Enriched Archean lithospheric mantle beneath western Churchill Province tapped during Paleoproterozoic orogenesis

Citation
Bl. Cousens et al., Enriched Archean lithospheric mantle beneath western Churchill Province tapped during Paleoproterozoic orogenesis, GEOLOGY, 29(9), 2001, pp. 827-830
Citations number
37
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
GEOLOGY
ISSN journal
0091-7613 → ACNP
Volume
29
Issue
9
Year of publication
2001
Pages
827 - 830
Database
ISI
SICI code
0091-7613(200109)29:9<827:EALMBW>2.0.ZU;2-1
Abstract
Ultrapotassic rocks of the Christopher Island Formation (Baker Lake basin) were emplaced across an enormous area (240 000 km(2) minimum) of the wester n Churchill Province ca. 1.83 Ga. These rocks extend across the Snowbird zo ne, a geophysical feature postulated by others to represent a Paleoproteroz oic suture that welded the Rae and Hearne domains. Minette dikes and flows of the Rae and Hearne domains display identical epsilon (Nd, 1830) values a nd incompatible element patterns, and thus appear to have originated from a common lithospheric-mantle source. Christopher Island Nd model ages cluste r at 2.8 Ga, and epsilon (Nd) data from one Archean lamprophyre and three 2 .45 to ca. 2.2 Ga mafic suites suggest that enriched lithospheric-mantle so urces beneath both the Rae and Hearne domains existed well before ca. 1.83 Ga, inconsistent with Paleoproterozoic suturing along the Snowbird zone. In contrast to commonly invoked models that envisage melting of local enriche d domains, Christopher Island ultrapotassic rocks appear to have originated from an extensive reservoir. We suggest that such a reservoir was created during an Archean metasomatic event, perhaps owing to flat subduction, and that it remained in nearly complete isolation until tapped during Paleoprot erozoic extension related to squeezing of western Churchill crust between f lanking Wopmay and Trans-Hudson orogens.