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）导致了对高温高压变质作用的认识（c。710-810 °C，20-23千巴）的超镁铁质岩石从北方沙克尔顿山脉。这一发现是沙克尔顿山脉榴辉岩相变质作用的第一个证据，据我们所知，也是泛非造山带榴辉岩相超基性岩的第一个描述。这些超镁铁质岩石的岩石学最好的解释是，它们标志着沙克尔顿山脉北方的缝合带，这可能是东冈瓦纳和西冈瓦纳之间的收敛网站的痕迹。迄今为止，沿着这个假定的缝合带，还没有发现真正年轻的新元古代地壳的证据。沿着这个假定的缝合带。因此，导致冈瓦纳超大陆合并的地球动力学过程仍然高度推测。来自沙克尔顿山脉的蛇绿基性岩石的可用Sm-Nd同位素数据（Talarico等人，1999年）是不确定的，因为他们产生不切实际的年轻或更老的元古代太古代的模式年龄。为了对前寒武纪末超大陆形成的基本问题做出贡献，我们打算集中于对选定的表壳岩和基底岩石进行同位素和地球化学技术研究，这些岩石可从以前对沙克尔顿山脉的考察中获得。这项工作将遵循，并将基于，目前正在进行的变质研究，这些岩石的PT演化。总体目标是更好地评估沙克尔顿山脉的构造演化，即区分中、新元古代地壳形成事件，并限制各种基性原岩的来源年龄和表壳围岩的来源。为此，拟开展Sm-Nd、Rb-Sr、Pb全岩同位素分析、Hf锆石原位分析、Sm-Nd石榴石、U-Pb单颗粒锆石和独居石年代学研究以及Ar-Ar分步角闪石定年。