报告题目：Source Enrichment Processes Responsible for Isotopic Anomalies in Oceanic Island Basalts

各位老师和同学：
应徐义刚研究员邀请，国际著名地球物理学家、英国剑桥大学Dan Mckenzie教授本周四将顺访我所并做“同位素室学术报告”2018年第6次报告。欢迎大家参加并积极参与讨论！
本周一下午和周三下午，Mckenzie教授将在南海海洋所和中山大学地球科学系做另外两个报告（报告摘要见附件），有兴趣的师生可自行前往聆听。
1月22日下午3：00，中科院南海海洋所（SCSIO） 题目：The structure of the oceanic lithosphere and asthenosphere
1月24日上午10：00，中山大学地球科学系（SYSU） 题目：Plate tectonics after 50 years
报告题目：Source Enrichment Processes Responsible for Isotopic Anomalies in Oceanic Island Basalts
报 告 人：Prof. Dan Peter McKenzie（剑桥大学）
报告时间：1月25日（周四）上午10:00
报告地点：标本楼一楼会议室
报告人简介：
Mckenzie教授，国际著名地球物理学家，1942年生于英国切尔南特，毕业于英国剑桥大学金学院，1963年获学士学位，1966年获硕士和博士学位，自1965年起在剑桥大学地质系工作至今。上世纪60～70年代，他与William J. Morgan和Xavier Le Pichon共同倡导板块构造学说，是板块构造学说的先驱之一。之后所做的地幔对流研究，是人类对地球内部认识的开端。发表论文200多篇，在地球物理学、大地构造学、地球化学等领域作出了杰出的、开创性的贡献。研究区域从地球延伸到金星和火星。
报告摘要：
Various schemes have been proposed to classify the isotopic observations from OIBs, but it is not clear whether any of them reflect the processes that produce the fractionation between parent and daughter elements. The obvious way forward is to use the correlation between isotopic ratios and elemental concentrations to extract the composition of the enriched material. But doing so is not straightforward for several reasons.
The mantle is surprisingly inhomogeneous, and, if more than two sources contribute to the composition of the melt, it is difficult to use the observations to disentangle the effects of magma mixing. Some of the larger oceanic islands are underlain by plumes, where the upwelling velocities reach 0.5 m/a. Therefore the composition of the material undergoing melting may change on a time scale as short as 10,000a. Another problem concerns the accuracy of the isotopic measurements, which may need to be made on samples as small as individual olivine melt inclusions.
The necessary measurements have now been made on a number of sample suites, in particular on post-glacial basalts from Iceland erupted in the last 10 ka. These show that the centre of Iceland is dominated by EMORB enrichment, in contrast to magmas from the far northeast and southwest, which have signatures like those of basalts from Reunion and model ages of about 400 Ma. The Icelandic data shows the importance of determining the composition of the enriching material from magmas that are erupted in a limited area in a short time interval. In SW Iceland there is no correlation between elemental concentrations and isotopic ratios from whole rock samples, but there is between ion probe measurements on melt inclusions.