Lithogeochemistry of Geological Units in the Parent Lake Area

The tables below summarize the lithogeochemical characteristics of geological units in the Parent Lake area. These units are described in the Geological Bulletin of the Parent Lake area covering this territory and in the Quebec Stratigraphic Lexicon. The 153 analyses used here come from samples collected during the Ministère‘s mapping campaign in the summer of 2019. They were selected based on certain criteria, including a sum of major oxides between 98.5% and 101.5% and a loss on ignition (LOI) <3%. These analyses were conducted by the Actlabs laboratory in Ancaster, Ontario.

Analyses were subject to an internal and laboratory quality assurance and control process. Thus, to ensure the accuracy and precision of the values provided by the laboratory, the Bureau de la connaissance géoscientifique du Québec (BCGQ) regularly inserts blanks, standards and duplicates. Reference materials represent ~10% of the analyses.

The majority of samples in the database were analyzed for major oxides, trace elements and metals. Analyses were performed using different techniques depending on elements, such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-AES) and neutron activation (INAA). For more information on the analysis and dissolution techniques used, refer to the information available for each sample in SIGÉOM à la carte.

Rare earth elements are normalized according to the values of Palme and O’Neill (2004). Anomalous, distinctive or significant contents are indicated in bold in the tables.

Supracrustal Rocks

The Parent Group corresponds to the southern half of sheet 35G11. The rock’s lithogeochemical characteristics were used to discriminate units. Most rare earth patterns display negative Nb-Ta anomalies with a strong negative slope, indicating an arc setting. However, a few units display more of a flat spider diagram, typical of oceanic rift environments. The distribution of Parent Group units is complex and their emplacement cannot be explained simply by the development of a volcanic arc. Indeed, other factors could influence the geochemical signatures of the rocks, such as crustal contamination or the presence of several contemporaneous magmatic chambers.

Intrusive Rocks

Intrusive rocks are particularly well represented in the northern part of sheet 35G11. Felsic intrusive rocks are limited in number and geographically limited. Mafic intrusive rocks are more abundant. Given the complex structure of the area, lithogeochemistry was used to clearly define units.

References

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