Experimental Study of Clinopyroxene Growth and Sector Zoning

单斜辉石生长及扇区分区的实验研究

• 批准号: 2133498
• 负责人: Benoit Welsch
• 金额: $ 37.99万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-01-01 至 2023-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2133498&HistoricalAwards=false
• 关键词: Experimental; Study; Clinopyroxene; Growth; Sector

Clinopyroxene is a major rock-forming mineral on Earth and other rocky planets, and one of the first solids crystallized by high temperature magmas and lavas. In theory, the chemical composition and the crystal shape of clinopyroxene can be used to extract information about the liquid from which the mineral formed (e.g., temperature, pressure, composition). When studying rock samples, the accuracy of such markers is critical in deciphering the dynamics of a large number of volcanic and magmatic systems, both on Earth and other planetary bodies. However, the crystallization processes of clinopyroxene are complex and still poorly understood, which hampers its potential as a tracer of magmas. The proposed work aims to refine the crystallization processes of clinopyroxene using a combination of laboratory experiments and advanced analytical methods. These results will complete previous datasets, provide new insights on the mineral at the microscopic scale, and pave the way for new research avenues. The tasks will nurture a collaboration between three academic institutes with premier experimental petrology laboratories (Brown University, the University of Hawaii, and the Universite de Lorraine), support the professional development of two early-career researchers, and provide a research opportunity for three undergraduate students. Clinopyroxene is one of the most complex igneous minerals in terms of its variability in texture and chemical zoning. Even today, its intricate complexity stands as a significant roadblock to reconstructing the history of clinopyroxene-bearing magmas. The rationale for this project stems from former characterizations of natural samples bearing complex sector zoning, and previous experiments on clinopyroxene + melt systems. This new work will exploit a trio of experimental apparatuses to address a broad range of crystallization conditions: heating stage microscope, 1-atm gas mixing furnace, and piston cylinder. The investigations will focus on major- and trace-element composition (in fine-scale detail to capture intricate zoning), growth features (habits, melt and solid inclusions, crystal defects) and the crystallization kinetics of clinopyroxene during the cooling of synthetic and natural melts. The experimental products will be analyzed using optical, electron probe, and transmission electron microscopies, and laser ablation inductively coupled mass spectrometry. The overarching goals are: to document the textural variation of clinopyroxene at various pressure, temperature, and cooling conditions; to establish the conditions (cooling rate, undercooling, melt composition) at which sector zoning occurs; and to examine major- and trace-element partitioning between clinopyroxene and melt, and between sectors in clinopyroxene. These goals are intended to advance the practical application of clinopyroxene thermobarometry, by establishing which sectors and elements faithfully record magmatic pressure-temperature conditions.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.

单斜辉石是地球和其他岩石行星上的一种主要造岩矿物，也是高温岩浆和熔岩最早结晶的固体之一。理论上，单斜辉石的化学成分和晶体形状可以用来提取关于矿物形成的液体的信息（例如，温度、压力、组成）。在研究岩石样本时，这些标记的准确性对于破译地球和其他行星上大量火山和岩浆系统的动态至关重要。然而，单斜辉石的结晶过程是复杂的，仍然知之甚少，这阻碍了其作为岩浆示踪剂的潜力。本论文的主要工作是结合实验室实验和先进的分析方法，对单斜辉石的结晶过程进行研究。这些结果将完善以前的数据集，在微观尺度上提供对矿物的新见解，并为新的研究途径铺平道路。这些任务将促进三个具有一流实验岩石学实验室的学术机构（布朗大学，夏威夷大学和洛林大学）之间的合作，支持两名早期职业研究人员的专业发展，并为三名本科生提供研究机会。单斜辉石是火成岩矿物中结构和化学分带最复杂的矿物之一。即使在今天，它错综复杂的复杂性仍然是重建含单斜辉石岩浆历史的重要障碍。这个项目的理由源于以前的表征天然样品轴承复杂的部门分区，和以前的实验单斜辉石+熔体系统。这项新工作将利用三个实验装置来解决广泛的结晶条件：加热台显微镜，1大气压气体混合炉和活塞缸。调查将侧重于主要和微量元素的组成（在精细尺度的细节，以捕捉复杂的分区），生长特征（习惯，熔体和固体夹杂物，晶体缺陷）和单斜辉石的结晶动力学在合成和天然熔体冷却。实验产物将使用光学、电子探针和透射电子显微镜以及激光烧蚀电感耦合质谱法进行分析。总体目标是：记录在不同的压力，温度和冷却条件下的单斜辉石的纹理变化;建立条件（冷却速率，过冷，熔体成分），其中部门分区发生;并检查主要和微量元素之间的单斜辉石和熔体的分区，单斜辉石部门之间。这些目标旨在通过确定哪些部门和元素忠实地记录岩浆压力-温度条件来推进单斜辉石热压法的实际应用。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。