Evolution of the Galapagos Mantle Plume

加拉帕戈斯地幔柱的演化（由海洋学/岩石学地球化学和OISE/美洲联合支持的项目）学术价值：目前的模型表明，在二叠纪-古新世期间，造成大火成岩省（LIPS）就位的大量玄武岩生产（对地球上的环境和生命产生了强烈影响）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养分。与地幔柱有关的火山岩是研究地球深部地球化学旋回的重要信息源。由于洋柱轨迹大部分被淹没，地幔柱的地球化学信息大多来自年轻洋岛玄武岩（OIB）的研究。相反，在大多数情况下，初始LIP阶段被大陆污染所掩盖。最近的岩石学模型表明，在最初的LIPS形成的地幔柱一般更热，更广泛地熔融比现代海洋岛屿的形成。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。加拉帕戈斯轨迹是证明地幔柱长期冷却的少数例子之一，它提供了从加勒比大火成岩省（CLIP）~90 Ma LIP阶段到加拉帕戈斯群岛最近OIB阶段的近连续记录。 这是因为大部分羽流轨迹在中美洲作为增生的火山岩保存下来，因此可以接近。然而，在加拉帕戈斯地幔柱的热演化和地球化学演化中，存在15-60 Ma的取样空白。在这里，它建议通过在巴拿马和哥斯达黎加的增生CLIP和羽轨迹采样，并进行详细的岩石学和地球化学研究，辅以羽动力学建模，以缩小这一差距。新的数据将与文献数据相结合，以提供一个连续的记录的加拉帕戈斯羽的演变，重点放在以下关键问题：1。最近观察到的羽流头部与羽流尾部的熔体之间的温差是由于羽流源温度的变化还是羽流传输的影响（羽流尾部与羽流头部的冷却效率更高）和/或岩性变化的动态影响（橄榄岩与辉石岩）？2.我们能否通过高温与上地幔值以上的3 He/4 He特征之间的相关性来追踪地幔柱的核心？3.从地幔柱的头部到尾部，橄榄岩和辉石岩源的取样是否有变化？这告诉我们地幔深处这些岩性的比例以及它们通过地幔柱取样的动态方面是什么？4.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是什么？拟议的研究将提供长期羽流的连续记录以及羽流演变、羽流过境影响和深部地球化学循环的关键信息。更广泛的影响：研究结果将在国际会议上介绍，并在同行评审的期刊上发表。PI Gazel（领导该项目）正处于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）教授现代分析方法的研究生课程，从而影响了CU的本科生和研究生以及访问科学家的培训。作为该项目的一部分，本科生将接受样品制备和电子探针分析方面的培训。该项目的主题和调查结果将纳入在纽约（包括K12学校）教授的课程，以及对非科学界的外联活动。Gazel每年都会带领来自哥斯达黎加大学（UCR）、LDEO和其他学术机构的学生和教师前往哥斯达黎加海洋综合体进行实地考察。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.