Single zircon age constraints on the tectonic juxtaposition of the Archean Abitibi greenstone belt and Pontiac subprovince, Quebec, Canada

Journal Article · Fri Nov 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90502-V· OSTI ID:5211757

Feng, R; Kerrich, R ^[1]

---

1. Univ. of Saskatchewan, Saskatoon (Canada)

Zircons from metasediments and granitoids in the high-grade Lacorne block within the low-grade Archean Abitibi greenstone belt have been dated by single zircon Pb-evaporation technique, yielding {sup 207}Pb/{sup 206}Pb minimum ages. Detrital zircons in the mature clastic metasediments of the Lacorne block display a range of ages from 2,691 {plus minus} 8 Ma to 3,042 {plus minus} 6 Ma. The younger zircon ages thus impose an upper limit for deposition and indicate that the high-grade Lacorne block is not basement to the Abitibi supracrustal sequence (2,747-2,680 Ma). Existence of abundant (69%) older detrital zircons (> 2,750 Ma) suggest in turn that the Abitibi supracrustal rocks are not the source of the Lacorne sediments. Two generations of granitoids occur in the Lacorne block, an early monosodiorite-monzonite-granodiorite-syenite series and a younger S-type garnet-muscovite granite series. This contrasts with granitoid magmatism in the Abitibi greenstone belt which ended at {approximately}2675 Ma. The Pontiac subprovince to the south of the Abitibi greenstone belt shares all of the above features of the Lacorne block, including detrital zircon ages as well as the composition and timing of granitoid magmatism. This is interpreted detrital zircon ages as well as the composition and timing of granitoid magmatism. This is interpreted to indicate that the Lacorne block was originally part of the same tectonic terrane as the Pontiac subprovince. After development of the MMGS magmatism (21,670-2,680 Ma), the Pontiac subprovince locally underthrust the Abitibi greenstone belt, and crustal thickening promoted partial melting of underthrust Pontiac metasediments to form the {approximately}2,644 {plus minus} 13 Ma S-type granites.

• OSTI ID: 5211757
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:11; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
CANADA
DEVELOPED COUNTRIES
GEOLOGIC HISTORY
GEOLOGIC MODELS
ISOTOPE DATING
ISOTOPES
LEAD ISOTOPES
METAMORPHIC ROCKS
MINERALS
NORTH AMERICA
PETROGENESIS
QUEBEC
ROCKS
SCHISTS
SILICATE MINERALS
TECTONICS
ZIRCON