GEOLOGY OF THE RIVIERE ARNAUD AREA AND ADJACENT COASTAL AREAS. RG 2001-06, 2001. 35 pages and 4 maps.
MADORE, L.., LARBI, Y.



Abstract

This new geological survey covers the Rivière Arnaud area (NTS 25D) in addition to the coastal regions of Ungava Bay (NTS 25C) and Hudson Strait (NTS 25E and 25F). The study area is underlain by Archean rocks of the Douglas Harbour domain (Superior Province). These Archean rocks are intruded by Early Proterozoic dykes (Payne River Dykes and Klotz Dykes), and partially overlain by thrust sheets. These nappes, composed of Early Proterozoic supracrustal sequences, belong to the Labrador Trough and the Ungava Trough. Within the study area, rocks associated to the Archean craton were subdivided into three lithodemic units: the Qimussinguat Complex, the Faribault-Thury Complex and the Diana structural Complex. The distinction between these units is based on typical lithological assemblages, as well as differences in the metamorphic grade and tectonic style. Rocks of the Qimussinguat Complex are generally metamorphosed to the granulite facies, whereas those of the Faribault-Thury Complex are at the amphibolite facies. The two complexes are essentially composed of orthogneisses of the tonalite-trondhjemite-granodiorite/granite suite, which enclose mafic remnants of gabbroic, basaltic or metasedimentary origin. In the Qimussinguat Complex, these remnants are rare and restricted in size. In the Faribault-Thury Complex, volcano-sedimentary rocks form a string of segments one to several kilometres in size, distributed over a distance exceeding 100 km. The Qimussinguat and Faribault-Thury complexes display structural fabrics typical of Archean deformation, dominated by a steeply-dipping foliation or gneissosity oriented NNW-SSE. The Diana structural Complex is mainly formed of Archean tonalitic orthogneisses that were reworked during the Proterozoic. It is characterized by a generally well-developed mylonitic foliation that affects both Archean and Early Proterozoic lithologies. Archean fabrics suggest a polyphase tectonic setting. The foliation and gneissosity are disturbed by complex folding of variable intensity, superimposed by ductile shear zones. Proterozoic fabrics indicate two distinct tectonic styles. The first is related to the thrusting of Early Proterozoic sequences onto the Archean basement, and the second, to dextral strike-slip movement in a transpressional setting. No evidence of Proterozoic deformation was observed in the Qimussinguat Complex. In the Faribault-Thury Complex, Early Proterozoic deformation is discrete and the associated metamorphism varies from the greenschist facies to the amphibolite facies. A preliminary geochronological study helped establish a sequence of events marking the geological history of the area. It begins with the emplacement of volcanic rocks and felsic plutonic rocks at 2.8 Ga, followed by two episodes of Archean metamorphism at 2.7 Ga and 2.6 Ga, and a Proterozoic metamorphic event at 1.8 Ga. Mapping has led to the discovery of two new mineralized showings and 10 anomalous occurrences. The mineralization essentially consists of Cu, Ag and Zn, found in metavolcanic or metasedimentary rock remnants. Mafic and ultramafic intrusions, mainly present in volcano-sedimentary belts, were also identified. Despite their relatively high Mg content, these rocks contain very few anomalous Ni, Cu and Cr values, and only one minor Cu showing was reported. With the exception of rocks in the Labrador Trough, where Ni-Cu-PGE showings were recently discovered in mafic-ultramafic rocks, paragneiss bands located in the eastern part of the Diana structural Complex as well as the Trempe and Buet volcano-sedimentary belts, included in the Faribault-Thury Complex, appear to represent the most interesting exploration targets

Details

Document type

Document produced by the Ministère
Geological reports

Field of activity

General geology

Type of survey

Geological survey

Cross-reference

Also see RG 2000-05

Document type

Document produced by the Ministère
Geological reports

Field of activity

General geology

Type of survey

Geological survey

Cross-reference

Also see RG 2000-05