Trace element variations in zoned minerals: a record of geochemical and environmental feedback

分区矿物中的微量元素变化：地球化学和环境反馈的记录

• 批准号: 612-2006
• 负责人: Halden, Norman
• 金额: $ 2.46万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2006
• 资助国家: 加拿大
• 起止时间: 2006-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=332462
• 关键词: Trace; element; variations; zoned; minerals

Zoning and layered patterns in rocks and minerals occur on a variety of length- and time-scales in many different environments throughout geologic time. Because minerals take time to grow such patterns must record changes in the environment. Zoned patterns may be interpreted as (1) the product of externally forced processes, for example, where there is evidence of chemical disequilibrium or (2) the product of self organization expressed as differences in growth form or oscillatory zoning patterns (OZP).  Distinguishing the two is important.  While in many instances external forcing has succeeded in explaining a number of patterns such as major element variations in minerals (e.g. garnet), externally driven variations cannot adequately explain the repetitive or periodic character of oscillatory patterns observed on a scale of microns in minerals such as apatite and zircon.   Both types of zoning can occur in the same mineral.   Geochemical self organization in minerals can produce very complex patterns and is essentially a short range process largely influenced by diffusion and mineral structure over the few microns encompassing the growth surface of the mineral.  At this local scale, the periodic or other structured patterns are an expression of reaction coupling and diffusive transport entirely in the absence of large-scale external forcing.  There are now a number of examples of spontaneously generated zoning and layered features in rocks and minerals that arise as the product of coupling and feedback between different systems including zonation in accessory minerals, agate, diagenetic carbonates, biogenic carbonate and cyclic layering in mafic and ultramafic rocks.

岩石和矿物中的分带和分层模式在整个地质时期的许多不同环境中以各种长度和时间尺度出现。因为矿物的生长需要时间，所以这种模式必须记录环境的变化。分区模式可以解释为（1）外部强制过程的产物，例如，存在化学不平衡的证据，或（2）自组织的产物，表现为生长形式或振荡环带模式（OZP）的差异。区分两者是重要的。虽然在许多情况下，外部强迫成功地解释了一些模式，例如，对于矿物（例如石榴石），外部驱动的变化不能充分解释在矿物（例如磷灰石和锆石）中在微米尺度上观察到的振荡图案的重复或周期性特征。 这两种类型的分带可以发生在同一种矿物中。 矿物中的地球化学自组织可以产生非常复杂的图案，并且基本上是一个短程过程，主要受矿物生长表面上几微米范围内的扩散和矿物结构的影响。周期性或其它结构化图案是反应耦合和扩散传输的表现，完全没有大的-规模的外部强迫。现在有许多岩石和矿物中自发产生的分带和分层特征的例子，这些分带和分层特征是不同系统之间耦合和反馈的产物，包括副矿物、玛瑙、成岩碳酸盐、生物碳酸盐岩和镁铁质、超镁铁质岩石中的旋回分层。