Applications and Limitations of Elastic Thermobarometry: Insights From Elastic Modeling of Inclusion‐Host Pairs and Example Case Studies
Applications and Limitations of Elastic Thermobarometry: Insights From Elastic Modeling of Inclusion‐Host Pairs and Example Case Studies
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DOI：
10.1029/2020gc009231
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发表时间：
2020-09
期刊：
影响因子：
3.7
通讯作者：
M. Cisneros;K. Befus
中科院分区：
文献类型：
--
作者：
M. Cisneros;K. Befus
利用矿物包裹体及其宿主在冷却和减压过程中的弹性演化差异，弹性热压法可用于约束矿物结晶的压力和温度条件。在这项工作中，我们研究了超过5,000个未经测试的包体-宿主对的压力-温度敏感性。钻石和锆石等矿物是理想的宿主矿物，因为它们的低压缩性使它们成为刚性的容器。高度可压缩的包裹体，如钠长石、石墨和石英，是最可靠的气压计。我们提供了三个来自不同地质背景的包体-主体对的案例研究，以展示与这些矿物对相关的优势和挑战。黄石火山口橄榄石中的磷灰石包裹体大多记录了负残余压力（张力），并表明岩浆结晶在~0.4 GPa。石榴子石中的金红石包裹体记录了近环境条件，并没有恢复合理的金红石包埋的变质条件。这些结果表明，刚性夹杂物可能有一个拉伸应变极限，弹性热压法的一个可能的限制。蓝片岩（锡罗斯，希腊）绿帘石中的钠长石包裹体记录地质合理的圈闭压力，但大范围的残余压力，可能是由两个阶段的复杂的各向异性。我们的理论和应用结果表明，弹性温压法有可能被用来了解岩石学过程在不同的地质环境，包括地幔，变质，岩浆环境，但每个弹性温压计需要仔细评估。
Elastic thermobarometry can be used to constrain the pressure and temperature conditions of mineral crystallization by exploiting the difference in the elastic evolution of a mineral inclusion and its host during cooling and decompression. In this work we examine the pressure‐temperature sensitivity of >5,000 untested inclusion‐host pairs. Hosts such as diamond and zircon are ideal host minerals because their low compressibility makes them rigid containment vessels. Highly compressible inclusions such as albite, graphite, and quartz serve as the most reliable barometers. We provide three case studies of inclusion‐host pairs from different geologic settings to demonstrate the advantages and challenges associated with these mineral pairs. Apatite inclusions in olivine from Yellowstone caldera mostly record negative residual pressures (tension) and suggest magmatic crystallization at ~0.4 GPa. Rutile inclusions in garnet from Verpeneset eclogites record near ambient conditions and do not recover reasonable metamorphic conditions of rutile entrapment. These results suggest that stiff inclusions may have a tensile strain limit, a possible limitation of elastic thermobarometry. Albite inclusions in epidote from a blueschist (Syros, Greece) record geologically reasonable entrapment pressures, but a large range of residual pressures that may be caused by the complex anisotropy of both phases. Our theoretical and applied results indicate that elastic thermobarometry has the potential to be used to understand petrologic processes in diverse geologic environments, including mantle, metamorphic, and magmatic settings but that each elastic thermobarometer requires careful evaluation.