Collaborative Research: RUI: Application of In-situ Produced Cosmogenic 36Cl to Central Andean Volcanism

最近地貌学领域的一项重要贡献是发展了一种量化地质表面侵蚀速率和暴露年龄的核心方法。该方法依赖于测量一些放射性核素和稳定核素，这些核素是在暴露于宇宙射线的岩石中不断就地产生的。我们之所以选择36Cl，是因为它易于测量，而且适用于火山岩。我们建议校准36Cl暴露年龄的方法，可追溯到600 Ka。然后将36Cl和40Ar/39Ar方法应用于安第斯山脉中部的火山岩，为安第斯山脉中部晚更新世到全新世的火山作用提供一个年代学框架。之所以选择安第斯山脉中部进行这项初步研究，是因为它可能是世界上大陆火山作用最好的例子，它的高海拔和极度干旱的环境导致了火山特征的极好保存（极低的侵蚀率）。此外，由于在高海拔地区宇宙射线的入射通量很高，宇宙成因同位素的产生率也将很高。将确定36Cl深度剖面，并在可能的情况下确定36Cl/10Be比率，以确保侵蚀速率远低于影响暴露年龄的侵蚀速率。该研究将有助于量化关于安第斯山脉中部火山作用的几个重要科学问题：(1)火山构造的生长和演化速度，(2)熔岩流的喷发频率和岩浆生产速度，以及(3)36Cl暴露年龄和侵蚀速率与Landsat成像数据的相关性。这项研究很重要，因为火山作用和构造作用密切相关，研究过程的任何结论都可能适用于全球。

9523565 de Silva Recently an important contribution to the field of geomorphology has been the development of a nuclear method for quantifying erosion rates and exposure ages of geological surfaces. the method relies on measurement of a number of radionuclides and stable nuclides which are continually being produced in situ in rocks exposed to cosmic rays. We have chosen to examine 36Cl due to its ease of measurement and applicability to volcanic rocks. We propose to calibrate the 36Cl method of exposure age dating up to 600 Ka. The 36Cl and 40Ar/39Ar methods will then be applied to Central Andes volcanic rocks to provide a chronological framework for late Pleistocene to Holocene volcanism in the Central Andes. The Central Andes has been selected for this pilot study because it is probably the finest example of continental volcanism in the world, and its high elevation and hyper-arid environment result in superb preservation (extremely low erosion rates) of volcanic features. In addition, since a high incident flux of cosmic rays is attained at high altitudes, cosmogenic isotope production rates will also be high. 36Cl depth profiles, and, if possible, 36Cl/10Be ratios will be determined to ensure that the erosion rate is well below that which would affect exposure ages. The proposed study will help to quantify several important scientific questions about central Andes volcanism: (1) the rate of growth and evolution of volcanic constructs, (2) the eruption frequency of lava flows and magma production rates, and (3) the correlation of 36Cl exposure ages and erosion rates with Landsat imaging data. The study is important as volcanism and tectonism are intimately related and any conclusions about the processes studied will likely be applicable globally.