Collisional Magmatism during the Amalgamation of Pangea: Implications for Crustal Growth Processes

盘古大陆合并过程中的碰撞岩浆作用：对地壳生长过程的影响

• 批准号: RGPIN-2018-05484
• 负责人: Braid, James
• 金额: $ 1.82万
• 依托单位: St. Francis Xavier University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=713702
• 关键词: Collisional; Magmatism; during; Amalgamation; Pangea

Continental crust covers almost 40% of the earth's surface and it is generally accepted that crustal growth has lasted from the early Archean to present-day. Traditionally, crustal growth was considered as accomplished primarily through island arc and continental arc magmatism with collisional orogenesis responsible for reworking of the continental crust. However, recent investigations of modern collisional orogens suggest that many magmatic rocks record depleted mantle isotopic signatures. This relationship suggests that continental subduction and collision zones may be key sites for the interaction and mass transfer between the crust and the mantle, the generation of juvenile magmas and the growth of continental crust. Magmatism occurs at different stages during the collisional process from continental subduction, exhumation to orogenic collapse, and much controversy still exists surrounding the (i) genesis of this magmatism, (ii) processes associated with crust and the mantle interaction, (iii) relationship of this magmatism to continental growth, and (iv) detailed evolution of the continental crust throughout earth's history. In order to investigate these relationships, I will focus on the late Paleozoic Variscan orogen of Western Europe, which formed during the assembly, and amalgamation of the most recent supercontinent, Pangea. This well-documented collisional orogen provides exposure of a wide range of magmatic rocks, which formed at different stages of the continental collision and, therefore, provides an excellent framework to investigate crust-mantle processes and crustal growth during supercontinent amalgamation and, in turn, assess the role of late Paleozoic collisional magmatism to the global crustal evolution. The proposed research will focus on key locations around the Variscan orogen that each contains exposed magmatic rocks that formed at different times during the continental collision. My students and I will study the field relationships, age (U/Pb geochronology) and structural evolution of magmatic rocks to provide a space-time framework for the regional tectonic evolution. These observations and data will then be used to help interpret the geochemistry and isotopic signatures to assess how the interaction between the crust and mantle potentially changes with the evolving collision process. This research is based solidly on my existing research strengths, and represents many undergraduate, graduate student and other HQP opportunities. The overall goal of my proposed program is to contribute to the understanding of the collisional magmatism during the Variscan Orogen, providing insight into the understanding of the genesis of orogenic magmatism, potential late Paleozoic crustal growth and the complex tectonics associated with supercontinent amalgamation.

大陆地壳几乎覆盖了地球表面的40%，人们普遍认为地壳生长从太古代早期一直持续到今天。传统上，地壳生长被认为主要是通过岛弧和大陆弧岩浆作用完成的，碰撞造山作用负责大陆地壳的改造。 然而，最近对现代碰撞造山带的研究表明，许多岩浆岩记录了贫乏的地幔同位素特征。 这种关系表明，大陆俯冲和碰撞带可能是地壳与地幔相互作用和质量传递、新生岩浆生成和大陆地壳生长的关键场所。 岩浆作用发生在从大陆俯冲、折返到造山崩塌的碰撞过程的不同阶段，围绕（i）岩浆作用的成因，（ii）与地壳和地幔相互作用有关的过程，（iii）地幔相互作用的关系仍然存在许多争议。这种岩浆作用导致大陆生长，以及（iv）整个地球历史上大陆地壳的详细演化。 为了研究这些关系，我将重点关注西欧晚古生代瓦里斯造山带，它是在最近的超级大陆盘古大陆的聚集和合并过程中形成的。这个有据可查的碰撞造山带提供了各种岩浆岩的暴露，这些岩浆岩是在大陆碰撞的不同阶段形成的，因此，为研究超大陆合并过程中的壳幔过程和地壳生长提供了一个极好的框架，反过来，评估晚古生代碰撞岩浆作用对全球地壳演化的作用。 拟议的研究将集中在瓦里坎造山带周围的关键位置，每个位置都包含在大陆碰撞期间不同时间形成的裸露岩浆岩。我和我的学生将研究岩浆岩的场关系、年龄（U/Pb年代学）和结构演化，为区域构造演化提供时空框架。 这些观测结果和数据将用于帮助解释地球化学和同位素特征，以评估地壳和地幔之间的相互作用如何随着不断演变的碰撞过程而发生变化。 这项研究牢固地基于我现有的研究优势，并代表了许多本科生、研究生和其他 HQP 的机会。我提出的计划的总体目标是促进对瓦里斯造山带期间碰撞岩浆作用的理解，深入了解造山岩浆作用的起源、潜在的晚古生代地壳生长以及与超大陆合并相关的复杂构造。