Collaborative Research: The Crystal Chemistry of Rock-Forming Chlorite

合作研究：造岩绿泥石的晶体化学

• 批准号: 0308588
• 负责人: Stephen Guggenheim
• 金额: $ 17.03万
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2007-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0308588&HistoricalAwards=false
• 关键词: Collaborative; Research; Crystal; Chemistry; Rock

Guggenheim and Guidotti0308588 and 0308546A major goal of metamorphic petrology is to understand the interrelationships among the crystallization conditions (temperature, pressure, bulk composition, chemical activities of volatile constituents, etc.) during metamorphic processes. Although chlorite is a common rock-forming metamorphic mineral believed to have a composition and crystal structure that relates to these conditions of crystallization, no structural studies of chlorite have been made to identify how petrologic factors affect the structure.In this project, single-crystal X-ray diffraction methods will be used to examine suites of well-characterized chlorite. For each suite except the Plumbago pluton suite, all samples contain graphite, so that the iron oxidation state is constrained. The metapelitic schists to be examined from Maine will have the following characteristics: (1) formation pressures at near 3.5 kbar, (2) Al saturated, (3) intermediate-to-high Mg2+-contents, and (4) varying formation temperatures. For comparison, a suite from the metamorphosed Plumbago mafic to ultramafic pluton in Maine, is selected because it is Mg-rich, but not Al-saturated. In addition, a more Fe-rich suite will be examined. After chemical analyses are made, structure refinements of chlorite crystals within each grade and between grades will be compared.The results of the study will help determine how Al, Mg, Fe2+, and vacancies are distributed in the various crystallographic sites of chlorite as a function of the pressure and temperature of crystallization and chlorite composition. These results will help to explain why there are relatively sharp compositional boundaries for the permissible composition range for metamorphic chlorites. In addition, an understanding of the variables involved in cation ordering may provide additional understanding of the controls limiting Ti, Fe3+, Mn, Ni, Cr, etc. substitutions. A major objective is to understand how these factors affect or control hydrogen bonding between the octahedral sheet and the 2:1 layer in chlorite. Most importantly, these data will eliminate the ad hoc aspect to previous attempts to formulate thermodynamic solution models for chlorite that are directly relevant to natural rocks.

Guggenheim和Guidotti0308588和0308546a变质岩学的主要目标是了解变质过程中结晶条件（温度，压力，散装组成，挥发性成分的化学活性等）之间的相互关系。 尽管氯酸盐是一种常见的岩石变质矿物质，据信具有与这些结晶条件有关的组成和晶体结构，但尚无对氯酸盐的结构研究来识别岩质因子如何影响结构。 X射线衍射方法将用于检查特征良好的绿色属套件。 对于除Plumbago Pluton Suite以外的每个套件，所有样品都包含石墨，因此铁氧化态受到限制。从缅因州进行检查的Metapelitic片岩将具有以下特征：（1）在接近3.5 kbar，（2）Al饱和，（3）中间至高的Mg2+contents和（4）（4）变化的地层温度下的地层压力。为了进行比较，选择了从缅因州变质铅膜片到超镁铁质岩石的套件，因为它富含mg，但不是饱和的。此外，还将检查一个更丰富的富裕套件。进行化学分析后，将比较每个年级内的氯酸盐晶体的结构改进。研究结果将有助于确定Al，Mg，Fe2+和空位如何分布在氯酸盐作为函数的各种晶体学位点中结晶的压力和温度和氯酸盐组成的温度。这些结果将有助于解释为什么变质氯酸盐允许的组成范围相对较清晰的组成边界。此外，对阳离子排序中涉及的变量的理解可能会提供对限制Ti，Fe3+，Mn，Ni，Cr等的控件的更多理解。一个主要目的是了解这些因素如何影响或控制八面体纸和2：1层之间的氢键。最重要的是，这些数据将消除以前试图制定与天然岩石直接相关的含氯酸盐的热力学溶液模型的尝试。