Geochemical, oxygen, and neodymium isotope compositions of metasediments from the Abitibi greenstone belt and Pontiac Subprovince, Canada: Evidence for ancient crust and Archean terrane juxtaposition

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90375-7· OSTI ID:6669344

Feng, R; Kerrich, R ^[1]; Maas, R ^[2]

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1. Univ. of Saskatchewan, Saskatoon (Canada)
2. Curtin Univ. of Technology, Perth (Australia)

The Abitibi greenstone belt (AGB) and Pontiac Subprovince (PS) in the southwestern Superior Province are adjacent greenstone-plutonic and metasedimentary-dominated terranes, respectively, separated by a major fault zone. Metasediments from these two contrasting terranes are compared in terms of major- and trace-element and O- and Nd-isotope compositions, and detrital zircon ages. The following two compositional populations of metasediments are present in the low-grade, Abitibi southern volcanic zone: (1) a mafic-element-enriched population (MEP) characterized by flat, depleted REE patterns; enhanced Mg, Cr, Co, Ni, and Sc; low-incompatible-element contents; and minor or absent normalized negative troughs at Nb, Ta, and Ti; and (2) a low-mafic-element population (LMEP) featuring LREE-enriched patterns; enhanced Rb, Cs, Ba, Th, and U contents; and pronounced normalized negative troughs at Nb, Ta, and Ti. These geochemical features are interpreted to indicate that the MEP sediments were derived from an ultramafic- and mafic-dominated oceanic provenance, whereas the LMEP sediments represent mixtures of mafic and felsic are source rocks. The PS metasediments are essentially indistinguishable from Abitibi LMEP on the basis of major-element and transition metal abundances, suggesting comparable types of source rocks and degrees of maturity, but are distinct in terms of some trace elements and O-isotope compositions. The Pontiac metasediments are depleted in [sup 18]O and enriched in Cs, Ba, Pb, Th, U, Nb, Ta, Hf, Zr, and total REE and also have higher ratios of Rb/K, Cs/Rb, Ba/Rb, Ta/Nb, Th/La, and Ba/La relative to the Abitibi LMEP. Two subtypes of REE patterns have been identified in PS metasediments. The first subtype is interpreted to be derived from provenances of mixed mafic and felsic volcanic rocks, whereas the Eu-depleted type has features that are typical of post-Archean sediments or Archean K-rich granites and volcanic equivalents. 100 refs., 9 figs., 4 tabs.

• OSTI ID: 6669344
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:3; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
58 GEOSCIENCES
NEODYMIUM
ISOTOPE RATIO
OXYGEN
RARE EARTHS
SEDIMENTS
CHEMICAL ANALYSIS
BARIUM
CESIUM
CHROMIUM
COBALT
ELEMENTS
EUROPIUM
GRANITES
HAFNIUM
LANTHANUM
MAGNESIUM
MIXTURES
NICKEL
NIOBIUM
ROCKS
RUBIDIUM
SCANDIUM
SOURCE ROCKS
TANTALUM
THORIUM
TITANIUM
URANIUM
VOLCANIC ROCKS
YTTERBIUM
ZIRCON
ZIRCONIUM
ACTINIDES
ALKALI METALS
ALKALINE EARTH METALS
DISPERSIONS
IGNEOUS ROCKS
METALS
MINERALS
NONMETALS
PLUTONIC ROCKS
SILICATE MINERALS
TRANSITION ELEMENTS
400102* - Chemical & Spectral Procedures
580000 - Geosciences