On the application of in situ monazite chemical geochronology to constraining P–T–t histories in high-temperature (>850 °C) polymetamorphic granulites from Prydz Bay, East Antarctica
On the application of in situ monazite chemical geochronology to constraining P–T–t histories in high-temperature (>850 °C) polymetamorphic granulites from Prydz Bay, East Antarctica
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DOI：
10.1144/0016-76492006-013
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发表时间：
2007-05
影响因子：
2.7
通讯作者：
D. Kelsey;D. Kelsey;M. Hand;C. Clark;C. Wilson
中科院分区：
文献类型：
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作者：
D. Kelsey;D. Kelsey;M. Hand;C. Clark;C. Wilson
我们提供了来自南极洲东部普里兹湾麻粒岩相变泥岩的基于电子探针的原位 (Th + U)-Pb 独居石化学年龄数据。独居石年龄数据定义了两个不同的年龄群体，即新元古代晚期到古生代早期（约 570–520 Ma）和新元古代（约 950–820 Ma），这证实了普里兹湾的多构造性质。我们的数据表明，普里兹湾海岸线型方向的相似性不足以表明时间等价。早古生代构造活动的最短持续时间至少为 60 Ma，受到富镁铝变泥岩的限制：粗粒斜方辉石所赋存的独居石定义了最古老的早古生代种群，而堇青石 + 斜方辉石辛辉岩定义了最年轻的早古生代种群。独居石的空间分布及其年龄与推断的矿物组合演化相关。我们能够在定量的P-T-t-矿物组合空间中表征早古生代构造作用的演化，证明普里兹湾超高温构造变质作用属于早古生代。当化学和动力学条件有利时，富铁铝变泥岩中新元古代遗传的存续对独居石中的高铅保留率具有影响。本文所应用的方法和逻辑可以完全且直接地转移到任何其他变质地体的询问。
We present electron microprobe-based in situ (Th + U)–Pb monazite chemical age data from granulite-facies metapelites in Prydz Bay, East Antarctica. The monazite age data define two distinct age populations, Late Neoproterozoic to Early Palaeozoic (c. 570–520 Ma) and Neoproterozoic (c. 950–820 Ma), that confirm the polytectonic nature of Prydz Bay. Our data suggest that similarity in lineation orientation along the Prydz Bay coast is not sufficient to necessarily indicate time-equivalance. The minimum duration of Early Palaeozoic tectonism, spanning at least 60 Ma, is constrained from an Mg–Al-rich metapelite: monazite hosted by coarse-grained orthopyroxene defines the oldest Early Palaeozoic population, whereas cordierite + orthopyroxene symplectites define the youngest Early Palaeozoic population. The spatial distribution of monazites and their ages is correlatable with the inferred mineral assemblage evolution. We are able to characterize the evolution of Early Palaeozoic tectonism in quantitative P–T–t–mineral assemblage space, demonstrating that ultrahigh-temperature tectono-metamorphism in Prydz Bay is of Early Palaeozoic age. The survival of Neoproterozoic inheritance in Fe–Al-rich metapelites has implications for high Pb retentivity in monazite when chemical and kinetic conditions are favourable. The approach and logic applied herein are entirely and directly transferable to the interrogation of any other metamorphic terrane.