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In some areas, hydrothermal systems also lead to the formation of large sulfide deposits that may contain key marine minerals.
Amy Gartman, PhD USGS Global Ocean Minerals The project’s lead researcher, on the most recent expedition, Ultra-fine scale seafloor mappingMendenhall postdocs Hope Ianiri, PhD, and Maria Figueroa, PhD, joined an international team of scientists including geologists, chemists, and biologists on a shipboard field trip aboard the R/V Falk (also)Operated by the Schmidt Ocean Institute.
The expedition’s research goals were multifaceted, but one of the main goals was to map the seafloor at ultra-high resolution. Only parts of the area the team visited had been previously mapped, and their new maps have orders of magnitude higher resolution, showing hydrothermal features in unprecedented detail.
Collecting samples with SuBastian
Based on these seafloor maps, the team then selected specific areas for further sample collection using the remotely operated vehicle (ROV) SuBastian. They collected geological and biological samples from hydrothermal environments ranging from hot black smoker chimneys to inactive sulfide spires. By sampling such a wide range of active hydrothermal environments, they hope to gain insight into how hydrothermal systems change over time.
Dr. Ianiri and Dr. Figueroa specifically collected rock and sediment cores from hydrothermal features and the surrounding area. Many of the rocks are fragments of hydrothermal chimneys, formed by precipitation of elements from the hydrothermal fluids, and therefore provide insight into the formation of marine minerals in this system.
In contrast, sediments closer to vents may have been deposited by hydrothermal plumes, the collapse of hydrothermal features, or sedimentation of water columns from primary production at the ocean surface. These sediments accumulated slowly over time, meaning deeper sediments are older. The scientists collected sediment cores up to 50 centimeters long, allowing them to tease out these different depositional processes over thousands of years.
Analyzing samples in the laboratory
Once collected, Dr. Ianiri and Dr. Figueroa will take the rocks and sediments back to PCMSC, where they and the Ocean Minerals team will analyze them further in the laboratory, performing a range of geochemical analyses.
For example, the Ocean Minerals team will measure major, minor, and trace elements and characterize the mineralogy of rocks and sediments. By looking at the mineralogy of sediment cores, they can begin to understand how hydrothermal processes and mineralization have changed over time.
In contrast, Dr. Ianiri will measure organic carbon stored in sediments. She will look for biomarkers, or compounds that act as “fingerprints” to identify hydrothermal and open-ocean sources. They will also measure the age of the rocks and sediments to understand when these different processes occurred. By combining these analyses with other geological, chemical and biological analyses conducted by colleagues on the expedition, the researchers will gain a comprehensive understanding of this hydrothermal system, including how the marine minerals were formed and the environmental context and ecosystems in which they occurred.
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