Evolution of the Galapagos Mantle Plume

加拉帕戈斯地幔羽流的演化(由EAR/Petroology&Amp；地球化学和OISE/America联合支持的项目)智力价值：目前的模型表明，导致二叠纪-古新世期间大型火成岩省(LIP)就位的大规模玄武岩生产(对地球上的环境和生命产生强烈影响)可能代表了为目前的一些海洋岛屿提供补给的地幔羽流的初始阶段。与地幔热柱有关的火山岩是有关地球深部地球化学循环的最重要信息来源。由于大洋热柱的轨迹大部分被淹没，有关地幔热柱的大多数地球化学信息来自对年轻的洋岛玄武岩(OIB)的研究。相反，在大多数情况下，最初的唇相被大陆污染所掩盖。最近的岩石学模拟表明，在最初的嘴唇形成期间，地幔羽流通常比现代洋岛形成期间更热，更广泛地融化。要限制这种长期冷却的起源和程度，需要了解地幔热柱从头到尾的持续冷却记录。加拉帕戈斯轨道是少数几个证明了地幔羽流长期冷却的例子之一，它提供了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阶段的几乎连续的记录。这是因为在中美洲，大部分羽流轨迹被保存为吸积的地体，因此是可以进入的。然而，加拉帕戈斯羽流的热和地球化学演化在15-60 Ma之间存在采样差距。为缩小这一差距，建议在巴拿马和哥斯达黎加对沉积的岩屑和羽流轨迹进行抽样，并进行详细的岩石学和地球化学研究，辅之以羽流动力学模型。新的数据将与文献数据相结合，以提供加拉帕戈斯羽流演化的连续记录，重点关注以下关键问题：1.最近观测到的从羽流头部熔体与羽流尾部熔体之间的温差是由于羽流源温度的变化，还是由于羽流过境的影响(更有效地冷却了羽流尾部与羽流头部)和/或岩性变化(橄榄岩与辉石岩)的动态效应？2.我们能否通过高温与上地幔上方升高的3He/4He信号之间的关联来追踪羽流的核心？橄榄岩和辉石岩源的采样从头到尾有变化吗？这告诉了我们关于地幔深处这些岩性的比例以及它们被羽流采样的动力学方面的什么？4.氦，放射性同位素和微量元素组成随岩性和/或时空变化而变化，这对地幔中不同地球化学域的大小和组成有何启示？拟议的研究将提供长期羽流的连续记录和关于羽流演化、羽流过境效应和深部地球化学循环的关键信息。广泛的地球科学界将对此感兴趣。广泛的影响：这项研究的结果将在国际会议上公布，并发表在同行评议的期刊上。皮加泽尔(领导该项目)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，因此影响了CU本科生和研究生以及来访科学家的培训。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。项目主题和调查结果将纳入在纽约教授的课程(包括K12学校)，以及面向非科学界的外联活动。Gazel领导每年一次的哥斯达黎加海洋综合体的实地考察，参加考察的有来自大学的学生和教职员工。哥斯达黎加大学(UCR)、LDEO和其他学术机构。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.