USAP-DC

Intellectual Merit:
Magmas generated during subduction of oceanic lithosphere beneath active continental margins typically have a calc-alkaline chemistry. However, igneous rocks with signatures usually associated with anorogenic magmatism are increasingly being found with calc-alkaline rocks in subduction zones. These enigmatic rocks provide insight into a variety of magmatic and structural processes that are fundamental to subduction zone dynamics but processes that lead to their petrogenesis remain a matter of debate. This project will investigate the Koettlitz Glacier Alkaline Province (KGAP) in the Transantarctic Mountains, which is a section through a Na-alkaline province bounded to the north and south by calc-alkaline magmatism. This province potentially contains key information on the thermo-mechanical processes leading to generation of Na-alkaline rocks in subduction systems. The PI will examine structures that bound the KGAP as well as intrusives and metasedimentary rocks contained within it to determine the tectonomagmatic history in the framework of two end-member hypotheses: the KGAP represents a crustal-scale extensional or transtensional domain in a subduction setting; or the KGAP formed in response to ridge subduction.

Broader impacts:
This study will train three graduate and three undergraduate students incorporating hands-on experience with state of the art instrumentation. Each summer, four high school students will be incorporated into various aspects of the laboratory-based research through the UCSB research mentorship program. This project will stimulate refinement of in-situ LA-ICPMS methods and development of collaborative linkages with Antarctic geologists at GNS Science in New Zealand. Results will be disseminated via papers and presentations at international conferences.

Person	Role
Cottle, John	Investigator

Antarctic Earth Sciences

Award # 1043152

NSF-ANT10-43152

None in the Database

Repository	Title (link)	Format(s)	Status
EarthChem	EarthChem Library #925.	None	bad_url

1. Nelson, D.A., Cottle, J.M. 2018. The secular development of accretionary orogens: linking the Gondwana magmatic arc record of West Antarctica, Australia and South America. Gondwana Research. (doi:10.1016/j.gr.2018.06.002)
2. Hagen-Peter, G.A., Cottle, J.M. 2017. Evaluating the relative roles of crustal growth versus reworking through continental arc magmatism: A case study from the Ross orogen, Antarctica. (doi:10.1016/j.gr.2017.11.006)
3. Hagen‐Peter, G., Cottle, J. M., Smit, M., & Cooper, A. F. (2016). Coupled garnet Lu–Hf and monazite U–Pb geochronology constrain early convergent margin dynamics in the Ross orogen, Antarctica. Journal of Metamorphic Geology, 34(4), 293–319. (doi:10.1111/jmg.12182)
4. Nelson, D. A., & Cottle, J. M. (2017). Long-Term Geochemical and Geodynamic Segmentation of the Paleo-Pacific Margin of Gondwana: Insight From the Antarctic and Adjacent Sectors. Tectonics, 36(12), 3229–3247. (doi:10.1002/2017tc004611)
5. Hagen-Peter, G., & Cottle, J. M. (2016). Synchronous alkaline and subalkaline magmatism during the late Neoproterozoic–early Paleozoic Ross orogeny, Antarctica: Insights into magmatic sources and processes within a continental arc. Lithos, 262, 677–698. (doi:10.1016/j.lithos.2016.07.032)