Spanning 2500 km along the western margin of North America are 780 Ma dykes, sills, and minor volcanic packages of the Gunbarrel Large Igneous Province. This study focuses on southern (northwestern United States) and central (northern British Columbia) Gunbarrel intrusions and metavolcanics rocks of the Irene and Huckleberry formation (Washington State). Southern Gunbarrel U–Pb ages range from 780 to 769 Ma and new U–Pb zircon dates for the Turah and Rogers Pass sills are 778.6 ± 0.7 and 778.7 ± 0.9 Ma, respectively. Southern Gunbarrel intrusions are medium- to coarse-grained diabases that are moderately evolved basaltic, continental tholeiites. Intrusions display negative Nb–Ta and positive Pb anomalies in normalized multielement plots, and εNd780 values vary from +3.6 to +1.5. The Irene and Huckleberry volcanic rocks are E-MORB in composition with higher εNd780 (+5 to +6) and likely represent partial melts of a mantle plume responsible for the Gunbarrel event. Assuming an Irene and Huckleberry parental magma, mixing models indicate that the southern Gunbarrel magmas were crustally contaminated, but local host rocks are not appropriate crustal contaminants. The modeling points to average upper crust as the crustal contaminant, with an εNd780 of approximately –2. This crustal contaminant likely resides on the craton impinged upon by the mantle plume. The remarkable geochemical homogeneity of Gunbarrel intrusions from the Yukon to Wyoming is best explained if primary, plume-derived E-MORB magmas were contaminated in large magma reservoirs near the plume centre and were then injected laterally into the crust 100s to 1000s of kilometres from the reservoir.
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Research Article|
February 12, 2019
Geochemical, isotopic, and U–Pb zircon study of the central and southern portions of the 780 Ma Gunbarrel Large Igneous Province in western Laurentia1
Alana Mackinder;
Alana Mackinder
a
Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
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Brian L. Cousens;
a
Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.Corresponding author: Brian L. Cousens (email: [email protected]).
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Richard E. Ernst;
Richard E. Ernst
a
Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.b
Faculty of Geology and Geography, Tomsk State University, 36 Lenin Ave, Tomsk 634050, Russia.
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Kevin R. Chamberlain
Kevin R. Chamberlain
b
Faculty of Geology and Geography, Tomsk State University, 36 Lenin Ave, Tomsk 634050, Russia.c
Department of Geology and Geophysics, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071-3006, USA.
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Alana Mackinder
a
Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.a
Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
Richard E. Ernst
a
Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.b
Faculty of Geology and Geography, Tomsk State University, 36 Lenin Ave, Tomsk 634050, Russia.
Kevin R. Chamberlain
b
Faculty of Geology and Geography, Tomsk State University, 36 Lenin Ave, Tomsk 634050, Russia.c
Department of Geology and Geophysics, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071-3006, USA.Corresponding author: Brian L. Cousens (email: [email protected]).
Publisher: Canadian Science Publishing
Received:
27 Mar 2018
Accepted:
28 Jan 2019
First Online:
23 Jul 2019
Online ISSN: 1480-3313
Print ISSN: 0008-4077
Published by NRC Research Press
Canadian Journal of Earth Sciences (2019) 56 (7): 738–755.
Article history
Received:
27 Mar 2018
Accepted:
28 Jan 2019
First Online:
23 Jul 2019
Citation
Alana Mackinder, Brian L. Cousens, Richard E. Ernst, Kevin R. Chamberlain; Geochemical, isotopic, and U–Pb zircon study of the central and southern portions of the 780 Ma Gunbarrel Large Igneous Province in western Laurentia. Canadian Journal of Earth Sciences 2019;; 56 (7): 738–755. doi: https://doi.org/10.1139/cjes-2018-0083
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Index Terms/Descriptors
- Absaroka Range
- absolute age
- Beartooth Mountains
- British Columbia
- Canada
- chemical composition
- diabase
- fractional crystallization
- Idaho
- igneous rocks
- intrusions
- isotope ratios
- isotopes
- large igneous provinces
- Laurentia
- Madison County Montana
- magmas
- mantle
- metals
- metamorphic rocks
- metavolcanic rocks
- mineral composition
- Montana
- Nd-144/Nd-143
- neodymium
- Neoproterozoic
- nesosilicates
- North America
- orthosilicates
- plutonic rocks
- Precambrian
- Proterozoic
- Purcell Mountains
- rare earths
- Rocky Mountains
- silicates
- sills
- stable isotopes
- Tobacco Root Mountains
- Tonian
- U. S. Rocky Mountains
- U/Pb
- United States
- upper Precambrian
- Washington
- Western Canada
- Wyoming
- zircon
- zircon group
- Huckleberry Formation
- Irene Formation
- Gunbarrel Province
- Rogers Pass Sill
- Turah Sill
Latitude & Longitude
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