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because it has undergone only a low degree of deformation and is subhorizontal. The southern half of the complex is exposed at the crest of a small dome. This is the eroded portion of the stratovolcano that has been preserved in an upright position. The complex comprises four volcanic sedimentary
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The
Thlewyco sequence represents the main construction phase of the volcano and forms an outward dipping, annular succession around the Innerring sequence, with an aggregate thickness of 2,500 metres (8,200 ft)-5,000 m (16,000 ft). Its stratigraphy changes dramatically around the
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The Kelsh sequence on the northwestern side comprises epiclastic volcarenite, rhyolite-dacite block breccia from lava domes, polymict breccia, and a conglomerate of andesite, dacite-rhyolite clasts, and andesitic tuff. The exposed succession consists of iron-formation, oolitic-stromatolitic
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carbonate, sulphidic volcaniclastic rocks and graphitic slate that marks the end of volcanism. The Kelsh sequence forms a broad apron that is interpreted as a shallow, submarine to subaerial, clastic fan derived by degradation of the volcanic pile (U-Pb zircon dated at 2.586 Ga).
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dome-flow complexes (U-Pb zircon dated at 2.692 Ga). The
Innerring and Thlewycho sequences represent a complex history of explosive eruptions from numerous eruptive centers.
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The
Innerring sequence, which constitutes the oldest rocks of the complex, represents the upper part of an eroded early phase of the volcano (U-Pb zircon igneous age of 2.708
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on turbiditic sequences confirm a secondary deposition of turbidite units at ca. 2.62-2.60 Ga that was widespread throughout the Slave province.
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sequences (Innerring, Thlewyco, Boucher-Regan, Kelsh) that correspond to the phases of growth and destruction of this stratovolcano.
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tuff and volcaniclastic rocks on the south side. Volcanism in this sequence ended with the eruption of large
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Age determinations in the Black River complex are similar to the ages of volcanic rock found in the upper
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and epivolcaniclastic units on the eastern side, to interlayered dacitic and andesitic lava and
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constitutes the Back Group of the
Yellowknife Supergroup and is somewhat anomalous in the
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flows, suggests that this northern flank of the volcano was submerged during deposition.
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Geochronology of the Back River volcanic complex, Nunavut-Northwest
Territories
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Villeneuve, Mike; Lambert, Maurice; van
Breemen, Otto; Mortensen, Jim (2001).
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as well as other volcanic centers in the western Slave province.
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47:. It is located 480 kilometres (298 mi) northwest of
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overlain by a thick succession of voluminous, nonwelded,
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The
Boucher-Regan sequence, with its predominance of
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272:Volcanoes of the Northwest Territories
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196:. Current Research 2001-F2. Ottawa:
85:crater, varying from five cycles of
20:A cutaway diagram of a stratovolcano
55:from which it takes its name. The
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152:Detrital zircon geochronology
169:Volcanism of Northern Canada
51:and to the northwest of the
198:Geological Survey of Canada
174:List of volcanoes in Canada
148:Yellowknife greenstone belt
26:Back River volcanic complex
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282:Stratovolcanoes of Canada
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37:Northwest Territories
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277:Volcanoes of Nunavut
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164:Volcanism of Canada
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287:Archean volcanoes
207:978-0-662-30757-0
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219:. Retrieved
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61:Slave craton
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95:pyroclastic
49:Yellowknife
266:Categories
248:65°N 108°W
221:2010-08-06
180:References
53:Back River
43:border in
216:456791531
144:Kam Group
87:andesitic
74:Gigaannum
68:Innerring
253:65; -108
158:See also
107:rhyolite
103:ash-flow
80:Thlewyco
146:of the
76:(Ga)).
57:volcano
41:Nunavut
30:Archean
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111:dacite
28:is an
239:108°W
194:(PDF)
129:Kelsh
236:65°N
212:OCLC
202:ISBN
109:and
99:tuff
91:lava
24:The
138:Age
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39:–
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