The source of Proterozoic anorthosite and rapakivi granite magmatism: evidence from combined in situ Hf–O isotopes of zircon in the Ahvenisto complex, southeastern Finland
The source of Proterozoic anorthosite and rapakivi granite magmatism: evidence from combined in situ Hf–O isotopes of zircon in the Ahvenisto complex, southeastern Finland
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DOI：
10.1144/jgs2014-013
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发表时间：
2014-10
影响因子：
2.7
通讯作者：
A. Heinonen;T. Andersen;O. T. Rämö;M. Whitehouse
中科院分区：
文献类型：
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作者：
A. Heinonen;T. Andersen;O. T. Rämö;M. Whitehouse
元古界斜长岩-芒果岩-紫苏花岗岩-花岗岩(AMCG)杂岩中的地块型斜长岩的同位素组成通常受地壳价值的控制。然而，几个AMCG岩套中含有橄榄石的斜长岩显示出年轻的特征，这表明不同程度的亏损地幔储集层参与了它们的成因。来自1.54-1.65Ga Fennoscandian环斑花岗岩-地块型斜长岩省1.64Ga Ahvenisto AMCG杂岩中的锆石Hf-O同位素数据显示，该套最原始的辉长岩类型中的年轻同位素信号相关(δ18Ozrn=5.4-6.6‰；初始ϵHf=−1.1-+3.4)，表明斜长岩具有亏损的地幔起源。这一信号在演化程度较高的同岩浆斜长岩(δ18Ozrn=6.3-7.8‰；初始ϵHf=−0.8-+2.0)中不明显，很可能是由于地壳物质对地幔原生岩浆的混染。与斜长岩共生的环斑花岗岩具有不同的同位素组成(δ18Ozrn=7.4~8.6Ozrn；初始ϵHf=−2.1~+0.5)，指示地壳来源。补充材料：完整的分析结果和分析颗粒的细节和扫描电子显微镜图像以及这两种方法的空间信息可在以下网站获得：http://www.geolsoc.org.uk/SUP18780.
The isotope compositions of massif-type anorthosites in Proterozoic anorthosite–mangerite–charnockite–granite (AMCG) complexes are commonly dominated by crustal values. Olivine-bearing anorthositic rocks in several AMCG suites have, however, been shown to display juvenile character, suggesting that variably depleted mantle reservoirs were involved in their genesis. A coupled in situ zircon Hf–O isotope dataset from the 1.64 Ga Ahvenisto AMCG complex in the 1.54–1.65 Ga Fennoscandian rapakivi granite–massif-type anorthosite province reveals correlated juvenile isotope signals (δ18Ozrn = 5.4–6.6‰; initial ϵHf = −1.1 to +3.4) in the most primitive gabbroic rock type of the suite suggesting a depleted mantle origin for the anorthositic rocks. This signal is not as prominent in the more evolved co-magmatic anorthositic rocks (δ18Ozrn = 6.3–7.8‰; initial ϵHf = −0.8 to +2.0), most probably owing to contamination of the mantle-derived primary magma by crustal material. A rapakivi granite associated with the anorthositic rocks has different isotope composition (δ18Ozrn = 7.4–8.6‰; initial ϵHf = −2.1 to +0.5) that points to a crustal source. Supplementary material: Full analytical results and details and SEM images of the analysed grains with spatial information on both methods are available at: http://www.geolsoc.org.uk/SUP18780.