Contributions to Mineralogy and Petrology

, Volume 95, Issue 2, pp 191–201 | Cite as

Primary alkaline magmas associated with the Quaternary Alligator Lake volcanic complex, Yukon Territory, Canada

  • G. E. Eiché
  • D. M. Francis
  • J. N. Ludden


The Alligator Lake complex is a Quaternary alkaline volcanic center located in the southern Yukon Territory of Canada. It comprises two cinder cones which cap a shield consisting of five distinct lava units of basaltic composition. Units 2 and 3 of this shield are primitive olivine-phyric lavas (13.5–19.5 cation % Mg) which host abundant spinel lherzolite xenoliths, megacrysts, and granitoid fragments. Although the two lava types have erupted coevally from adjacent vents and are petrographically similar, they are chemically distinct. Unit 2 lavas have considerably higher abundances of LREE, LILE, and Fe, but lower HREE, Y, Ca, Si, and Al relative to unit 3 lavas. The 87Sr/86Sr and 143Nd/144Nd isotopic ratios of these two units are, however, indistinguishable. The differences between these two lava types cannot be explained in terms of low pressure olivine fractionation, and the low concentrations of Sr, Nb, P, and Ti in the granitoid xenoliths relative to the primitive lavas discounts differential crustal contamination. The abundance of spinel lherzolite xenoliths and the high Mg contents in the lavas of both units indicates that their compositional differences originated in the upper mantle. The Al and Si systematics of these lavas suggests that, compared to unit 3 magmas, the unit 2 magmas may have segregated at greater depths from a garnet lherzolite mantle. The identical isotopic composition and similar ratios of highly incompatible elements in these two lava units argues against their differences being a consequence of random metasomatism or mantle heterogeneity. The lower Y and HREE contents but higher concentrations of incompatible elements in the unit 2 lavas relative to unit 3 can be most simply explained by differential partial melting of similar garnet-bearing sources. The unit 2 magmas thus appear to have been generated by smaller degrees of melting at a greater depth than the unit 3 magmas. The contemporaneous eruption of two distinct but volumetrically restricted primary magmas from adjacent vents at the Alligator Lake volcanic complex suggests that volcanism in this region of the Canadian Cordillera is controlled by localized, small batch processes.


Olivine Incompatible Element Cinder Cone Garnet Lherzolite Lava Type 
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  1. Allegre CJ, Dupre B, Lambret B, Richard P (1981) The subcontinental versus suboceanic debate, I. Lead-neodymium-strontium isotopes in primary alkali basalts from a shield area: the Ahaggar suite. Earth Planet Sci Lett 52:85–92Google Scholar
  2. Bevier ML (1979) Miocene peralkaline volcanism in west-central British Columbia — its temporal and plate-tectonics setting. Geology 7:389–392Google Scholar
  3. Bevier ML (1983) Implications of chemical and isotopic composition for petrogenesis of Chilcotin Group Basalts, British Columbia. J Petrol 24:207–226Google Scholar
  4. Boettcher AL, O'Neill Jr (1980) Stable isotope, chemical, and petrographic studies of high-pressure amphiboles and micas: evidence for metasomatism in the mantle source regions of alkali basalts and kimberlites. Am J Sci 280-A:594–621Google Scholar
  5. Dawson JB (1984) Contrasting types of upper mantle metasomatism? In: Kornprobst J (ed) Kimberlites II: the mantle and crust-mantle relationships. Elsevier, Amsterdam pp 289–294Google Scholar
  6. DePaolo DJ, Wasserburg GJ (1976) Inferences about magma sources and structure from variations in 143Nd/144Nd. Geophys Res Lett 3:743–776Google Scholar
  7. Feisinger and Nicholls (1977) Petrography and petrology of Quaternary volcanic rocks, Quesnel Lake region, east-central British Columbia. Geol Assoc Can Spec Pap 16:25–38Google Scholar
  8. Ford CE, Russell DG, Craven JA, Fisk MR (1983) Olivine-liquid equilibria: temperature, pressure, and composition dependence of the crystal/liquid cation partition coefficients for Mg, Fe2+, Ca, and Mn. J Petrol 24:256–265Google Scholar
  9. Francis DM (1976) The origin of amphibole in lherzolite xenoliths from Nunivak Island, Alaska. J Petrol 17:357–378Google Scholar
  10. Francis DM (1983) Magma evolution in a Proterozoic rifting environment. J Petrol 24:556–582Google Scholar
  11. Francis DM (1987) Mantle-melt interactions recorded in spinel lherzolite xenoliths from the Alligator Lake volcanic complex, Yukon, Canada. J Petrol (in press)Google Scholar
  12. Francis DM, Ludden JN (1986) Fe-rich olivine nephelinite primary magmas from Fort Selkirk, Yukon, Canada. EOS 67:390Google Scholar
  13. Frey FA, Green DH (1974) The mineralogy, geochemistry and origin of lherzolite inclusions in Victorian basanites. Geochim Cosmochim Acta 38:1023–1059Google Scholar
  14. Frey FA, Prinz M (1978) Ultramafic inclusions from San Carlos, Arizona: petrologic and geochemical data bearing on their petrogenesis. Earth Planet Sci Lett 38:129–176Google Scholar
  15. Frey FA, Green DH, Roy SD (1978) Integrated models of basalt petrogenesis: a study of quartz tholeiites to olivine melilitites from South Eastern Australia utilizing geochemical and experimental petrological data. J Petrol 19:463–513Google Scholar
  16. Fujii T, Scarfe CM (1985) Composition of liquids coexisting with spinel lherzolite at 10 Kb and the genesis of MORBs. Contrib Mineral Petrol 90:18–28Google Scholar
  17. Green DH (1971) Compositions of basaltic magmas as indicators of conditions of origin: applications to oceanic volcanism. Phil Trans R Soc Lond, Ser A 268:707–725Google Scholar
  18. Green DH (1973) Conditions of melting of basanite magma from garnet peridotite. Earth Planet Sci Lett 17:456–465Google Scholar
  19. Green DH, Edgar AD, Beasley P, Kiss E, Ware NG (1974) Upper mantle source for some hawaiites, mugearites and benmoreites. Contrib Mineral Petrol 48:33–43Google Scholar
  20. Griffin WL, Murthy VR (1969) Distribution of K, Rb, Sr, and Ba in minerals relevant to basalt genesis. Geochim Cosmochim Acta 33:1389–1414Google Scholar
  21. Hanson GN, Langmuir CH (1978) Modelling of major elements in mantle-melt systems using trace element approaches. Geochim Cosmochim Acta 42:725–742Google Scholar
  22. Jaques AL, Green DH (1980) Anhydrous melting of peridotite at 0–15 kb pressure and the genesis of tholeiitic basalts. Contrib Mineral Petrol 73:287–310Google Scholar
  23. Kay RW, Gast PW (1973) The rare earth content and origin of alkali-rich basalts. J Geol 81:653–682Google Scholar
  24. Lloyd FE, Bailey DK (1975) Light element metasomatism of the continental mantle: the evidence and the consequences. Phys Chem Earth 9:381–416Google Scholar
  25. Macdonald A, Katsura T (1964) Chemical composition of Hawaiian lavas. J Petrol 5:82–133Google Scholar
  26. McKenzie D (1985) The generation and compaction of partially molten rock. J Petrol 25:713–765Google Scholar
  27. Menzies MA, Murthy VR (1980) Nd and Sr isotope geochemistry of hydrous mantle nodules and their host alkali basalts: implications for local heterogeneities in metasomatically veined mantle. Earth Planet Sci Lett 46:323–334Google Scholar
  28. Menzies MA, Wass SY (1983) CO2- and LREE-rich mantle below eastern Australia: a REE and isotopic study of alkaline magmas and apatite-rich mantle xenoliths from the Southern Highlands Province, Australia. Earth Planet Sci Lett 65:287–302Google Scholar
  29. Mysen BO, Virgo D (1980) Trace element partitioning and melt structure: an experimental study at 1 atm pressure. Geochim Cosmochim Acta 44:1917–1930Google Scholar
  30. Nicholls J, Stout MZ, Fiesinger DW (1982) Petrologic variations in Quaternary volcanic rocks, British Columbia, and the nature of the underlying upper mantle. Contrib Mineral Petrol 79:201–218Google Scholar
  31. Pearce JA, Alabaster T, Shelton AW, Searle MP (1981) The Oman ophiolite as a Cretaceous arc-basin complex: evidence and implications. Phil Trans R Soc London A300:299–317Google Scholar
  32. Prescott JP (1984) Ultramafic xenoliths and the nature of the upper mantle beneath Western Canada and Alaska. Unpubl MSc Thesis, McGill UniversityGoogle Scholar
  33. Ringwood AE (1975) Composition and Petrology of the Earth's mantle. McGraw-Hill, New York, p 618Google Scholar
  34. Roden MF, Frey FA, Francis DM (1984a) An example of consequent metasomatism in peridotite inclusions from Nunivak Island, Alaska. J Petrol 25:546–577Google Scholar
  35. Roden MF, Frey FA, Clague DA (1984b) Geochemistry of tholeiitic and alkalic lavas from the Koolan Range, Oahu, Hawaii: implications for Hawaiian volcanism. Earth Planet Sci Lett 69:141–158Google Scholar
  36. Roeder PL, Emslie RF (1970) Olivine-liquid equilibrium. Contrib Mineral Petrol 29:275–289Google Scholar
  37. Scarfe CM, Mysen BO, Rai CS (1979) Invariant melting behavior of mantle material: partial melting of two lherzolite nodules. Carnegie Inst Washington Yearb 78:498–501Google Scholar
  38. Sen G (1982) Composition of basaltic liquids generated from a partially depleted lherzolite at 9 kb pressure. Nature 299:336–338Google Scholar
  39. Sleep NH (1974) Segregation of magma from a mostly crystalline mush. Bull Geol Soc Am 85:1225–1232Google Scholar
  40. Souther JG (1977) Volcanism and tectonic environments in the Canadian Cordillera — a second look. In: Barager WRA, Coleman LC, Hall JM (eds) Volcanic regimes in Canada. Geol Assoc Can Spec Pap 16:3–24Google Scholar
  41. Souther JG, Armstrong RL, Harakal J (1984) Chronology of the peralkaline, late Cenozoic Mount Edziza Volcanic Complex, northern British Columbia, Canada. Geol Soc Am Bull 95:337–349Google Scholar
  42. Stosch HG (1982) Geochemistry and mineralogy of two spinel peridotite suites from Dreiser Weiher, West Germany. Geochim Cosmochim Acta 44:457–470Google Scholar
  43. Streckeisen A (1976) To each plutonic rock its proper name. Earth Sci Rev 12:1–33Google Scholar
  44. Sun SS, Hanson GN (1975) Evolution of the mantle: geochemical evidence from alkali basalt. Geology 3:297–302Google Scholar
  45. Takahashi E, Irvine TN (1981) Stoichiometric control of crystal/liquid single-component partition coefficients. Geochim Cosmochim Acta 45:1181–1185Google Scholar
  46. Takahashi E, Kushiro I (1983) Melting of a dry peridotite at high pressure and basalt magma genesis. Am Mineral 68:859–879Google Scholar
  47. Takahashi E, Scarfe CM (1985) Melting of peridotite to 14 GPa and the genesis of komatiite. Nature 315:566–568Google Scholar
  48. Wass SY, Rogers NW (1980) Mantle metasomatism — precursor to continental alkaline volcanism. Geochim Cosmochim Acta 44:1811–1823Google Scholar
  49. Watson EB (1982) Melt infiltration and magma evolution. Geology 10:236–240Google Scholar
  50. Wheeler JO (1961) Whitehorse map-area, Yukon Territory: Geol Surv Can Mem 312Google Scholar
  51. Wood DA (1979) A variably veined suboceanic upper mantle — genetic significance for mid-ocean ridge basalt from geochemical evidence. Geology 7:499–503Google Scholar

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • G. E. Eiché
    • 1
  • D. M. Francis
    • 1
  • J. N. Ludden
    • 2
  1. 1.Department of Geological SciencesMcGill UniversityMontrealCanada
  2. 2.Département de GéologieUniversité de MontréalMontréalCanada

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