Geodynamic evolution of Proterozoic supracrustal rocks from the northern Shackleton Range, East Antarctica

东南极洲沙克尔顿山脉北部元古代表壳岩石的地球动力学演化

• 批准号: 12693305
• 负责人: Professor Dr. Hartwig E. Frimmel
• 金额: --
• 依托单位: Lehrstuhl für Geodynamik und Geomaterialforschung
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2005
• 资助国家: 德国
• 起止时间: 2004-12-31 至 2007-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/12693305?language=en
• 关键词: Geodynamic; evolution; Proterozoic; supracrustal; rocks

Preliminary work to this project (Schmädicke & Will, 2006) led to the recognition of high-temperature and high-pressure metamorphism (c. 710-810 °C, 20-23 kbar) of ultramafic rocks from the northern Shackleton Range. This finding is the first evidence of eclogite-facies metamorphism in the Shackleton Range and, to our knowledge, the first description of eclogite-facies ultramafic rocks in a generally perceived Pan-African orogen. The petrology of these ultramafic rocks is best explained by them marking a suture zone within the northern Shackleton Range, which possibly traces the convergence site between East- and West-Gondwana. To date, no evidence of truly juvenile Neoproterozoic crust has been found along this postulated suture zone. Thus the geodynamic processes that led to the amalgamation of the Gondwana supercontinent remain highly speculative. Available Sm-Nd isotope data from allegedly ophiolitic mafic rocks of the Shackleton Range (Talarico et al., 1999) are not conclusive, because they yield either unrealistic young or older Proterozoic to Archean model ages. To contribute to the fundamental question of supercontinent formation towards the end of the Precambrian, we intend to focus on isotopic and geochemical techniques on selected supracrustal and basement rocks, available from a previous expedition to the Shackleton Range. This work will follow, and will be based upon, currently on-going metamorphic studies on the PT evolution of these rocks. The overall goal is to better assess the tectonic evolution of the Shackleton Range, i.e. to distinguish between Meso- and Neoproterozoic crust-forming events and to constrain both the age of the source for the various mafic protoliths and the provenance of the supracrustal country rocks. To this effect, it is planned to carry out Sm-Nd, Rb-Sr and Pb whole rock isotope analyses, Hf zircon in-situ analyses, and geochronological studies by means of Sm-Nd garnet, U-Pb single zircon and/or monazite as well as stepwise Ar-Ar hornblende dating.

该项目的初步工作（Schmädicke＆Will，2006年）导致了从北部Shackleton范围内的高温和高压变质（c。710-810°C，20-23 kbar）的高压变质（c。710-810°C，20-23 kbar）。这一发现是沙克尔顿范围内的叶绿石变质的第一个证据，据我们所知，在普遍认为的泛非造成膜中，对叶虫的超镁铁质岩石的首次描述。这些超镁铁质岩石的岩石学可以通过标记北沙克尔顿山脉内的一个缝合区域来解释，这可能会追溯到东甘德瓦纳之间的收敛地点。迄今为止，在这个假定的缝合区尚未发现真正的少年新元古代地壳的证据。导致冈瓦纳超大型融合的地球动力学过程仍然高度投机。来自Shackleton系列的据称是蛇纹岩的物理岩石（Talarico等，1999）的可用SM-ND同位素数据不是结论性的，因为它们会产生不现实的年轻或年长的properorogiac，以使其对Archean模型年龄产生。为了为前寒武纪末期的超大型形成的基本问题做出贡献，我们打算关注从先前的探险到Shackleton范围的选定的上库和地下室岩石上的同位素和地球化学技术。这项工作将遵循并将基于目前正在进行的有关这些岩石PT进化的变质研究。总体目标是更好地评估Shackleton范围的构造演化，即区分间质和新元古代壳形成事件，并限制各种Mafic Protoliths的来源的年龄和跨乡村岩石的出处。 To this effect, it is planned to carry out Sm-Nd, Rb-Sr and Pb whole rock isotope analyses, Hf zircon in-situ analyses, and geochronological studies by means of Sm-Nd garnet, U-Pb single zircon and/or monazite as well as stepwise Ar-Ar hornblende dating.