Abstract
Granulite-facies xenoliths from an Upper Devonian lamprophyre dyke near Tangier, Nova Scotia, provide new information about the lower crust in the Meguma Zone. Two mineralogically and chemically distinet groups of xenoliths occur. Both groups contain quartz+feldspar+biotite+Fe−Ti oxides+sulfides. In addition, group A contains garnet+graphite±[aluminosilicates+spinel±sapphirine (hight Al2O3 subgroups A1 and A2)] or [clinopyroxene+sphene+apatite (high CaO sub-group A3)]. Group B has highly variable proportions of orthopyroxene (B1), clinopyroxene (B2), and amphibole (B3). Trace-element contents of the highly aluminous xenoliths compare closely with average to upper crustal model compositions and are similar in many aspects to other “undepleted” granulite-facies rocks. LowP-T sedimentary assemblages of quartz-chlorite-clay minerals-calcite-albite or paragonite can account for the compositions of group A xenoliths. Within group B, a high-MgO (MgO>13 wt%) subgroup with high transition-metal contents, and low-MgO (MgO<9 wt%) sub-groups with higher LIL (large-ion-lithophile) element contents exist. Although the rare-earth and high-field-strength elements indicate a tholeiitic or low-K calc-alkaline chemistry, the LIL elements are as high as those from high-K calc-alkaline volcanic are rocks. Isotopically, group A ranges from εNdt=-2.56 to-0.80 and87Sr/86Sr t =0.7046 to 0.7182 fort=370 Ma. For group B these values are +1.45 to +5.33 and 0.7028 to 0.7048, respectively. Model ages (TCHUR) are correspondingly low and are tightly constrained (544±52 Ma). These “young” ages contrast with the middle Proterozoic Nd model ages of the overlying Meguma Zone low-grade flysch. This time-inverted stratigraphy appears to be the product of a tectonic break between a younger autochthonous Tangier lower crust (≡Avalon), and an older allochthonous Meguma Group upper crust.
Similar content being viewed by others
References
Abbey S (1983) Studies in “standard samples” of silicate rocks and minerals 1969–1982. Geol Surv Can Pap 83-15
Arndt NT (1977) The partitioning of nickel between olivine and ultrabasic and basic komatiitic liquids. Carnegie Inst Washington Yearb 76:553–557
Arndt NT, Goldstein SL (1987) Use and abuse of crust-formation ages. Geology 15:893–895
Barbey P, Capdevila R, Hameurt J (1982) Major and transition trace-element abundances in the Khondalite suite of the granulite Belt of Lapland (Fennoscandia): evidence for an early Proterozoic flysch belt. Precambrian Res 16:273–290
Barbey P, Convert J, Moreau B, Capdevila R, Hameurt J (1984) Petrogenesis and evolution of an early Proterozoic collisional orogenic belt of Lapland and the Belmorides (Fennoscandia). Bull Geol Soc Fin 56:161–188
Blatt H, Middleton G, Murray R (1980) Origin of sedimentary rocks. Prentice-Hall, Inc., Englewood, New Jersey
Cavell PA (1985) The geochronology and petrogenesis of the Big Spruce Lake alkaline complex. PhD Thesis, University of Alberta
Chatterjee AK, Giles PS (1988a) Al-rich pyroxenes in granulite xenoliths from Tangier: implications to lower continental crust, eastern Meguma Zone. Nova Scotia. Atl Geosci Colloq 1988, Antigonish, Nova Scotia
Chatterjee AK, Giles PS (1988b) Meguma Zone basement II:P-T evolution of granulite xenoliths (abstract). GAC-MAC Joint Annual Meeting Prog Abstr 13:A19
Chatterjee AK, Giles PS (in press) Major, trace elements and isotopic data for the granulite-facies lower crustal xenoliths, eastern Meguma Zone, Nova Scotia, NS Mines and Miner Branch Report of Activities: Part A
Clarke DB (1970) Tertiary basalts from Baffin Bay possible primary magma from the mantle. Contrib Mineral Petrol 25:203–224
Clarke DB, Chatterjee AK (1988) Meguma Zone basement I: Sr−Nd isotopic study of the Liscomb Complex and the origin of peraluminous granites in the Meguma Zone (abstract). GAC-MAC Joint Annual Meeting Prog Abstr 13:A21
Clarke DB, Halliday AN (1980) Strontium isotope geology of the South Mountain Batholith, Nova Scotia. Geochim Cosmochim Acta 44:1045–1058
Clarke DB, Halliday AN (1985) Sm/Nd isotopic investigation of the age and origin of the Meguma Zone meta-sedimentary rocks. Can J Earth Sci 22:102–107
Clarke DB, O'Hara MJ (1979) Nickel and the existence of high-MgO liquids in nature. Earth Planet Sci Lett 44:153–158
Clarke DB, Halliday AN, Hamilton PJ (1988) Neodymium and strontium isotopic constraints on the origin of the peraluminous granitoids of the South Mountain Batholith, Nova Scotia. Chem Geol 73:15–24
Douma SL (1988) The mineralogy, petrology and geochemistry of the Port Mouton Pluton, Nova Scotia, Canada. Unpubl MSc Thesis, Dalhousie University
Downes H, Leyreloup A (1986) Granulitic xenoliths from the French Massif Central-petrology, Sr and Nd isotope systematics and model age estimates. In: Dawson JB, Carswell DA, Wedepohl KH (eds) The nature of the lower continental crust. Geol Soc Spec Publ 24, pp 319–330
Dupuy C, Leyreloup A, Vernieres J (1977) The lower continental crust of the Massif Central (Bournac, France)-With special references to REE, U and Th composition, evolution, heat-flow production. In: Ahrens LH (ed) Phys Chem Earth 11, pp 401–415
Eberz GW, Clarke DB, Chatterjee AK, Giles PS (1988) Meguma Zone basement III: geochemistry of lower crustal xenoliths (abstract). GAC-MAC Joint Annual Meeting Prog Abstr 13:A35
Giles PS, Chatterjee AK (1986) Peraluminous granites of the Liscomb Complex. Nova Scotia Department of Mines and Energy, Tenth Annual Open House and Review of Activities. Prog and Summaries: 83–89
Giles PS, Chatterjee AK (1987) Lower crustal xenocrysts and xenoliths in the Tangier dyke, eastern Meguma Zone, Nova Scotia. NS Dept Mines Energy Rep 87–5:85–88
Graves MC, Zentilli M (1988) The lithochemistry of metal-enriched coticules in the Goldenville-Halifax transition zone of the Meguma Group, Nova Scotia. In: Current Research, part B. Geol Surv Can Pap 88-1B:251–261
Gray CM (1977) The geochemistry of Central Australian granulites in relation to the chemical and isotopic effects of granulitefacies metamorphism. Contrib Mineral Petrol 65:79–89
Griffin WL, O'Reilly SY (1987) The composition of the lower crust and the nature of the continental Moho—xenolithic evidence. In: Nixon PH (ed) Mantle Xenoliths. John Wiley and Sons. New York, pp 413–430
Hart SR, Davis KE (1978) Nickel partitioning between olivine and silicate melt. Earth Planet Sci Lett 40:203–219
Heier KS (1973) Geochemistry of granulite-facies rocks and problems of their origin. Philos Trans R Soc London A273:429–442
Hofmann AW (1988) Chemical differentiation of the Earth; the relationship between mantle, continental crust, and oceanic crust. Earth Planet Sci Lett 90:297–314
Hon R, Hill M, Hepburn JC, Smith C (1984) Composition and age of source materials for the late Proterozoic magmas in the Avalon Terrane of eastern North America—evidence from the Boston Platform (abstract). Geol Soc Am Abstr Progr 16:543
Jackson SE, Fryer BJ, Gosse W, Healey DC, Longerich HP, Strong DF (1990) Determination of the precious metals in geological materials by inductively coupled plasma-mass spectrometry (ICP-MS) with nickel sulphide fire-assay collection and tellurium coprecipitation. Chem Geol 83:119–132
Jenner GA, Longerich IIP, Jackson SE, Fryer BJ (1990) ICP-MS —a powerful tool for high-precision trace element analysis in earth sciences: evidence from analysis of selected USGS reference samples. Chem Geol 83:133–148
Kay RW, Kay SM (1986) Petrology and geochemistry of the lower continental crust: an overview. In: Dawson JB, Carswell DA, Wedepohl KH (eds) Geol Soc Spec Publ 24:147–159
Kempster RMF, Clarke DB, Reynolds PH, Chatterjee AK (1989) Late Devonian lamprophyric dykes in the Meguma Zone of Nova Scotia. Can J Earth Sci 26:611–613
Keppie JD (1989) Northern Appalachian terranes and their accretionary history. Geol Soc Am Spec Pap 230:159–192
Keppie JD, Dallmeyer RD (1987) Dating transcurrent terrane accretion: an example from the Meguma and Avalon composite terranes in the northern Appalachians. Tectonics 6:831–847
Krogh TE, Keppie JD (1990) Age of detrital zircon and titanite in the Meguma Group, southern Nova Scotia, Canada: clues to the origin of the Meguma Terrane. Tectonophysics 177:307–323
Krogh TE, Strong DF, O'Brien SJ, Papezik VS (1988) Precise U−Pb zircon dates from the Avalon Terrane in Newfoundland. Can J Earth Sci 25:442–453
Le Breton N, Thompson AB (1988) Fluid-absent (dehydration) melting of biotite in metapelites in the early stages of crustal anatexis. Contrib Mineral Petrol 99:226–237
Longerich HP, Jenner GA, Fryer BJ, Jackson SE (1990) Inductively coupled plasma-mass spectrometric analysis of geological samples: a critical evaluation based on case studies. Chem Geol 83:105–118
Maccarone E, Paglionico A, Piccarreta G, Rottura A (1983) Granulite-amphibolite facies meta-sediments from the Serre (Calabria, Southern Italy): their protoliths and processes controlling their chemistry. Lithos 16:95–111
MacDonald MA, Clarke DB (1985) The petrology, geochemistry, and economic potential of the Musquodoboit Batholith, Nova Scotia. Can J Earth Sci 22:1633–1642
McCulloch MT, Black LP (1984) Sm−Nd isotopic evidence of Enderby granulites and evidence for the redistribution of Sm and Nd during metamorphism. Earth Planet Sci Lett 71:46–58
McCulloch MT, Wasserburg GJ (1978) Sm−Nd and Rb−Sr chronology of continental crust formation. Science 200:1003–1011
McKenzie CB, Clarke DB (1975) Petrology of the South Mountain Batholith, Nova Scotia. Can J Earth Sci 12:1209–1218
Matsumoto R, Iijima A (1983) Chemical sedimentology of some Permo-Jurassic and Tertiary bedded cherts in Central Honshu, Japan. In: Iijima A, Hein JR, Siever R (eds) Siliceous deposits in the Pacific region. Elsevier, pp 175–192, New York
Muecke GK, Clarke DB (1981) Geochemical evolution of the South Mountain Batholith, Nova Scotia: rare earth element evidence. Can Mineral 19:133–145
Muecke GK, Elias P, Reynolds PH (1988) Hercynian/Alleghanian overprinting of an Acadian terrane: 40Ar/39Ar studies in the Meguma Zone, Nova Scotia Canada. Chem Geol 73:153–167
Owen JV, Greenough JD, Hy C, Ruffman A (1988) Xenoliths in a mafic dyke at Popes Harbour, Nova Scotia: implications for the basement to the Meguma Zone. Can J Earth Sci 25:1464–1471
Pearce JA (1983) Role of the subcontinental lithosphere in magma genesis at active continental margins. In: Hawkesworth CJ, Norry MJ (eds) Continental basalts and mantle xenoliths. Shiva Publishing Ltd., Nantwich, pp 230–249
Robinson P, Higgins N, Jenner GA (1986) Determination of rare-earth elements, yttrium and scandium in rocks by an ion exchange-x-ray fluorescence technique. Chem Geol 55:121–137
Rock NMS (1983) Nature and origin of calc-alkaline lamprophyres: minettes, vogesites, kersantites and spessartites. Trans R Soc Edinburgh Earth Sci 74:193–227
Rudnick RL, McLennan SM, Taylor SR (1985) Large ion lithophile elements in rocks from high-pressure granulite facies terrains. Geochim Cosmochim Acta 49:1645–1655
Ruffman A, Greenough JD (1990) The weekend dykes, a newly recongnized mafic dyke swarm on the eastern shore of Nova Scotia, Canada. Can J Earth Sci 27:644–648
Samama JC (1986) Ore fields and continental weathering. Van Nostrand Reinholt, New York
Sawyer EW (1986) The influence of source rock type, chemical weathering and sorting on the geochemistry of clastic sediments from the Quetico Metasedimentary Belt, Superior Province Canada. Chem Geol 55:77–95
Schenk PE (1971) Southeastern Atlantic Canada, northwestern Africa, and continental drift. Can J Earth Sci 8:1218–1251
Schenk PE (1981) The Meguma Zone of Nova Scotia—a remnant of western Europe, South America, or Africa. Memoir 7:119–148
Senior A, Leake BE (1978) Regional metasomatism and the geochemistry of the Dalradian meta-sediments of Connemara, Western Ireland. J Petrol 19:585–625
Shaw DM, Cramer JJ, Higgins MD, Truscott MG (1986) Composition of the Canadian Precambrian Shield and the continental crust of the Earth. In: Dawson JB, Carswell DA, Wedepohl KH (eds) The nature of the lower continental crust. Geol Soc Spec Publ 24:275–282
Sheraton JW, Collerson KD (1984) Geochemical evolution of Archaean granulite-facies gneisses in the Vestfold Block and comparisons with other Archaean gneiss complexes in the East Antarctic Shield. Contrib Mineral Petrol 87:51–64
Sighinolfi GP, Gorgoni C (1979) Chemical evolution of high-grade metamorphic rocks—anatexis and remobilization from granulite terrains. Chem Geol 22:157–176
Sivell W (1986) A basaltic-ferroblastic granulite association, Oonagalabi gneiss complex, Central Australia: magmatic variation in the Early Proterozoic rift. Contrib Mineral Petrol 93:381–394
Smalley PC, Field D, Lamb RC, Clough PWL (1983) Rare earth, Th-Hf-Ta and large-ion lithophile element variations in metabasites from the Proterozoic amphibolite-granulite transition zone at Arendal, South Norway. Earth Planet Sci Lett 63:446–458
Stosch HG, Lugmair GW, Seck HA (1986) Geochemistry of granulite-facies lower crustal xenoliths: implications for the geological history of the lower continental crust below the Eifel, West Germany. In: Dawson JB, Carswell DA, Wedepohl KH (eds) The nature of the lower continental crust. Geol Soc Spec Publ 24:309–317
Taylor SR, McLennan SM (1985) The continental crust: its composition and evolution. Blackwell Scientific Publications, Oxford
Tobschall HJ (1975) Geochemische Untersuchungen zum stofflichen bestand und Sedimentationsmilieu paläozoischer mariner Tone: der Gehalt der Hauptelemente und der Spurenelemente Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb und Ba in den Steiger Schiefern. Chem Erde 34:105–167
van den Kamp PC, Leake BE, Senior A (1976) The petrography and geochemistry of some Californian arkoses with application to identifying gneisses of meta-sedimentary origin. J Geol 84:195–212
Weaver BL, Tarney J (1980) Rare earth geochemistry of Lewisian granulite-facies gneisses, Northwest Scotland: implications for the petrogenesis of the Archaean lower continental crust. Earth Planet Sci Lett 51:279–296
Weaver CE, Pollard LD (1973) The chemistry of clay minerals. Elsevier, New York
Whitford DJ, Nicholls IA, Taylor SR (1979) Spatial variations in the geochemistry of Quaternary lavas across the Sunda Arc in Java and Bali. Contrib Mineral Petrol 70:341–356
Wickham SM (1987) The segregation and emplacement of granitic magmas. J Geol Soc London 144:281–297
Williams H, Hatcher RD (1982) Suspect terrains and accretionary history of the Appalachian orogen. Geology 10:530–536
Windrim DP, McCulloch MT, Chappell BW, Cameron WE (1984) Nd isotope systematics and chemistry of Central Australian sapphirine granulites: an example of rare earth mobility. Earth Planet Sci Lett 70:27–39
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Eberz, G.W., Clarke, D.B., Chatterjee, A.K. et al. Chemical and isotopic composition of the lower crust beneath the Meguma Lithotectonic Zone, Nova Scotia: evidence from granulite facies xenoliths. Contr. Mineral. and Petrol. 109, 69–88 (1991). https://doi.org/10.1007/BF00687201
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00687201