Rock alterations | UDaily


Photos and illustrations courtesy of Jessica Warren and Tammy Beeson

Sierra Patterson’s interest in rocks, a recent University of Delaware graduate, began when she was a child and her great-uncle sent Patterson’s grandmother’s letters from her home in Arizona. Along with these letters he would also send a stone. His grandmother would read the letters to Patterson, show him the stones, and eventually start giving him the stones to keep.

This sparked a life of collecting rocks. Patterson began traveling to rock and gemstone shows with her father and estimates that she has around 300 pounds of stones in her bedroom at home. When she arrived at UD for a visit as a high school student, she realized she could study rocks and have a potential career in the field.

“I didn’t realize it was a career until I visited UD,” Patterson said. “I saw that they had a really great mineralogical museum and we went in and I spoke to someone there. My high school did not offer any kind of earth science course. I started to get more interested in it and applied for geological sciences at UD.

During her undergraduate studies at UD, Patterson worked on a research project with Jessica Warren, associate professor in the Department of Earth Sciences. They examined the alteration of mineral assemblages in abyssal peridotites – the main type of rock in the Earth’s upper mantle, the layer under the crust – of the Gakkel Ridge, a tectonic plate boundary located in the Arctic Ocean. .

Work began in 2017 with two other members of Warren’s lab group, Kendra Lynn and Cécile Prigent, both postdocs at the time, assisting Patterson with his first research project.

This research was recently published in the scientific journal Lithos with Patterson as the main author on the paper.

Patterson recently obtained a master’s degree in geological science from the University of South Carolina. She said it was amazing getting this research experience as an undergraduate at UD and thanks Warren, Lynn and Prigent for all of their help and advice.

“I definitely wouldn’t be where I am today without everything Jessica has done for me,” Patterson said. “Also, the two co-authors, Kendra and Cécile, have been great working with this project, it has really been a joint effort.

Warren said Patterson has set the bar high in terms of undergraduate research.

“Sierra stuck with that research when she was here and even when she was working on an MA she was going back and forth with us on drafts, so that was a huge engagement,” Warren said. “The other two co-authors on the article were both post-docs in my group and also spent a lot of time with Sierra, teaching her things and looking at samples with her. So it was nice to have such a collaborative effort.

Gakkel Ridge Research

To conduct the study, the research team examined 40 Gakkel’s peridotites from 19 dredges extending approximately 600 kilometers from the ridge.

The samples were collected during a 2001 research campaign of a German and US expedition to the Arctic Circle that collected rock samples from the seabed by dredging, essentially dragging a wire basket across the seabed.

“Every time they do that, they put a detector higher on the dredge wire that measures temperature anomalies and particle anomalies,” Warren said. “From there, they would see anomalies indicating the possibility of a hydrothermal plume.”

Warren said people are excited about hydrothermal plumes – spots on the ocean floor where warm fluids gush out – because they support unique ecosystems and communities of organisms in the deep ocean. But finding them is like finding a needle in a haystack.

Because Gakkel Ridge has plates that take a long time to separate, it is generally cool, which is not necessarily an environment in which scientists would expect to find a lot of hydrothermal vents.

However, the results of this study show minerals from hydrothermal alterations suggesting a probable relationship with the sites of the vent fields.

“We had spent a lot of time looking at the Gakkel samples and discussing how we could understand hydrothermal processes from a rock’s point of view,” Warren said. “There was data from the ocean water showing the activity of the hydrothermal plume, but no one had gone to the rocks and asked, ‘Does that confirm this and can we? tell more about what happened? ‘ “

To analyze the samples, they used a scanning electron microscope at UD WM Keck Center for Advanced Microscopy and Microanalysis (Keck CAMM), looking at the petrography, or description and classification, of rock minerals.

They rated these rock samples on a scale of 1 to 5, with 1 indicating unmodified minerals and 5 indicating completely weathered, finding most of them to be around 3.5 – moderately to heavily weathered.

Patterson said that by examining the weathering of mineral assemblages, they were able to learn more about temperature and pressure conditions from the flow of fluids in the oceanic lithosphere, the solid and rigid outer layer of the associated planet. to the oceanic crust.

“One of the most important and exciting findings of this article and project is that our models, which are then supported by petrographic observations, suggest that the formation of minerals, especially tremolite and talc, requires temperatures above 500 degrees Celsius, ”Patterson said. “This implies that the circulation of the hydrothermal fluid can be at depths greater than 20 kilometers in the Gakkel lithosphere.”

American Geophysical Union Conference

In addition to having recently published this article, another beneficial aspect of Patterson’s research is that in 2018 she had the opportunity to attend the American Geophysical Union Conference in Washington DC, where she gave a presentation. by poster on research.

“It was wonderful because not only did I get to talk about the research which was a great practice and people gave great feedback, but one of the people we spoke to ended up being a criticism on paper, ”Patterson said.

She added that it was a great experience to be in a big city for almost a week, to learn about new instruments in the field, and that she was able to network and meet many scientists, this which was particularly beneficial as she was on the pitch. to apply to graduate schools.

“With the graduate school around the corner and graduate applications, I was able to meet my future master’s advisor at the time, Michael Bizimis, at the conference, which was really nice because that it helped put a face to a name, ”Patterson said. “I also joined the Mineralogical Society of America, the Geological Society of America, and an organization of women in geology. It was so much fun and a great experience. “


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