Mechanisms of rifting, heat flow, and mantle convection (Abstract)
Integrated gravity, thermal, and tectonic models suggest thinning of the lithosphere by buoyant intrusion of mantle beneath the northern Rio Grande Rift. The rift is a series of elogate, en echelon, rift valleys bounded by normal faults which downdrop basins between regionally up-lifted shoulders. Geophysical signatures consisting of high heat flow (>2.5 HFU), volcanism (>10 my), and a moderate level of seismicity (M approximately 5.5/100 yrs) are asymmetric to the structural rift, occurring on its west flank. Gravity models indicate lithospheric thinning and presence of lateral inhomogeneities in the crust. Thermal models, consistent with meager petrologic data, indicate increased geothermal gradients, requirements for crustal sources of abnormally high heat content, and a relatively shallow partial melt zone. Convective models create dynamic upwelling, predict high surface heat flow over the upwelling, and increase surface topography above the thermal plume. The conducting lithosphere, in moving over upwelling arms of the convection cell, destroys its symmetry, both shortening the eastern limb and elongating the limb under the westward moving plate. Asymmetric convective transport of heat westward provides sustained melt conditions for evolution of basalt magma. Plume flow and isolated buoyant magma bodies provide uplift of the plate forming inhomogeneities in the crust, surface volcanics west of the rift, and volcanic piles along major faults of the rift's west flank. Rift mechanics consist of convective heat transport which provides energy through gravitational instability, thins the lithosphere, uplifts regionally elevated shoulders, creates normal faulting through extension of the elastic crust, extrudes voluminous basalts through major crustal fault zones, and generates high surface heat flow.
- Research Organization:
- Los Alamos Scientific Lab., NM
- OSTI ID:
- 5384416
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 9:1; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
150202* -- Geology & Hydrology of Geothermal Systems-- Non-USA-- (-1989)
CONVECTION
EARTH CRUST
EARTH MANTLE
ENERGY TRANSFER
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GEOTHERMAL GRADIENTS
GRAVITY SURVEYS
HEAT FLOW
HEAT TRANSFER
NEW MEXICO
NORTH AMERICA
RIFT ZONES
RIO GRANDE RIFT
SEISMIC SURVEYS
TEMPERATURE GRADIENTS
UPWELLING
USA
VOLCANISM