Page 216 - Caldera Volcanism Analysis, Modelling and Response

Characterisation of Archean Subaqueous Calderas in Canada 191

of of by flow by talus faults
indicative massive suggestive and Heterolithic deposit; a intracaldera
to currents flow caused of
massive flows hydroclastic processes; tuff resedimentation density vertical flows subaqueous of brecciation fragmentation flow represents Locus: caldera to site Faults hydrothermal

Subaqueous lava brecciated and autoclastic fragmentation lapilli stratified synvolcanic subaqueous and Lateral basalt in characteristic processes; autoclastic granulation. mass a is breccia deposit. adjacent margin. silicification

(a-1) to (a-2) changes thermal breccia chaotic scree setting and extensive

lobate with lapilli basalt pillows BIF , segments Heterolithic mafic felsic

lithofacies: to with flows flow contain units clasts of presence stratified tuffs lapilli pumice lithofacies: Mg high massive, and breccia 2–20 breccia; columnar-jointed lobate-pillowed into Chaotic 30–40 m-thick of rafts and (2–5 m-thick) by and BIF

volcanic coherent felsic extensive breccia subangular to massive and subordinate volcanic and tholeiitic 50–80 m-thick of composed pillow fragment massive into up-section breccia. facies large of blocks, flows. mafic facies dominated and chert,

Felsic 2–30 m-thick brecciated terminations; banding; to angular flow-banding; m-thick breccias containing Mafic (10–11%), pillowed, pillow m-thick grade and pillow breccia composed volcaniclastic and breccia silicified with

(a-1) tuff (a-2) mafic flows flows flows and felsic clasts clasts

mafic

volcanic and lithofacies

Felsic lithofacies volcanic

(a)

lobes with

and
flows

lava contemporaneous dykes

Felsic felsic