Lamprophyres in the Ross Orogen, Antarctica
The mechanisms by which the deep crustal delaminates or "founders" and is returned to the mantle remains a fundamental problem in earth science. Specifically, little is known about the temporal and spatial scales over which this processoccurs or the mechanisms that trigger such catastrophic events. Igneous rocks highly enriched in potassium, called lamprophyres, are often emplaced during, and immediately after, termination of subduction and therefore potentially provide direct insight into foundering. These enigmatic rocks are important because they represent near-primary mantle melt compositions and therefore their age, geochemistry andpetrologic evolution reveal key information on both the composition of the upper mantle and its thermal state. Of equal importance, they reveal how these key parameters vary through both space and time. By evaluating lamprophyres along a subduction zone margin it is possible to extract: 1) local-scale information, such as the timing and duration of melting and the role of igneous crystallization processes in generation of isotopic heterogeneities; 2) along-strike variations in mantle source composition, temperature, and depth of melting 3) the plate-scale forces that control foundering and termination of subduction. This project will study a suite of lamprophyres along the axis of the Transantarctic Mountains, emplaced during the latest stages of the Neoproterozoic - Ordovician Ross orogeny, Antarctica (roughly 505 to 470 million years before present). High-precision geochronology (age determinations) will be combined with geochemical measurements on the rocks and minerals to understand the mechanisms and timing of deep crustal foundering/delamination.
Funding:
NSF-ANT-1443296 to J. Cottle: 09/01/15 - 08/30/18. “Petrologic Constraints on Subduction Termination From Lamprophyres, Ross Orogen, Antarctica” NSF Abstract
Publications:
Collaborators:
Dr. Simon Cox (GNS, Science, NZ)
Funding:
NSF-ANT-1443296 to J. Cottle: 09/01/15 - 08/30/18. “Petrologic Constraints on Subduction Termination From Lamprophyres, Ross Orogen, Antarctica” NSF Abstract
Publications:
Collaborators:
Dr. Simon Cox (GNS, Science, NZ)
Alkaline magmatism within a continental arc, Ross orogen, Antarctica.
A-type Magmatism in the Transantarctic Mountains, Antarctica: Magmas generatedduring the early stages of the Neoproterozic - lower Paleozoic Ross Orogeny have similar compositions and similar emplacement histories in both the Southern Royal Society Range and Skelton Glacier areas. These alkaline or 'A'- type magmas have not been described from elsewhere in the Transantarctic Mountains (TAM). In the dry valleys to the north, and the central TAM to the south, Ross magmatism has the characteristic calc-alkaline signature of convergence and subduction along the paleo-pacific margin of the East Antarctic craton. 'A' type magmas, however, require an extensional or transtensional tectonic regime, despite their occurrence in a supposed convergent margin. Research is focussed on establishing the nature of magmatism immediately to the south of the Skelton Glacier in order to establish the scale of segmentation between convergent and extensional margins of the TAM. Comparison of the Ross Orogen of Southern Victoria land with present day active margins around the world will enable a paleotectonic reconstruction of this segment of the Gondwana Margin and an assessment of its relevance to the evolution of the orogenic belt extension through New Zealand and Australia.
Funding:
NSF-ANT-1043152 to J. Cottle: 01/01/11 - 12/31/13. “Exploring the Significance of Na-Alkaline Magmatism in Subduction Systems, a Case Study From the Ross Orogen, Antarctica”
Publications:
•Hagen-Peter, G. Cottle J.M., Smit, M.A. 2016. Coupled garnet Lu-Hf and monazite U-Pb geochronology constrain early convergent margin dynamics in the Ross orogen, Antarctica. Journal of Metamorphic Geology. DOI: 10.1111/jmg.12182. Hagen-Peter_etal_2016_JMG
•Hagen-Peter, G. Cottle J.M., Tulloch, A.J., Cox, S.C. 2015. Mixing between lithospheric mantle and crustal components in a short-lived subduction-related magma system in the Dry Valleys area, Antarctica: Insights from U-Pb and Hf isotopes and whole-rock geochemistry. GSA Lithosphere. doi:10.1130/L384.1 Hagen-Peter_etal_Lithosphere
•Cottle, J.M., & Cooper, A.F. 2006: The Fontaine Pluton: an early calc-alkaline gabbro from southern Victoria Land, Antarctica. New Zealand Journal of Geology & Geophysics v.49(2) p.177-189.
•Cottle, J.M., & Cooper, A.F. 2006: Geology, geochemistry and geochronology of an A-type granite in the Mulock Glacier Area, southern Victoria land, Antarctica. New Zealand Journal of Geology & Geophysics v.49(2) p.191-202
Collaborators:
Prof. Alan Cooper (University of Otago)
Dr. Simon Cox (GNS, Science, NZ)
Dr. Andy Tulloch (GNS, Science, NZ)
Note: Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Funding:
NSF-ANT-1043152 to J. Cottle: 01/01/11 - 12/31/13. “Exploring the Significance of Na-Alkaline Magmatism in Subduction Systems, a Case Study From the Ross Orogen, Antarctica”
Publications:
•Hagen-Peter, G. Cottle J.M., Smit, M.A. 2016. Coupled garnet Lu-Hf and monazite U-Pb geochronology constrain early convergent margin dynamics in the Ross orogen, Antarctica. Journal of Metamorphic Geology. DOI: 10.1111/jmg.12182. Hagen-Peter_etal_2016_JMG
•Hagen-Peter, G. Cottle J.M., Tulloch, A.J., Cox, S.C. 2015. Mixing between lithospheric mantle and crustal components in a short-lived subduction-related magma system in the Dry Valleys area, Antarctica: Insights from U-Pb and Hf isotopes and whole-rock geochemistry. GSA Lithosphere. doi:10.1130/L384.1 Hagen-Peter_etal_Lithosphere
•Cottle, J.M., & Cooper, A.F. 2006: The Fontaine Pluton: an early calc-alkaline gabbro from southern Victoria Land, Antarctica. New Zealand Journal of Geology & Geophysics v.49(2) p.177-189.
•Cottle, J.M., & Cooper, A.F. 2006: Geology, geochemistry and geochronology of an A-type granite in the Mulock Glacier Area, southern Victoria land, Antarctica. New Zealand Journal of Geology & Geophysics v.49(2) p.191-202
Collaborators:
Prof. Alan Cooper (University of Otago)
Dr. Simon Cox (GNS, Science, NZ)
Dr. Andy Tulloch (GNS, Science, NZ)
Note: Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation