Geochemical Investigation of Paleocene-Eocene Seafloor Volcanism in the Oregon Coast Range: Products of the Yellowstone Hot Spot?

俄勒冈海岸范围古新世-始新世海底火山活动的地球化学调查：黄石热点的产物？

• 批准号: 9418458
• 负责人: Douglas Pyle
• 金额: $ 12.09万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-02-01 至 1997-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9418458&HistoricalAwards=false
• 关键词: Geochemical; Investigation; Paleocene; Eocene; Seafloor

9418458 Pyle Recent geophysical data suggest the Oregon Coast Range reaches thicknesses as great as 30 km and its seismic structure is similar to oceanic plateau, flood basalt provinces. Preliminary He analyses of olivine from an OCR picrite indicate a deep mantle plume source. The 3He/4He ratios of an OCR picrite crushed in vacuo (R/Ra 13.0) overlaps values found for Snake River Plain lavas and more recent products of the Yellowstone hotspot. Fusion experiments on this sample prove that the high 3He/4He ratio is not cosmogenic, and is a signature of the mantle source of the picrite. Voluminous volcanism and high 3He/4He ratios are intriguing evidence that the Yellowstone hospot contributed to OCR volcanism, and therefore, has been active since at least 64 Ma. To further test this hypothesis, we propose a combined Sr, Nd, Pb, Ar, He, and O isotopic study of the OCR basalts. We will focus on volcanic rocks from the Roseburg and Siletz River formations to: 1) determine the mantle source composition for these OCR basalts and evaluate their relationship to the Yellowstone plume; 2) constrain the age and duration of volcanism within the OCR. We will also complete a detailed major and trace element study of the OCR to evaluate regional melting conditions (depth and amount) to understand the spatial distributions of possible tectonic settings.

9418458派尔最近的地球物理数据表明，俄勒冈州海岸山脉达到厚度高达30公里，其地震结构类似于海洋高原，洪水玄武岩省。 初步的He分析表明，从OCR苦橄岩橄榄石深地幔柱源。 3 He/4 He比值的OCR苦橄岩粉碎在真空中（R/Ra 13.0）重叠的蛇河平原熔岩和黄石热点最近的产品中发现的值。 对该样品的聚变实验证明，高的3 He/4 He比值不是宇宙成因的，而是苦橄岩地幔来源的标志。 大量的火山活动和高的3 He/4 He比值是有趣的证据，表明黄石公园的热点有助于OCR火山活动，因此，至少从64 Ma开始一直活跃。 为了进一步验证这一假设，我们提出了一个组合的Sr，Nd，Pb，Ar，He和O同位素研究的OCR玄武岩。 我们将重点研究罗斯堡和锡莱茨河地层的火山岩，以：1）确定这些OCR玄武岩的地幔源成分，并评估它们与黄石羽流的关系; 2）限制OCR内火山活动的年龄和持续时间。 我们还将完成OCR的详细主要和微量元素研究，以评估区域熔融条件（深度和量），以了解可能的构造环境的空间分布。