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Research Spending & Results

Award Detail

Awardee:UNIVERSITY OF ALASKA FAIRBANKS
Doing Business As Name:University of Alaska Fairbanks Campus
PD/PI:
  • Sean Regan
  • (907) 474-5386
  • sregan5@alaska.edu
Award Date:06/04/2021
Estimated Total Award Amount: $ 290,273
Funds Obligated to Date: $ 290,273
  • FY 2021=$290,273
Start Date:07/01/2021
End Date:06/30/2024
Transaction Type:Grant
Agency:NSF
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.050
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Collaborative Research: Arc plutonism along the Denali Fault, Alaska: Possible fault controls on incremental magma transport and assembly along a long-lived strike-slip fault
Federal Award ID Number:2120831
DUNS ID:615245164
Parent DUNS ID:048679567
Program:Tectonics
Program Officer:
  • Stephen Harlan
  • (703) 292-7707
  • sharlan@nsf.gov

Awardee Location

Street:West Ridge Research Bldg 008
City:Fairbanks
State:AK
ZIP:99775-7880
County:Fairbanks
Country:US
Awardee Cong. District:00

Primary Place of Performance

Organization Name:University of Alaska Fairbanks Campus
Street:
City:Fairbanks
State:AK
ZIP:99775-7880
County:Fairbanks
Country:US
Cong. District:00

Abstract at Time of Award

Volcanoes above subduction zones almost always appear as an irregular or curvy line on the surface of the earth. Scientists have a general idea of why these “arc” volcanoes, such as the Cascade arc, create linear chains, but whether vertical faults that penetrate deep in the crust control their specific location, composition, and potential eruptive volume is a subject of much debate. Volcanoes erode quickly so a study of their large magmatic roots, called plutons, will provide a more spatially and temporally complete record to better understand whether vertical faults provide direct conduits between deeper crust, where magma is produced, and the upper crust, where magma forms a reservoir for volcanic eruptions. The Alaska Range has been shaped by subduction and translation for tens of millions of years, as southern Alaska moves westward relative to the Alaskan interior along the active Denali fault, which extends for over 2000 km and ruptured during a magnitude (Mw) 7.9 earthquake in 2002. A suite of 45-35-million-year-old arc plutons are spatially associated with the Denali fault. This proposed research will study the physical relationships of melt transport along a long-lived strike-slip fault (the Denali fault) to test how continental-scale structures may control the rates of transport of melt to the surface, geometry of pluton growth, and magma evolution. In addition, the Principal Investigators will try to use plutons analyzed during this study to provide better constraints on the long-term slip rate of the Denali fault. The project will include undergraduate students, graduate students, and professors from public universities that have diverse undergraduate programs. The tallest peak in North America, Denali (formerly Mt. McKinley), includes arc plutons of this study that are cut by the Denali fault. Outreach efforts will include developing a social media presence for the Denali fault and updating public-science dissemination exhibits at the Museum of the North in Fairbanks and Denali National Park. We will develop curriculum for the GeoForce learning community, a STEM-focused organization focused on engaging rural and first-generation students from Alaska. Crustal-scale structures are often linked to the transport of lower crustal melts through the upper crust. However, the mechanism(s) by which and if melt is transported along active strike-slip faults is still an ongoing problem in the petrology community. Distinguishing disparate mechanism(s) or combinations therein is critical for unraveling the complex interplay of granitoid petrogenesis in the upper crust, mass and thermal mantle-surface communication, and how structural processes are manifested in a petrologic system. The Denali Fault is a classic long-lived orogenic (> 2000 km) dextral strike-slip fault system with > 400 km of lateral offset associated with, and perhaps localizing, arc plutonism for over ~70 My. This research project will test the hypothesis that crustal-scale faults can facilitate melt transport and pluton construction that results in systematic temporal-spatial geochemical and petrophysical patterns linked to strike-slip motion. The research will include collecting a fault-relative petrochemical and petrophysical dataset on a suite of Eocene plutons on both sides and along a ~350 km transects of the Denali Fault to evaluate how magmatic processes are manifested at the spatial and temporal scales relevant to magma transport and emplacement along an orogenic-scale strike slip fault. Field characterization combined with whole rock major and trace element geochemistry, zircon U-Pb geochronology, and O isotopic tracer analysis will be applied with these fundamental objectives: 1) identify petrographic, geochemical, isotopic, and/or structural gradients and 2) interpret results as they relate to pluton geometry as well as to the Denali Fault. In addition to testing kinematic controls on granitoid petrogenesis, these data will resolve a long-standing problem in Cordilleran geology, by evaluating a potential Denali Fault piercing point. Preliminary data indicate a possible pluton correlation may exist across the Denali Fault that would indicate an average slip rate of 8-10 mm/yr since 40 Ma, similar to the present-day dextral slip rate in this section of the fault. Data from this study will provide a recipe for distinguishing actually offset plutons from a suite of similar intrusive bodies preferentially emplaced along a fault system and help explain temporal-spatial petrochemical and petrophysical variability during continental arc assembly along strike-slip faults. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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