U-Th-Pb Geochronology and Mineral Pb Systematics of Quaternary Basalt

EAR-9909590DePaoloDevelopment将继续使用一种新的方法来确定年轻的玄武岩火山岩的年龄，这是地球上喷发的最丰富的熔岩类型。这项研究包括测量火山岩中矿物、玻璃和基质中的铅同位素组成，以及测量矿物、玻璃和基质中的铀/铅和钍/铅比值。这项研究需要一种特殊的方法来测量铅同位素比率。这一办法是用以前的赠款制定的，但我们希望改进决议。有了这项新技术，就有可能更好地了解岩浆在地球上产生并输送到地表喷发的过程。这项工作的重点将是将这项技术应用于海底镁铁质熔岩，特别是那些低钾含量的熔岩。低钾熔岩广泛存在于地球上，用其他方法测年尤其困难。初步工作表明，许多玄武岩矿物中的铅同位素变化比预期的要大。这些变化的原因和影响也将被进一步调查。将要测量的岩石和矿物将从夏威夷、美国西部和意大利收集，并将从其他来源获得更多的海底熔岩。为了帮助解释铅同位素数据，还将进行锶和钕同位素分析。

EAR-9909590DePaoloDevelopment will continue on a new method for determining the ages of young basaltic volcanic rocks, the most abundant lava type erupted on the earth. The research involves measurements of Pb isotopic composition combined with measurements of U/Pb and Th/Pb ratios in minerals, glass and groundmass in volcanic rocks. The research requires a special approach to measuring Pb isotope ratios. The approach had been developed with a previous grant, but we hope to improve the resolution. With this new technique it will be possible to better understand the processes by which magma is produced in the earth and transported to the surface for eruption. The work will focus on application of the technique to submarine mafic lavas, particularly those with low potassium concentrations. Low-K lava is widespread on the earth, and particularly difficult to date by other methods. Preliminary work shows that Pb isotopes in minerals of many basalts are more variable than expected. The causes and implications of these variations will befurther investigated as well. The rocks and minerals that will be measured will be collected from Hawaii, the western U.S., and Italy, and additional submarine lavas will be obtained from other sources. To help interpret the Pb isotope data, analyses of Sr and Nd isotopes will also be made.