DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
The Dancelou Suite was named by Simard et al. (2013) in the Kuujjuaq and Ungava Bay area to group poorly deformed, late tectonic granitic intrusions that cut older units. It has been recognized farther south in the Saffray Lake (Lafrance et al., 2014) and Jeannin Lake (Charette et al., 2016) areas, as well as in small areas in the western portion of the Henrietta Lake area (Lafrance et al., 2016). As part of a synthesis of the Southeastern Churchill Province (SECP) (Lafrance et al., 2018), different lithotectonic domains were identified. These authors have reassigned outcrops of the Dancelou Suite to the Qarliik Suite, since they are located in the Falcoz Lithotectonic Domain. Hence, the Dancelou Suite was restricted to the Baleine Lithotectonic Domain (Lafrance et al., in preparation).
The Dancelou Suite consists of homogeneous and massive biotite granite forming well-circumscribed kilometric plutons or dykes intruding older units. Simard et al. (2013) divided the Dancelou Suite into two informal units: grey granite (pPdac1) and pink granite (pPdac2). A third informal unit of pegmatitic granite (pPdac3) has been identified in the Jeannin Lake area (Charette et al., 2016). Pegmatitic phases associated with unit pPdac2 have been described elsewhere in the Core Zone, but their very limited volume does not justify the definition of a subunit. These pegmatites, previously included in unit pPdac2 by Simard et al. (2013), were subsequently reassigned to unit pPdac3 by Lafrance et al. (in preparation).
Units pPdac1 and pPdac2 correspond to two mutually cutting phases, indicating contemporaneous emplacement. It is common to observe these two types of granite on the same outcrop. Unit pPdac3 cuts the other two granite units of the Dancelou Suite.
Dancelou Suite 1 (pPdac1): Fine-Grained Grey Granite
Unit pPdac1 granite is homogeneous, weakly foliated or massive and fine to medium grained. The grey colour is characteristic, giving it the appearance of tonalite on outcrops. However, feldspar staining and thin-section observation highlight a significant amount of K-feldspar (30-45% of the rock). Granite contains 4-10% brownish biotite flakes. These flakes contain small zircon grains surrounded by a very clear dark brown pleochroic aureole. The rock also contains 1-5% muscovite as disseminated flakes or altering plagioclase (sericite), as well as minor accessory minerals including epidote, allanite, apatite and opaque minerals. Myrmekitic textures are commonly observed in thin sections.
Dancelou Suite 2 (pPdac2): Massive Pink Granite
Unit pPdac2 granite is distinguished by a pinkish colour and a medium grain size with, in several places, decimetric coarse to pegmatitic clusters. Pegmatite injections are also observed cutting pink granite, which are interpreted as a late phase of the Dancelou Suite (pPdac3). Unit pPdac2 granite is also distinguished by its low ferromagnesian mineral content (<5% of the rock). These consist of small flakes of brown biotite and chlorite containing small zircon grains. Granite also contains up to 2% muscovite and, more locally, low amounts of hematite, epidote and apatite. Igneous textures are well preserved, especially graphic textures, but a beginning of recrystallization is regularly observed at grain edges in thin sections. Plagioclase is weakly to moderately sericitized.
Dancelou Suite 3 (pPdac3): Massive Pegmatitic Granite
Pegmatitic granite intrudes into other units of the Dancelou Suite; this unit is interpreted as belonging to a late phase of the unit. Granite is light pink and contains <5% ferromagnesian minerals, mainly brown-red biotite flakes, which are variously chloritized. Muscovite is ubiquitous (<5%). Intrusive rock shows slight recrystallization along feldspar grains, while quartz zones form subgrains having undulatory extinction. Plagioclase is weakly sericitized and accessory minerals including epidote, hematite, apatite, garnet and zircon are sparse.
Thickness and distribution
The Dancelou Suite forms kilometric plutons that cover a total area of ~1410 km2 scattered throughout the Baleine Domain. Unit pPdac2 (727 km2) is concentrated mainly in the central and northern parts of the domain, while the larger masses of unit pPdac3 (581 km2) are concentrated to the south in the Jeannin Lake area. Unit pPdac1 is limited (101 km2) to a few small kilometric plutons in the Saffray Lake and Kuujjuaq areas.
Paleoproterozoic ages obtained in the Dancelou Suite are consistent with field observations indicating late tectonic emplacement. Dating suggests that the pegmatitic granite unit (pPdac3) would be older than the granite unit (pPdac2); however, field relationships indicate the opposite. Samples collected in different units come from different areas, hence it is possible that different pegmatitic phases intruded at different times.
Dancelou Suite granites cut all Archean and Paleoproterozoic units of the Baleine Domain. They also contain up to 15% enclaves of the various surrounding units.
At the western edge of the De Pas Supersuite (pPdep), several non-pegmatitic pink granite outcrops, many of which are similar to unit pPdac2 granite, have been assigned to unit pPdep5. It is difficult to distinguish these units given their similar appearance, but it is likely that some of unit pPped5 pink granites actually belong to the Dancelou Suite.
Does not apply.