Death Valley bright spot: A midcrustal magma body in the southern Great Basin, California?

Voogd, B. de; Serpa, Laura; Brown, L. D.; Hauser, Ernest C.; Kaufman, S.; Oliver, Jack; Troxel, Bennie W.; Willemin, James H.; Wright, Lauren

doi:10.1130/0091-7613(1986)14<64:dvbsam>2.0.co;2

Cited by 52 publications

(31 citation statements)

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“…This reflector is interpreted as the top of a thickened reflective lower crust localized under the coastline and immediately south of the San Sebastián fault zone (Figure 12). Lower crustal reflectivity has been observed in different tectonic settings and is generally attributed to layering, either caused by igneous intrusions [Holliger and Levander, 1994], high pore pressure and partial melting [Brown et al, 1980;Devoogd et al, 1986], or by mylonitic foliation associated with shearing within fault zones [e.g., Hurich et al, 1985;Mcdonough and Fountain, 1988;Wang et al, 1989]. The limited heat flow data [Pollack et al, 1993] and the absence of recent magmatic activity along this portion of the northern margin of the SA plate are not indicative of a hot thermal state of the lower crust and mantle beneath this region.…”

Section: South American Continentmentioning

confidence: 98%

Crustal structure of the South American–Caribbean plate boundary at 67°W from controlled source seismic data

Magnani¹,

Zelt²,

Levander³

et al. 2009

J. Geophys. Res.

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[1] We present the results of new seismic reflection and wide-angle data across the SE Caribbean plate boundary. The 550 km long N-S profile crosses the structures involved in the active 55 Ma long continent-arc oblique collision between the Caribbean (CAR) and the South American (SA) plate. From the north to the south these structures include the accretionary prism, the extinct volcanic arc (Leeward Antilles arc), the Tertiary Bonaire basin, the continental-size dextral strike-slip fault system (San Sebastián-El Pilar fault), the allochthonous exhumed terranes, and the authocthonous fold and thrust belt (Caribbean Mountain system) and foreland basin. The wide-angle data show that these elements are characterized by different velocity structures and that they are separated by sharp lateral velocity variations. The Leeward Antilles arc exhibits a velocity structure similar to that of the Lesser Antilles active volcanic arc, indicating that the extinct arc has not been modified by the collision with the SA plate. The data show a $20 km change in crustal thickness across the San Sebastián fault, suggesting that the dextral strike-slip fault is a crustal feature that likely continues in the mantle as a primary strand of the plate boundary between the South American and the Caribbean plates. South of the strike-slip fault and beneath the exhumed eclogitic terranes, the data image a north dipping, high-velocity (>6.5 km/s) anomaly in the upper crust (3-11 km), indicating that high-pressure/low-temperature rocks are the likely lithologies responsible for the high seismic velocities and suggesting that exhumation of these assemblages is enabled by the strike-slip fault.

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Section: South American Continentmentioning

confidence: 98%

Crustal structure of the South American–Caribbean plate boundary at 67°W from controlled source seismic data

Magnani¹,

Zelt²,

Levander³

et al. 2009

J. Geophys. Res.

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“…Several authors (deVoogd et al 1986;Serpa et al 1988) suggest a midcrustal bright spot below southern Death Valley is associated with the Split Cone, a Quaternary basalt center formed along and offset by the southern Death Valley fault. They suggest lowangle faults provided migration pathways for the basalt magma.…”

Section: A Detachment Systemsmentioning

confidence: 99%

Status of volcanism studies for the Yucca Mountain Site Characterization Project

Crowe¹,

Perry²,

Murrell³

et al. 1995

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; ifs unique idenfzfier assigned to fhis appendix is LA-EES-13-LV-12-95-002. To obtain rgerences bgore fhe appendix is issued, confacf Kean Finnegan at (7021-794-7273 ABSTRACTChapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment. Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the two cycles of the Postcaldera basalt, the Older postcaldera basalt and the Younger postcaldera basalt. The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR, it has been problematic to establish the geochronology of the center; and it probably formed during multiple, timeseparate eruptive events, an unexpected difference from typical monogenetic basaltic volcanic centers. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The Crater Flat volcanic zone is defined and described as one of many alternative models of the structural controls of the distribution of Plio-Quaternary basalt centers in the YMR. Geophysical data are described for the YMR and are used as an aid to understand the distribution of basaltic volcanic centers. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the Basin and Range province. Geochemical and isotopic data are described that indicate basalt of the southern Great Basin was derived from ancient lithospheric mantle. The long time of activity and characteristic small volume of the Postcaldera basalt of the YMR result in one of the lowest eruptive rates in a volcanic field in the southwest United States. Quaternary lavas of the YMR lack plagioclase phenocrysts and fractionated at high pressure in the lower crust or upper mantle before ascent and eruption. The compositional variation of the Lathrop Wells center provides strong evidence of formation from separate and unrelated magma batches. Chapter 5 summarizes current concepts of the segregation, ascent, and eruption of basalt magma. Magma ascending as dikes probably followed northwest-trending structure at depth and diverted at shallow depths following the direction of maximum compressive stress. Chapter 6 summarizes the history of volcanism studies (1979 through early 1994), including work f...

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“…The Consortium for Continental Reflection Profiling (COCORP) collected 250 km of deep seismic reflection data in the vicinity of Death Valley, California [8,20] Figure 1 shows the location of COCORP lines 9 and 11 within central Death Valley. These profiles provided information on the upper crustal fault blocks, as well as other features of the deep crust and upper mantle associated with the development of the central Death Valley pull-apart basin and surrounding area.…”

Section: Tectonic Settingmentioning

confidence: 99%

“…These profiles provided information on the upper crustal fault blocks, as well as other features of the deep crust and upper mantle associated with the development of the central Death Valley pull-apart basin and surrounding area. References [8,21] interpreted a strong reflecting zone at mid-crustal depth, termed the Death Valley bright spot, as evidence of magma in the middle crust. Reference [2] traced the bright spot reflections to the surface location of a young volcanic cone and interpreted a mid-crustal reflective zone at approximately 15 km depth in central Death Valley, including the bright spot, to suggest the reflecting horizon is domed upward beneath the basin [22].…”

Section: Tectonic Settingmentioning

confidence: 99%

“…It represents an ideal region to study basin evolution and structure because it is actively deforming, there is little vegetation, and the sedimentation rates are low. As a result of these attributes, numerous models have been developed to describe the basin evolution and to determine which processes may be important in that evolution [1][2][3][4][5][6][7] Of particular interest here is the presence of a high amplitude seismic reflection anomaly, termed the Death Valley "bright spot" [8] (Figure 1) which has been suggested to be associated with a magmatic intrusion and volcanism in central Death Valley. Reference [9] did not find evidence for such a feature elsewhere in the region in his seismic studies and, similarly, a magnetotelluric study [10,11] north of the seismic study area did not find supporting evidence for magma in the crust.…”

Section: Introductionmentioning

confidence: 99%

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Imaging the Deep Structure of the Central DeathValley Basin Using Receiver Function, Gravity,and Magnetic Data

Hussein¹,

Serpa²,

Doser³

et al. 2011

IJG

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We use receiver function, gravity, and magnetic data to image the deep structures of central Death Valley. Receiver function analysis suggests the Moho is 24 km deep in the central part of the basin and deepens to 33 km to the east and 31 km to the west. The estimated lower crustal density is 2900 kg/m 3 , which suggests a gabbroic composition, whereas the upper crustal density, excluding basin sediments, is estimated to average 2690 kg/m 3 or approximately a quartzofeldspathic composition. We modeled the magnetic sources as upper crustal to suggest a relatively shallow Curie depth in this region of high heat flow. We developed models to test the hypothesis that a low-density, non-magnetic body (magma or fluid-rich material?) within the lower crust at a depth of 15 km could coincide with the location of the Death Valley bright spot imaged on a deep seismic reflection profile. Those models suggest that if there is a low density region in the mid to lower crust in the area of the bright spot, then the region is also likely to be underplated by mafic or ultramafic materials which may have contributed to heating, uplift, and thinning of the crust during extension.

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Death Valley bright spot: A midcrustal magma body in the southern Great Basin, California?

Cited by 52 publications

References 0 publications

Crustal structure of the South American–Caribbean plate boundary at 67°W from controlled source seismic data

Crustal structure of the South American–Caribbean plate boundary at 67°W from controlled source seismic data

Status of volcanism studies for the Yucca Mountain Site Characterization Project

Imaging the Deep Structure of the Central DeathValley Basin Using Receiver Function, Gravity,and Magnetic Data

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