CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Eiche, G.
Date : 1985.
Title : Petrology of Quaternary alkaline lavas from the Alligator Lake Volcanic Complex, Yukon Territory, Canada
Publication : Unpublished M.Sc. thesis. McGill University, Dept. of Geological Sciences, Montreal
Issue :
Page(s) :
Abstract
Primitive and differentiated basaltic lava types alkaline affinity comprise the five extrusive units of the Quaternary Alligator Lake volcanic complex of southwestern Yukon. The chemical distinctiveness of units 1, 4, and 5 (hypersthene-, quartz-, and nepheline-normative, respectively) suggests that these lavas had a complex history involving the differentiation of their magmas after leaving their mantle sources. Most lava flows as comprising units 2 and 3, however, are alkali olivine basalts and basanites which have high Mg contents (13.5-19.5 cation%) and host spinel 1herzolite xenoliths, indicating that their compositions reflect primary magmas derived directly from the mantle. However, although the lavas from both units 2 and 3 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; lower HREE, Y, Ca, Si, and Al; and similarratios of highly incompatible elements and isotopes relative to unit 3. These features are most explained if unit 2 magmas segregated at greater depths than unit 3 magmas from a garnet-bearing mantle by smaller degrees of partial melting relative to unit 3. Thus, the lavas of units 2 and 3 reflect the existence of two contrasting primary magma types.
Bibliography of Canadian Geomorphology