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- Title
Melt–Fluid and Fluid–Fluid Immiscibility in a Na<sub>2</sub>SO<sub>4</sub>–SiO<sub>2</sub>–H<sub>2</sub>O System and Implications for the Formation of Rare Earth Deposits.
- Authors
CUI, Hao; ZHONG, Richen; XIE, Yuling; WANG, Xiaolin; CHEN, Huan
- Abstract
Liquid–liquid immiscibility has crucial influences on geological processes, such as magma degassing and formation of ore deposits. Sulfate, as an important component, associates with many kinds of deposits. Two types of immiscibility, including (i) fluid–melt immiscibility between an aqueous solution and a sulfate melt, and (ii) fluid–fluid immiscibility between two aqueous fluids with different sulfate concentrations, have been identified for sulfate–water systems. In this study, we investigated the immiscibility behaviors of a sulfate‐ and quartz‐saturated Na2SO4–SiO2–H2O system at elevated temperature, to explore the phase relationships involving both types of immiscibility. The fluid–melt immiscibility appeared first when the Na2SO4–SiO2–H2O sample was heated to ∼270°C, and then fluid–fluid immiscibility emerged while the sample was further heated to ∼450°C. At this stage, the coexistence of one water‐saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed. The three immiscible phases remain stable over a wide pressure–temperature range, and the appearance temperature of the fluid–fluid immiscibility increases with the increased pressure. Considering that sulfate components occur extensively in carbonatite‐related deposits, the fluid–fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite‐related rare earth deposits.
- Subjects
IMMISCIBILITY; ORE deposits; HIGH temperatures; AQUEOUS solutions; RARE earth metals; SULFATES
- Publication
Acta Geologica Sinica (English Edition), 2021, Vol 95, Issue 5, p1604
- ISSN
1000-9515
- Publication type
Article
- DOI
10.1111/1755-6724.14795