Melting and storage conditions of rhyolites in the Snake River Plain Province , USA

美国蛇河平原省流纹岩的融化和储存条件

• 批准号: 398667061
• 负责人: Professor Dr. Francois Holtz, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/398667061?language=en
• 关键词: Melting; storage; conditions; rhyolites; Snake

The Snake River Plain-Yellowstone province preserves a unique record of bimodal magmatism (basalt-rhyolite) resulting from basaltic magma underplating and subsequent crustal recycling. The proposed project focuses on the generation and storage of rhyolites in the Snake River Plain (SRP) and is designed to clarify the “crustal recycling” processes occurring at depth as a result of basaltic magma underplating. A variety of generation models are currently proposed (fractionation, assimilation, partial melting) but they are not tested experimentally and, as a consequence tend to remain qualitative. Starting from one end-member hypothesis and assuming that rhyolites are formed from partial melting of crustal material, high pressure experiments will be conducted to determine the geochemical signature (major and trace elements) of partial melts produced from typical protoliths. Two main source types which are under debate will be tested: hydrothermally altered rhyolites and mafic basaltic rocks. The experimental results and the composition of the experimental melts will be compared with the composition of glasses in natural samples from the ICDP cores and from selected eruptive units covering the 16 Ma activity of the SRP. The geochemical compositions of the natural glasses will also be used to apply a new barometer recently calibrated by the proponents. Selected samples from a few eruptive units (e.g., Kimberley and Sugar City core) will be used to check if large eruptions result from different magma batches stored at various P-T conditions. The results will contribute to understand the nature of the source rocks of the rhyolites, the conditions of melting and of magma storage prior to eruption (depth, temperature, volatile contents), and the evolution of magma storage conditions in space and time.

蛇河平原-黄石省保留了由玄武岩岩浆底侵和随后的地壳循环产生的双峰岩浆作用（玄武岩-流纹岩）的独特记录。拟议项目的重点是蛇河平原（SRP）流纹岩的生成和储存。旨在阐明由于玄武岩浆底侵而在深处发生的“地壳回收”过程。目前提出了多种生成模型（分馏、同化、部分熔融），但它们没有经过实验测试，因此往往保持定性。从一个端元假说出发，假设流纹岩是由地壳物质部分熔融形成的，将进行高压实验以确定将测试由典型原岩产生的部分熔体的地球化学特征（主要元素和微量元素）：热液蚀变流纹岩和镁铁质玄武岩岩石的实验结果和成分。实验熔体将与来自 ICDP 核心和覆盖 SRP 16 Ma 活动的选定喷发单元的天然样品中的玻璃成分进行比较。天然玻璃的地球化学成分也将用于应用最近校准的新气压计。支持者从一些喷发单元（例如金伯利和糖城核心）中选取的样本将用于检查在不同 P-T 条件下储存的不同岩浆批次是否会导致大规模喷发。研究结果将有助于了解流纹岩烃源岩的性质、喷发前的熔化和岩浆储存条件（深度、温度、挥发物含量）以及岩浆储存条件在空间和时间上的演变。