Crystallization of columbite-tantalite in pegmatites: Experimental constraints and implication for natural systems

伟晶岩中铌铁矿-钽铁矿的结晶：实验限制和对自然系统的影响

• 批准号: 63444183
• 负责人: Professor Dr. Francois Holtz, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/63444183?language=en
• 关键词: Crystallization; columbite; tantalite; pegmatites; Experimental

Tantalum (Ta) is a key element of the high-tech industry and economic concentrations of Tabearing minerals occur exclusively in granitic pegmatites, mainly as minerals from the columbitetantalite group [(Mn,Fe)(Nb,Ta)206]- Our understanding of the formation of economic Ta ore deposits requires information on the crystallization conditions of Ta-bearing minerals, such as crystallization temperature and Ta solubility in pegmatitic melts, which is not available up to now. Crystallization processes ih pegmatitic systems can occur over a wide temperature range from 900 to 400°C and constraints on crystallization temperatures are crucial to model the reactions leading to the formation of Ta-bearing minerals in economic concentrations. The goal of an ongoing proposal was to get experimental data on the crystallization conditions of columbite-group minerals. The project was built around two points: i) solubility measurements of the manganese end members of the columbite-group minerals as a function of temperature in highly-fluxed pegmatitic melts and ii) the calibration of thermometers to constrain the temperature range of crystallization of Tabearing minerals (Ta in zircon and Zr in tantalite; stability field of manganotantalite and ferrotapiolite pairs). The experiments were conducted in parallel with investigations of the geochemistry and textural features of zircon associated with Ta mineralization in natural pegmatites. Different types of experiments have been conducted with success in the last 14 months. The available results are very promising and should have a strong impact on our knowledge of processes leading to Ta mineralizations. To complement with success the tasks (i) and (ii) listed above, complementary studies are necessary and justify the prolongation of the project for a few months. During this prolongation, we will focus on 3 points: I) we will determine in more detail the solubility dependence of manganotantalite and zircon on the ASI [Al/Na+K+Li)] of the melt, in order to characterize the role of excess Al and excess alkalis on the complexing of rare metal cations in silicate melts; 2) we will calibrate the Zr-in-tantalite thermometer down lo low temperatures; and 3) we will investigate the incorporation mechanisms of hafnium and tantalum in zircon because natural zircon associated with tantalite always coniain significant amounts of Hf.

Tantalum (Ta) is a key element of the high-tech industry and economic concentrations of Tabearing minerals occur exclusively in granitative pegmatites, mainly as minerals from the columbitetantalite group [(Mn,Fe)(Nb,Ta)206]- Our understanding of the formation of economic Ta ore deposits requires information on the crystallization conditions of Ta-bearing minerals, such as crystallization temperature and Ta solubility in Pegmatistic融化，到目前为止尚不可用。 IH PEGMATITIC系统的结晶过程可能在900至400°C的较宽范围内发生，并且对结晶温度的限制对于建模导致在经济浓度下形成含Ta含量的矿物的反应至关重要。正在进行的建议的目的是获取有关柱状矿物质矿物质的结晶条件的实验数据。该项目围绕两个点建立：i）柱状矿物矿物质的锰最终成员的溶解度测量，这是高度溶解的pegmatitic熔体中温度的函数，ii）校准量限制了校准的校准，以限制Taberation Minerals的结晶温度范围（Zircon and Zircon in Zircon and Zr in Tantantalite poiratitial Piartior Piartior Piartiol playtiol plairite;稳定性;实验是根据对天然pegmatites矿化相关的锆石的地球化学和质地特征的研究并行进行的。在过去的14个月中，已经成功进行了不同类型的实验。可用的结果非常有前途，应该对我们对导致矿化的过程的了解产生强大的影响。为了完成上述任务（i）和（ii）的成功，必须进行完整的研究，并证明该项目的延长几个月。在此延长过程中，我们将重点关注3点：i）我们将更详细地确定熔体对熔融剂和锆石对ASI [al/na+k+li）]的溶解度依赖性，以表征过量的Al和过量碱在硅胶熔体中稀有金属阳离子络合的多余Al和过量碱的作用； 2）我们将校准低温下降的Zr-In-in-tantalite温度计； 3）我们将调查锆石中hafnium和tantalum的保险机制，因为与诱变相关的天然锆石总是圆锥体的大量HF。