High pressure phases in ophiolites - products of electrical discharges?

蛇绿岩中的高压相 - 放电产物？

基本信息

批准号：
335612051
负责人：
Professor Dr. Christian Gerhard Ballhaus
金额：
--
依托单位：
Abteilung Geochemie/Petrologie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2022-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/335612051?language=en
关键词：
pressure phases ophiolites products electrical

项目摘要

In recent times, high pressure minerals have been discovered in lithologies of ophiolite complexes. The high pressure phases noted include diamond, coesite, pseudomorphs of coesite after stishovite, and high pressure polymorphs of TiO2. They are intimately intergrown with highly reduced phases like moissanite SiC, Si-Fe alloys, metallic Ti, Ti carbides, and nitrides. Taken at face value, these unusual mineral assemblages have the potential to question well established models for the genesis and emplacement history of ophiolite complexes. It is proposed here that these assemblages neither reflect the tectonic history of the rocks nor their redox state. Novel experimental techniques will be employed to test if high pressure phases and highly reduced minerals can be stabilized locally by electric discharges. When a lightning bolt hits a rock, temperatures suffice to stabilize plasmas which, upon cooling, may precipitate compounds that are seemingly highly reduced but do not reflect reducing conditions during their formation. If lithologies do not disintegrate upon impact of a thunderbolt, thermal expansion can generate pressures sufficiently high that coesite, stishovite, and diamond may be stabilized. Positive results would have important implications: (1) high pressure phases do not necessarily reflect the tectonic history of the lithologies, and (2) nominally highly reduced phases like SiC or Si-Fe-Ti alloys may not monitor their redox histories.

最近，在蛇绿岩复合物的岩性中发现了高压矿物质。指出的高压阶段包括钻石，甲虫，石座岩之后的小甲虫的假晶和TiO2的高压多晶型物。它们与高度降低的相结合，例如Moissanite SiC，Si-Fe合金，Metallic Ti，Ti碳化物和氮化物。这些异常的矿物组合以面值为单位，有可能质疑蛇绿岩络合物的起源和扩增历史的良好模型。这里建议这些组合既不反映岩石的构造历史，也不反映其氧化还原状态。将采用新颖的实验技术来测试是否可以通过电气排放来局部稳定高压阶段和高度减少的矿物质。当闪电撞击岩石时，温度足以稳定血浆，冷却后可能会沉淀出似乎高度降低但在其形成过程中不反映降低条件的化合物。如果岩性在雷电的影响下不会分解，则热膨胀会产生足够高的压力，以至于可以稳定甲壳岩，石座和钻石。积极的结果将具有重要的含义：（1）高压阶段不一定反映岩性的构造历史，（2）名义上降低了SIC或Si-Fe-Ti合金等较高的相位可能不会监测其氧化还原历史。