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首页> 外文期刊>Contributions to Mineralogy and Petrology >In-situ hafnium and lead isotope analyses of detrital zircons from the Devonian sedimentary basin of NE Greenland: a record of repeated crustal reworking
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In-situ hafnium and lead isotope analyses of detrital zircons from the Devonian sedimentary basin of NE Greenland: a record of repeated crustal reworking

机译：格陵兰东北部泥盆纪沉积盆地碎屑锆石的原位ha和铅同位素分析：多次地壳重工的记录

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An intramontane collapse basin developed within the hanging wall above the large-scale extensional Fjord Regional Detachment of NE Greenland in middle to late Devonian times. The continental clastic sediments within the basin are derived locally from Laurentian source rocks, which makes them well suited for a study of the crustal evolution of the source terrain. This is the first integrated in-situ Pb and Hf isotope study to be presented, and zircon data on a selected sandstone from the basin are combined with Sm-Nd whole-rock data on sand/siltstones. Nd whole-rock ages of two samples of sandstones and a siltstone are 2.0–2.1 Ga. Peak frequencies of zircon 207Pb/206Pb ages at 1,764–1,912 Ma, and 176Hf/177Hf values at 0.28142–0.28163 (tDM=2.47 to 2.06) for the sandstone suggest the generation of a considerable volume of juvenile continental crust in the ultimate zircon provenance at 1.9–2.0 Ga. The Hf isotopic compositions of Archaean zircons in the sandstone are distinct from those of the source materials of Proterozoic protocrust at 1.9–2.0 Ga, but zircons with elevated Hf-tDM ages of up to 2.47 Ga can be related to a component of Archaean crust or reworked Archaean material in the ultimate zircon source area. Zircon 207Pb/206Pb ages are also recorded at 1,480–1,572, 1,318 and 1,014 Ma (Grenvillian). The Hf isotope compositions of these zircons are consistent with reworking of the Proterozoic protocrust at these times, with little or no juvenile input. The Proterozoic zircons form two distinct groups defined by 176Yb/177Hf>0.05055 and 176Yb/177Hf<0.03301, and the latter group overlaps with Yb-Hf isotope data on the Archaean zircons. The two groups may represent zircons derived from evolved granites and intermediate to mildly felsic rocks, respectively. The repeated reworking of the continental crust also comprised erosion and deposition of sediments in the Proterozoic (the Krummedal sequence and the Eleonore Bay Supergroup, EBS) and intrusion of Caledonian anatectic granites in the EBS, which both represent provenance components to the Devonian sediments. No discrete Caledonian Pb-Pb zircon ages are recorded, but Caledonian magmatism may be represented by strongly discordant zircons which form arrays with a lower intercept age at ca. 400 Ma and an upper intercept at 1,600–2,000 Ma. One undated zircon records a 176Hf/177Hf ratio of 0.282218, higher than that of the Proterozoic protocrust in Caledonian/late-Caledonian times (380–450 Ma) which may represent a Caledonian mantle contribution.
机译：在泥盆纪中期至晚期，在格陵兰东北部大型伸展性峡湾支队上方的悬壁内形成了一个山内塌陷盆地。盆地内的大陆性碎屑沉积物是从Laurentian烃源岩中局部提取的，这使其非常适合研究烃源地壳的地壳演化。这是首次提出的原位Pb和Hf同位素综合研究，将盆地中选定砂岩上的锆石数据与砂/粉砂岩中Sm-Nd全岩石数据相结合。两个砂岩和粉砂岩样品的Nd全岩时代为2.0–2.1 Ga。锆石207 Pb / 206 Pb的峰值频率分别为1,764-1,912 Ma和176 Hf砂岩的/ 177 Hf值为0.28142-0.28163（tDM = 2.47至2.06），表明在1.9-2.0 Ga的锆石最终产地中生成了大量的幼年陆壳。砂岩中古生界锆石的同位素组成与原生原生壳的原始物质在1.9–2.0 Ga处不同，但是Hf-tDM 年龄高至2.47 Ga的锆石可能与古生界的成分有关在终极锆石源区域中结壳或重新加工过的太古代材料。锆石207 Pb / 206 Pb的年龄也记录在1,480–1,572、1,318和1,014 Ma（格伦维尔）。这些锆石的H同位素组成与这些时期的元古代原生壳的再造一致，几乎没有或没有任何少年投入。元古代锆石形成两个不同的组，分别由176 Yb / 177 Hf> 0.05055和176 Yb / 177 Hf <0.03301定义，后者与Yb-Hf重叠太古锆石的同位素数据。两组分别代表锆石，分别来自演化的花岗岩和中等至轻质的长英质岩石。大陆壳的反复改造还包括在元古代（Krummedal序列和Eleonore Bay Supergroup，EBS）沉积物的侵蚀和沉积，以及在EBS中侵入喀里多尼亚的晚花岗岩，这两者都是泥盆纪沉积物的物源成分。没有记录离散的古苏格兰的Pb-Pb锆石年龄，但古苏格兰的岩浆作用可能由强烈不协调的锆石代表，它们形成了大约在20世纪时具有较低拦截年龄的阵列。 400 Ma，上截距为1,600–2,000 Ma。一个未标日期的锆石记录的176Hf / 177Hs比为0.282218，高于古苏格兰/晚卡尔顿时期（380-450 Ma）的元古代原生壳，这可能代表了古苏格兰的地幔贡献。

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  • 来源
    《Contributions to Mineralogy and Petrology》 |2001年第1期|83-94|共12页
  • 作者

    T.-L. Knudsen; W. Griffin; E. Hartz; A. Andresen; S. Jackson;

  • 作者单位

    Mineralogical-Geological Museum Sars Gate 1 0562 Oslo Norway;

    GEMOC ARC National Key Centre Department of Earth and Planetary Sciences Macquarie University NSW 2109 Australia;

    Department of Geology University of Oslo P.O. Box 1047 Blindern 0313 Oslo Norway;

    Department of Geology University of Oslo P.O. Box 1047 Blindern 0313 Oslo Norway;

    GEMOC ARC National Key Centre Department of Earth and Planetary Sciences Macquarie University NSW 2109 Australia;

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