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

本文是对阿留申岛弧火山岩中高场强元素(HFSe；Ti，Ta，Nb，Zr，Hf)和Lu-Hf同位素体系的研究。这项研究的主要目的是限制HFSE的细节和相关的稀土元素在俯冲带中的行为。具体地说，这项研究将评估在俯冲岩浆形成过程中HFSE表现保守与非保守的条件。高场强元素丰度和Hf-ND同位素将在沿大洋阿留申弧全长收集的熔岩中进行测量。分析方法将包括：(1)在钢套聚四氟乙烯容器中溶解样品；(2)用94Zr、176Lu、180Hf、180Ta的混合尖峰加入样品；(3)用离子交换化学分离感兴趣的元素；(4)在多收集器电感耦合等离子体质谱仪上用同位素稀释法分析样品。这项研究将记录阿留申高频SE和Hf同位素地球化学沿弧形和跨弧形的变化。沿弧线物理条件的有据可查的变化，特别是推断的阿留申山脉东部和西部俯冲板块和地幔楔体的相对温度，以及弧形不同部分下方地幔源区是否存在俯冲沉积物，将为解释观测到的高频SE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.