Chemical and Os isotopic study of Cretaceous potassic rocks from Southern Brazil

Carlson, Richard W.; Esperança, Sonia; Svisero, Darcy P.

doi:10.1007/s004100050230

Cited by 125 publications

(61 citation statements)

References 49 publications

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“…This apparent conflict can be readily explained by the presence of mixed source rocks (Irving, 1980;Menzies, 1983;Foley, 1992a,b;Harte et al, 1993), where the vast majority of incompatible elements reside in non-peridotitic trace minerals such as phlogopite, Ti-oxides, and apatite (among others) that have been reported from composite mantle xenoliths. Hence, the Rb-Sr, Sm-Nd, Lu-Hf, and U-ThPb radiogenic isotope systems utilized here are unlikely to fingerprint signatures from a pure peridotite substrate, for which Os isotope compositions would be more suitable (Carlson et al, 1996. Rather, they provide time-integrated information about the metasomatic component(s) in the mantle source region.…”

Section: High Mg and Compatible Trace Elementsmentioning

confidence: 95%

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Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

Tappe

Foley

Kjarsgaard

et al. 2008

Geochimica et Cosmochimica Acta

256

104

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New U-Pb perovskite ages reveal that diamondiferous ultramafic lamprophyre magmas erupted through the Archean crust of northern Labrador and Quebec (eastern Canada) .2). These contrasting isotopic characteristics of aillikites/carbonatites and mela-aillikites, along with subtle differences in their modal carbonate, SiO 2 , Al 2 O 3 , Na 2 O, Cs-Rb, and Zr-Hf contents, are consistent with two distinctive metasomatic assemblages of different age in the mantle magma source region.Integration of petrologic, geochemical, and isotopic information leads us to propose that the isotopically enriched component originated from a reduced phlogopite-richterite-Ti-oxide dominated source assemblage that is reminiscent of MARID suite xenoliths. In contrast, the isotopically depleted component was derived from a more oxidized phlogopite-carbonate dominated source assemblage. We argue that low-degree CO 2 -rich potassic silicate melts from the convective upper mantle were preferentially channelled into an older, pre-existing MARID-type vein network at the base of the North Atlantic craton lithosphere, where they froze to form new phlogopite-carbonate dominated veins. Continued stretching and thinning of the cratonic lithosphere during the Late Neoproterozoic remobilized the carbonate-rich vein material and induced volatile-fluxed fusion of the MARID-type veins and the cold peridotite substrate. Isotopic modelling suggests that only 5-12% trace element contribution from such geochemically extreme MARID-type material is required to produce the observed compositional shift from the isotopically most depleted aillikites/carbonatites towards enriched mela-aillikites.We conclude that cold cratonic mantle lithosphere can host several generations of contrasting vein assemblages, and that each may have formed during past tectonic and magmatic events under distinctively different physicochemical conditions. Although cratonic MARID-type and carbonate-bearing veins in peridotite can be the respective sources for lamproite and carbonatite magmas when present as the sole metasome, their concomitant fusion in a complex source region may give rise to a whole new variety of deep volatile-rich magmas and we suggest that orangeites (formerly Group 2 kimberlites), kamafugites, and certain types of ultramafic lamprophyre are formed in this manner.

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Section: High Mg and Compatible Trace Elementsmentioning

confidence: 95%

“…be expected if recycled continental crust material represents this isotopically enriched component (Hofmann et al, 1986;Carlson et al, 1996). Furthermore, it should be noted that the initial Sr-Nd-Hf-Pb isotope signatures of mela-aillikites are unlike any of the time-integrated isotope compositions from crustal lithologies in the region (cf.…”

mentioning

confidence: 99%

Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

Tappe

Foley

Kjarsgaard

et al. 2008

Geochimica et Cosmochimica Acta

256

104

View full text Add to dashboard Cite

show abstract

“…Element order in the abscissa follows the increasing compatibility of the element according to Hofmann (1997). Data are from: this work; Conticelli et al (1991Conticelli et al ( , 1997Conticelli et al ( , 2002; Conticelli & Peccerillo (1992); Carlson et al (1996), Tappe et al (2003), . Note that within-plate ultrapotassic rocks (i.e., leucitite from Virunga; kamafugites from Brazil and Toro Ankole) have no negative spikes at Ta, Nb, and Ti, and no positive spikes at Th, U, and Pb, whereas within-plate kamafugites have a negative spike at K, which is not observed in Italian rocks (from Conticelli et al, 2007).…”

Section: Excursion Notesmentioning

confidence: 99%

The Vesuvius and the other volcanoes of Central Italy

Avanzinelli¹,

Cioni²,

Conticelli³

et al. 2017

GFT

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“…Cretaceous small volume, alkaline, intra-plate magmatic rocks (e.g., Carlson et al, 1996;Gibson et al, 1996Gibson et al, , 1999Comin-Chiaramonti et al, 1997, 2005Velázquez et al, 2006), which occur between the western borders of the early Cretaceous Paraná flood basalt province (e.g., Hawkesworth et al, 1992Hawkesworth et al, , 2000 and western Paraguay. The Paraná flood basalt province has been ascribed to mantle plume activity whereas the small volume intra-plate magmatism was mainly triggered by recurrent lithospheric extension (above references).…”

Section: Geodynamic Setting and Geological Framework Of The Intra-plamentioning

confidence: 99%

Pre-Cenozoic intra-plate magmatism along the Central Andes (17–34°S): Composition of the mantle at an active margin

Lucassen

Franz

Romer

et al. 2007

Lithos

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Chemical and Os isotopic study of Cretaceous potassic rocks from Southern Brazil

Cited by 125 publications

References 49 publications

Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

The Vesuvius and the other volcanoes of Central Italy

Pre-Cenozoic intra-plate magmatism along the Central Andes (17–34°S): Composition of the mantle at an active margin

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