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Structure, genesis and resources efficiency of dolomite: New insights and remaining enigmas
Chemical Geology ( IF 3.6 ) Pub Date : 2021-03-24 , DOI: 10.1016/j.chemgeo.2021.120191
Wen Kai Cai , Jia Hui Liu , Chun Hui Zhou , John Keeling , Ulrich A. Glasmacher

Dolomite can form as a major mineral component of marlstones and limestones and is an important sink for magnesium in the marine environment. Dolomite is widely distributed in time and space and is considered an intrinsic ingredient in the evolution of the Earth’s crust. The crystal structure and genesis of dolomite record fundamental geochemical and environmental processes of significance in the Earth’s element cycle process, carbon storage, and paleoenvironments, with relevance to the exploration for minerals and fossil fuels, management and maintenance of the environment, and the use of carbonate minerals by industry. The review brings together new advances and insights from recent studies on dolomite structure, geological genesis, laboratory synthesis, and applications. In the mantle, dolomite may adapt to increasing pressure by structural rearrangement and undergoes crystal phase transitions. At present, four high-pressure polymorphs have been identified. The phase transitions allow dolomite to survive subduction into the mantle, possibly into the transition zone, but stability is not fully predictable and is influenced by factors that include initial degree of cation ordering in dolomite and Fe and Mn substitution for Mg in the dolomite crystal lattice. The presence of Fe and Mn is influenced by the environment of dolomite formation. The key factors controlling formation of dolomite, including transition or recrystallization from precursor high-Mg calcite or proto-dolomite, at low temperatures remain ambiguous. Sulfate-reducing bacteria, methanogens, and aerobic bacteria, the exudates or relevant extracellular polymeric substances, fluctuating environmental conditions, and the negatively charged surfaces of clay minerals all can mediate high-Mg calcite/proto-dolomite formation at low temperature. As for secondary dolomite, formed by Mg2+ replacement of Ca2+ in carbonate minerals, several models have been proposed and widely adopted, including: near-surface dolomitization, burial dolomitization, and hydrothermal dolomitization. The formation of massive deposits of dolomite in marine sediments probably involves multiple dolomitization processes. Yet the “dolomite problem” remains enigmatic. Mg isotope analysis, an emerging technology, offers a new approach to further investigate the genesis of dolomite. In the laboratory, synthesis of dolomite at low temperature has yet to be achieved. Fundamental scientific research on dolomite is expected to inform the sustainable use of dolomite resources. Traditional uses of dolomite typically in construction materials, refractory, and flux continue. Now, the use of dolomite and its calcined products is being expanded into environmental protection, soil improvement, thermochemical energy storage and biomedical materials.



中文翻译:

白云岩的结构,成因和资源效率:新见解和未解之谜

白云石可以作为马林岩和石灰石的主要矿物成分形成,并且是海洋环境中镁的重要汇。白云石在时间和空间上分布广泛,被认为是地壳演化的内在成分。白云岩的晶体结构和成因记录了在地球元素循环过程,碳储存和古环境中具有重要意义的基本地球化学和环境过程,与矿物和化石燃料的勘探,环境的管理和维护以及矿物的使用有关。工业生产碳酸盐矿物。该综述汇集了有关白云岩结构,地质成因,实验室合成和应用的最新研究的最新进展和真知灼见。在地幔中 白云石可能通过结构重排而适应增加的压力,并经历晶体相变。目前,已鉴定出四种高压多晶型物。相变使白云石能够俯冲到地幔中,甚至可能进入过渡带,但其稳定性尚无法完全预测,并受包括白云石中阳离子有序度的初始程度以及白云石晶格中Mg的Fe和Mn替代的因素影响。Fe和Mn的存在受白云石形成环境的影响。在低温下,控制白云石形成的关键因素(包括从前体高镁方解石或原白云石的转变或重结晶)仍然模棱两可。减少硫酸盐的细菌,产甲烷菌和好氧细菌,渗出物或相关的细胞外聚合物质,变化的环境条件以及粘土矿物带负电的表面都可以在低温下介导高镁方解石/原白云石的形成。至于由镁形成的次生白云岩2+替代Ca 2+在碳酸盐矿物中,已提出并广泛采用了几种模型,包括:近地表白云石化,埋藏白云石化和热液白云石化。在海洋沉积物中大量白云岩沉积物的形成可能涉及多个白云石化过程。然而,“白云岩问题”仍然是个谜。镁同位素分析是一种新兴技术,为进一步研究白云石的成因提供了一种新方法。在实验室中,尚未实现在低温下合成白云石。对白云石的基础科学研究有望为白云石资源的可持续利用提供信息。白云石通常在建筑材料,耐火材料和助熔剂中的传统用途仍在继续。现在,白云石及其煅烧产品的用途正在扩大到环保领域,

更新日期:2021-04-09
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