Strain and Grain Size Analysis of a Deformed Archean Pyroclastic Flow, Temagami, Ontario

Abstract

<p> The Archean pyroclastic conglomerate studied has six clast types which can be condensed to four clast families based on lithology. The quartz clasts have an average strain of X:Y:Z=1.21:1:0.55 while the pumice clasts have an average strain of X:Y:Z=1.27:1:0.47. The difference is strain between these clast families can be attributed to their different viscosities. The quartz clasts have an assumed viscosity ratio between the clasts and the matrix of unity and are taken to represent the strain in the rock as a whole. The sulphide and black clasts have strain ratios much higher than the quartz because of recrystallization of the sulphide and cleavage formation effecting the black clasts.</p> <p> The sedimentary structure of the deposit and its position between mafic pillow basalts indicate that the deposit is a result of the deposition of a subaqueous pyroclastic debris flow in a proximal environment.</p>