exchange cars, a two hour trip both ways.  This exchange took a majority of the day so there was sadly no time left for field work.  This was definitely a disappointment, but the group handled it well.  The day was instead spent relaxing, uploading information from the field and doing any other minor housekeeping chores.  Emily Randall (’20 College of Wooster and Team Keck member) created a map locating every coordinate where a sample had been taken.  Finally towards the end of the day a few members went on a hike along an ATV path that wound towards the mountains behind the camp site.

A panoramic taken from the hike.

Although no field work was conducted it was a productive day.

 

Lab Character(s)

May 25th, 2017

Chapel Hill, NC – Every scientist who works in a lab knows that labs have unique characters. The Isotope Geochemistry lab at UNC Chapel Hill was bustling with Ph.D. researchers, graduate students, undergraduate students, and researchers from other institutions, including Appalachian State University and The College of Wooster. We could tell it was a happy lab community by all of the happy faces. The faces weren’t just on the researchers; they were drawn on windows, hoods, and sticky notes.  Here are few to brighten your day.

There was a single angry face in the bunch. We called this Samarium Face (Sm-face) because Sm is apparently a finicky element to analyze by mass spectrometry. Maybe someone should make a Sm-face emoji.

Isotope analysis by TIMS is FUN

May 23rd, 2017

Chapel Hill, NC – Wooster Geologists have been hard at work preparing samples for isotope analysis. Now that sample preparation is complete, the next step is to analyze them on the thermal ionization mass spectrometer (TIMS). In the TIMS, a sample heats up until it ionizes, created a beam of charged particles.

The charged particles are sent through a mass spectrometer, which accelerates the ions through a curved path in a magnetic field. The ions separate based on their mass to charge ratio. The separated beams of ions are sent to collectors that convert the ions into an electrical signal that can be used to determine the sample’s isotopic composition. Figure from Revesz et al. (2001).

For a complete overview of how the TIMS works, check out this website at SERC.

 

Our tiny samples get loaded onto tiny filaments that heat up in the instrument. The filaments are stored in neat, orderly rows in a cabinet in the TIMS lab. If you look closely, you’ll see the flat ribbon onto which we’ll mount our samples.

You can imagine that the filament loading process is as meticulous as the sample preparation work. Here, Ben Kumpf (’18) pipettes a sample onto the filament.

This is what our sample looks like before we heat up the filament. It’s a single drop.

The filaments will get loaded into the TIMS instrument. This is one of the TIMS instruments here at the University of North Carolina Chapel Hill that we’ll use to analyze for strontium (Sr).

This is the exciting part, when we hope that all of our hard work as paid off. It’s a lot of effort for a single data point, but we know it’s well worth it.

References

Revesz, K.M., Landwehr, J.M., and Keybl, J. 2001. Measurement of bigsymbol13C and bigsymbol18O Isotopic Ratios Of CaCO3 using a Thermoquest Finnigan GasBench II Delta Plus XL Continuous Flow Isotope Ratio Mass Spectrometer with Application to Devils Hole Core DH-11 Calcite: USGS Open-File Report 01-257. US Government Printing Office.

Extracting a single element from a rock

May 20th, 2017

Chapel Hill, NC – As you know, Ben Kumpf (’18) and I are working in the Isotope Geochemistry lab at UNC Chapel Hill. We are measuring isotopes of strontium (Sr), lead (Pb) and neodymium (Nd) in basaltic pillow lavas from northern British Columbia. In order to measure the elements, we need to isolate them from the rest of the elements that make up our rocks. We purify individual elements using the method of column chemistry. A column is like a filter for elements; we pass our sample through the column and the column captures the element of interest, then we release and collect the element off the column to be analyzed later.

The first step to preparing our samples is to dissolve our rock powders in an acid solution. Ben Kumpf (’18) weighs small amounts of rock powder into Teflon vials. We add a series of acids to the vials and let them sit on a hotplate for a day or two until the powders are completely dissolved.

Once the samples are dissolved, we measure out a small amount of the solution into a new vial to run it through the column chemistry process. The first step to make a column “load” solution is to dry the sample solution down to a powder on a hotplate.

To the dried-down powder, we add an acid that is appropriate for the column that we’re using. For Sr, we’re adding nitric acid to the vials.

Now we’re ready to set up the columns. Dr. Ryan Mills (psychedelic lab coat) is showing Ben Kumpf (’18) how to add the resin.

This is what a column looks like up close. It’s suspended above a waste beaker. The white material that is filling the tube and neck is the resin. You can see it still settling out of solution. The resin that we use to isolate Sr was developed in response to the Chernobyl accident when it became necessary to remove radioactive Sr from milk (Vajda and Kim, 2010).

The chemical column process involves adding a series of solutions to the columns in a sequence that cleans the resin, conditions the resin for the sample load solution, introduces the sample, and rinses the sample through the resin. There’s a lot of pipetting and waiting for the solutions to move through the column during this stage.

Samples are centrifuged prior to loading. The centrifuge separates any undissolved solids from the liquid so that we only add the liquid portion to the column.

These columns are loaded with our Pb solutions.

Now that our sample has passed through the column, we release all of the Sr or Pb off of the column and collect it in our sample vial.

The last step in the process is to dry down the sample one final time. This makes a tiny bead at the bottom our vial. We will load this bead into a mass spectrometer to measure the isotope composition.

Now you can see why we need do our sample preparation in a clean lab.

References

Vajda, N. and Kim, C.-K. 2010. Determination of radiostrontium isotopes: A review of analytical methodology. Applied Radiation and Isotopes 68: 2306-2326.

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