Terrestrial Heat Flow along the Rio Grande Rift, New Mexico and Southern Colorado

Reiter, Marshall; Edwards, Charles L.; Hartman, Harold; Weidman, C. D.

doi:10.1130/0016-7606(1975)86<811:thfatr>2.0.co;2

Cited by 151 publications

(60 citation statements)

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“…The top boundary of the cross-sectional model constitutes a specified head equal to the water table elevation and ranges [Reiter, 1975] and the 40 m CNV-R temperature profile measured as part of this study [Walvoord, 1998] there is no observable discharge other than springs located just below the mesa can be rationalized if we consider the role of highly permeable alluvial valley fill. The hydraulic conductivity of the alluvium is more than 5 orders of magnitude higher than underlying sediments [Stone et al, 1983], and alluvial channels have been cited as principal locations of discharge in some areas of the San Juan Basin [Brown, 1976;Stone et al, 1983].…”

Section: Boundary Conditionsmentioning

confidence: 99%

Groundwater flow and geochemistry in the Southeastern San Juan Basin: Implications for microbial transport and activity

Walvoord¹,

Pegram²,

Phillips³

et al. 1999

Water Resources Research

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Abstract. Recent confirmation of widespread microbial activity in the deep subsurface has raised the question whether microbes were transported to their current residence from the surface or whether they have survived in situ since sediment deposition. As a part of a larger study addressing these and related questions, we have characterized the microbiology and hydrogeology of a Late Cretaceous sandstone and shale sequence in the southeastern San Juan Basin, New Mexico, near a 3.39 Ma volcanic intrusion. Deep core samples were analyzed for microbial activity to assess recolonization of the previously sterilized zone around the intrusion. Groundwater geochemistry and isotopic data were used to improve the understanding of the flow regime. We modeled the geochemical evolution of the groundwater from the recharge area to each sample location and used the resultant mass transfers to correct measured C activities. The •4C ages provided the basis for calibrating a cross-sectional flow model that intersects the intrusion. Based on microbial activity data, hydrogeologic modeling results supported the inference that groundwater velocities were adequate to transport microbes into the previously sterilized region in the time since the volcanic intrusion. Evidence of upward groundwater flow near the intrusion and high vertical hydraulic conductivities for shale suggest considerable hydraulic connection between lithologic units, which may influence the nutrient distribution and promote enhanced microbial activity near lithologic interfaces. Cores were collected for microbiological, geochemical, and physical analyses from boreholes drilled at two adjacent locations. The first of these, a vertical borehole, was intended to be far enough away from the volcanic neck that the strata would not have been affected by the heat from volcanism. The second borehole was drilled at an angle directed toward the intrusion in order to sample along the paleothermal gradient. The geological constraints based on an assumption of localized sterilization due to heating associated with the volcanic intrusion provided a basis for evaluating the relative contributions of transport and in situ survival to the microbial community structure at this site. A microbial transport origin would be supported if microbes could be found in previously heated sediments near the intrusion, i.e., within the paleothermal aureole. Alternatively, if microbes were absent near the intrusion, this would suggest that microbial transport was insufficient to recolonize the sterilized zone. An in situ survival origin would be supported by the existence of microbes exclusively outside of the paleothermal aureole. The study site also enabled exami-1409

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Section: Boundary Conditionsmentioning

confidence: 99%

Groundwater flow and geochemistry in the Southeastern San Juan Basin: Implications for microbial transport and activity

Walvoord¹,

Pegram²,

Phillips³

et al. 1999

Water Resources Research

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“…Hartse (1991) proposes the base of the seismogenic layer at Arroyo del Coyote is consistent with the regional geothermal gradient predicted from heat-fl ow data in the southern Rio Grande Rift and quartz plasticity in granitic rocks beginning at ~300 °C (Reiter et al, 1986;Tullis and Yund, 1977). Within a few km of the Arroyo del Coyote site a reliable heat-fl ow measurement was made (92 ± 2 mW (milliwatts) m -2 ; Reiter et al, 1975;Fig. 1).…”

Section: Reliability Of the Heat-flow Valuementioning

confidence: 57%

“…This measurement allows estimates of upper crustal temperatures. The heat-fl ow measurement near the Arroyo del Coyote site (Reiter et al, 1975) is thought to be reliable for several reasons: fi rst, two different depth zones at the site provide similar values (94 and 90 mW m -2 averaging 92 ± 2 mW m -2 ), which is consistent with the absence of perturbing effects to the geothermal gradient; second, the heat-fl ow site is located east of the synrift sediments where relatively little subsurface temperature disturbance by groundwater fl ow is expected; and third, the average heat-fl ow value (92 ± 2 mW m -2 ) at the site is close to the background heat fl ow for the northern part of the southern Rio Grande Rift estimated from bottom hole temperatures at fi ve deep petroleum tests where local hydrothermal activity is absent (~95 ± 4 mW m -2 ; Reiter et al, 1986).…”

Section: Reliability Of the Heat-flow Valuementioning

confidence: 99%

Subsurface temperatures and crustal strength changes within the seismogenic layer at Arroyo del Coyote in the Socorro seismic area, central Rio Grande Rift, New Mexico

Reiter¹

2005

Geol Soc America Bull

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From 1962 to 1995, 572 events with moment magnitudes greater than 1.3 occurred in the Socorro seismic area. The activity seems to be related to uplift resulting from magma replenishment of a cogeographical magma body at 19 km depth. A distinct microearthquake swarm at Arroyo del Coyote where focal depths are well determined, a nearby reliable heat-fl ow measurement, and a largely granitic upper-crust, make the site ideal for considering upper crustal strength inferred from experimentally determined elastic moduli as a function of temperature and confi ning pressure at in situ conditions. The experimental data may be interpreted to imply that strength across the seismogenic layer (~6-10 km) is much more dependent upon in situ temperatures than in situ stresses. Normalized Young's moduli and bulk moduli decrease at temperatures predicted for the seismogenic layer at Arroyo del Coyote. The elastic moduli versus depth profi le can be explained by the thermoelastic response of microcracking. It is suggested that the effect of microcracking weakens the rock and therefore the asperity and surface strength along fault surfaces where seismic events likely occur. The seismogenic layer is also within a temperature regime that generally corresponds to the temperature regime for a semibrittle zone model of crustal weakening with possible plastic deformation. Both the elastic moduli data and the semibrittle zone temperature regime suggest the seismic layer at Arroyo del Coyote is a layer of crustal weakening with depth, different from a stronger crust with depth across a seismogenic layer, as often presented in frictional resistance models. Whereas temperatures at the base of the Arroyo del Coyote swarm are consistent with in situ plastic deformation and the lack of upper-crustal earthquakes at deeper depths, the experimental data for elastic moduli at these same temperatures indicate elastic deformation. The confl icting character of deformation between experimental and in situ observations illustrates the dependence of rheology on strain rate.

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“…The RioGrande Rift Zone is an ancient rift zone which has retained relatively high heat flow as shown on Figure 4.1 (Reiter et al 1975.) This is another area where a HVDC intertie might be considered since it holds the potential for conductance at depth.…”

Section: Tectonic Rift Areas Colorado-new Mexicomentioning

confidence: 99%

HVDC power transmission electrode siting and design

Holt¹,

Dabkowski²,

Hauth³

1997

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Terrestrial Heat Flow along the Rio Grande Rift, New Mexico and Southern Colorado

Cited by 151 publications

References 0 publications

Groundwater flow and geochemistry in the Southeastern San Juan Basin: Implications for microbial transport and activity

Groundwater flow and geochemistry in the Southeastern San Juan Basin: Implications for microbial transport and activity

Subsurface temperatures and crustal strength changes within the seismogenic layer at Arroyo del Coyote in the Socorro seismic area, central Rio Grande Rift, New Mexico

HVDC power transmission electrode siting and design

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