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| Titel |
Central Arctic Crustal Modeling Constrained by Potential Field data and
recent ECS Seismic Data |
| VerfasserIn |
John Evangelatos, Gordon Oakey, Rick Saltus |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146612
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| Publikation (Nr.) |
 EGU/EGU2017-10644.pdf |
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| Zusammenfassung |
| 2-D gravity and magnetic models have been generated for several transects across the
Alpha-Mendeleev ridge complex to study the regional variability of the crustal structure and
identify large scale lateral changes. The geometry and density parameters for the models have
been constrained using recently acquired seismic reflection and refraction data collected
jointly by Canada and the United States as part of their collaborative Arctic ECS
programs.
A total of fifteen models have been generated perpendicular to the ridge complex,
typically 50 to 150 km apart. A minimalist approach to modeling involved maintaining a
simple, laterally continuous density structure for the crust while varying the model geometry
to fit the observed gravity field. This approach is justified because low amplitude
residual Bouguer anomalies suggest a relatively homogenous density structure within
the ridge complex. These models have provided a new measure of the regional
variability in crustal thickness. Typically, models with thinner crust correspond with
deeper bathymetric depths of the ridge which is consistent with regional isostatic
equilibrium.
Complex “chaotic” magnetic anomalies are associated with the Alpha-Mendeleev ridge
complex, which extends beneath the surrounding sedimentary basins. Pseudogravity
inversion (magnetic potential) of the magnetic field provides a quantifiable areal extent of
∼1.3 x106 km2. Forward modeling confirms that the magnetic anomalies are not
solely the result of magnetized bathymetric highs, but are caused to a great extent
by mid- and lower crustal sources. The magnetization of the crust inferred from
modeling is significantly higher than available lab measurements of onshore volcanic
rocks.
Although the 2-D models cannot uniquely identify whether the crustal protolith was
continental or oceanic, there is a necessity for a significant content of high density and highly
magnetic (ultramafic) material. Based on the crustal thickness estimates from our regional
2-D gravity models and the two possible protoliths, we determine volumetric estimates of the
volcanic composition to ∼ 6 × 106 km3 for the mid- and upper-crust and between 10 × 106
and 14 × 106 km3 within the lower crust — for a total of at least ∼16 × 106 km3. This
exceeds any estimates for the onshore circum-Arctic HALIP by more than an order of
magnitude. |
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