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Nature of assean lake ancient crust, Manitoba: a combined SHRIMP–ID-TIMS U–Pb geochronology and Sm–Nd isotope study
- Source :
-
Precambrian Research . Sep2003, Vol. 126 Issue 1/2, p55. 40p. - Publication Year :
- 2003
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Abstract
- The Assean Lake Crustal Complex (ALCC) located at the northwest periphery of the Superior Province in northern Manitoba, Canada, hosts an ancient assembly of rocks that record a complex and prolonged crustal history spanning more than two billion years from ∼3.9 to 1.8 Ga. A supracrustal assemblage consisting of amphibolite-grade greywacke, quartz arenite, arkose, mafic to intermediate volcanics, and to a lesser extent iron formation dominates the ALCC and likely formed in a shallow marine arc/back-arc setting. The supracrustal rocks are intruded by amphibolite-grade, calc-alkaline tonalite to granite orthogneiss. Nd model ages for felsic para- and orthogneisses range from ∼3.5 to 4.2 Ga and suggest that Paleoarchean basement may be preserved at Assean Lake. SHRIMP U–Pb zircon ages and ID-TIMS conventional U–Pb zircon and monazite ages show that felsic magmatism occurred at ∼3.1–3.2 Ga whereas a record extending back to at least 3.9 Ga is preserved in detritus in paragneiss that may have a depositional age of ∼3.2 Ga. Orthogneiss was metamorphosed at ∼2.68 Ga whereas local migmatisation of paragneiss occurred at ∼2.61 Ga. Monazite growth events at ∼2.6, 2.45, and 1.8 Ga might represent episodes of accretion of Archean crustal segments including the ALCC and possibly the Sask craton (Trans-Hudson basement) along the northwest Superior Province margin. At present, matching segments of the exotic ALCC are unknown but remnants may exist in parts of the Sask craton. [Copyright &y& Elsevier]
- Subjects :
- *LEAD
*SAMARIUM
*ISOTOPES
*GEOLOGY
*LAKES
*MAGMATISM
*ARCHAEAN stratigraphic geology
Subjects
Details
- Language :
- English
- ISSN :
- 03019268
- Volume :
- 126
- Issue :
- 1/2
- Database :
- Academic Search Index
- Journal :
- Precambrian Research
- Publication Type :
- Academic Journal
- Accession number :
- 10694775
- Full Text :
- https://doi.org/10.1016/S0301-9268(03)00127-X