| Title | Geology of the Winokapau Lake area, Grenville Province, central Labrador |
| Download | Downloads |
| Author | Thomas, A |
| Source | Geological Survey of Canada, Paper no. 89-18, 1993, 86 pages (1 sheet), https://doi.org/10.4095/193324 |
| Year | 1993 |
| Publisher | Natural Resources Canada |
| Document | serial |
| Lang. | English |
| Maps | Publication contains 1 map |
| Map Info. | geological, lithological, structural, 1:100,000 |
| Media | paper; on-line; digital |
| Related | This publication contains Thomas, A; (1991). Geology,
Winokapau Lake area, Newfoundland, Geological Survey of Canada, "A" Series Map no. 1763A |
| File format | pdf |
| Province | Newfoundland and Labrador |
| NTS | 13E/03; 13E/04; 13E/05; 13E/06 |
| Area | Winokapau Lake; Churchill River; Winokapau Lake; Elizabeth Lake; Fig River; Trans Labrador Highway; Disappointment Lake; Metchin River; Labrador |
| Lat/Long WENS | -64.0000 -63.0000 53.5000 53.0000 |
| Subjects | geochemistry; geochronology; igneous and metamorphic petrology; structural geology; paleo-helikian; Aphebian; plutonic rocks; granodiorites; gabbros; igneous rocks; gneisses; orthogneisses; metamorphic
rocks; granites; lithology; folds; faults, thrust; faults; foliation; lineations; structural features; mineral assemblages; metamorphic facies; granulite facies; metamorphism; dunites; pressure-temperature conditions; zircon dates; uranium lead
dates; argon argon dates; radiometric dates; norites; major element analyses; whole rock analyses; trace element analyses; analyses; geochemical analyses; minor element geochemistry; trace element geochemistry; sapphirine; field relations; textural
analyses; metamorphism, retrograde; greenschist facies; phase relations; norm analyses; Grenville Province; Winokapau Lake Granodiorite; Shabogamo Gabbro; Disappointment Lake Gneiss; North Pole Brook Intrusive Suite; sphene dates; monazite dates;
biotite dates; hornblende dates; Proterozoic |
| Illustrations | sketch maps; photographs; analyses; Concordia diagrams; photomicrographs |
| |
| Program | Canada-Newfoundland Co-operative Mineral Program, 1982-1984 |
| Program | Canada-Newfoundland Mineral Development Agreement, 1984-1989 |
| Released | 1994 01 01; 2016 02 02 |
| Abstract | Precambrian crystalline rocks within the northern part of the Grenville Structural Province near Winokapau Lake southeast of Churchill Falls, Labrador, constitute a mixed paragneiss, orthogneiss,
granitoid, and gabbroid terrane. A range of hills in the eastern and southern parts of the area mark an allochthonous crustal block, the Wilson Lake allochthon, underlain primarily by granulite facies quartzofeldspathic paragneiss containing the
mineral assemblage hypersthene + sillimanite + biotite + quartz + plagioclase + potassium feldspar ± sapphirine ± cordierite. Lowlands are underlain by parautochthonous rocks comprising amphibolite to granulite facies quartzofeldspathic paragneiss,
orthogneiss, and deformed porphyritic granitoid and gabbroid rocks. Paragneiss in the parautochthon is characterized by the mineral assemblage sillimanite + biotite + quartz + plagioclase + potassium feldspar ± hypersthene ± sapphirine ± cordierite ±
muscovite ± kyanite ± garnet whereas orthogneiss and deformed granitoid-gabbroid rocks contain the assemblage biotite + plagioclase ± potassium feldspar ± hypersthene ± hornblende ± garnet ± quartz. The protolith of paragneiss in the Winokapau Lake
area is at least Aphebian in age, and is correlated with that of the Disappointment Lake gneiss in and around the Red Wine Mountains massif to the north, which is a continuation of the Wilson Lake allochthon that has undergone a similar tectonic
history. The orthogneiss is correlated with essentially undeformed Paleohelikian granitoid rocks belonging to the Trans Labrador Batholith, located north of the present study area. Both the parautochthonous and allochthonous blocks have undergone
extensive deformation during at least two major orogenic events. U-Pb dates of 1676 and 1603 Ma on zircons obtained from the paragneiss are the result of a newly identified mid-Paleohelikian orogenic event known as the Labradorian orogeny. Similar
U-Pb dates ranging from 1653 to 1635 Ma have also been obtained from the orthogneiss. Granulite facies peak metamorphic conditions prevailed during this event with temperatures having exceeded 700 C and pressures 6 x 105 kPa. In contrast, a number of
younger U-Pb and 40Ar/39Ar mineral ages have been derived from the orthogneiss, and range from 1013 to 991 Ma. These represent reworking of the rocks during the Grenvillian Orogeny under middle to upper amphibolite facies metamorphic conditions, with
indicated temperatures in the range 500 to 600 C and pressures of up to 7 x 105 kPa. Rocks within the Winokapau Lake area form an integral part of the mid-Proterozoic Grenville orogenic terrane, which extends entirely across central Labrador,
continuing into both the southwestern United States and the Scandinavian countries. |
| GEOSCAN ID | 193324 |
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