Emplacement age and isotopic composition of the Prairie Lake carbonatite complex, Northwestern Ontario, Canada

Abstract

Alkaline rock and carbonatite complexes, including the Prairie Lake complex (NW Ontario), are widely distributed in the Canadian region of the Midcontinent Rift in North America. It has been suggested that these complexes were emplaced during the main stage of rifting magmatism and are related to a mantle plume. The Prairie Lake complex is composed of carbonatite, ijolite and potassic nepheline syenite. Two samples of baddeleyite from the carbonatite yield U–Pb ages of 1157.2±2.3 and 1158.2±3.8 Ma, identical to the age of 1163.6±3.6 Ma obtained for baddeleyite from the ijolite. Apatite from the carbonatite yields the same U–Pb age of ~1160 Ma using TIMS, SIMS and laser ablation techniques. These ages indicate that the various rocks within the complex were synchronously emplaced at about 1160 Ma. The carbonatite, ijolite and syenite have identical Sr, Nd and Hf isotopic compositions with a 87Sr/86Sr ratio of ~0.70254, and positive εNd(t)1160 and εHf(t)1160 values of ~+3.5 and ~+4.6, respectively, indicating that the silicate and carbonatitic rocks are co-genetic and related by simple fractional crystallization from a magma derived from a weakly depleted mantle. These age determinations extend the period of magmatism in the Midcontinent Rift in the Lake Superior area to 1160 Ma, but do not indicate whether the magmatism is associated with passive continental rifting or the initial stages of plume-induced rifting.

Mineralogy and genesis of pyrochlore apatitite from The Good Hope Carbonatite, Ontario: A potential niobium deposit

“…Anhedral single crystals of apatite in the Prairie Lake heterogeneous carbonatites, in marked contrast to Good Hope apatite, in common with many other carbonatite apatites (Hornig-Kjarsgaard, 1998; Wang et al , 2014; Doroshkevich et al ., 2017), exhibits smooth chondrite-normalised REE distribution patterns with La/Nd CN 1.26–2.0 (see fig. 3 in Wu et al , 2017). Apatite in allotriomorphic granular apatitite cumulates occurring as megaxenoliths in the Prairie Lake heterogeneous carbonatite exhibit smooth La–Lu distribution patterns with La/Nd CN ratios ranging from 1.36–1.53 and 1.85–2.01 for pyroxene apatitite and wollastonite apatitite, respectively (Fig.…”

“…The Good Hope carbonatite is a satellite intrusion of the well-known Prairie Lake alkaline rock and carbonatite complex (Sage, 1987; Zurevinski and Mitchell, 2015; Wu et al, 2017), located adjacent to the Dead Horse Creek Road, northwest of the town of Marathon, ~26 km north of the shore of Lake Superior at 49°02'N, 86°43'W (Fig. 1).…”

“…The carbonatites are emplaced in continental shield Archean gneisses of the Wawa Subprovince. The Prairie Lake complex has an emplacement age of ~1160 Ma (Rukhlov and Bell, 2010; Wu et al , 2017). The age of the Good Hope carbonatite has yet to be determined but given the geological disposition is unlikely to differ from that of Prairie Lake.…”

Origin of kimberlite from the base of the upper mantle

“…Large igneous provinces form when the plume head successfully penetrates the whole upper mantle, causing large degrees of partial melting 29,30 . This explains the fact that large igneous provinces are often proceeded by carbonatite 31 .…”

U–Th–Pb geochronology and simultaneous analysis of multiple isotope systems in geological samples by LA-MC-ICP-MS

“…In terms of trace elements, apatite is usually characterized by high Sr and Nd contents (up to several thousand ppm) and extremely low Rb/Sr ratios (normally 87 Rb/ 86 Sr < 0.0001). 10,157 Therefore, apatite is suited to Sr and Nd isotopic analysis (e.g., ref. 10, 158 and 159) and U-Pb geochronology by LA-MC-ICP-MS (e.g., ref.…”