- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Faculty Research and Publications /
- Wrangellia flood basalts in Alaska: A record of plume-lithosphere...
Open Collections
UBC Faculty Research and Publications
Wrangellia flood basalts in Alaska: A record of plume-lithosphere interaction in a Late Triassic accreted oceanic plateau. Greene, Andrew R.; Scoates, James; Weis, Dominique
Abstract
The Wrangellia flood basalts are part of one of the best exposed accreted oceanic plateaus on Earth. They provide important constraints on the construction of these vast submarine edifices and the source and temporal evolution of magmas for a plume head impinging beneath oceanic lithosphere. Wrangellia flood basalts (∼231–225 Ma) extend ∼450 km across southern Alaska (Wrangell Mountains and Alaska Range) where ∼3.5 km of mostly subaerial flows are bounded by late Paleozoic arc volcanics and Late Triassic limestone. The vast majority of the flood basalts are light rare earth element (LREE) -enriched high-Ti basalt (1.6–2.4 wt % TiO2) with uniform ocean island basalt (OIB) -type Pacific mantle isotopic compositions (ɛ Hf(t) = +9.7 to +10.7; ɛ Nd(t) = +6.0 to +8.1; t = 230 Ma). However, the lowest ∼400 m of stratigraphy in the Alaska Range is LREE-depleted low-Ti basalt (0.4–1.2 wt % TiO2) with pronounced negative high field strength element (HFSE) anomalies and Hf isotopic compositions (ɛ Hf(t) = +13.7 to +18.4) that are decoupled from Nd (ɛ Nd(t) = +4.6 to +5.4) and displaced well above the OIB mantle array (Δɛ Hf = +4 to +8). The radiogenic Hf of the low-Ti basalts indicates involvement of a component that evolved with high Lu/Hf over time but not with a correspondingly high Sm/Nd. The radiogenic Hf and HFSE-depleted signature of the low-Ti basalts suggest pre-existing arc lithosphere was involved in the formation of flood basalts that erupted early in construction of part of the Wrangellia plateau in Alaska. Thermal and mechanical erosion of the base of the lithosphere by the impinging plume head may have led to melting of arc lithosphere or interaction of plume-derived melts and subduction-modified mantle. The high-Ti lavas dominate the main phase of construction of the plateau and were derived from a depleted mantle source distinct from the source of MORB and with compositional similarities to that of ocean islands (e.g., Hawaii) and plateaus (e.g., Ontong Java) in the Pacific Ocean. An edited version of this paper was published by AGU. Copyright 2008 American Geophysical Union.
Item Metadata
Title |
Wrangellia flood basalts in Alaska: A record of plume-lithosphere interaction in a Late Triassic accreted oceanic plateau.
|
Creator | |
Contributor | |
Publisher |
American Geophysical Union
|
Date Issued |
2008
|
Description |
The Wrangellia flood basalts are part of one of the best exposed accreted oceanic plateaus on Earth. They provide important constraints on the construction of these vast submarine edifices and the source and temporal evolution of magmas for a plume head impinging beneath oceanic lithosphere. Wrangellia flood basalts (∼231–225 Ma) extend ∼450 km across southern Alaska (Wrangell Mountains and Alaska Range) where ∼3.5 km of mostly subaerial flows are bounded by late Paleozoic arc volcanics and Late Triassic limestone. The vast majority of the flood basalts are light rare earth element (LREE) -enriched high-Ti basalt (1.6–2.4 wt % TiO2) with uniform ocean island basalt (OIB) -type Pacific mantle isotopic compositions (ɛ Hf(t) = +9.7 to +10.7; ɛ Nd(t) = +6.0 to +8.1; t = 230 Ma). However, the lowest ∼400 m of stratigraphy in the Alaska Range is LREE-depleted low-Ti basalt (0.4–1.2 wt % TiO2) with pronounced negative high field strength element (HFSE) anomalies and Hf isotopic compositions (ɛ Hf(t) = +13.7 to +18.4) that are decoupled from Nd (ɛ Nd(t) = +4.6 to +5.4) and displaced well above the OIB mantle array (Δɛ Hf = +4 to +8). The radiogenic Hf of the low-Ti basalts indicates involvement of a component that evolved with high Lu/Hf over time but not with a correspondingly high Sm/Nd. The radiogenic Hf and HFSE-depleted signature of the low-Ti basalts suggest pre-existing arc lithosphere was involved in the formation of flood basalts that erupted early in construction of part of the Wrangellia plateau in Alaska. Thermal and mechanical erosion of the base of the lithosphere by the impinging plume head may have led to melting of arc lithosphere or interaction of plume-derived melts and subduction-modified mantle. The high-Ti lavas dominate the main phase of construction of the plateau and were derived from a depleted mantle source distinct from the source of MORB and with compositional similarities to that of ocean islands (e.g., Hawaii) and plateaus (e.g., Ontong Java) in the Pacific Ocean.
An edited version of this paper was published by AGU. Copyright 2008 American Geophysical Union.
|
Subject | |
Genre | |
Type | |
Language |
eng
|
Date Available |
2016-12-01
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
|
DOI |
10.14288/1.0075971
|
URI | |
Affiliation | |
Citation |
Greene, Andrew R.; Scoates, James S.; Weis, Dominique. (2008). Wrangellia flood basalts in Alaska: A record of plume-lithosphere interaction in a Late Triassic accreted oceanic plateau. Geochemistry, Geophysics, Geosystems, 9(12), Q12004,
|
Publisher DOI |
10.1029/2008GC002092
|
Peer Review Status |
Reviewed
|
Scholarly Level |
Faculty
|
Copyright Holder |
Weis, Dominique
|
Rights URI | |
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
Attribution-NonCommercial-NoDerivatives 4.0 International