Physical Volcanology, Hydrothermal Alteration and Massive ...

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generally aligned in the strike direction. In thin section, these rocks are composed of 20%foliated (primary?) fine laths of plagioclase and 15% quartz in a secondary matrix of 40%chlorite, 10% biotite, and 2% epidote.Pillow breccia and hyaloclastite are exposed in the outcrop east of the water tower.These rocks consist of approximately 25% amygdaloidal pillow fragments (5-50 cm) in amatrix consisting of 30% hyaloclastite and 70% amygdaloidal flows. The pillow brecciafragments contain 10-20% carbonate filled amygdules (now weathering pits) which rangein size from 1-4 mm. The hyaloclastite portion of the matrix consists of 0.5-2 cmrecrystallized massive angular andesite fragments. The flow portion of the matrix consistsof vaguely defined amygdaloidal (20-50% amygdules) flows. Flows become the dominantrock type on the north portion of the outcrop.Pillowed flows are exposed in the outcrop north of the water tower. This rockconsists of well-formed 1-4 m (in the long dimension) amygdaloidal pillows with 25-30%,1-20 mm carbonate-filled amygdules. The amygdules show a bimodal size distribution;most amygules are 1-4 mm, with another distinct grouping at 5-20 mm. Massive pillowselvages vary from 5-15 cm thick.AREA "17"Stop 17-1: Upper "L" Dome Collapse BrecciaArea 17 is located immediately east of the Lyon Lake, Creek Zone, Sub-CreekZone, and Sturgeon Lake orebodies. The southern one-third of this area is composed ofHigh Level Lake Succession pyroclastic flow deposits, Tailings Lake Succession debrisflow deposits and associated sediments, and Mattabi Succession Pyroclastic flow deposits.The central one-third of the area is composed of a complex sequence of rhyolitic to dacitic"L" Succession pyroclastic flow deposits, volcaniclastic sedimentary rocks, and andesiticto dacitic lava flows. The northern one-third of the area is dominated by a dacitic lavadome which is capped by dome-derived debris flow deposits, volcaniclastic sedimentaryrocks, graphitic sedimentary deposits, and iron formation (see Figure 10).32
13LEGEND OF GEOLOGICAL UNITS SYMBOLS15 Andes it ic to Doc it ic Intrus ions14 Sodium Amphibole-rictl lotrusion13 Swamp Lake Success ion12 No Nome Lake/Lyon Lake Succession11 Lava Dome Assac iated Sed imen ts/Debr is F I ow Depos its10 Lyon Lake Dacitic Lava Dome Complex9 "L" VOICQO iclostic Sediments/Debris Flow Deposits8 "L" Lova Flows7Upper "L" Pyroclastic Deposits6 Midddle "L" Pyroclastic DepositsSLower "L" Pyroclastic Deposits4 Mottabi Success ion Pyroclastic Flow DepositsJ Toil ings Lake Succession2 High Level Lake Pyroclastic Flow Deposits1 High Level Lake Mesobreccio DepositsGeologicalContact (inFerred)Massive Sulfide DepositSynvolcon ic Feu ItLate FaultOutcrop LocationsRoodso 400FEET800NIFigure 10.Creek Zone,location.Geological plan mapand sturgeon Lakein the vicinity of theorebodies, with fieldLyon Lake,trip stop33
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Page 39 and 40: REFERENCESBusby - Spera, C., 1984,
Page 41: associated with the Lyon Lake massi

Physical Volcanology, Hydrothermal Alteration and Massive ...

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