Kinematic analysis of fractures in the Great Rift, Idaho: Implications for subsurface dike geometry, crustal extension, and magma dynamics
Holmes AA, Rodgers DW, Hughes SS. 2008. Kinematic analysis of fractures in the Great Rift, Idaho: Implications for subsurface dike geometry, crustal extension, and magma dynamics. Journal of Geophysical Research. 113
Extension across the southern Great Rift of the Eastern Snake River Plain (ESRP),Idaho, was measured to calculate the dimensions of underlying dikes and interpret magmatic and extensional processes. Cumulative rift-perpendicular extension ranges from 0.64 to 4.50 m along the 14 km long Kings Bowl segment, from 1.33 to 4.41 m along the 14 km long New Butte segment, and from 0.74 to 1.57 m along the 4 km long Minidoka segment. Along strike of each segment, extension increases toward coevalvents. Each rift segment is interpreted to be underlain by a subsurface dike, whose dimensions are calculated using buoyancy equilibrium and boundary element models.Dikes are calculated to have tops that are 950–530 m deep, bottoms that are 23–31 km deep, and widths that taper to zero from a maximum of 2–21 m. Modeling suggests that the Kings Bowl dike has a maximum probable width of 8 m and a volume of 2 km 3, about 400 times the volume of its coeval lava flow. Dike widths and ages at the southern Great Rift provide evidence for a Holocene ESRP strain rate of about 1 to 3x10^16 s^-1, which is as much as an order of magnitude slower than strain rates in the adjacent, seismically active Basin and Range province. Eruptive fissures are present where rift width is <1650 m. This corresponds to a depth to dike top of <700 m, which we propose was the depth where vesiculation initiated, thus increasing magma pressure and inducing eruption.
- Type
- Journal Article
- Authors
- Holmes, Adrian; Rodgers, David; Hughes, Scott
- Units
- CRMO
- Keywords
- basalts, Bear Trap Cave, Blaine County Idaho, case studies, controls, detection, dikes, fissures, geophysical methods, gravity anomalies, gravity methods, high-resolution methods, Idaho, igneous rocks, intrusions, Kings Bowl, lava tubes, mafic composition, magnetic anomalies, magnetic methods, microgravity methods, migration, pollutants, pollution, Power County Idaho, preferential flow, Snake River plain, United States, volcanic features, volcanic rocks