Jan Mayen Island, seen from the R/V Poseidon, July 2012
The Elkins Research Group
My group's research focuses on using geochemistry to better understand Earth's dynamic processes, in particular how magmas are generated in the Earth's mantle layer and how they are emplaced to form new crust. Most of this work involves measuring major elements, trace elements, and isotope compositions in igneous rocks from continental rifts, ocean basins, hotspots, and anomalous volcanic areas, and using those geochemical measurements to interpret magma origins. Some recent and ongoing research projects are described below:
The Kane-Atlantis Supersegment of the Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a classic, slow-spreading mid-ocean ridge setting, and the Kane-Atlantis supersegment is among the best mapped and most intensively studied parts of that ridge. It contains many second-order ridge segments that exhibit a range of ridge morphologies, including both symmetrically- and asymmetrically-spreading sections. Ridges that diverge at slow rates, which constitute as much as 80% of the global mid-ocean ridge system, appear to be particularly sensitive to the factors that control ridge symmetry and crustal accretionary style, with as many as half of slow-spreading ridge segments exhibiting asymmetric character created by long-lived detachment faulting. For this project, we will measure short-lived U-series isotope compositions in fresh basalts from the entire supersegment, with the goal of directly comparing the volcanism occurring at symmetric segments to asymmetric segments. The study focuses on the recent (2012) suite of samples collected from the Kane-Atlantis supersegment under chief scientists Charlie Langmuir and Javier Escartin, with the goal of exploring the deeper Earth characteristics beneath mid-ocean ridges. The ultimate goal of this study is to develop a more complete global model for crustal creation at mid-ocean ridges and the factors that control that critical tectonic process. Research collaborations for this project include Harvard University, University of Wyoming, and LLNL. There is room for one additional masters student (or one part of a larger doctoral project) to work on this NSF-funded study.
North Atlantic Mid-Ocean Ridges
The mid-ocean ridge system north of Iceland (including the Kolbeinsey, Mohns, Knipovich, and Gakkel Ridges) provides an excellent set of circumstances for assessing mantle melting and ocean crust generation at slow and ultraslow spreading rates. These ridges range from 18 to less than 12 mm/yr. in spreading rate, and experience variable influence and magmatic input from the Iceland and Jan Mayen hotspots. The regional mantle composition varies dramatically along the ridge axis, as does seafloor axial depth, which ranges from the subaerial rifting on Iceland to regions with little or no basaltic crust along the Gakkel Ridge. Much of my past research has focused on the geochemical makeup of fresh basalts erupted along this system of mid-ocean ridges, which provide clues to the melting processes occurring in the underlying mantle melting regime.
In addition to major and trace element concentrations and Sr-Nd-Hf-Pb radiogenic isotope compositions, our research added U-Th-Pa-Ra short-lived isotope measurements to the North Atlantic ridge data set. These isotopes are sensitive to the melting process, particularly melting rate and the presence of the mineral garnet in the melting regime. The results suggest that a combination of mantle temperature variations and source compositional heterogeneities influence the production of magma and growth of new ocean crust in the Arctic Ocean (Elkins et al., 2011; 2014). This work was the result of collaboration with scientists from WHOI in Woods Hole, MA, University of Wyoming, Ecole Normale Superieure de Lyon, University of Bristol, GEOMAR in Kiel, Germany, and University of Iowa. Further research into the geochemistry of North Atlantic and global MORB is ongoing with these and additional partners, including UT at Austin and University of Southampton. No large project in my group currently focuses on this region, but there is room for future study and potential graduate student research.
Jan Mayen Island and the Eggvin Bank
The group's recent research has included a focused case study of the geographic region immediately around the Jan Mayen Island volcanic hotspot in the North Atlantic basin, for which we measured the geochemistry of lavas from the Northern Kolbeinsey Ridge, the Southern Mohns Ridge, and Jan Mayen Island itself. In collaboration with scientists at GEOMAR in Kiel, Germany, we went to sea aboard the R/V Poseidon in 2012 to map the seafloor on the Northern Kolbeinsey Ridge and shallow Eggvin Bank (see Yeo et al., 2016), to sample fresh lava flows, and to add additional high resolution images for select areas using the AUV Abyss. That expedition resulted in the identification of a previously unknown, large, volcanically active seamount on the Eggvin Bank.
Geochemical analysis of these newly collected basalt samples, and comparison with lavas from the nearby Southern Mohns Ridge and Jan Mayen Island, produced much higher resolution geochemical coverage than previously existed for this tectonically and volcanically interesting region. New major and trace element data, Sr-Nd-Hf-Pb radiogenic isotope data, and U-Th-Ra isotope data has produced new insights into the role of eclogite rocks in the mantle source region beneath Jan Mayen Island and the Eggvin Bank, which seem to both overlie anomalous mantle compositions and melting regimes (Elkins et al., 2016a; 2016b). This work was the product of collaboration between scientists at University of Wyoming, GEOMAR in Kiel, Germany, University of Bergen, University of Iowa, and Ecole Normale Superieure de Lyon. As a follow-up, researchers returned to this area in July 2016 to conduct additional mapping and sampling research. This NSF-funded project has been completed and published, but there could be future research opportunities in this area.
Geochemical Modeling of Uranium-Series Isotopes
Measured isotopic compositions for the U-series system (isotopes of the elements U, Th, Pa, Ra, and others) in basalts are commonly interpreted through comparison with complex model calculations of the melting process. These models consider the importance of timing in the melt process as well as the effects of time on short-lived isotopic decay. Ongoing developments in modeling aim to improve the accuracy of our interpretations of regional and global geochemical data sets, leading to a better understanding of melting and melt transport processes on Earth. Some of this work is being conducted in collaboration with a team of scientists through the ENKI modeling project. Students with experience in computer coding and programming and an interest in applied modeling for graduate study should contact me about modeling opportunities.
The Central Atlantic Magmatic Province
This enormous large igneous province formed at the Triassic-Jurassic boundary, when initial rifting of the central Atlantic contributed to the breakup of Pangea. That rift ultimately formed the central Atlantic ocean basin. In contradiction with some earlier research, recent geochemical results (e.g., Merle et al., 2014) have suggested that continental rifting initiated without the influence of a mantle plume, causing the mantle lithosphere and underlying asthenosphere to extensively melt. We have measured new hafnium isotope compositions to further test working hypotheses for CAMP magma formation. This research seeks to better understand the role of the mantle in the initiation of continental rifting and eventual ocean basin formation, and is being conducted with collaborators from the University of Padova, UT at Austin, University of South Carolina, and several universities in Brazil. This research has been funded by UNL's College of Arts and Sciences, and our new results were presented at the Fall AGU Meeting in 2017 (Elkins et al., 2017 AGU Eos; manuscript in prep.). An NSF grant proposal to conduct additional geochemistry research on CAMP is planned for 2018 and will include opportunities for student research.
The Central Highlands Diffuse Igneous Province
This study explores the recent and diffuse volcanic activity and its associations with faulting and tectonic activity in Vietnam. The project aims to test working models for extension and volcanic activity in this collision-adjacent region, to better explain the tectonic setting and understand why volcanism and active faulting are occurring in Indochina. One scenario is that rifting is occurring in an extensional environment associated with volcanism, adjacent to the formerly diverging South China Sea. An alternative, preferred based on preliminary results, is that tectonic extrusion associated with the Himalayan collision is causing block rotation and coupled mantle upwelling. With structural geologist and tectonicist C. Burberry from UNL and collaborators from the Vietnam Academy of Science and Technology (VAST), we conducted exploratory fieldwork in the winter of 2016-2017 and are planning a larger field and laboratory-based study. The preliminary research and fieldwork was funded by UNL's College of Arts and Sciences and was presented at the Fall AGU Meeting in 2017 (Burberry et al., 2017 AGU Eos; manuscript in prep.). The NSF proposal for this project is currently pending and would support multiple graduate students.
Facilities
The group's geochemical research is principally conducted in the UNITE (University of Nebraska Isotope and Trace Element) geochemistry lab in Bessey Hall at the University of Nebraska-Lincoln, in collaboration with larger mass spectrometry facilities, including University of Wyoming, UT at Austin, and University of South Carolina, among others. The UNITE lab, an ISO-7 cleanroom with class-100 flow boxes for handling of low-level materials, is used for the separation of trace metals from geologic materials. Additional geochemical work and measurements are conducted in top-notch facilities at collaborating institutions, including those listed below.
Funding
To-date, this group's research has been funded through multiple grants from the National Science Foundation, as well as through generous internal faculty research grants from Bryn Mawr College and UNL's College of Arts and Sciences.
Collaborating Institutions
Past and ongoing collaborations have included scientific researchers at WHOI, University of Wyoming, GEOMAR, Ecole Normale Superieure de Lyon, University of Bristol, University of Bergen, University of Iowa, Harvard University, UT at Austin, University of Padova, University of South Carolina, VAST, and LLNL, among others.
My group's research focuses on using geochemistry to better understand Earth's dynamic processes, in particular how magmas are generated in the Earth's mantle layer and how they are emplaced to form new crust. Most of this work involves measuring major elements, trace elements, and isotope compositions in igneous rocks from continental rifts, ocean basins, hotspots, and anomalous volcanic areas, and using those geochemical measurements to interpret magma origins. Some recent and ongoing research projects are described below:
The Kane-Atlantis Supersegment of the Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a classic, slow-spreading mid-ocean ridge setting, and the Kane-Atlantis supersegment is among the best mapped and most intensively studied parts of that ridge. It contains many second-order ridge segments that exhibit a range of ridge morphologies, including both symmetrically- and asymmetrically-spreading sections. Ridges that diverge at slow rates, which constitute as much as 80% of the global mid-ocean ridge system, appear to be particularly sensitive to the factors that control ridge symmetry and crustal accretionary style, with as many as half of slow-spreading ridge segments exhibiting asymmetric character created by long-lived detachment faulting. For this project, we will measure short-lived U-series isotope compositions in fresh basalts from the entire supersegment, with the goal of directly comparing the volcanism occurring at symmetric segments to asymmetric segments. The study focuses on the recent (2012) suite of samples collected from the Kane-Atlantis supersegment under chief scientists Charlie Langmuir and Javier Escartin, with the goal of exploring the deeper Earth characteristics beneath mid-ocean ridges. The ultimate goal of this study is to develop a more complete global model for crustal creation at mid-ocean ridges and the factors that control that critical tectonic process. Research collaborations for this project include Harvard University, University of Wyoming, and LLNL. There is room for one additional masters student (or one part of a larger doctoral project) to work on this NSF-funded study.
North Atlantic Mid-Ocean Ridges
The mid-ocean ridge system north of Iceland (including the Kolbeinsey, Mohns, Knipovich, and Gakkel Ridges) provides an excellent set of circumstances for assessing mantle melting and ocean crust generation at slow and ultraslow spreading rates. These ridges range from 18 to less than 12 mm/yr. in spreading rate, and experience variable influence and magmatic input from the Iceland and Jan Mayen hotspots. The regional mantle composition varies dramatically along the ridge axis, as does seafloor axial depth, which ranges from the subaerial rifting on Iceland to regions with little or no basaltic crust along the Gakkel Ridge. Much of my past research has focused on the geochemical makeup of fresh basalts erupted along this system of mid-ocean ridges, which provide clues to the melting processes occurring in the underlying mantle melting regime.
In addition to major and trace element concentrations and Sr-Nd-Hf-Pb radiogenic isotope compositions, our research added U-Th-Pa-Ra short-lived isotope measurements to the North Atlantic ridge data set. These isotopes are sensitive to the melting process, particularly melting rate and the presence of the mineral garnet in the melting regime. The results suggest that a combination of mantle temperature variations and source compositional heterogeneities influence the production of magma and growth of new ocean crust in the Arctic Ocean (Elkins et al., 2011; 2014). This work was the result of collaboration with scientists from WHOI in Woods Hole, MA, University of Wyoming, Ecole Normale Superieure de Lyon, University of Bristol, GEOMAR in Kiel, Germany, and University of Iowa. Further research into the geochemistry of North Atlantic and global MORB is ongoing with these and additional partners, including UT at Austin and University of Southampton. No large project in my group currently focuses on this region, but there is room for future study and potential graduate student research.
Jan Mayen Island and the Eggvin Bank
The group's recent research has included a focused case study of the geographic region immediately around the Jan Mayen Island volcanic hotspot in the North Atlantic basin, for which we measured the geochemistry of lavas from the Northern Kolbeinsey Ridge, the Southern Mohns Ridge, and Jan Mayen Island itself. In collaboration with scientists at GEOMAR in Kiel, Germany, we went to sea aboard the R/V Poseidon in 2012 to map the seafloor on the Northern Kolbeinsey Ridge and shallow Eggvin Bank (see Yeo et al., 2016), to sample fresh lava flows, and to add additional high resolution images for select areas using the AUV Abyss. That expedition resulted in the identification of a previously unknown, large, volcanically active seamount on the Eggvin Bank.
Geochemical analysis of these newly collected basalt samples, and comparison with lavas from the nearby Southern Mohns Ridge and Jan Mayen Island, produced much higher resolution geochemical coverage than previously existed for this tectonically and volcanically interesting region. New major and trace element data, Sr-Nd-Hf-Pb radiogenic isotope data, and U-Th-Ra isotope data has produced new insights into the role of eclogite rocks in the mantle source region beneath Jan Mayen Island and the Eggvin Bank, which seem to both overlie anomalous mantle compositions and melting regimes (Elkins et al., 2016a; 2016b). This work was the product of collaboration between scientists at University of Wyoming, GEOMAR in Kiel, Germany, University of Bergen, University of Iowa, and Ecole Normale Superieure de Lyon. As a follow-up, researchers returned to this area in July 2016 to conduct additional mapping and sampling research. This NSF-funded project has been completed and published, but there could be future research opportunities in this area.
Geochemical Modeling of Uranium-Series Isotopes
Measured isotopic compositions for the U-series system (isotopes of the elements U, Th, Pa, Ra, and others) in basalts are commonly interpreted through comparison with complex model calculations of the melting process. These models consider the importance of timing in the melt process as well as the effects of time on short-lived isotopic decay. Ongoing developments in modeling aim to improve the accuracy of our interpretations of regional and global geochemical data sets, leading to a better understanding of melting and melt transport processes on Earth. Some of this work is being conducted in collaboration with a team of scientists through the ENKI modeling project. Students with experience in computer coding and programming and an interest in applied modeling for graduate study should contact me about modeling opportunities.
The Central Atlantic Magmatic Province
This enormous large igneous province formed at the Triassic-Jurassic boundary, when initial rifting of the central Atlantic contributed to the breakup of Pangea. That rift ultimately formed the central Atlantic ocean basin. In contradiction with some earlier research, recent geochemical results (e.g., Merle et al., 2014) have suggested that continental rifting initiated without the influence of a mantle plume, causing the mantle lithosphere and underlying asthenosphere to extensively melt. We have measured new hafnium isotope compositions to further test working hypotheses for CAMP magma formation. This research seeks to better understand the role of the mantle in the initiation of continental rifting and eventual ocean basin formation, and is being conducted with collaborators from the University of Padova, UT at Austin, University of South Carolina, and several universities in Brazil. This research has been funded by UNL's College of Arts and Sciences, and our new results were presented at the Fall AGU Meeting in 2017 (Elkins et al., 2017 AGU Eos; manuscript in prep.). An NSF grant proposal to conduct additional geochemistry research on CAMP is planned for 2018 and will include opportunities for student research.
The Central Highlands Diffuse Igneous Province
This study explores the recent and diffuse volcanic activity and its associations with faulting and tectonic activity in Vietnam. The project aims to test working models for extension and volcanic activity in this collision-adjacent region, to better explain the tectonic setting and understand why volcanism and active faulting are occurring in Indochina. One scenario is that rifting is occurring in an extensional environment associated with volcanism, adjacent to the formerly diverging South China Sea. An alternative, preferred based on preliminary results, is that tectonic extrusion associated with the Himalayan collision is causing block rotation and coupled mantle upwelling. With structural geologist and tectonicist C. Burberry from UNL and collaborators from the Vietnam Academy of Science and Technology (VAST), we conducted exploratory fieldwork in the winter of 2016-2017 and are planning a larger field and laboratory-based study. The preliminary research and fieldwork was funded by UNL's College of Arts and Sciences and was presented at the Fall AGU Meeting in 2017 (Burberry et al., 2017 AGU Eos; manuscript in prep.). The NSF proposal for this project is currently pending and would support multiple graduate students.
Facilities
The group's geochemical research is principally conducted in the UNITE (University of Nebraska Isotope and Trace Element) geochemistry lab in Bessey Hall at the University of Nebraska-Lincoln, in collaboration with larger mass spectrometry facilities, including University of Wyoming, UT at Austin, and University of South Carolina, among others. The UNITE lab, an ISO-7 cleanroom with class-100 flow boxes for handling of low-level materials, is used for the separation of trace metals from geologic materials. Additional geochemical work and measurements are conducted in top-notch facilities at collaborating institutions, including those listed below.
Funding
To-date, this group's research has been funded through multiple grants from the National Science Foundation, as well as through generous internal faculty research grants from Bryn Mawr College and UNL's College of Arts and Sciences.
Collaborating Institutions
Past and ongoing collaborations have included scientific researchers at WHOI, University of Wyoming, GEOMAR, Ecole Normale Superieure de Lyon, University of Bristol, University of Bergen, University of Iowa, Harvard University, UT at Austin, University of Padova, University of South Carolina, VAST, and LLNL, among others.