Abstract:
In the Elliot lake region of northern Ontario, Yolcanlc lava piles
represent the lowermost units of the Huronian SUpergroup. These rocks
general1y trend east-west and belong to the Elliot lake Group. They are
s1tuated on the north and south limbs or the QuIrke lake Syncline.
The volcanIc rocks of this study contain a secondary minerai
assemblage consisting of actinolite, biotite, chlorIte, eptdote/cllnozoislte
tttanomagnettte and calcite characteristic of greenschist metamorphism.
Compilation of data suggests that metamorphism of the volcanic rocks
proceeded between 325- and 425-C and between 2.4 and 4.7 kb.
Geochemtcally these lavas represent tholeiitic and calc-alkaline
assemblages. The tholeiites are character1sttcally enriched tn Fe and Tt
and consist mainly of basalts, basaltic andesites and andesites. These
rocks are believed to have formed by the partIal melting of a peridottte
source at low P-T. In contrast, the calc-alkaline rocks are depleted in Fe
and TI, but show a signIficant enrichment In 51 and Zr; andesIte Is the major
rock type for thIs assemblage. I·t Is postUlated that the calc-alkalIne sU1te
of rocks was the result of eIther the partIal meltIng of abasaltic·magma at
shallow depth, or the melttng of s1al1c crustal materIal due to the added
we1ght of tholeiitIc material on an unstable crust and to downwarplng
processes Inttlated by convection cells.
