Letter. Experimental confirmation of high-temperature silicate liquid immiscibility in multicomponent ferrobasaltic systems
Letter. Experimental confirmation of high-temperature silicate liquid immiscibility in multicomponent ferrobasaltic systems
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DOI：
10.2138/am-2015-5285
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发表时间：
2015-05
影响因子：
3.1
通讯作者：
T. Hou;I. Veksler
中科院分区：
文献类型：
--
作者：
T. Hou;I. Veksler
本文报道了一项实验研究的结果，其目的是在1100°C以上的温度下测试富硅和富铁多组分熔体之间是否存在稳定的超液相线不混溶。四对潜在的不混溶成分是在1150℃和1200℃的1atm气体混合炉(Ar/H2-CO2气体混合物)中进行的，氧逸度相当于QFM缓冲液的氧逸度。将预合成的富硅和富铁起始组合物对负载在铂丝环中，在1300℃下分别熔融，然后接触并在恒温下保持24小时以上，本研究使用的四对组合物中有三对没有混合。在富Fe液相中观察到了一些依赖于温度的化学再平衡，但在不相容的情况下，两种液体的成分保持不同，并在接触处显示出明显的成分梯度。一对液体结晶了一些鳞石英，而其他成分则明显高于液线。总体而言，实验结果与早先的离心机研究结果很好地一致，并证实在高达1200°C的温度下，一些富铁的玄武岩-安山岩成分中存在稳定的超液相线不混溶。
Abstract Here we report the results of an experimental study aimed at testing the existence of stable, superliquidus immiscibility between silica- and Fe-rich multicomponent melts at temperatures above 1100 °C. Four pairs of the potentially immiscible compositions were tested in a 1-atm gas-mixing furnace (Ar/H2-CO2 gas mixture) at 1150 and 1200 °C and at the oxygen fugacity corresponding to that of the QFM buffer. Pre-synthesized pairs of the silica-rich and Fe-rich starting compositions were loaded in Pt wire loops, fused separately at 1300 °C, then brought in contact and kept at constant experimental temperature for more than 24 h. Three pairs of compositions out of four used in this study did not mix. Some temperature-dependent chemical re-equilibration was observed in the Fe-rich liquid phase but, in the cases of immiscibility, the two liquids remained compositionally distinct and showed sharp compositional gradients at contacts. One pair of liquids crystallized some tridymite, whereas the other compositions were clearly above the liquidus. Overall, the results of the experiments are in good agreement with the earlier centrifuge study and confirm the existence of stable, super-liquidus immiscibility in some Fe-rich basaltic-andesitic compositions at temperatures up to 1200 °C.