Revised stratigraphic nomenclature for Aphebian and other rock units, southern Labrador Trough, Grenville Province

1980 ◽  
Vol 17 (5) ◽  
pp. 668-670 ◽  
Author(s):  
T. Rivers
Keyword(s):  
Metamorphic Complex ◽  
Grenville Province ◽  
Intrusive Suite ◽  
Stratigraphic Nomenclature

Stratigraphically equivalent Aphebian strata occurring in both the Churchill and Grenville Provinces have different group and formational names. The stratigraphy was first defined within the Churchill Province, and it is proposed that use of these names be extended to cover equivalent units within the Grenville Province. The nomenclature of the Knob Lake Group will thus replace that of the Gagnon Group. Two other changes in terminology are proposed in accordance with a recent amendment to the Code of Stratigraphic Nomenclature. Shabogamo Gabbro is renamed Shabogamo Intrusive Suite, and the name Ashuanipi Metamorphic Complex is proposed instead of Ashuanipi Complex.

Geology and geochronology of Helikian magmatism, western Labrador

1981 ◽  
Vol 18 (7) ◽  
pp. 1211-1227 ◽  
Author(s):  
Christopher Brooks ◽  
Richard J. Wardle ◽  
Toby Rivers
Keyword(s):  
Volcanic Rocks ◽  
High Grade ◽  
Regional Mapping ◽  
Grenville Province ◽  
Felsic Volcanism ◽  
High Grade Metamorphism ◽  
Narrow Belt ◽  
Intrusive Suite ◽  
Magmatic History ◽  
Magma Series

The Shabogamo intrusive suite, a predominantly gabbroic magma series intrusive into a variety of Archean, Aphebian, and Helikian units in the Churchill and Grenville Provinces of western Labrador, is reliably dated at circa 1375 Ma using both the Rb/Sr and Sm/Nd methods on whole rocks and mineral separates. The suite is thus synchronous with Elsonian magmatism in Labrador, which is characterized by the intrusion of large volumes of gabbroic, anorthositic, and associated magma, and so invites petrogenetic correlations on a regional scale.Gabbros of the Shabogamo intrusive suite are emplaced into volcanics and volcaniclastics of the Blueberry Lake group, which are provisionally dated at 1540 ± 40 Ma. The volcanic rocks are therefore of similar age to, and probably correlative with, the upper Petscapiskau Group and Bruce River Group felsic volcanics, which occur further east in a narrow belt within the Grenville Foreland zone. The linear disposition of centres of felsic volcanism in the Grenville Foreland zone about 1500 Ma ago is suggestive of the development of a major ensialic rift at least 300 km in length at that time. A twofold magmatic history during the Helikian of this part of Labrador is now emerging from the field mapping and geochronological studies. Early extrusive felsic volcanism about 1500 Ma ago confined to a linear belt immediately north of the Grenville Province was followed by voluminous mafic magmatism (with emplacement of gabbroic, anorthositic, and associated rocks) occurring over a wide area both within and outside of the present location of the Grenville Province.Rb/Sr dating of Aphebian quartzofeldspathic schists from within the Grenville Province near Wabush – Labrador City shows that the high-grade metamorphism and development of a penetrative schistosity were Grenvillian features formed about 1000 Ma ago. This result effectively precludes the possibility of a Hudsonian metamorphic imprint, a feasible interpretation that was raised during regional mapping of the area.

Eclogitized gabbros from the eastern Grenville Province: textures, metamorphic context, and implications

1993 ◽  
Vol 30 (1) ◽  
pp. 159-173 ◽  
Author(s):  
Aphrodite Indares
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Grenville Province ◽  
Mafic Rocks ◽  
Deep Burial ◽  
Mineral Assemblages ◽  
First Occurrence ◽  
Intrusive Suite ◽  
Very High

Undeformed lenses of olivine–orthopyroxene–gabbro belonging to the 1429 Ma Shabogamo Intrusive Suite (Parautochthonous Belt of the eastern Grenville Province) host the first occurrence of eclogite mineral assemblages reported from the Grenville Province. These rocks preserve igneous textures overprinted by eclogite mineralogy and by textures related to subsequent unloading. High-pressure signatures include omphacite pseudomorphs after augite, plagioclase replacement by garnet + kyanite + corundum, and orthopyroxene–omphacite–garnet coronas between olivine and plagioclase. Transformations related to decompression include replacement of garnet + kyanite + corundum by spinel + plagioclase, growth of plagioclase collars between clinopyroxene and garnet, and de-jadeitization of omphacite. Clinopyroxenes with numerous plagioclase inclusions and garnets surrounded by clinopyroxene–plagioclase symplectites in granoblastic mafic rocks from the same area are also evidence of decompression from high pressures. These rocks record pressure–temperature (P–T) conditions of 1600 MPa at 700–800 °C and steep subsequent P–T paths. It is suggested that the entire parautochthon in this part of the Grenville Province experienced deep burial during the Grenvillian metamorphism. In contrast, the Grenvillian metamorphic signature in the overlying allochthonous sheet is known to be minor, thus precluding any relationship between its emplacement and very high Grenvillian pressures in the parautochthon.

Docking of the Central Metasedimentary Belt to Laurentia in geon 12: evidence from the 1.17-1.16 Ga Chevreuil intrusive suite and host gneisses, Quebec

2000 ◽  
Vol 37 (2-3) ◽  
pp. 253-269 ◽  
Author(s):  
Louise Corriveau ◽  
Otto van Breemen
Keyword(s):  
High Pressure ◽  
North America ◽  
Metamorphic Event ◽  
Grenville Province ◽  
Layered Gabbro ◽  
Peak Metamorphism ◽  
Magma Emplacement ◽  
Reactivation Event ◽  
Intrusive Suite ◽  
Tectonic Boundaries

The Chevreuil intrusive suite (1.17-1.16 Ga) represents a chronological field marker of regional extent that intruded the Central Metasedimentary Belt in the western Grenville Province of Quebec after peak metamorphism. Style and site of magma emplacement, and extent of deformation of Chevreuil plutons and dykes permit unravelling of the early Grenvillian evolution of the belt with respect to cratonal North America. The suite comprises a series of vertically layered gabbro stocks and monzonite-diorite-gabbro sheet intrusions, and a swarm of microdiorite dykes that cut across gneisses. The dykes display systematic variations in extent of deformation across the belt. We targeted U-Pb geochronology on gneisses within the identified strain windows; they preserve the record of a ca. 1.20 Ga high pressure-temperature (P-T) metamorphic event. The sheet intrusions define magmatic corridors all along, and concordant with, the western, northern, and eastern tectonic boundaries of the belt. The concordant and elongate shape of these bodies results from emplacement, not deformation. Chevreuil magmas thus sealed the belt boundaries largely in their current positions, with the implication that docking of Elzevirian and pre-Elzevirian terranes with cratonal North America predates 1.17 Ga. We interpret the 1.20 Ga metamorphism as evidence for the initiation of Grenvillian continent-continent collision during the culmination of the Elzevirian orogeny at ca. 1.22 Ga. Emplacement-related fabrics indicate that the Chevreuil suite and the coeval Morin anorthosite suite intruded during renewed orogenesis. This orogenic pulse (Shawinigan) is not accretionary, but represents a strongly partitioned, compressive, intraplate reactivation event.

The Zirconometry and Thermochronology of Migmatized Gneisses of the Gondaray Metamorphic Complex (Greater Caucasus)

2020 ◽  
Vol 75 (5) ◽  
pp. 481-495
Author(s):  
V. Yu. Gerasimov ◽  
V. A. Snezhko ◽  
J. Mosar ◽  
A. N. Pismennyi ◽  
N. L. Enna ◽  
...  
Keyword(s):  
Metamorphic Complex ◽  
Greater Caucasus
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