Geochemical probing of continental lithosphere through time in transported terranes

迁移地体中大陆岩石圈随时间变化的地球化学探测

• 批准号: 3782-2011
• 负责人: Dostal, Jaroslav
• 金额: $ 2.4万
• 依托单位: Saint Mary's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=568324
• 关键词: Geochemical; probing; continental; lithosphere; through

Geochemical studies show that rift-related basaltic rocks typically inherit the isotopic signature of their mantle sources. Most studies focus on suites of volcanic or plutonic rocks that were emplaced within a narrow time interval and then compare these rocks with coeval suites in adjacent terranes. My approach is to investigate the geochemical/ isotopic characteristics of rift-related igneous suites in specific terranes over a long range of time. This approach enables me to evaluate the long-term relationship between the crust and the underlying sub-continental lithospheric mantle (SCLM, the lower part of the rigid lithospheric plate) in a variety of tectonic settings, and to determine whether or not the crust and SCLM were coupled during the major tectonic events such as rifting, drifting and accretion. The potential coupling/decoupling between the crust and the SCLM during these events is critical to the identification and understanding of the global-scale tectonic and magmatic processes. Evidence (or a lack thereof) for changes in the SCLM will answer important geodynamic questions such as (i) do terranes retain their SCLM when transferred across an ocean? (ii) is the SCLM replaced following collisional orogenesis? (iii) do superplumes replace the SCLM beneath supercontinents? and (iv) is coupling between the crust and SCLM enduring and common or does it change with time, and if so, when and why? To build on previous research, I will investigate the coupling/decoupling of the SCLM and crust primarily during the Paleozoic evolution of peri-Gondwanan terranes. These transported terranes originated along the margin of Gondwana (precursor supercontinent) in the Neoproterozoic, rifted from that margin in the Early Paleozoic and were transferred across an ocean to collide with Laurentia or Baltica (precursor continents) before the end of the Paleozoic.

地球化学研究表明，与裂谷有关的玄武质岩石通常继承了其地幔来源的同位素特征。大多数研究集中在一个狭窄的时间间隔内侵位的火山岩或深成岩套，然后将这些岩石与相邻岩石中的同时代套进行比较。我的方法是调查地球化学/同位素特征的裂谷有关的火成岩套在特定的岩石在很长一段时间。这种方法使我能够评估长期之间的关系，地壳和下伏的次大陆岩石圈地幔（SCLM，刚性岩石圈板块的下部）在各种构造环境，并确定是否地壳和SCLM耦合在主要的构造事件，如裂谷，漂移和增生。在这些事件中，地壳和SCLM之间的潜在耦合/解耦对于识别和理解全球尺度的构造和岩浆过程至关重要。SCLM变化的证据（或缺乏证据）将回答重要的地球动力学问题，如（i）当跨越海洋转移时，海洋生物是否保留了它们的SCLM？(ii)SCLM是在碰撞造山作用后被替换的吗？(iii)超级地幔柱会取代超级大陆下的SCLM吗？地壳与SCLM之间的耦合是持久的和普遍的还是随时间而变化的，如果是，何时以及为什么？ 为了建立在以前的研究，我将调查的耦合/解耦的SCLM和地壳主要是在古生代的古冈瓦纳古陆演化。这些被搬运的岩石沿着起源于新元古代的冈瓦纳大陆边缘（前体超大陆），在早古生代从该边缘裂陷，并在古生代结束前被转移到大洋与劳伦大陆或波罗的海大陆（前体大陆）碰撞。