Collaborative Research: High Field Strength Elements and Hf-Nd Isotope Systematics in Aleutian Lavas: Implications for Conservative Element Behavior in Subduction Zones

本文对阿留申岛弧火山岩中高场强元素（HFSE; Ti, Ta, Nb, Zr, Hf）和Lu-Hf同位素系统进行了研究。研究的主要目的是约束俯冲带中高强度强震和相关稀土元素行为的细节。具体而言，该研究将评估在俯冲岩浆形成过程中，HFSE表现为保守与非保守的条件。高场强元素丰度和Hf-Nd同位素将在沿海洋阿留申弧的整个长度收集的熔岩中进行测量。分析方法将涉及(1)在钢护套特氟龙容器中溶解样品；(2) 94Zr、176Lu、180Hf、180Ta混合尖峰样品；(3)用离子交换化学分离感兴趣的元素；(4)在多收集器ICP质谱仪上对样品进行同位素稀释分析。本研究将记录阿留申岛HFSE和Hf同位素地球化学的沿弧和跨弧变化。充分记录的沿弧物理条件的变化，特别是推断出阿留申群岛东部和西部俯冲板块和地幔楔的相对温度，以及弧不同部分地幔源中俯冲沉积物的存在或不存在，将为解释观测到的HFSE和Hf同位素变化提供地质背景。

VervoortEAR-0230261This is a study of high field strength element (HFSE; Ti, Ta, Nb, Zr, Hf) and Lu-Hf isotopic systematics in volcanic rocks of the Aleutian island arc. The main objective of the study is to constrain the details of HFSE and related rare-earth element behavior in subduction zones. Specifically, the study will evaluate the conditions under-which HFSE behave conservatively versus non-conservatively during subduction magma genesis. High field strength element abundances and Hf-Nd isotopes will be measured in lavas collected from along the full length of the oceanic Aleutian arc. The analytical approach will involve (1) dissolution of samples in steel-jacketed Teflon vessels; (2) spiking of samples with a mixed 94Zr, 176Lu, 180Hf, 180Ta spike; (3) separation of elements of interest with ion-exchange chemistry; and (4) analysis of samples by isotope dilution on a multi-collector ICP mass spectrometer. This study will document along-arc and cross-arc changes in Aleutian HFSE and Hf isotope geochemistry. Well-documented changes in physical conditions along the arc, in particular the inferred relative temperature of the subducting plate and mantle wedge in the eastern versus western Aleutians, and the presence or absence of subducted sediment in the mantle source beneath different parts of the arc, will provide the geologic context for interpreting the observed HFSE and Hf isotopic variation.