Collaborative Research: Geochemical Studies of the Southern Lesser Antilles

这是康奈尔大学和布朗大学的合作项目。本文拟通过野外考察、岩石学研究、主元素、微量元素、Sr、Nd、Pb、O同位素测定和K-Ar定年等多学科方法，对圣卢西亚、圣文森特和格林纳达地区岩浆的成因和演化进行研究。岩石学研究将包括微探针和激光烧蚀-电感耦合等离子体质谱研究。本研究的直接目标是：(1)确定了弧壳对格林纳达和圣卢西亚地幔源岩浆演化的贡献；(2)利用这些岩浆中镁质最多的岩浆（其中一些岩浆自地幔楔中产生以来仅轻微演化）来研究其熔融程度和源富集程度；(3)确定这些岛屿上的岩浆成分是如何随时间变化的。实现这些目标使我们能够处理几个更广泛的目标。这些都是:加深了对(1)岛弧岩浆生成和演化过程的认识，(2)加勒比海地区的构造演化，(3)发生或不发生地壳同化的必要条件，(4)从俯冲板块向岛弧岩浆的物质输送，(5)不相容元素从俯冲带向深部地幔的质量通量。通过改进实验知识库，专注于几个地方，并拥有广泛的数据，我们相信我们可以大大改进早期的模型。

This is a collaborative project between Cornell and Brown Universities. We propose to study magma genesis and evolution in St. Lucia, St. Vincent, and Grenada through a multi-disciplinary approach that will include field work, petrographic study, major element, trace element, Sr, Nd, Pb and O isotope determination, and K-Ar dating. Petrographic study will include both micro probe and laser-ablation- inductively-coupled-plasma-mass-spectrometry studies. The immediate objectives of this study are to: (1) determine the contribution of arc crust to the evolution of mantle- derived magmas in Grenada and St. Lucia, (2) use the most magnesian of these magmas, some of which are only slightly evolved since production in the mantle wedge, to investigate degree of melting and source enrichment, and (3) determine how magma composition has changed through time on these islands. Achieving these objectives allows us to address several broader objectives. These are: enhanced understanding of (1) magma generation and evolution processes in island arcs, (2) tectonic evolution of the Caribbean region, (3) the conditions necessary for crustal assimilation to occur or not to occur, (4) mass transport from the subducting slab to island arc magmas, and (5) mass fluxes of incompatible elements to the deep mantle from subduction zones. By focusing on a few localities with an improved experimental knowledge base, and having a wide range of data, we believe we can substantially improve earlier models.