New aspects of kimberlite-related metasomatism

与金伯利岩相关的交代作用的新方面

• 批准号: RGPIN-2019-03988
• 负责人: Kopylova, Maya
• 金额: $ 2.19万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737324
• 关键词: New; aspects; kimberlite; related; metasomatism

Petrological problems surrounding kimberlites are on the forefront of mantle petrology. We do not yet understand the genesis of kimberlites, as well as their melt compositions in the mantle and in the shallow crust before their emplacement. I will explore the role of metasomatism in 1) pre-conditioning the mantle to the birth of kimberlite melts, and in 2) controlling the mineralogy and textures of kimberlites in the crust. Kimberlite melts are not equilibrated with the ambient mantle, and the enigmatic missing link between kimberlites and the mantle is believed to have formed through mantle metasomatism. We will study megacrysts and fenitized olivinites in contact with carbonatites of alkaline-ultramafic massifs as proxies for the geologic relationships between the metasomatized mantle and kimberlite melts, unavailable for the direct observation at depths >200 km. Independent constraints on metasomatic agents will be obtained from fluids trapped as diamond inclusions in fibrous and octahedrally-grown, gem-quality diamonds and deduced from geochemistry of metasomatic mantle minerals. The second line of research deals with metasomatic reactions between xenoliths of silicic crustal rocks and host kimberlites. Crustal contamination in kimberlites can amount to more than half of the kimberlite volume, significantly impacting the diamond grade and the economics of the mine. Crustal contamination leads to melt hybridization and metasomatic replacement of silicic xenoliths, with mini-skarn reaction zones around the xenoliths. I will investigate the metasomatic transfer of elements in this process and subsequent kimberlite recrystallization and texture development. The proposed research will be based on detailed petrographic, geochemical and mineralogical studies as well as geochemical modelling and petrological experiments. The project is innovative in many ways. It is based on previously uncharacterized occurrences of megacrysts and diamonds, novel trap sites for mantle fluids in diamond fractures, novel massif analogues of kimberlite parent rocks and novel ideas about the genesis of pyroclastic kimberlites. The proposed research will be significant for the fundamental petrology and practical geology. The study of mantle metasomatism will contribute to solving the outstanding problem of the origin of carbonate-rich primary melts in the mantle, their composition, and the composition of their metasomatized mantle source. The practical significance of the proposal relates to the quantification of the diamond ore dilution and recognition of hybrid kimberlite minerals impacting the ore extraction. If we find the causal link between the kimberlite textures, the ore dilution and the country rock architecture, we will be able to predict many major characteristics of diamond deposits simply on the basis of crustal geology.

金伯利岩周围的岩石学问题位于地幔质学的最前沿。我们尚不了解金伯利岩的起源，以及它们在地幔和浅层地壳中的融化成分。我将探讨1）在金伯利特融化的诞生中预先调节地幔的作用，并在2）控制地壳中金伯利岩的矿物学和质地。金伯利岩融化不与环境地幔平衡，据信金伯利特和地幔之间的神秘缺失联系已通过地幔变性形成。我们将研究与碱性 - 欧洲法属地层接触的巨晶和矿化橄榄石，作为代理，用于跨层次的地幔与金伯利特融化之间的地质关系，无法直接观察到深度> 200 km> 200 km。将从被困在纤维和八面体生长的宝石品质钻石的钻石夹杂物的流体中获得对分生代理的独立约束，并从代理地幔矿物的地球化学推导出来。第二行研究涉及硅质地壳岩石和宿主金伯利岩之间异种反应。金伯利岩中的地壳污染可能占金伯利岩体积的一半以上，从而显着影响钻石等级和矿山的经济性。地壳污染导致熔融杂交和硅质异种的替代，并在异种石上围绕着小型skarn反应区。我将在此过程中调查元素的分类转移以及随后的金伯利特重结晶和纹理发展。 拟议的研究将基于详细的岩石学，地球化学和矿物学研究以及地球化学建模和岩石学实验。该项目在许多方面都是创新的。它基于先前未经表征的巨晶和钻石，钻石骨折中地幔液的新型陷阱部位，金伯利特父母岩石的新型地块类似物以及有关金蛋白原菌的生成的新思想。 拟议的研究对于基本质学和实践地质学将很重要。地幔交代主义的研究将有助于解决地幔中富含碳酸盐的原发性熔体，其组成以及其代理化地幔源的组成的鲜明问题。该提案的实际意义与钻石矿石稀释以及影响矿石提取的杂化金伯利矿物的识别有关。如果我们发现金伯利特纹理，矿石稀释和乡村岩石建筑之间的因果关系，我们将能够仅根据甲壳地质的基础来预测钻石沉积物的许多主要特征。