Neoproterozoic deformation in the Radok Lake region of the northern Prince Charles Mountains, east Antarctica; evidence for a single protracted orogenic event
Neoproterozoic deformation in the Radok Lake region of the northern Prince Charles Mountains, east Antarctica; evidence for a single protracted orogenic event
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DOI：
10.1016/s0301-9268(00)00079-6
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发表时间：
2000-10
影响因子：
3.8
通讯作者：
S. Boger
中科院分区：
文献类型：
--
作者：
S. Boger
对构造受限的长英质侵入岩进行的离子探针测年表明，查尔斯王子山脉北部的岩石在一次长期的新元古代构造事件中发生了变形。变形经历了四个逐渐变得离散的阶段，以响应南北向的连续挤压。在研究区(拉多克湖)，在∼990 Ma发生了大量的花岗岩侵入体，与区域广泛的岩浆作用、峰期变质作用、亚水平剪切和卧式褶皱作用同时发生。随后的垂直褶皱和剪切带的发展发生在∼940 Ma，而新的锆石生长在∼900 Ma限制了沿低角度糜棱岩和假千里岩适应的变形的最后阶段。这一最后的变形阶段是麻粒岩在中角闪岩相岩石上异地侵位的原因。这项研究对变形时间施加的年龄限制排除了NPCM的高级返工，正如最近的一些文献所假设的那样。此外，NPCMS中990-900 Ma的造山作用比澳大利亚、东非和南极其他地区发现的其他相关的格伦维尔古老造山带的造山作用至少年轻50Myr。这种明显的年龄差异意味着，这些带很可能是不可关联的，就像之前在重建罗迪尼亚超大陆时所暗示的那样。
Ion microprobe dating of structurally constrained felsic intrusives indicate that the rocks of the northern Prince Charles Mountains (nPCMs) were deformed during a single, long-lived Neoproterozoic tectonic event. Deformation evolved through four progressively more discrete phases in response to continuous north–south directed compression. In the study area (Radok Lake), voluminous granite intrusion occurred at ∼990 Ma, contemporaneous with regionally extensive magmatism, peak metamorphism, and sub-horizontal shearing and recumbent folding. Subsequent upright folding and shear zone development occurred at ∼940 Ma, while new zircon growth at ∼900 Ma constrains a final phase of deformation that was accommodated along low-angle mylonites and pseudotachylites. This final period of deformation was responsible for the allochthonous emplacement of granulites over mid-amphibolite facies rocks in the nPCMs. The age constraints placed on the timing of deformation by this study preclude the high-grade reworking of the nPCMs as is postulated in some of the recent literature. Furthermore, 990–900 Ma orogenesis in the nPCMs is at least 50 Myr younger than that recognised in other previously correlated Grenville aged orogenic belts found in Australia, east Africa and other parts of the Antarctic. This distinct age difference implies that these belts are probably not correlatable, as has been previously suggested in reconstructions of the supercontinent Rodinia.