Paleochemistry of V, Mo and Other Oxyanions as Recorded in Ferromanganese Deposits

本研究将利用一种新的分析技术——固体激光烧蚀，结合电感耦合等离子体质谱仪（LA-ICP-MS）来确定锰铁矿床含水氧化铁相中一组微量元素的高分辨率剖面。目标样品范围从缓慢聚集的含氢地壳到快速聚集的热液地壳和浅水结核，目的是研究海水中以氧离子形式存在的V、Mo等微量元素（包括P、U、as、Se、Cr等）的古化学性质。虽然这些元素在地壳中的浓度可能因各种因素而变得复杂，但据推测，由氧化铁相清除的各种氧离子之间的比值可能与它们在海水中的古比值有关，并可能与沉积时的环境条件有关。其他元素的测定，包括稀土和232钍，将有助于解释地壳化学。230将在快速形成的样品的年轻部分进行测定，以完善年表。ICP-MS的高灵敏度，加上激光烧蚀（约50 um）的采样分辨率，有助于显著提高锰铁结壳在古海洋学研究中的实用性。

9416602 COLLIER This study will make use of a new analytical technique, Laser Ablation of solids, integrated with an Inductively-Coupled Plasma Mass Spectrometer (LA-ICP-MS) to determine high-resolution profiles of a group of trace elements in the hydrous iron oxide phases of ferromanganese deposits. Target samples range from slowly accumulating hydrogenous crusts to rapidly accumulating hydrothermal crusts and shallow-water nodules with the goal to study the paleochemistry of V, Mo and other minor/trace elements present in seawater as oxyanions (including P, U, As, Se, Cr, and others). Although the concentration of these elements in the crust may be complicated by a variety of factors it is hypothesized that the ratios between various oxyanions scavenged by the iron oxide phases can be related to their paleo-ratios in seawater and possibly to environmental conditions at the time of deposition. The determination of other elements, including REEs and 232Th, will aid in the interpretation of crust chemistry. 230Th will be determined in the younger portions of rapidly-formed samples in order to refine chronologies. The high sensitivity of the ICP-MS, coupled with the sampling resolution of laser ablation (approximately 50 um) contribute to the long-term goal of significantly improving the utility of ferromanganese crusts for paleoceanographic studies.