Collaborative Research: Timescales of Magmatic Differentiation and Crustal Assimilation Beneath Iceland: Combined U-Series and Oxygen Isotope Studies

本研究将测量冰岛Krafla火山现代熔岩全岩样品、基质分离物和斜长石分离物中的226 Ra-230 Th不平衡和氧同位素组成。这种方法将适用于两个相对广泛的变化范围内的全岩（226 Ra）/（230 Th）和d18 O之间的不同喷发，也详细分离和分析一个以上的大小部分斜长石分离从同一熔岩。 由于氧同位素在共存的斜长石和硅酸盐液体之间的分馏是相对众所周知的，在晶体中测量的d18 O可以直接与它们结晶的液体中d18 O的变化有关。因此，早期形成的晶体d18 O可以保存岩浆混合或地壳同化发生之前的液体成分的记录。克拉夫拉熔岩中斜长石的氧同位素组成的多样性，无论是在不同的喷发和单一的熔岩，将提供信息的相对影响的幔源和地壳来源的材料和过程中产生的中间熔岩。通过测定相同晶体群的年龄，可以确定混合/同化的时间，提供有关这些岩浆过程速率的前所未有的信息。智力价值：本项目的结果将通过将有关岩浆分异和地壳同化过程发生的时间尺度的信息与地壳和地幔物质的质量平衡联系起来，增强我们对这些过程的理解。这些结果将有重要的影响，在地壳水库系统的质量和热量平衡方面，并将在冰岛的地壳结构，水库体积和地热活动的地球物理观测的广泛的工作机构相比。这些结果将为今后在冰岛其他地区和其他构造环境中研究岩浆混合和地壳同化提供背景和基础。 更广泛的影响：该项目将通过支持女性PI的早期职业发展来扩大代表性不足的群体对地球科学的参与。 此外，我们预计研究生将广泛参与该项目作为他或她的论文项目的一部分或全部，本科生将参与该项目的技术方面;因此，该项目的资金将支持下一代科学家的教育和培训。 最后，此次合作的一个明确目标是PI库珀将与研究生一起前往WHOI，以获得PIMMS专门进行U系列分析的经验。 她将把这些专业知识转移到华盛顿大学的新分析设施，这些技术随后将应用于各种固体地球和海洋学问题。

EAR-0307123SimsThis study will measure 226Ra-230Th disequilibria and oxygen isotope compositions in whole-rock samples, groundmass separates and plagioclase separates from recent lavas of Krafla volcano in Iceland. This approach will be applied both on the relatively broad scale of variations in whole-rock (226Ra)/(230Th) and d18O between different eruptions, and also in detail by separating and analyzing more than one size fraction of plagioclase separates from the same lava. Because the fractionation of oxygen isotopes between coexisting plagioclase and silicate liquid is relatively well-known, d18O measured in crystals can be related directly to variations in d18O of the liquids from which they crystallized. Thus, d18O of early-formed crystals can preserve a record of the compositions of liquids before magma mixing or crustal assimilation occurred. The diversity of oxygen-isotope composition of plagioclase in Krafla lavas, both between different eruptions and within a single lava, will provide information on the relative influence of mantle-derived and crustally-derived material and the process of producing intermediate lavas. By dating the same crystal populations, the timing of mixing/assimilation can be established, providing unprecedented information about the rates of these magmatic processes.Intellectual Merit: The results of this project will enhance our understanding of the processes of magmatic differentiation and crustal assimilation by linking information about the timescales over which such processes occur to mass balance of crustally-derived and mantle-derived material. These results will have important implications in terms of the mass and heat balance of crustal reservoir systems, and will be compared to the extensive body of work in Iceland on geophysical observations of crustal structure, reservoir volume, and geothermal activity. These results will provide background and groundwork for future studies of magma mixing and crustal assimilation in other areas of Iceland and in other tectonic settings. Broader Impacts: This project will serve to broaden the participation of underrepresented groups in the geosciences by supporting the early career development of a female PI. Furthermore, we anticipate that a graduate student will be extensively involved in this project as part or all of his or her thesis project, and that an undergraduate will be involved in the technical aspects of this project; funding for this project would therefore support the education and training of the next generation of scientists. Finally, an explicit goal of this collaboration is that the PI Cooper will travel to WHOI with the graduate student in order to gain experience in U-series analyses specifically by PIMMS. She will transfer this expertise to the new analytical facilities at UW, and these techniques will subsequently be applied to a variety of solid earth and oceanographic problems.