Diamond formation in Earth's mantle

地幔中的钻石形成

• 批准号: RGPIN-2017-06041
• 负责人: Stachel, Thomas
• 金额: $ 3.42万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=665776
• 关键词: Diamond; formation; Earth; mantle

***Diamond exploration and mining is the principal economic driving force in Canada's remote North. However, current levels of production will be unsustainable unless new deposits are discovered within the next few years. To help develop more efficient exploration strategies, we will geochemically fingerprint the conditions deep in the Earth's mantle that enhanced or prevented diamond formation in the distant past.*******The investigations outlined below are expected to produce not only ground-breaking basic research but also new and better methods for diamond exploration.*******1. Processes of diamond formation****The layered internal structure of diamond can be compared to tree rings in that both can reveal complex and extended growth histories. I direct a multi-collector ion microprobe facility, which will enable us to obtain profiles of carbon and nitrogen isotopic compositions and nitrogen contents at high spatial resolution across diamond growth zones. These profiles allow us to deduce the chemical character of the original diamond-forming fluids or melts and reveal if they were methane- or carbonate-bearing. By studying diamonds with known ages of crystallization, we will be able to follow variations in the preferred modes of diamond precipitation through time.*******2. Unconventional diamond deposits****Archean cratons are large, stable blocks of the Earth's crust that are older than 2.5 billion years. The lithospheric mantle beneath such cratons is the source of >99% of current diamond production, and the rock type harzburgite is its key diamond substrate. However, younger areas of the crust can also host world-class diamond deposits. The rock type eclogite is a key diamond substrate in such unconventional deposits, but our preliminary results suggest that lherzolite may also be important. We will investigate two such diamond-bearing areas beneath the Canadian Shield (sampled by kimberlite volcanoes at Fort à la Corne and the Victor Mine) that were strongly affected by tectonic/thermal events less than two billion years ago. By studying the diamonds, their inclusions, and the associated mantle rocks, we aim to determine the diamond-forming conditions in the lithospheric mantles of these areas through time.*******3. New Canadian diamond deposits****Diamonds from two new deposits will be used to probe the mantle roots of little-studied deep sections of the Canadian Shield:****(1) The Chidliak kimberlite field (Baffin Island). This area is underlain by a small cratonic fragment of unclear origin, and its diamond source rocks have not yet been investigated.****(2) The Gahcho Kue diamond mine. This mine provides unique access to an exceptionally thick section of lithospheric mantle in the southern Slave Craton.*******The knowledge gained in all three study themes will be crucial to future exploration for new diamond deposits in Canada.*******

***钻石勘探和采矿是加拿大偏远北部的主要经济动力。但是，除非在未来几年内发现新的存款，否则当前的生产水平将是不可持续的。为了帮助制定更有效的勘探策略，我们将在地球上深处的地球上的条件上进行地球指纹，从而增强或阻止了遥远的过去的钻石形成。钻石形成的过程****可以将钻石的分层内部结构与树环进行比较，因为两者都可以揭示复杂和扩展的生长历史。我指导一个多核心离子微探针设施，这将使我们能够在跨钻石生长区的高空间分辨率下获得碳和氮同位素组合物和氮含量。这些轮廓使我们能够推断出原始的钻石形成长笛或熔体的化学特征，并揭示它们是否是甲烷或碳酸盐含量的。通过研究具有已知结晶年龄的钻石，我们将能够遵循随着时间的推移钻石精度的首选模式的变化。**** 2。非常规的钻石沉积物**** Archhen Craton是地球地壳中大的稳定块，年龄超过25亿年。在这样的克拉通下面的岩石圈地幔是当前钻石生产> 99％的来源，岩石型哈尔兹堡是其关键的钻石底物。但是，外壳的年轻地区也可以容纳世界一流的钻石沉积物。岩石型叶绿石是这种非常规沉积物中的关键钻石底物，但是我们的初步结果表明餐铁矿也可能很重要。我们将调查在加拿大盾牌下方的两个这样的钻石区域（由康纳堡（Fort-la Corne）和维克多矿（Victor Mine）的金伯利特火山（Kimberlite火山取样），这些区域在不到20亿年前就受到构造/热事件的强烈影响。通过研究钻石，它们的夹杂物和相关的地幔岩，我们旨在随着时间的推移确定这些区域岩石圈地幔中的钻石形成条件。**** 3。来自两个新沉积物的新加拿大钻石沉积物****钻石将用于探测加拿大盾牌的深层深层地幔的根源：****（1）Chidliak Kimberlite Field（Baffin Island）。该区域的底层是一个不清楚的小碎片，其钻石源岩石尚未进行。****（2）Gahcho kue钻石矿。该矿山在南部奴隶克拉顿（Slouth Slave Craton）中提供了独特的岩石圈地幔部分。