Ultrapotassic Magmas along the Flanks of the Oligo-Miocene Rio Grande Rift, USA: Monitors of the Zone of Lithospheric Mantle Extension and Thinning Beneath a Continental Rift

Gibson, S. A.; Thompson, R. N.; Leat, P. T.; Morrison, M. A.; Hendry, G. L.; Dickin, A. P.; Mitchell, J. G.

doi:10.1093/petrology/34.1.187

Cited by 105 publications

(59 citation statements)

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“…There are depletions in some of the HFSE, most notably Nb and Ti, relative to the other incompatible elements, and also low abundances overall for the HREE, (Yb~<2 ppm, Lu~<l ppm; Table 3). These trace element characteristics are distinctive and similar to those of various worldwide occurrences of mafic potassic magmas, as well as those for subduction-related magmas, except that the absolute element concentrations and ratios are far higher than those in any reported volcanic arc magmas (Thompson et al, 1984;Luhr et al, 1989, Thompson et al, 1989Sheppard and Taylor, 1992;Gibson et al, 1993). Figure 5 also shows that there are distinct differences in incompatible trace element abundances and ratios between the minettes discussed here, which can be used to divide them into two main groups.…”

Section: Minette Geochemistrysupporting

confidence: 70%

“…This indicates that these lamprophyres have undergone limited fractionation and retain compositions close to primary mantle melts. It is now widely accepted that such volatile-rich, mafic, potassic magmas are formed by small degree melting either, of metasomatized sub-continental lithospheric mantle (SCLM); or, of metasomatic veins within the SCLM (Luhr et al, 1989;McKenzie, 1989;Sheppard and Taylor, 1992;Gibson et al, 1993Gibson et al, , 1995Thompson and Gibson, 1994). Such melts are therefore either dominantly or wholly lithospheric in origin and preserve the best evidence for the composition of the SCLM.…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry of late Caledonian minettes from Northern Britain: implications for the Caledonian sub-continental lithospheric mantle

et al. 1996

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The geochemistry of late Caledonian minettes from across the orogenic belt is compared in order to constrain the composition of the Caledonian sub-continental lithospheric mantle (SCLM). All the minettes are similar petrographically and chemically and several samples have characteristics typical of near primary mantle melts. Samples from the Northern Highlands and the Caledonian foreland show enrichment in many trace elements (notably LILE and LREE) relative to those from the Grampians, the Southern Uplands and northern England, coupled with distinct Nd and Sr isotope characteristics. Processes such as fractional crystallization, crustal assimilation, and partial melting played a negligible role in creating the differences between the two groups which reflect long-term, time-integrated differences in the compositions of their SCLM sources. The Great Glen Fault appears to represent the boundary between these two lithospheric mantle domains. Other currently exposed Caledonian tectonic dislocations cannot be correlated directly with compositional changes within the SCLM. The chemical provinciality displayed by the minettes shows some resemblance to that within other late Caledonian igneous suites, including the newer granites, suggesting that the minettes may represent the lithospheric mantle contributions to these rocks.

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Section: Minette Geochemistrysupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Geochemistry of late Caledonian minettes from Northern Britain: implications for the Caledonian sub-continental lithospheric mantle

et al. 1996

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“…Most of these rocks were emplaced between 33 and 20 Ma, spanning the Oligocene flare-up and initial extension of the Rio Grande rift system [Gibson et al, 1993]. These areas include the Navajo Volcanic Field , the Dulce area , the Spanish Peaks [Penn and Lindsey, 2009], and the Middle Park lamproite [Thompson et al, 1997] (Figure 1).…”

Section: Cenozoic Volcanismmentioning

confidence: 99%

A rootless rockies—Support and lithospheric structure of the Colorado Rocky Mountains inferred from CREST and TA seismic data

Hansen

Dueker

Stachnik

et al. 2013

Geochem Geophys Geosyst

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[1] Support for the Colorado high topography is resolved using seismic data from the Colorado Rocky Mountain (CRM) Experiment and Seismic Transects. The average crustal thickness, derived from P wave receiver function imaging, is 48 km. However, a negative correlation between Moho depth and elevation is observed, which negates Airy-Heiskanen isostasy. Shallow Moho (<45 km depth) is found beneath some of the highest elevations, and therefore, the CRM are rootless. Deep Moho (45-51 km) regions indicate structure inherited from the Proterozoic assembly of the continent. Shear wave velocities from surface wave tomography are mapped to density employing empirical velocity-to-density relations in the crust and mantle temperature modeling. Predicted elastic plate flexure and gravity fields derived from the density model agree with observed long-wavelength topography and Bouguer gravity. Therefore, lowdensity crust and mantle are sufficient to support much of the CRM topography. Centers of Oligocene volcanism, e.g., the San Juan Mountains, display reduced crustal thicknesses and lowest average crustal velocities, suggesting that magmatic modification strongly influenced modern lithospheric structure and topography. Mantle velocities span 4.02-4.64 km/s at 73-123 km depth, and peak lateral temperature variations of 600 C are inferred. S wave receiver function imaging suggests that the lithosphereasthenosphere boundary is 100-150 km deep beneath the Colorado Plateau, and 150-200 km deep beneath the High Plains. A region of negative arrivals beneath the CRM above 100 km depth correlates with low mantle velocities and is interpreted as thermally modified/metasomatized lithosphere resulting from Cenozoic volcanism.

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“…lamproites) and in lamprophyre magmas of post-collisional settings (i.e. minettes) (Foley 1992, Gibson et al 1992, and are, therefore, correlated with the metasomatic process at the source and not necessarily with the tectonic setting. Eu-negative anomalies are not present in Gameleira Lamprophyres.…”

Section: Petrology Of Gameleira Lamprophyresmentioning

confidence: 99%

Petrology of Gameleira potassic lamprophyres, São Francisco Craton

Cid

Campos

Nardi

et al. 2012

An. Acad. Bras. Ciênc.

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Gameleira lamprophyres are dykes and mafic microgranular enclaves associated with the shoshonitic Gameleira monzonite. This association belongs to the Paleoproterozoic alkaline magmatism from Serrinha nucleus, northeast Brazil. The liquidus paragenesis is diopside, pargasite, apatite and mica. Reverse zoning was identified in the groundmass alkali feldspar and was related to the undercooling of lamprophyric magma during the emplacement, with high growth rate of pargasite/edenite inducing disequilibrium between feldspars and liquid. Chemical data indicate that the lamprophyres are basic rocks (SiO 2 < 48 wt%), with alkaline character (Na 2 O + K 2 O > 3 wt%) and potassic signature (K 2 O/Na 2 O ≈ 2). High contents of MgO and Cr are consistent with a signature of a primary liquid, and such concentrations, as well as Al, K, P, Ba, Ni-and light rare earth elements, are consistent with an olivine-free metasomatic mantle source enriched in amphibole, clinopyroxene and apatite. By contrast, the ultrapotassic lamprophyres from Morro do Afonso, contemporaneous alkaline ultrapotassic magmatism in Serrinha nucleus, were probably produced by melting of a clinopyroxene-phlogopite-apatite enriched-source. The identification of different mineral paragenesis in the source of potassic and ultrapotassic lamprophyres from Serrinha nucleus can contribute to the understanding of the mantle heterogeneities and tectonic evolution of this region.

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Ultrapotassic Magmas along the Flanks of the Oligo-Miocene Rio Grande Rift, USA: Monitors of the Zone of Lithospheric Mantle Extension and Thinning Beneath a Continental Rift

Cited by 105 publications

References 0 publications

Geochemistry of late Caledonian minettes from Northern Britain: implications for the Caledonian sub-continental lithospheric mantle

Geochemistry of late Caledonian minettes from Northern Britain: implications for the Caledonian sub-continental lithospheric mantle

A rootless rockies—Support and lithospheric structure of the Colorado Rocky Mountains inferred from CREST and TA seismic data

Petrology of Gameleira potassic lamprophyres, São Francisco Craton

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