Constraints on the Tectonomagmatic Evolution of the Pacific Margin of Gondwana from U-Pb Geochronology of Magmatic Rocks in the Transantarctic Basement

横贯南极基底岩浆岩U-Pb年代学对冈瓦纳太平洋边缘构造岩浆演化的制约

• 批准号: 9615398
• 负责人: John Encarnacion
• 金额: $ 4.83万
• 依托单位: Saint Louis University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-06-01 至 2001-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9615398&HistoricalAwards=false
• 关键词: Constraints; Tectonomagmatic; Evolution; Pacific; Margin

Encarnaci_n OPP 9615398 Abstract Basement rocks of the Transantarctic Mountains are believed to record a change in the paleo-Pacific margin of Gondwana from a rifted passive margin to a tectonically active margin (Ross orogen). Recent hypothesis suggest that the passive margin phase resulted from Neoproterozoic rifting of Laurentia from Antarctica ("SWEAT" hypothesis). The succeeding active margin phase (Ross orogeny) was one of several tectonic events ("Pan African" events) that resulted from plate convergence/transpression that was probably a consequence of the assembly of components of the Gondwana supercontinent. Although these basement units provide one of the keys for understanding the break up and assembly of these major continental masses, few precise ages are available to address the following important issues: (1) Is there any pre-rift high-grade cratonal basement exposed along the Transantarctic Mountains, and what is/are its precise age? Is this age compatible with a Laurentia connection? (2) What is the age of potential rift/passive margin sediments (Beardmore Group) along the Queen Maud Mountains sector of the orogen? (3) What is the relative and absolute timing of magmatism and contractional deformation of supracrustal units in the orogen? Was deformation diachronous and thus possibly related to transpressional tectonics, or did it occur in a discrete pulse that is more compatible with a collision? How does contraction of the orogen fit in with emplacement of voluminous plutonic and volcanic rocks? The answers to these questions are central to understanding the kinematic evolution of this major orogenic belt and its role in Neoproterozoic-Early Paleozoic continental reconstructions and plate kinematics. Hence, this award supports funding for precise U-Pb dating, using zircon, monazite, baddeleyite, and/or titanite from a variety of magmatic rocks in the Queen Ma ud Mountains, which can address the foregoing problems. In addition to the issues above, precise dating of volcanics that are interbedded with carbonates containing probable Middle Cambrian fauna could potentially provide a calibration point for the Middle Cambrian, which will fill a gap in the absolute time scale for the early Paleozoic.

Encarnaci_电话：9615398 摘要横贯南极山脉的基底岩石被认为记录了冈瓦纳古太平洋边缘从裂谷被动边缘到构造活动边缘（罗斯造山带）的变化。 最近的假说认为，被动陆缘阶段是新元古代南极劳伦提斯裂谷作用的结果（SWEAT假说）。 随后的活动边缘阶段（罗斯造山带）是几个构造事件（"泛非洲"事件），导致板块会聚/平移，这可能是一个结果的组装的组成部分冈瓦纳超大陆。 虽然这些基底单元为理解这些主要大陆块体的分裂和组装提供了关键之一，但几乎没有精确的年龄可以解决以下重要问题： (1)沿横贯南极山脉是否出露有裂谷前的高级变质基底，其确切年龄是多少？ 这个年龄和劳伦提斯家族的关系相符吗 (2)沿着造山带的毛德皇后山地段，潜在的裂谷/被动边缘沉积物（比尔德摩尔群）的年龄是多少？ (3)造山带中地壳上单元的岩浆活动和收缩变形的相对和绝对时间是什么？ 是 变形穿时，因此可能有关 转换挤压构造，还是它发生在一个离散的脉冲，更符合碰撞？造山带的收缩如何与大量的深成岩和火山岩的侵位相适应？ 这些问题的答案是核心的运动学演化的主要造山带和新元古代-早古生代大陆重建和板块运动学的作用的理解。因此，该奖项支持资助精确的U-Pb测年，使用锆石，独居石，baddeleyite，和/或从各种岩浆岩在毛德皇后山，可以解决上述问题。 除了上述问题之外，与可能含有中寒武世动物群的碳酸盐互层的火山岩的精确定年可能为中寒武世提供校准点，这将填补早古生代绝对时间尺度的空白。