Strongly potassic mafic magmas from lithospheric mantle sources during continental extension and heating: evidence from Miocene minettes of northwest Colorado, U.S.A.

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

doi:10.1016/0012-821x(90)90055-3

Cited by 120 publications

(51 citation statements)

References 42 publications

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“…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). An additional period of ultrapotassic volcanism occurred in northwest Colorado at 10-8 Ma [Leat et al, 1991;Thompson et al, 1990] during a renewed period of rift activity Ingersoll, 2001;Landman and Flowers, 2013]. Therefore, thermal modification of the mantle lithosphere probably began in the Oligocene and likely continued until at least the end of the Miocene.…”

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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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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“…In spite of the subduction-related features (increase of LILEs and Nb trough in the normalized traceelement patterns; Harangi, 2001b), there is no evidence for contemporaneous subduction. Small-volume ultrapotassic magmas are thought to be generated in the continental lithospheric mantle in response to thinning of the lithosphere or to the heat fl ux of upwelling hot mantle beneath the continental plate (McKenzie, 1989;Thompson et al, 1990). In the Carpathian-Pannonian region, the striking coincidence with the main rifting phase of the Pannonian Basin supports the fi rst explanation.…”

Section: Role Of Extensionmentioning

confidence: 99%

Genesis of the Neogene to Quaternary volcanism in the Carpathian-Pannonian region: Role of subduction, extension, and mantle plume

Harangi

Lenkey

2007

Cenozoic Volcanism in the Mediterranean Area

124

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Neogene to Quaternary volcanism of the Carpathian-Pannonian region is part of the extensive volcanic activity in the Mediterranean and surrounding regions. Using the spatial and temporal distribution of the magmatic rocks, their major-and traceelement features, and Sr-Nd-Pb isotope characteristics, we suggest that lithospheric extension in the Pannonian Basin had a major role in the generation of the magmas. Dehydration of subducting slab should have resulted in thorough metasomatism in the mantle wedge during Cretaceous to early Miocene that would have lowered the melting temperature, therefore playing an indirect role in the generation of magmas later on. Mixing between mantle-derived magmas and lower-crustal melts was an important process at the fi rst stage of the silicic and calc-alkaline magmatism in the Northern Pannonian Basin. However, the crustal component gradually decreased with time, which is consistent with magmatic activity in a continuously thinning continental plate. Calc-alkaline volcanism along the Eastern Carpathians was mostly postcollisional and could have been related to slab break-off processes. However, the fairly young (<1.5 Ma) potassic magmatism at the southeasternmost segment of the Carpathian volcanic arc could be explained by lithospheric delamination under the Vrancea zone. Alkaline basaltic volcanism began at the end of rifting of the Pannonian Basin (11 Ma) and continued until recently. We suggest that a mantle plume beneath the Pannonian Basin is highly unlikely and the mafi c magmas were formed by small degree partial melting in a heterogeneous asthenospheric mantle, which has been close to the solidus temperature due to the lithospheric extension in the Miocene. Magmatism appears to have been in a waning phase for the last 2 m.y., but recent volcanic eruptions (<200 k.y.) indicate that future volcanic activity cannot be unambiguously ruled out.

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“…Some Northern Highland minettes also contain discrete xenoliths of probable cognate origin consisting of coarse-grained, (>5 mm), mixtures of phlogopite- PHLOGOPITES/ / 9 , 9 , 9 gO~ BIOTIT biotite and clinopyroxene, with variable amounts of hornblende, apatite and rare interstitial K-feldspar. They resemble cognate xenoliths reported from other mafic minettes (Thompson et al, 1989) and probably formed as side wall precipitates in the feeder dykes. Taken together, the textural features also indicate that mica was a common liquidus phase in the minettes.…”

Section: Petrography and Mineral Chemistrymentioning

confidence: 88%

“…Such melts are therefore either dominantly or wholly lithospheric in origin and preserve the best evidence for the composition of the SCLM. Production of the late Caledonian minettes was probably triggered by heating associated with post-orogenic extension and collapse (Watson, 1984;Thompson et al, 1989;Shand et al, 1994). Other attempts to investigate the role of the SCLM and its role in Caledonian magmatism have been restricted to interpolating data from the Siluro-Devonian volcanics (Thirlwall, 1981(Thirlwall, , 1982(Thirlwall, , 1986, and the extensive Newer Granite suite (Halliday, 1984;Halliday et al, 1985;Frost and O'Nions, 1985;Clayburn, 1988).…”

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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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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Strongly potassic mafic magmas from lithospheric mantle sources during continental extension and heating: evidence from Miocene minettes of northwest Colorado, U.S.A.

Cited by 120 publications

References 42 publications

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

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

Genesis of the Neogene to Quaternary volcanism in the Carpathian-Pannonian region: Role of subduction, extension, and mantle plume

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

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