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Viscous flow and diffusion in highly depolymerized water-rich melts: improvement of experimental methods and implication for natural system

高度解聚富水熔体中的粘性流动和扩散：实验方法的改进及其对自然系统的启示

基本信息

批准号：
118067152
负责人：
Professor Dr. Harald Behrens
金额：
--
依托单位：
Abteilung Experimentelle und Angewandte Mineralogie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2009
资助国家：
德国
起止时间：
2008-12-31 至 2014-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/118067152?language=en
关键词：
Viscous flow diffusion highly depolymerized

项目摘要

The transport properties of water-rich strongly depolymerized melts are still under debate. So far no experimental techniques are available to determine the viscosity of highly depolymerized melts at elevated temperatures and pressures. Such viscosity data are crucial to understand kinetic processes during crystallization and eruptive processes of natural systems such as hydrous pegmatites arid phonolites. The falling sphere method (Stokes law) has been successfully used for viscosity determination at various conditions. However, its application to low viscosity melts is mainly limited by the achievable experimental duration. In the first part of the project (first 12 months), we have developed a new set-up allowing rapid heat and rapid quench of samples in internally heated gas pressure vessels (IHPV) and set up a new system of vertically oriented cold seal pressure vessels (CSPV) for rapid heat/rapid quench. Additionally, we have conducted viscosity determinations of pegmatitic melts in the high (micropenetration) and low viscosity range (falling sphere). The preliminary results show that the viscosity of water-rich pegmatite melts is significantly lower (up to 2 - 3 log units) than predicted by available models. In the second part of the project we plan to use the rapid heat and rapid quench devices to determine more accurately the individual effects of fluxing elements such as F, Li (eventually B and P) in silicate melts. The setup will also be used to determine the diffusivity of HFSE (Nb and Ta) in pegmatitic melts, which is of importance to constrain the genetic models proposed for the formation of economic HFSE concentrations. Finally we plan lo delermine the viscosity of water-rich, phonolites which will be useful for modeling ascent and degassing of phonolite melts.

富含水的强解聚熔体的传输特性仍然存在争议。迄今为止，尚无实验技术可用于测定高温高压下高度解聚熔体的粘度。这些粘度数据对于理解水合伟晶岩和响岩等自然系统的结晶和喷发过程中的动力学过程至关重要。落球法（斯托克斯定律）已成功用于各种条件下的粘度测定。然而，其在低粘度熔体中的应用主要受到可实现的实验持续时间的限制。在该项目的第一部分（前 12 个月），我们开发了一种新装置，允许在内部加热气体压力容器 (IHPV) 中快速加热和快速淬火样品，并建立了一种用于快速加热/快速淬火的垂直定向冷密封压力容器 (CSPV) 的新系统。此外，我们还对伟晶岩熔体在高粘度范围（微渗透）和低粘度范围（落球）进行了粘度测定。初步结果表明，富含水的伟晶岩熔体的粘度明显低于现有模型的预测（高达 2 - 3 个对数单位）。在该项目的第二部分中，我们计划使用快速加热和快速淬火装置来更准确地确定硅酸盐熔体中助熔元素（例如 F、Li（最终是 B 和 P））的单独影响。该装置还将用于确定伟晶岩熔体中 HFSE（Nb 和 Ta）的扩散率，这对于限制为形成经济 HFSE 浓度而提出的遗传模型非常重要。最后，我们计划确定富含水的响岩的粘度，这将有助于模拟响岩熔体的上升和脱气。