Tectonic significance of the Tibbit Hill volcanics: geochemical evidence from Richmond area, Quebec

Pintson, Hillar; Kumarapeli, P. S.; Morency, Maurice

doi:10.4095/120034

Cited by 5 publications

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“…For example, in their investigations on the effect of alteration and metamorphism on the mobility of elements in metabasalts from other localities, Condie, Viljoen, and Kable (1977), and Muecke, Pride and Sarker (1979) have reached similar conclusions. Several other authors including Pearce and Cann (1973), Ludden and others (1982), Pintson, Kumarapeli, and Morency (1985), and Coish and others (1985) demonstrated also that Ti, Zr, Y, and the REE typically remain immobile during metamorphism.…”

Section: Geochemistrymentioning

confidence: 89%

“…The Tibbit Hill mafic and felsic metavolcanic rocks have been described in detail by previous investigators (metabasalts : Booth, 1950;Christman, 1959;Osberg, 1965;Clark and Eakins, 1968;Pieratti, 1976;Coish and others, 1985;Pintson, Kumarapeli, and Morency, 1985;Pintson, 1986;metacomendites: Kumarapeli and others, 1989). Therefore, only brief generalized descriptions of these rocks are given.…”

Section: Petrographic Descriptionsmentioning

confidence: 89%

“…Previous geochemical studies of the basalts were restricted mainly to two widely separated segments of the volcanic belt ( fig. 1): one in Vermont (Coish and others, 1985) and the other in the Richmond area of Quebec (Pintson, Kumarapeli, and Morency, 1985;Pintson, 1986). These studies show the effect of metamorphism and alteration on the incompatible elements was minimal.…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry and petrogenesis of the Tibbit Hill metavolcanic suite of the Appalachian fold belt, Quebec-Vermont; a plume-related and fractionated assemblage

Abdel-Rahman¹

1999

American Journal of Science

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The Late NeoProterozoic metavolcanic Tibbit Hill Formation (THF) covers a large crustal segment exposed along a belt about 250 km long in the Appalachian fold belt (Quebec-Vermont). It is predominantly basaltic in composition but contains a minor component of felsic and intermediate alkaline volcanic lithologies. Geochemically, the Tibbit Hill Formation forms a continuum in composition and exhibits a wide range of SiO 2 (44-76 wt. percent), covering the entire spectrum from alkali basalt to trachyte and comendite. This mildly alkaline suite is relatively enriched in incompatible elements and exhibits a wide range of Zr (138-1493 ppm), Nb (15-139 ppm), and Y (18-185 ppm) concentrations, among other elements. The concentrations of the HFSE and the REE gradually increase toward the more evolved lithologies. The chondrite normalized REE patterns are fractionated (LREE-enriched over HREE), parallel to subparallel, and generally uniform but with negative Eu-anomalies developed in the more felsic varieties. These geochemical features underline the comagmatic nature of the entire suite and are consistent with a fractionated basalt to comendite suites. The incompatible element profiles suggest that most of these elements including Nb, Zr, Ti, Y, and the REE have not been affected by metamorphism, as they remained largely intact within the THF rocks. Chemical features of the mafic rocks are typical of within-plate basalts and suggest that their melts were derived from a fertile or plume-related mantle source. Chemical features of the felsic and intermediate rocks are typical of anorogenic A 1 type suites, related to hotspots, mantle plumes, or continental rift zones. This is consistent with the regional geological context with the volcanism, associated with an Iapetan RRR triple junction, occurring shortly before the onset of seafloor spreading. Geochemical modelling shows that the THF basaltic magma was produced by a very small degree of batch partial melting (F ‫؍‬ 2.5 percent) of a garnetbearing primitive mantle source (garnet lherzolite). A final basaltic melt segregation depth is estimated at 80 to 100 km. Melting probably occurred within the thermal anomaly of a rising mantle plume beneath the Sutton Mountains triple junction (near the Quebec-Maine border). Fractionation of THF basaltic magma produced minor trachytic and comenditic magmas. The volcanic assemblage of the Afar rift (for example, Boina centre) appears to represent a modern analogue to the THF volcanic suite.

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Section: Geochemistrymentioning

confidence: 89%

Section: Petrographic Descriptionsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Geochemistry and petrogenesis of the Tibbit Hill metavolcanic suite of the Appalachian fold belt, Quebec-Vermont; a plume-related and fractionated assemblage

Abdel-Rahman¹

1999

American Journal of Science

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“…A rifting episode dating back to late Precambrian to early Paleozoic time is marked by arenites filling early graben structures (Hofmann, 1972;Kumarapeli, 1985), diabase dykes (∼700 million years; Murthy, 1971) intruding Grenvillian basement rocks, alkalic and carbonatite complexes (∼565 Ma; Gittins et al, 1967) intruding the graben floor at Lake Nipissing (Doig, 1970;Kumarapeli, 1985), and by the bimodal character of alkalic or transitional Tibbit Hill volcanic rocks (Hadrynian to early Cambrian; Pintson et al, 1985) in southern Québec.…”

Section: Geology and Tectonic Settingmentioning

confidence: 99%

Evolution of faulting and paleo-stress field within the Ottawa graben, Canada

Rimando

Benn

2005

Journal of Geodynamics

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“…Such rift-related volcanic suites are commonly bimodal and the Tibbit Hill volcanics were thought to be no exception. Within-plate, mildly alkaline to transitional basalts constitute the bulk of the THF (Pintson et al, 1985). Comenditic rocks occur locally in the Waterloo area, Quebec (Kumarapeli et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Geochemistry of mantle-related intermediate rocks from the Tibbit Hill volcanic suite, Quebec Appalachians

Abdel‐Rahman

Kumarapeli

1998

Mineral. mag.

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We present a study on major and trace element geochemistry of some intermediate lithologies from the predominantly basaltic Tibbit Hill volcanic suite in the Humber Zone of the Quebec Appalachians. The intermediate rocks probably formed as lava flows in the volcanic sequence. Their presence shows that this rift-related, c. 554 Ma volcanic sequence is not bimodal (basaltic-comenditic) as previously thought, but consists of a spectrum of compositions ranging from mafic through intermediate to felsic lithologies. The entire volcanic sequence is poly-deformed and generally metamorphosed to greenschist facies conditions. The intermediate rocks of the Tibbit Hill Formation are trachyandesitic, trachytic and comenditic in composition, and exhibit a wide range of SiO2 content (52 to 68 wt.%). Mg is highly depleted in most samples. Variations of silica versus the alkalis show that most of the samples are alkaline in nature. The rocks display a tholeiitic trend on a standard AFM diagram. In general, the examined rocks also exhibit a wide range of Sr (15 to 174 ppm), Rb (0 to 156 ppm), Zr (155 to 899 ppm), Nb (18 to 123 ppm), and Y (18 to 94 ppm). The concentration of Hf and Ta are generally low (6.6–14.8 ppm, and 3.3–6.6 ppm, respectively), compared to those of Zr and Nb. Nevertheless, these rocks contain relatively high concentrations of the HFS elements, thus reflecting an enriched source. The suite is also relatively enriched in the rare earth elements (REE), and exhibits fractionated, subparallel REE pattems; the latter are generally uniform and conformable. Chemical features of these volcanic rocks are typical of those of anorogenic A1 type suites, related to hotspots, mantle plumes, or continental rift zones. This is consistent with earlier interpretation of volcanism associated with an Iapetan RRR triple junction, occurring shortly before the onset of seafloor spreading. At that stage of crustal evolution, alkaline to transitional basaltic magma pierced into the crust, and experienced fractionation to produce the liquids of intermediate composition. Rare earth element geochemical modelling supports the hypothesis that the most evolved composition for which REE data are available (comendite; 67.9 wt.% SiO2) was produced by 20% fractional crystallization of the least evolved trachyandesite (56.7 wt.% SiO2) of this intermediate volcanic assemblage.

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Tectonic significance of the Tibbit Hill volcanics: geochemical evidence from Richmond area, Quebec

Cited by 5 publications

References 0 publications

Geochemistry and petrogenesis of the Tibbit Hill metavolcanic suite of the Appalachian fold belt, Quebec-Vermont; a plume-related and fractionated assemblage

Geochemistry and petrogenesis of the Tibbit Hill metavolcanic suite of the Appalachian fold belt, Quebec-Vermont; a plume-related and fractionated assemblage

Evolution of faulting and paleo-stress field within the Ottawa graben, Canada

Geochemistry of mantle-related intermediate rocks from the Tibbit Hill volcanic suite, Quebec Appalachians

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