Hao Ming, Zhou Wen-Yi, Hrubiak Rostislav, Kenney-Benson Curtis, Kavanagh Janine L, Davis William, Zhang Jin S
Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, USA.
Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA.
Sci Adv. 2024 Sep 6;10(36):eado8550. doi: 10.1126/sciadv.ado8550.
The eruption of deeply sourced kimberlite magma offers the fastest route to bring deep-seated volatiles back to the Earth's surface. However, the viscosity of kimberlite magma, a factor governing its migration and eruption dynamics within Earth, remains poorly constrained. We conducted synchrotron in situ falling sphere viscometry experiments to examine kimberlite magma with different volatile contents (0 to 5 wt % HO and 2 to 8 wt % CO) under high pressure-temperature conditions. The results reveal that the viscosity of volatile-rich kimberlite magma is ~1 to 2 orders lower than that of mid-ocean ridge basalt (MORB) and comparable to the ultramobile pure carbonate melt. Using the measured viscosity values, we simulated the ascent and eruption process of kimberlite magma. We found that a minimum content of ~0.5 wt % water in the primitive magma is necessary to allow the ultrafast eruption process of kimberlite, thereby enabling the preservation of diamonds and high-pressure mineral inclusions transported by the magma.
深部来源的金伯利岩岩浆喷发是将深部挥发物带回地球表面的最快途径。然而，金伯利岩岩浆的粘度，这一控制其在地球内部迁移和喷发动力学的因素，仍然受到的限制较少。我们进行了同步辐射原位落球粘度测定实验，以研究在高压高温条件下具有不同挥发物含量（0至5 wt% H₂O和2至8 wt% CO₂）的金伯利岩岩浆。结果表明，富含挥发物的金伯利岩岩浆的粘度比大洋中脊玄武岩（MORB）低约1至2个数量级，与超活动纯碳酸盐熔体相当。利用测得的粘度值，我们模拟了金伯利岩岩浆的上升和喷发过程。我们发现，原始岩浆中至少需要约0.5 wt%的水含量，才能使金伯利岩实现超快喷发过程，从而使岩浆携带的钻石和高压矿物包裹体得以保存。
