Evolution of the Galapagos Mantle Plume

加拉帕戈斯地幔柱的演化（由EAR/岩石与地球化学和OISE/Americas联合支持的项目）知识价值：目前的模型表明，在二叠纪-古新世（对地球上的环境和生命产生强烈影响）期间，造成大火成岩省（LIPS）侵位的大量玄武岩生产可能代表了地幔柱的初始阶段，这些地幔柱为目前的一些海洋岛屿提供了食物。与地幔柱相关的火山岩是研究地球深部地球化学旋回最重要的信息来源。由于海洋羽流轨迹大部分被淹没，大多数关于地幔羽流的地球化学信息来源于对年轻海洋岛玄武岩（OIB）的研究。相反，在大多数情况下，最初的LIP阶段被大陆污染所掩盖。最近的岩石学模拟表明，在lip形成初期，地幔柱通常比现代海洋岛屿形成期间更热，融化范围更广。要限制这种长期冷却的起源和程度，需要了解地幔柱从头到尾的连续冷却记录。加拉帕戈斯轨道是少数几个证明地幔柱长期冷却的例子之一，它提供了一个几乎连续的记录，从加勒比海大火成岩省（CLIP）的~90 Ma LIP阶段到加拉帕戈斯群岛最近的OIB阶段。这是因为大部分烟柱轨迹被保存为中美洲的累积地形，因此是可以进入的。然而，加拉帕戈斯地幔柱的热地球化学演化在15-60 Ma之间存在一个采样缺口。在这里，我们建议通过对巴拿马和哥斯达黎加的吸积CLIP和羽流轨迹进行采样，并进行详细的岩石学和地球化学研究，并辅以羽流动力学建模，来弥补这一差距。新数据将与文献数据相结合，提供加拉帕戈斯羽流演变的连续记录，重点关注以下关键问题：最近观察到的羽头和羽尾熔体之间的温差是由于羽源温度的变化还是羽流传输的影响（羽尾比羽头更有效地冷却）和/或岩性变化的动态影响（橄榄岩vs辉石岩）？我们能否通过高温与上地幔值以上3He/4He特征的对比来追踪地幔柱的核心？从地幔柱的头部到尾部，橄榄岩和辉石岩的取样是否有变化？这告诉我们地幔深处这些岩性的比例，以及地幔柱取样的动力学方面的信息？氦、放射性同位素和微量元素组成是否随岩性和/或时空变化而变化，这告诉我们地幔中不同地球化学域的大小和组成？拟议的研究将提供长寿命羽流的连续记录和羽流演化的关键信息，羽流过境的影响和深层地球化学循环。它将引起广泛的地球科学界的兴趣。更广泛的影响：研究结果将在国际会议上发表，并发表在同行评议的期刊上。PI Gazel（领导这个项目）正处于他职业生涯的早期阶段。该项目支持LDEO的基础设施。PI Class管理LDEO的超净实验室，并在哥伦比亚大学（CU）教授现代分析方法研究生课程，从而影响了CU的本科生和研究生以及访问科学家的培训。作为这个项目的一部分，本科生将接受样品制备和电子微探针分析方面的培训。项目主题和研究结果将纳入纽约（包括K12学校）的课程，以及向非科学界的推广活动。Gazel带领每年一次的哥斯达黎加海洋综合体实地考察，来自哥斯达黎加大学（UCR）， LDEO和其他学术机构的学生和教师参加了这次考察。该项目涉及LDEO、IPGP（法国）和UCR之间的国际合作。

Evolution of the Galapagos Mantle Plume(project jointly supported by EAR/Petrology & Geochemistry and OISE/Americas)Intellectual Merit: Current models suggest that the massive basaltic production responsible for the emplacement of large igneous provinces (LIPS) during the Permian-Paleocene (with a strong impact on the environment and life on the planet) may represent the initial phases of mantle plumes that feed some of the current ocean-islands. Volcanic rocks related to mantle plumes are the most important source of information on the deep Earth geochemical cycles. Because oceanic plume tracks are largely submerged, most geochemical information on mantle plumes is derived from studies of young ocean island basalts (OIB). In contrast, the initial LIP phase in most cases is obscured by continental contamination. Recent petrological modeling suggests that during initial LIPS formation the mantle plumes are generally hotter and melted more extensively than during formation of modern ocean islands. Constraining the origin and degree of such secular cooling requires knowledge of a continuous cooling record of a mantle plume from head to tail. The Galapagos track is one of the few examples where secular cooling of the mantle plume has been demonstrated, and it offers a near continuous record from the ~90 Ma LIP phase of the Caribbean Large Igneous Province (CLIP) to the recent OIB phase at the Galapagos Islands. This is because much of the plume track is preserved as accreted terranes in Central America and thus is accessible. Nevertheless, there is a sampling gap from 15-60 Ma in the thermal and geochemical evolution of the Galapagos Plume. Here it is proposed to close this gap through sampling of the accreted CLIP and plume tracks in Panama and Costa Rica and conducting a detailed petrological and geochemical study complemented by modeling of plume dynamics. The new data will be integrated with literature data to provide a continuous record of the evolution of the Galapagos Plume with focus on the following key questions:1. Is the recently observed temperature difference between melts from a plume head versus a plume tail due to changes in the plume source temperature or an effect of plume transit (more efficient cooling of the plume tail vs. plume head) and/or a dynamic effect of a change in lithology (peridotite vs. pyroxenite)?2. Can we trace the core of the plume through correlation between high temperatures and elevated 3He/4He signatures above upper mantle values?3. Is there a change in the sampling of peridotite versus pyroxenite sources from plume head to tail and what does this tell us about the proportions of those lithologies deep in the mantle and the dynamic aspects of their sampling by the plume?4. Do helium, radiogenic isotope, and trace-element compositions change with lithology and/or spatially-temporally, and what does this tell us about the size and composition of the different geochemical domains in the mantle?The proposed study will provide a continuous record of a long-lived plume and key information on the evolution of a plume, effects of plume transit and deep geochemical cycles. It will be of interest to the broad Earth science community.Broader Impacts: The results of the study will be presented at international meetings and published in peer-reviewed journals. PI Gazel (who leads the project) is in the early phase of his career. The project supports the infrastructure at LDEO. PI Class manages the ultraclean laboratory at LDEO and teaches a graduate course in Modern Analytical Methods at Columbia University (CU) thus impacting the training of undergraduate and graduate students of CU as well as visiting scientists. Undergraduate students will be trained in sample preparation and electron-microprobe analyses as part of this project. The project topics and findings will be factored into courses taught in New York (including K12 schools), and outreach activities to the non-scientific community. Gazel lead a yearly field trip to the Costa Rican oceanic complexes, attended by students and faculty from the Univ. of Costa Rica (UCR), LDEO and other academic institutions. The project involves an international collaboration between LDEO, the IPGP (France) and the UCR.