Effect of Hotspots on the Evolution of Microplates around the Nazca Plate

了解海底火山岩化学成分的变化对于了解洋壳的形成过程和地幔中海底岩浆的来源都很重要。最近的研究表明，主量元素和微量元素化学既受来源差异的控制，也受岩浆上升到海底期间来源熔融和随后结晶的程度控制。然而，铅、钕和锶的同位素组成显然反映了原始地幔来源。通过研究地壳岩石的全部化学成分，应该可以确定各种地幔来源在地壳成因中的重要性。本项目的目标是完成东太平洋纳斯卡板块边界扩张中心玄武岩的铅、钕和锶同位素测量。对这些样品进行了常量元素和微量元素分析。这项研究的主要目标是确定地幔热点在该区域主要地壳板块解体中所起的作用。这种复杂的板块碎裂历史导致了在过去3000万年中出现了许多瞬间的微板块。要研究的样本来自复活节和胡安·费尔南德斯微孔板以及加拉帕戈斯传播中心。该项目的首席调查员非常有资格进行这项研究，并且是地壳岩石同位素组成方面的权威。

Understanding the variation in the chemical composition of sea-floor volcanic rocks is important to understanding both the processes that produce the oceanic crust and origin of sea-floor magmas in the mantle. Recent research has shown that the major and trace element chemistry can be controlled by both source differences as well as the extent of source melting and subsequent crystallization of the magma during its ascent to the sea-floor. The isotopic composition of lead, neodymium and strontium, however, apparently reflects the original mantle source. By examining the complete chemistry of crustal rocks it should be possible to determine the importance of various mantle sources in the crustal genesis. The objective of the present project is to complete lead, neodynium and strontium isotope measurements on spreading center basalts from the boundaries of the Nazca Plate in the eastern Pacific. Major and trace element analyses have already been completed on these samples. The major goal of the study is to determine the role that mantle hotspots have played in the break- up of major crustal plates in the region. This complex history of plate fragmentation has led to a number of transient microplates during the last 30 million years. Samples to be studied are from the Easter and Juan Fernandez Microplates and the Galapagos Spreading Center. The principal investigator on this project is highly qualified to perform the research and is an authority on the isotope composition of crustal rocks.