概括
在极高的压力 (240-250 kbar) 和温度 (1000-1400°C) 下,烯石石榴石转化为伊尔梅尼特类型的阶段. 这种高压转化证实了对这种矿物阶段的先前预测.
科学领域:
- 矿物物理 矿物物理
- 高压地质化学 高压地质化学
- 材料科学 材料科学 材料科学
背景情况:
- 烯石榴石 (Mg3Al2Si3O12) 是地球上层地幔的一个重要组成部分.
- 在极端条件下理解其相变对于地力学模型至关重要.
- 之前的理论工作预测了高压转化为伊尔梅尼特类型结构.
研究的目的:
- 为了实验性地确定 pyrope garnet 的相变的压力和温度条件.
- 描述由此产生的高压阶段的结构和格子参数.
- 为了验证关于Pyrope高压行为的理论预测.
主要方法:
- 使用钻石压机产生高压 (240-250 kbar).
- 使用激光加热来达到高温 (1000-1400°C).
- 使用X射线衍射分析了得到的相位,以确定格子参数.
主要成果:
- 观察了在指定的压力和温度范围内,pyrope石榴石的转化为ilmenite类型结构.
- 确定了ilmenite类型相的格子参数:a0 = 4.755 ± 0.002 Å和c0 = 13.360 ± 0.005 Å.
- 计算出与石榴石到伊尔梅尼特过渡相关的显著负面体积变化 (-7.1%).
结论:
- 实验证实了在地幔相关的压力和温度下,pyrope石榴石的转化为ilmenite类型结构.
- 这些发现证实了克拉克等人早些时候的预测. 和林格伍德地区.
- 这项研究为了解地球深层内部的矿物行为和相位平衡提供了关键数据.
相关概念视频
Ions as Acids and Bases
Salts with Acidic Ions
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
Precipitation of Ions
Predicting Precipitation
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is:
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is:
Qualitative Analysis
For solutions containing mixtures of different cations, the identity of each cation can be determined by qualitative analysis. This technique involves a series of selective precipitations with different chemical reagents, each reaction producing a characteristic precipitate for a specific group of cations. Metal ions within a group are further separated by varying the pH, heating the mixture to redissolve a precipitate, or adding other reagents to form complex ions.
For instance, group IV...
For instance, group IV...
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview
Nitrous acid and nitric acids are two types of acids containing nitrogen, among which nitrous acid is weaker than nitric acid. Nitrous acid with a pKa value of 3.37 ionizes in water to give a nitrite ion and the hydronium ion.
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by water loss...
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by water loss...
Titration of Polyprotic Base with a Strong Acid
The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
Acid Mine Drainage
Mining activities that disturb sulfide-rich rocks, particularly those containing pyrite (FeS₂), initiate a cascade of geochemical and microbiological processes with serious environmental implications. When exposed to air and water, pyrite undergoes oxidation, releasing sulfate, ultimately forming sulfuric acid and mobilizing heavy metals into surrounding water systems. This phenomenon, known as acid mine drainage (AMD), results in low pH waters laden with toxic elements that threaten aquatic...


