Isotopic Studies of Madagascan Basalts and Deccan Picritic Lavas

这是一个由两部分组成的项目，将继续调查马达加斯加和印度德干圈闭白垩纪洪水玄武岩的来源和岩石成因。建议与A. Saunders和M. Storey （U. Leicester, uk）合作完成对马达加斯加熔岩和岩脉的研究。具体计划是：(a)继续对300个记录良好的样本子集进行Nd、Pb和Sr同位素分析；(b)马奥尼协助计划于1991年对马达加斯加北部主要的剩余暴露进行实地考察；(c)对从中选出的样本进行同位素工作。本研究的第二个重点是对德干圈闭北部一组独特的近原生泥质熔岩和伴生玄武岩进行同位素（Pb, Nd, Sr）研究。与西高止山脉地层相比，这些样品明显富含高度不相容的元素。然而，它们不相容的元素模式表明，有些可能很少受到大陆物质的影响。此外，因为它们可能代表了德干最早的一些喷发，所以计划是获得高质量的40Ar-39Ar日期（来自俄勒冈州立大学的R. Duncan）。

This is a two-part project to continue investigation of the sources and petrogenesis of Cretaceous flood basalts in Madagascar and the Deccan Traps of India. It is proposed to complete study of Madagascan lavas and dikes, conducted in collaboration with A. Saunders and M. Storey (U. Leicester, U.K.). Specifically the plan is: (a) to continue Nd, Pb, and Sr isotopic analysis of a subset of 300 well-documented samples; (b) for Mahoney to contribute to a planned 1991 field trip to the major remaining exposures in northern Madagascar; and (c) to conduct isotopic work on selected samples therefrom. The second focus of the proposed work is an isotopic (Pb, Nd, Sr) study of a unique collection of near-primary picritic lavas and associated basalts in the northern Deccan Traps. These samples are markedly enriched in highly incompatible elements compared to the Western Ghats formations. However, their incompatible element patterns suggest that some are likely to be affected little by continental material. Also, because they may represent some of the earliest eruptions in the Deccan, the plan is to obtain high-quality 40Ar-39Ar dates (from R. Duncan, OSU).