Tectonic studies, upper mantle studies, tectonic settings of diamond deposits

构造研究、上地幔研究、钻石矿床的构造背景

• 批准号: 8375-2008
• 负责人: Helmstaedt, Herwart
• 金额: $ 2.19万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2010
• 资助国家: 加拿大
• 起止时间: 2010-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=450281
• 关键词: Tectonic; studies; upper; mantle; tectonic

The two main themes of the planned research are the tectonic settings of diamond deposits, in particular primary diamond deposits occurring in kimberlites and other igneous rocks, and problems of diamond storage in the Earth's lithosphere. The first theme involves studying the various hierarchies of tectonic controls on primary diamond deposits, including the formation of the diamond-bearing source rocks in the roots cratons, the preservation of diamonds until they are transported to the surface, and the regional and local structural controls of kimberlite formation and near-surface emplacement. This research will focus mainly on the kimberlites of the Slave and Superior Provinces of the Canadian Shield, where deep-crustal and upper mantle geophysical data were collected by the LITHOPROBE and POLARIS programs. The second theme involves laboratory studies of diamonds from the Slave Province and South Africa to investigate whether intracrystalline strain in brown diamonds indicates that these deformed diamonds were stored metastably in the lithosphere. The possibility of metastable storage is suggested by recent advances in high-pressure, high-temperature (HPHT) treatment of natural diamonds which have shown that brown diamonds can be transformed (annealed?) into yellow or white diamonds after a relatively short period (as little as 20 minutes) of treatment under conditions that only slightly overstep the minimum pressure and temperature of the diamond stability field. The proposed research is designed to test the annealing hypothesis and its implications for xenolith and xenocryst-based upper mantle models in which it is commonly assumed that diamond-bearing assemblages were transported from depths corresponding to the pressures of the diamond stability field. The results may have a profound impact on current models for area selection in diamond exploration.

计划研究的两个主要主题是钻石矿床的构造环境，特别是金伯利岩和其他火成岩中的原生钻石矿床，以及地球岩石圈中钻石储存的问题。第一个主题涉及研究对原生钻石矿床的各种层次的构造控制，包括根岩中含钻石源岩的形成，钻石在被运送到地表之前的保存，以及金伯利岩形成和近地表侵位的区域和局部构造控制。这项研究将主要集中在加拿大地盾的奴隶省和上级省的金伯利岩上，LITHOPROBE和POLARIS计划收集了那里的深地壳和上地幔地球物理数据。第二个主题是对来自奴隶省和南非的钻石进行实验室研究，以调查棕色钻石中的晶内应变是否表明这些变形的钻石储存在岩石圈中。亚稳存储的可能性是由最近的进展，在高压，高温（HPHT）处理天然钻石，表明棕色钻石可以转化（退火？）在仅稍微超过金刚石稳定性场的最小压力和温度的条件下，经过相对短的时间（少至20分钟）的处理后，变成黄色或白色金刚石。拟议的研究旨在测试退火假说及其对捕虏体和捕虏体为基础的上地幔模型的影响，在该模型中，人们通常认为，金刚石组合从对应于金刚石稳定性场的压力的深度输送。这些结果可能对目前钻石勘探区域选择的模型产生深远影响。