Collaborative Research: Argon Retentivity and Closure Temperature in Micas and Amphiboles

合作研究：云母和角闪石中的氩气保留率和闭合温度

• 批准号: 0106987
• 负责人: Peter Dahl
• 金额: $ 8.58万
• 依托单位: Kent State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2005-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0106987&HistoricalAwards=false
• 关键词: Collaborative; Research; Argon; Retentivity; Closure

EAR-0107054/0106987Foland/DahlPotassium-bearing micas and amphiboles are widely used in 40Ar/39Ar age studies to determine thermochronologic histories and are recognized to have ages that reflect temperature, although the actual mechanism(s) and controls are neither well understood nor well documented. This research will investigate the factors governing Ar retention and 40Ar/39Ar ages of mica and amphibole in slowly-cooled terranes. Relationships in specimens from the Adirondack Lowlands of New York will be studied. The research will test the often-assumed volume diffusion control of argon loss, while also seeking to evaluate alternative mechanisms and factors governing argon retention and ages of individual mica and amphibole crystals. Specific objectives of the research are to clarify: (1) the mechanism(s) of argon loss in nature and the question of volume-diffusion control on argon retention and closure, with specific examination of the roles of stress and fluids (in addition to temperature); (2) the crystal-chemical dependence of retention; and (3) the roles of microstructures and other factors. The research will involve an array of modern microanalytical techniques on individual crystals, including: 40Ar/39Ar and Rb/Sr geochronology, featuring UV laser-ablation Ar microanalysis; chemical microanalysis; transmission electron microscopy for elucidation of microtextures; X-ray diffraction determination of crystal structures; and, analyses of O and H isotopes. This research targets the next level of understanding of these mineral ages and, thus, their use in interpreting, deciphering, and refining crustal histories.

Foland/Dahl含钾云母和角闪石被广泛用于40 Ar/39 Ar年龄研究，以确定热年代学历史，并被认为具有反映温度的年龄，尽管实际的机制和控制既没有很好的理解，也没有很好的记录。 本文研究了缓冷岩石中云母和角闪石的Ar保留和~（40）Ar/~（39）Ar年龄的影响因素。 将研究来自纽约阿迪朗达克低地标本的亲缘关系。 这项研究将测试经常假设的体积扩散控制氩损失，同时也寻求评估替代机制和因素的氩保留和年龄的个别云母和角闪石晶体。 研究的具体目标是澄清：（1）自然界中氩损失的机制和氩保留和封闭的体积扩散控制问题，具体检查应力和流体（除温度外）的作用;（2）保留的晶体化学依赖性;（3）微观结构和其他因素的作用。 这项研究将涉及一系列关于单个晶体的现代微量分析技术，包括：40 Ar/39 Ar和Rb/Sr地质年代学，其中包括紫外激光烧蚀Ar微量分析;化学微量分析;用于阐明微观结构的透射电子显微镜;晶体结构的X射线衍射测定;以及O和H同位素分析。 这项研究的目标是对这些矿物年龄的下一个层次的理解，因此，它们在解释，破译和精炼地壳历史中的用途。