Pyritic Quartz Pebble Conglomerate in the Hurwitz Group, District of Keewatin

A thin formation of folded mafic flows resting unconformably on Archean basement is informally named the Spi Lake basalt. Stratigraphic, structural, and textural evidence suggests that these lavas were probably fed from a diabase dike swarm dated at 2250+ m.y. by the Geological Survey of Canada. The Spi Lake basalt is overlain by conglomerate that may represent the base of the Hurwitz Group.

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Geochronology of Archean and Proterozoic Rocks in the Southern District of Keewatin

Canadian Journal of Earth Sciences ◽

10.1139/e75-011 ◽

1975 ◽

Vol 12 (1) ◽

pp. 95-114 ◽

Cited By ~ 7

Author(s):

R. K. Wanless ◽

K. E. Eade

Keyword(s):

Volcanic Rocks ◽

Southern District ◽

Quartz Monzonite ◽

Minimum Age ◽

First Time ◽

Hurwitz Group ◽

Age Determinations

Rb–Sr and U–Pb dating techniques have been utilized to identify and date Archean supracrustal rocks within the Churchill structural province in regions where K–Ar age determinations have recorded only the effects of younger Hudsonian orogeny. The age of emplacement of Archean granodiorite has been established at 2550 m.y., a determination that also provides a minimum age for volcanic rocks intruded by the granodiorite.The overlying Proterozoic Hurwitz Group volcanic rocks have been dated for the first time at 1808 ± 35 m.y. (Upper Aphebian). A post-Hurwitz Group quartz monzonite pluton intruded the granodiorite gneiss at 1772 ± 22 m.y. and the age of the post-tectonic Nueltin Lake Granite has been established at 1700 ± 16 m.y. (Paleohelikian).It is concluded that the Hurwitz Group cannot be correlated with the Huronian succession in Ontario as the Hurwitz Group rocks are 300 to 400 m.y. younger than the Huronian strata.

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The Spi Group: a post-Archean, pre-2.1 Ga rift succession, Trans-Hudson hinterland

Canadian Journal of Earth Sciences ◽

10.1139/e91-166 ◽

1991 ◽

Vol 28 (11) ◽

pp. 1863-1872 ◽

Cited By ~ 7

Author(s):

Judith G. Patterson

Keyword(s):

Alluvial Fan ◽

History Of ◽

Group A ◽

Hurwitz Group ◽

Archean Basement

A succession of mafic flows intercalated with sandstone and overlain by conglomerate, herein named the Spi Group, lies unconformably on Archean basement and is preserved in a syncline near Spi Lake, N.W.T. An alluvial fan setting near active rift fault escarpments is the interpreted environment of deposition. The nearby Montgomery Lake Group, Mackenzie Lake metasediments, and Padlei Formation at the base of the Hurwitz Group are possible correlatives of the Spi Group; diabase dykes of the Kaminak swarm, common in the Archean basement, are possibly related to the mafic flows. Correlation with the upper, coarse clastic part of the Hurwitz Group (Tavani Formation) is discounted because the Spi conglomerate does not contain clasts of Hurwitz lithology. The Montgomery Lake, Padlei and Spi successions are interpreted as being rift-related, and are older than the 2.1 Ga gabbro that intrudes the Hurwitz Group. Recognition of widespread rifting in this part of the Hearne Province constrains tectonic modelling of the preorogenic history of the Trans-Hudson hinterland.

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