Isotopic variations in continental basaltic lavas as indicators of mantle heterogeneity: Examples from the western U.S. Cordillera

Lum, Clinton C. L.; Leeman, William P.; Foland, Ken A.; Kargel, Jeff A.; Fitton, J. Godfrey

doi:10.1029/jb094ib06p07871

Cited by 85 publications

(30 citation statements)

References 54 publications

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“…One includes processes that occur after magma generation (fractional crystallization and/or contamination), whereas the other includes processes that occur during or prior to magma generation (differences in the melting depth, mantle composition, and/or degree of partial melting to form primary magma). Although some workers report crustal contamination in B&R basalts [Walker and Coleman, 1991;Glazner and Farmer, 1992;Yogodzinski et al, 1996], others Kempton et al, 1991;Fraser et al, 1985;Perry et al, 1987;Fitton et al, 1988;Leat et al, 1988;Lum et al, 1989;Reid and Ramos, 1996;Menzies et al, 1983;Beard and Johnson, 1997;DePaolo and Daley, 2000] suggest that in many cases isotopic compositions of continental basalts still reflect variation in the mantle source. Thus isotopic and geochemical compositions of basalts from the B&R have been used to study mantle chemical characteristics [Daley and DePaolo, 1992;Feuerbach et al, 1993;Bradshaw et al, 1993;Farmer et al, 1989Farmer et al, , 1995Rogers et al, 1995;Cooper and Hart, 1990;Livaccari and Perry, 1993;Smith et al, 1999b;Menzies et al, 1985;Ormerod et al, 1991].…”

Section: Major Element Variations In Basalts Across the Basin And Rangementioning

confidence: 99%

“…Ruled bars are for melting columns with average e Nd of > +0.5. Melting depths for the Snake River basalts shown for reference (average of data from Lum et al [1989]). The East Pacific Rise shows analogous melting calculation for primitive MORB near the Tamayo Fracture Zone [Bender et al, 1984], assuming melt pooling from a triangular-shaped melting regime .…”

Section: Mantle Melting Modelmentioning

confidence: 99%

“…Table 1 for all values and references). The star is the average of Snake River basalts [Lum et al, 1989].…”

Section: Correcting For Crustal Differentiationmentioning

confidence: 99%

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A mantle melting profile across the Basin and Range, SW USA

et al. 2002

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[1] The major and trace element composition of late Cenozoic basalts (0 -10 Ma) across the Basin and Range province (B&R) preserve a clear signal of mantle melting depth variations. FeO, Fe 8.0 , and Tb/Yb increase, whereas Si 8.0 and Al 8.0 decrease, from west to east across the B&R along a profile at 36°-37°N. These variations are qualitatively consistent with shallower melting beneath the Western Great Basin (WGB) than in the central B&R. In order to quantify the depth range and percent of decompression melting, we invert primary Na 2 O and FeO contents of basalts using a melting model based on the partitioning of FeO and MgO in olivine and Na 2 O in clinopyroxene. An independent inversion, using the rare earth elements (REE), corroborates the melting depths obtained from the major element model and places most of the melting beneath the central B&R in the garnet-peridotite stability field. We find that the shape of the melting region across the B&R closely mimics the shape of the mantle lithosphere, as inferred from geological and geophysical observations. Melting across the study area occurs largely within the asthenosphere and generally stops at the base of the mantle lithosphere. In the WGB, melting paths are shallow, from 75 to 50 km, and in some cases extend almost to the base of the crust. These melting paths are consistent with adiabatic melting in normal-temperature asthenosphere, beneath an extensively thinned (or absent) mantle lithosphere. Shallow melting is consistent with geobarometry and isotopic compositions of local mantle xenoliths. Lithospheric thinning was caused by thermal erosion during Mesozoic subduction and/or simple shear or foundering during Cenozoic extension. In contrast, melting beneath the central B&R occurs beneath thick mantle lithosphere and requires mantle potential temperatures 200°C hotter than normal (melting paths from 140 to 100 km). The excess temperature beneath the central B&R is consistent with active upwelling of hot mantle in this region.

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Section: Major Element Variations In Basalts Across the Basin And Rangementioning

confidence: 99%

Section: Mantle Melting Modelmentioning

confidence: 99%

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A mantle melting profile across the Basin and Range, SW USA

et al. 2002

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“…Numerous isotopic and trace-element studies of basalt have demonstrated that basalt in the western United States is derived from either asthenospheric mantle (equivalent to oceanic mantle) or ancient lithospheric mantle that has been isolated from asthenospheric convection for periods of greater than a billion years (Menzies et al 1983;Hart 1985;Perry et al 1987Perry et al ,1988Lum et al 1989;Menzies 1989;Kempton et al 1991;Fitton et al 1991;Daley and DePaolo 1992). Perry et al (1987Perry et al ( ,1988 proposed that the source of basalt in the western United States depends on 4-5 the timing and intensity of lithospheric extension relative to the timing of basalt eruption.…”

Section: The Role O F the Mantle In Basaltic Volcanismmentioning

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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“…Numerous isotopic and trace-element studies of basalt have demonstrated that basalt in the western United States is derived from either asthenospheric mantle (equivalent to oceanic mantle) or ancient lithospheric mantle that has been isolated from asthenospheric convection for periods of greater than a billion years (Menzies et al, 1983;Hart, 1985;Perry et al, 1987Perry et al, , 1988Lum et al, 1989;Menzies, 1989;Kempton et ai., 1991;Fitton et al, 1991;Daley and DePaolo, 1992). Perry et al (1987Perry et al ( , 1988 proposed that the source of basalt in the western United States depends on the timing and intensity of lithospheric extension relative to the timing of basalt eruption.…”

Section: The Role Of the Mantle In Basaltic Volcanismmentioning

confidence: 99%