A metamorphic perspective on the Pan African overprint in the Amery area of Mac. Robertson Land, East Antarctica
A metamorphic perspective on the Pan African overprint in the Amery area of Mac. Robertson Land, East Antarctica
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DOI：
10.1017/s0954102097000400
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发表时间：
1997-09
影响因子：
1.6
通讯作者：
I. Scrimgeour;M. Hand
中科院分区：
文献类型：
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作者：
I. Scrimgeour;M. Hand
Mac 的 Amery 地区。罗伯逊地位于普里兹湾早古生代麻粒岩地形和查尔斯王子山北部中新元古代麻粒岩地形 (nPCM) 之间。与显示出明显简单的近等压历史的 nPCM 相比，Amery 地区暴露的麻粒岩包含反应结构，表明存在更复杂的演化。 Peak-M1中元古代组合形成于c。 700 MPa 和 800°C，最初经历近等压冷却。随后温度 (M2) 的升高导致在约 450 MPa 和 700°C 的变辉石中形成堇青石-尖晶石组合。 M2 的发生时间尚未确定，但现有数据强烈表明，它是与东北部普里兹湾的构造运动同时期的早古生代事件。因此，阿默里地区麻粒岩的变质演化反映了两个不相关的造山事件之间的地形尺度热干扰模式。在没有记录 M1 等压冷却后的岩石中，M2 在 M1 组合上的叠加导致 M2 堇青石-尖晶石辛晶石的形成，而牺牲了峰值 M1 石榴石和硅线石。这种纹理通常被解释为反映近等温减压，但与阿默里地区的单个构造热事件无关。
The Amery area of Mac. Robertson Land lies between the early Palaeozoic granulite terrain of Prydz Bay and Meso-Neoproterozoic granulites in northern Prince Charles Mountains (nPCM). In contrast to the nPCM which shows an apparently simple near-isobaric history, granulites exposed in the Amery area contain reaction textures suggesting a more complex evolution. Peak-M1 Mesoproterozoic assemblages formed at c. 700 MPa and 800°C and initially underwent a near-isobaric cooling. A subsequent increase in temperature (M2) resulted in the formation of cordierite-spinel assemblages at ~450 MPa and 700°C in metapelite. The timing of M2 is not firmly established, however existing data strongly suggest it is an early Palaeozoic event coeval with tectonism in Prydz Bay to the north-east. Thus the metamorphic evolution of granulites in the Amery area reflects a terrain-scale thermal interference pattern between two unrelated orogenic events. In rocks not recording post-M1 isobaric cooling, the superposition of M2 on M1 assemblages resulted in the formation of M2 cordierite-spinel symplectites at the expense of peak M1 garnet and sillimanite. This texture, commonly interpreted to reflect near-isothermal decompression, has no relevance in terms of a single tectonothermal event in the Amery area.