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 and modeling major elements, trace elements, and isotope compositions in igneous rocks from continental rifts, ocean basins, hotspots, and anomalous volcanic areas, and using that work to interpret magma origins. Some former and ongoing research projects are described below:
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 calculations consider the importance of timing in the melt process, including the effects of time on short-lived isotopic decay. Ongoing developments in modeling aim to improve our interpretations of regional and global geochemical data sets, leading to a better understanding of melting and melt transport processes on Earth. Recent work has been conducted in collaboration with scientists at LDEO, University of Utah, and others. This is currently an NSF-funded CAREER project, and research efforts are ongoing and active, with papers and projects already underway (e.g., Elkins et al., 2019, 2023; Elkins and Spiegelman, 2021; Elkins and Lambart, 2024). Some possible research directions in geochemical modeling are explored here.
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, the group at UNL measured short-lived U-series disequilibria and radiogenic (Sr-Nd-Pb-Hf) isotope compositions in fresh basalts from the supersegment, with the goal of evaluating magma origins on short and long length-scales. The study focuses on the 2012 suite of samples collected from the Kane-Atlantis supersegment under chief scientists Charlie Langmuir and Javier Escartin aboard the R/V Knorr. The ultimate goal of this study is to develop a more complete model for ocean crust formation at mid-ocean ridges and for the factors that control that process. Research collaborations for this project included Harvard University and the University of Wyoming. This project funded two graduate students and several undergraduate researchers, and ultimately involved a large number of colleagues and students in aspects of the research. Data analysis is complete, and publications exploring the new data set are in progress.
The Central Highlands Diffuse Igneous Province
This study explored the recent and diffuse volcanic activity and its associations with faulting and tectonic activity in Vietnam. The project aimed to test working models for tectonics 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 East Vietnam/South China Sea. An alternative, preferred based on our field and remote sensing results, is that tectonic extrusion associated with the Himalayan collision is causing block rotation and coupled mantle upwelling. Together with co-PI and structural geologist and tectonicist C. Burberry from UNL, and collaborators Hoang Nguyen from the Vietnam Academy of Science and Technology (VAST) and J. Lassiter at University of Texas at Austin, we developed and worked on a large NSF-funded project to study the tectonic setting of the Central Highlands. This project incorporated several seasons of field structural measurements, remote sensing methods, and geochemical analysis of basalts and xenoliths to better understand the origins of volcanic and tectonic activity in Indochina. This project supported multiple graduate students, and has produced one manuscript (Hobbs et al., 2023) and two additional draft manuscripts in progress (Richard et al., 2024; in prep.).
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 measured new hafnium isotope compositions to further test working hypotheses for CAMP magma formation. This research sought to better understand the role of the mantle in the initiation of continental rifting and eventual ocean basin formation, and was conducted with collaborators from the University of Padova, UT at Austin, University of South Carolina, and several universities in Brazil. This research was funded entirely by UNL's College of Arts and Sciences, and was published in Elkins et al. (2020).
North Atlantic Mid-Ocean Ridges
The mid-ocean ridge system north of Iceland (including the Kolbeinsey, Mohns, Knipovich, and Gakkel Ridges) provides an exciting 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. Our 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 suggested 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. Future research into the geochemistry of North Atlantic and global MORB is possible with these and additional partners, including the University of Southampton, and would include investigating the crustal accretionary process at mid-ocean ridges with very slow spreading rates but unusually high mantle temperatures and magma fluxes.
Jan Mayen Island and the Eggvin Bank
Additional past research includes an NSF-funded, 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 segment, 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, which hosts fresh popping rocks in the summit crater.
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 (including Elkins) returned to this area in July 2016 to conduct additional mapping and sampling research.
Facilities
The group's geochemical measurements are principally conducted in the UNITE (University of Nebraska Isotope and Trace Element) geochemistry lab in Bessey Hall at the University of Nebraska-Lincoln, which was built and is managed by Dr. Elkins and our research team. Our research is also conducted in collaboration with a number of external 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 primarily equipped for the separation of trace metals from geologic materials, and in the coming year we hope to add alpha counting capabilities to our facilities for measurement of additional short-lived isotopes. Additional geochemical work and measurements for individual projects 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, LDEO, University of Wyoming, University of Utah, 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, and VAST, 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 and modeling major elements, trace elements, and isotope compositions in igneous rocks from continental rifts, ocean basins, hotspots, and anomalous volcanic areas, and using that work to interpret magma origins. Some former and ongoing research projects are described below:
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 calculations consider the importance of timing in the melt process, including the effects of time on short-lived isotopic decay. Ongoing developments in modeling aim to improve our interpretations of regional and global geochemical data sets, leading to a better understanding of melting and melt transport processes on Earth. Recent work has been conducted in collaboration with scientists at LDEO, University of Utah, and others. This is currently an NSF-funded CAREER project, and research efforts are ongoing and active, with papers and projects already underway (e.g., Elkins et al., 2019, 2023; Elkins and Spiegelman, 2021; Elkins and Lambart, 2024). Some possible research directions in geochemical modeling are explored here.
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, the group at UNL measured short-lived U-series disequilibria and radiogenic (Sr-Nd-Pb-Hf) isotope compositions in fresh basalts from the supersegment, with the goal of evaluating magma origins on short and long length-scales. The study focuses on the 2012 suite of samples collected from the Kane-Atlantis supersegment under chief scientists Charlie Langmuir and Javier Escartin aboard the R/V Knorr. The ultimate goal of this study is to develop a more complete model for ocean crust formation at mid-ocean ridges and for the factors that control that process. Research collaborations for this project included Harvard University and the University of Wyoming. This project funded two graduate students and several undergraduate researchers, and ultimately involved a large number of colleagues and students in aspects of the research. Data analysis is complete, and publications exploring the new data set are in progress.
The Central Highlands Diffuse Igneous Province
This study explored the recent and diffuse volcanic activity and its associations with faulting and tectonic activity in Vietnam. The project aimed to test working models for tectonics 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 East Vietnam/South China Sea. An alternative, preferred based on our field and remote sensing results, is that tectonic extrusion associated with the Himalayan collision is causing block rotation and coupled mantle upwelling. Together with co-PI and structural geologist and tectonicist C. Burberry from UNL, and collaborators Hoang Nguyen from the Vietnam Academy of Science and Technology (VAST) and J. Lassiter at University of Texas at Austin, we developed and worked on a large NSF-funded project to study the tectonic setting of the Central Highlands. This project incorporated several seasons of field structural measurements, remote sensing methods, and geochemical analysis of basalts and xenoliths to better understand the origins of volcanic and tectonic activity in Indochina. This project supported multiple graduate students, and has produced one manuscript (Hobbs et al., 2023) and two additional draft manuscripts in progress (Richard et al., 2024; in prep.).
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 measured new hafnium isotope compositions to further test working hypotheses for CAMP magma formation. This research sought to better understand the role of the mantle in the initiation of continental rifting and eventual ocean basin formation, and was conducted with collaborators from the University of Padova, UT at Austin, University of South Carolina, and several universities in Brazil. This research was funded entirely by UNL's College of Arts and Sciences, and was published in Elkins et al. (2020).
North Atlantic Mid-Ocean Ridges
The mid-ocean ridge system north of Iceland (including the Kolbeinsey, Mohns, Knipovich, and Gakkel Ridges) provides an exciting 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. Our 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 suggested 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. Future research into the geochemistry of North Atlantic and global MORB is possible with these and additional partners, including the University of Southampton, and would include investigating the crustal accretionary process at mid-ocean ridges with very slow spreading rates but unusually high mantle temperatures and magma fluxes.
Jan Mayen Island and the Eggvin Bank
Additional past research includes an NSF-funded, 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 segment, 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, which hosts fresh popping rocks in the summit crater.
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 (including Elkins) returned to this area in July 2016 to conduct additional mapping and sampling research.
Facilities
The group's geochemical measurements are principally conducted in the UNITE (University of Nebraska Isotope and Trace Element) geochemistry lab in Bessey Hall at the University of Nebraska-Lincoln, which was built and is managed by Dr. Elkins and our research team. Our research is also conducted in collaboration with a number of external 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 primarily equipped for the separation of trace metals from geologic materials, and in the coming year we hope to add alpha counting capabilities to our facilities for measurement of additional short-lived isotopes. Additional geochemical work and measurements for individual projects 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, LDEO, University of Wyoming, University of Utah, 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, and VAST, among others.
