Rare earth distribution in Archean granitoid plutons of the Wabigoon volcanic–plutonic belt, northwestern Ontario

D. Birk, T. Koljonen, Rolf Rosenberg

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Abstract

Rare earths (La to Lu, Y) are investigated for five Archean granitoid stocks of Kenoran age that intrude the Wabigoon volcanic–plutonic belt. Homogeneous granodiorites are characterized by low total rare earth concentrations (ΣREE), with chondrite-normalized REE patterns that show steep negative slopes, no Eu anomalies, and enrichment of Lu. A hypabyssal porphyry of possible volcanic affiliation displays similar REE patterns, but is more depleted in heavy REE. Zone plutons yield patterns of steep slope, no Eu anomalies, with or without Lu enrichment. REE concentrations decrease from monzodioritic margins, to granodioritic cores, to aplitic apophyses.These plutons carry REE concentrations similar to the Canadian Shield average, but notably lower than some published averages for granitoids. No secular change is evident for the Archean interval.ΣREE decreases during differentiation with no appreciable fractionation of heavy over light REE, until the end stages. Late differentiates suffer depletion in heavy REE by hornblende fractionation. Lu enrichment correlates with deuteric metasomatism, as evidenced by microcline megacrysts. Eu anomalies are absent because fractionation of divalent Eu is prevented by high concentrations of Sr and Ba.Quantitative source modeling should consider the complete magma history of emplacement, crystallization, and deuteric metasomatism.

Original languageEnglish
Pages (from-to)270-289
Number of pages20
JournalCanadian Journal of Earth Sciences
Volume16
Issue number2
DOIs
Publication statusPublished - 1979
MoE publication typeNot Eligible

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granitoid
pluton
Archean
fractionation
metasomatism
anomaly
microcline
porphyry
granodiorite
chondrite
hornblende
shield
emplacement
crystallization
magma
history
modeling
distribution

Cite this

@article{cd72f9177a48495d96ee840ec3ba6766,
title = "Rare earth distribution in Archean granitoid plutons of the Wabigoon volcanic–plutonic belt, northwestern Ontario",
abstract = "Rare earths (La to Lu, Y) are investigated for five Archean granitoid stocks of Kenoran age that intrude the Wabigoon volcanic–plutonic belt. Homogeneous granodiorites are characterized by low total rare earth concentrations (ΣREE), with chondrite-normalized REE patterns that show steep negative slopes, no Eu anomalies, and enrichment of Lu. A hypabyssal porphyry of possible volcanic affiliation displays similar REE patterns, but is more depleted in heavy REE. Zone plutons yield patterns of steep slope, no Eu anomalies, with or without Lu enrichment. REE concentrations decrease from monzodioritic margins, to granodioritic cores, to aplitic apophyses.These plutons carry REE concentrations similar to the Canadian Shield average, but notably lower than some published averages for granitoids. No secular change is evident for the Archean interval.ΣREE decreases during differentiation with no appreciable fractionation of heavy over light REE, until the end stages. Late differentiates suffer depletion in heavy REE by hornblende fractionation. Lu enrichment correlates with deuteric metasomatism, as evidenced by microcline megacrysts. Eu anomalies are absent because fractionation of divalent Eu is prevented by high concentrations of Sr and Ba.Quantitative source modeling should consider the complete magma history of emplacement, crystallization, and deuteric metasomatism.",
author = "D. Birk and T. Koljonen and Rolf Rosenberg",
year = "1979",
doi = "10.1139/e79-027",
language = "English",
volume = "16",
pages = "270--289",
journal = "Canadian Journal of Earth Sciences",
issn = "0008-4077",
publisher = "National Research Council of Canada",
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}

Rare earth distribution in Archean granitoid plutons of the Wabigoon volcanic–plutonic belt, northwestern Ontario. / Birk, D.; Koljonen, T.; Rosenberg, Rolf.

In: Canadian Journal of Earth Sciences, Vol. 16, No. 2, 1979, p. 270-289.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Rare earth distribution in Archean granitoid plutons of the Wabigoon volcanic–plutonic belt, northwestern Ontario

AU - Birk, D.

AU - Koljonen, T.

AU - Rosenberg, Rolf

PY - 1979

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N2 - Rare earths (La to Lu, Y) are investigated for five Archean granitoid stocks of Kenoran age that intrude the Wabigoon volcanic–plutonic belt. Homogeneous granodiorites are characterized by low total rare earth concentrations (ΣREE), with chondrite-normalized REE patterns that show steep negative slopes, no Eu anomalies, and enrichment of Lu. A hypabyssal porphyry of possible volcanic affiliation displays similar REE patterns, but is more depleted in heavy REE. Zone plutons yield patterns of steep slope, no Eu anomalies, with or without Lu enrichment. REE concentrations decrease from monzodioritic margins, to granodioritic cores, to aplitic apophyses.These plutons carry REE concentrations similar to the Canadian Shield average, but notably lower than some published averages for granitoids. No secular change is evident for the Archean interval.ΣREE decreases during differentiation with no appreciable fractionation of heavy over light REE, until the end stages. Late differentiates suffer depletion in heavy REE by hornblende fractionation. Lu enrichment correlates with deuteric metasomatism, as evidenced by microcline megacrysts. Eu anomalies are absent because fractionation of divalent Eu is prevented by high concentrations of Sr and Ba.Quantitative source modeling should consider the complete magma history of emplacement, crystallization, and deuteric metasomatism.

AB - Rare earths (La to Lu, Y) are investigated for five Archean granitoid stocks of Kenoran age that intrude the Wabigoon volcanic–plutonic belt. Homogeneous granodiorites are characterized by low total rare earth concentrations (ΣREE), with chondrite-normalized REE patterns that show steep negative slopes, no Eu anomalies, and enrichment of Lu. A hypabyssal porphyry of possible volcanic affiliation displays similar REE patterns, but is more depleted in heavy REE. Zone plutons yield patterns of steep slope, no Eu anomalies, with or without Lu enrichment. REE concentrations decrease from monzodioritic margins, to granodioritic cores, to aplitic apophyses.These plutons carry REE concentrations similar to the Canadian Shield average, but notably lower than some published averages for granitoids. No secular change is evident for the Archean interval.ΣREE decreases during differentiation with no appreciable fractionation of heavy over light REE, until the end stages. Late differentiates suffer depletion in heavy REE by hornblende fractionation. Lu enrichment correlates with deuteric metasomatism, as evidenced by microcline megacrysts. Eu anomalies are absent because fractionation of divalent Eu is prevented by high concentrations of Sr and Ba.Quantitative source modeling should consider the complete magma history of emplacement, crystallization, and deuteric metasomatism.

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