HIGH TEMPERATURE MAGMATIC GAS: MINERAL DEPOSITION AND GAS/WALLROCK REACTION

高温岩浆气体：矿物沉积和气体/壁岩反应

• 批准号: 2105876
• 负责人: Hanna Nekvasil
• 金额: $ 40.52万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2105876&HistoricalAwards=false
• 关键词: TEMPERATURE; MAGMATIC; GAS; MINERAL; DEPOSITION

The association of volcanic activity with ore deposits has been long recognized, but exactly how volcanic activity leads to ore deposit formation remains unknown. Since lavas and ash are generally metal-poor, volcanologists have speculated that metal transport must occur by the gas given off during rise of the magma towards the surface. Volcanic gas in eruptive plumes has been studied extensively because it can be directly sampled. However, volcanic gas has already lost much of its metal load to the volcanic subsurface structure through precipitation of vapor-deposited minerals and by reaction with rock deep within the volcanic edifice. Access to the natural gas before it has lost much of its dissolved load is very limited because of the scarcity of high temperature fumaroles and their extreme hazard. These problems have, thus far, made it impossible to bridge the knowledge gap between volcanic activity and formation of associated ore deposits. This project will utilize a new unique experimental design to simulate this process of gas release from magma in the laboratory. This technique will be used to characterize the chemical nature of magmatic gas just as it is released from magma and to observe its chemical modification as it produces vapor-deposited phases and reacts chemically with rock. Characterization of the new minerals produced will take advantage of the strength of synchrotron X-rays at Brookhaven National laboratory, that will allow analysis of micron-sized particles and provide information of how the metals are incorporated into the crystalline structures. The results of this research will provide a basis for new understanding of barren vs. economically important subvolcanic regions that will aid in future economic deposit exploration on Earth and other planetary bodies. They will further our understanding of vapor-deposited mineral stability and metal incorporation– a subject applied heavily in the materials science industry. As part of outreach to this industry, the geological community, and planetary science, a publically accessible database will be developed to store electronic versions of synthesis methods for a variety of minerals and materials found in nature. This project also has an educational component geared to providing experimental experience to undergraduate geology students as a first step in ensuring that the next generation of geoscientists are prepared with an entire tool bag of approaches with which to further our scientific understanding of natural processes.This work focuses on the compositional evolution of high temperature F-Cl-S-bearing magmatic gases in the high-temperature subvolcanic region (or just above shallowly emplaced plutons). In this regime, magmatic gas begins its transformation to volcanic gas through loss of much of its dissolved solute load by precipitation of minerals and reaction with wallrock. Laboratory-scale experiments will be conducted in order to elucidate (i) the nature of mineral phases produced during cooling of the magmatic gas, (ii) the trace elements these minerals incorporate, and (iii) the crystallographic controls on trace element incorporation into the vapor-deposited minerals. These experiments will simulate the formation of natural magmatic gas by decompression boiling of volatile-saturated rhyolite and phonolite, and simulate the production of vapor-deposited phases by allowing this gas to cool in a strong thermal gradient. Gas/rock reaction will be investigated by reacting a synthetic basalt and rhyolite glass in the stream of gas given off by the boiling magma. These reaction experiments will yield the products of magmatic gas/wallrock reaction and indicate how magmatic gas/wallrock reaction affects trace element mobilization. Analysis will combine bulk chemistry, SEM, and Synchrotron X-ray microprobe techniques (hard and tender-energy X-ray fluorescence microanalysis, microbeam X-ray absorption spectroscopy, and microdiffraction) to characterize bulk chemical transport, microscopic phase distribution in the vapor-deposited material and on reaction surfaces, and localized chemical speciation in the vapor-deposited minerals.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

火山活动与矿床的关系早已为人们所认识，但火山活动究竟是如何导致矿床存款形成的，至今仍不清楚。由于熔岩和火山灰一般都不含金属，火山学家推测，金属的迁移一定是通过岩浆上升到地表时释放的气体进行的。火山喷发羽流中的火山气体已经被广泛研究，因为它可以直接取样。然而，火山气体已经通过气相沉积矿物的沉淀和与火山建筑物深处的岩石反应，将其大部分金属负载损失到火山地下结构中。在天然气失去大部分溶解负荷之前，由于高温多孔材料的稀缺及其极端危险性，获得天然气的机会非常有限。迄今为止，这些问题使得人们无法弥合火山活动与伴生矿床形成之间的知识鸿沟。该项目将利用一种新的独特的实验设计，在实验室中模拟岩浆释放气体的过程。这一技术将用于确定岩浆气体从岩浆中释放时的化学性质，并观察其在产生气相沉积相和与岩石发生化学反应时的化学变化。对新矿物的表征将利用布鲁克海文国家实验室的同步加速器X射线的强度，这将允许分析微米级颗粒，并提供金属如何融入晶体结构的信息。这项研究的结果将提供一个基础，为新的认识贫瘠与经济上重要的次火山地区，这将有助于未来的经济存款勘探地球和其他行星机构。它们将进一步加深我们对气相沉积矿物稳定性和金属结合的理解-这是一个在材料科学工业中应用广泛的主题。作为对这一行业、地质界和行星科学的外联工作的一部分，将开发一个可通过电子方式访问的数据库，以储存自然界中发现的各种矿物和材料的合成方法的电子版本。该项目还有一个教育部分，旨在为地质学本科生提供实验经验，作为确保下一代地球科学家准备好一整套方法的第一步，以促进我们对自然过程的科学理解。（或略高于浅侵位岩体）。在这种状态下，岩浆气体通过矿物沉淀和与围岩反应而失去大部分溶解的溶质负荷，开始转化为火山气体。将进行实验室规模的实验，以阐明（一）在岩浆气体冷却过程中产生的矿物相的性质，（二）这些矿物结合的微量元素，和（三）微量元素掺入气相沉积矿物的晶体学控制。这些实验将模拟天然岩浆气体通过挥发物饱和的流纹岩和响岩减压沸腾而形成的过程，并通过使这种气体在强热梯度中冷却来模拟气相沉积相的产生。将通过使合成玄武岩和流纹岩玻璃在沸腾岩浆释放的气流中反应来研究气体/岩石反应。这些反应实验将产生岩浆气/围岩反应的产物，并表明岩浆气/围岩反应如何影响微量元素的活化。分析将结合联合收割机体化学，扫描电镜和同步加速器X射线微探针技术（硬能和弱能X射线荧光显微分析、微束X射线吸收光谱和显微衍射）来表征气相沉积材料中和反应表面上的本体化学传输、微观相分布，和蒸汽中的局部化学形态该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，更广泛的影响审查标准。

项目成果

Experimental constraints on siderite clumped isotope thermometry

菱铁矿团块同位素测温的实验限制

• DOI: 10.1016/j.gca.2022.12.012
• 发表时间: 2023
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: Holme, Ella A.;Henkes, Gregory A.;Tosca, Nicholas J.;Rasbury, E. Troy;Young, Jordan M.;Schaub, D.R.;Nekvasil, Hanna;Hurowitz, Joel A.
• 通讯作者: Hurowitz, Joel A.