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

计划研究的两个主要主题是钻石矿床的构造环境，特别是发生在金伯利岩和其他火成岩中的初级钻石矿床，以及地球岩石圈中钻石储存的问题。第一个主题涉及研究构造对原生金刚石矿床的不同层次控制，包括根克拉通中含金刚石烃源岩的形成，钻石在运输到地表之前的保存，以及金伯利岩形成和近地表就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尔省和苏利伯里省的金伯利岩上，那里的地壳深部和上地幔的地球物理数据是由LITHOPROBE和POLARIS项目收集的。第二个主题涉及对来自奴隶省和南非的钻石进行实验室研究，以调查棕色钻石的晶内应变是否表明这些变形钻石在岩石圈中是亚稳态储存的。在高压高温（HPHT）处理天然钻石方面的最新进展表明，在仅略高于钻石稳定场的最低压力和温度的条件下，经过相对较短的时间（仅20分钟）处理后，棕色钻石可以转变（退火）为黄色或白色钻石，这表明亚稳态储存的可能性。提出的研究旨在验证退火假设及其对基于捕虏体和异晶的上地幔模型的影响，在这些模型中，通常假设含金刚石组合是从与金刚石稳定场压力相对应的深度运输的。研究结果将对现有的金刚石勘探区域选择模型产生深远的影响。

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.