Isotopic Studies of Madagascan Basalts and Deccan Picritic Lavas

这是一个由两部分组成的项目，旨在继续调查马达加斯加和印度德干圈闭白垩纪溢流玄武岩的来源和岩石成因。拟与A.Saunders和M.Storey(英国莱斯特大学)合作完成对马达加斯加熔岩和岩墙的研究。具体来说，计划是：(A)继续对300个有充分记录的样本的子集进行Nd、Pb和Sr同位素分析；(B)让马奥尼为计划于1991年前往马达加斯加北部剩余的主要曝光点进行实地考察作出贡献；(C)对从中选定的样本进行同位素工作。拟议工作的第二个重点是对德干北部圈闭中独特的近原始苦橄岩熔岩和相关玄武岩的同位素(铅、钕、锶)研究。与西高止组相比，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，其中一些可能几乎不受大陆物质的影响。此外，由于它们可能代表了德干地区最早的喷发，该计划将获得高质量的40Ar-39Ar年代(来自俄亥俄州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).