...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Volcanology and Geothermal Research >Thermodynamic modeling of post-entrapment crystallization in igneous phases
【24h】

Thermodynamic modeling of post-entrapment crystallization in igneous phases

机译：火成岩期包埋后结晶的热力学模型

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Inclusions of quenched silicate liquid in igneous phenocryst phases represent important windows into the pre-eruption chemistry of volcanic rocks. Melt inclusions are subject to a variety of potential modifications after entrapment, which obscure the connection between final inclusion composition, and entrapment conditions. We concentrate on the effects of post-entrapment crystallization (PEC) in the cooling inclusion. PEC is neither an isobaric nor an isochoric process. Pressure decreases between 2 and 27 bars per degree of cooling, depending on the chemistry of melt and host and on the degree of PEC. In the equilibrium case, between about 50% and 65% of this pressure effect is due to thermal expansivity of the liquid, 10-35% from thermal expansivity of the host, and 5-40% from mass transfer between the inclusion and host. This complicates the application of simple element-partitioning schemes for back-calculating the effects of post-entrapment crystallization except in the simplest cases. We present a thermodynamic algorithm for PEC correction. This method is based on the self-consistent thermodynamic model set used in the MELTS software package. The algorithm moves backward through the PEC process, incrementally adding equilibrium crystal composition to the liquid while accounting for consequent variations in pressure and oxygen fugacity. Entrapment conditions are assumed to have been reached when the instantaneous liquidus solid composition most closely matches that of the bulk host crystal. Besides giving information on the degree of PEC and initial inclusion composition, the proposed algorithm can provide constraints on the pressure, temperature and oxygen fugacity at the time of entrapment. Olivine- and orthopyroxene-hosted inclusions from Popocatepetl, Mexico help constrain pre-eruption conditions for mixed magmas from recent eruptive products. Feldspar-hosted inclusions from Satsuma-Iwojima, Japan suggest that these magmas were substantially undersaturated with respect to supercritical vapor phase at the time of entrapment and underwent on the order of 29% post-entrapment crystallization. Quartz-hosted inclusions can potentially be employed in more silicic compositions, but this will require refinement of existing thermodynamic models.
机译：在火成发晶相中包含淬灭的硅酸盐液体，代表了火山岩喷发前化学的重要窗口。熔体夹杂物在被截留后会发生各种潜在的变化，这会掩盖最终夹杂物成分与截留条件之间的联系。我们专注于冷却夹杂物中包埋后结晶（PEC）的影响。 PEC既不是等压过程也不是等容过程。压力根据冷却液和基质的化学性质以及PEC的程度在每冷却度2至27巴之间降低。在平衡情况下，这种压力作用的约50％至65％是由于液体的热膨胀性引起的，是由于主体的热膨胀性引起的10-35％，而由于夹杂物与主体之间的质量传递引起的是5-40％。除最简单的情况外，这使简单的元素分配方案的应用复杂化，以反计算包埋后结晶的效果。我们提出一种用于PEC校正的热力学算法。该方法基于MELTS软件包中使用的自洽热力学模型集。该算法在PEC过程中向后移动，将平衡晶体组成逐步添加到液体中，同时考虑了压力和氧​​气逸度的随之变化。当瞬时液相线固体成分与主体基质晶体的成分最接近时，假定已经达到了夹带条件。除了给出有关PEC的程度和初始夹杂物组成的信息外，所提出的算法还可以限制截留时的压力，温度和氧逸度。来自墨西哥Popocatepetl的橄榄石和邻苯二甲酚包裹的包裹体有助于限制近期喷发产品中混合岩浆的喷发前条件。来自日本萨摩市岩岛的长石包裹体表明，这些岩浆在包裹时相对于超临界汽相而言基本上是不饱和的，并经历了包裹后结晶的29％。石英质夹杂物可能会被用于更多的硅质成分，但这将需要完善现有的热力学模型。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号