Developing of a machine learning force field for sodium-rich silicate systems: a framework for future boron isotope fractionation modelling

Abstract

Magma is a mixture of solids, liquids, and volatiles formed by the partial melting of rocks within the Earth’s crust and mantle. Its solid fraction consists mainly of silica minerals such as olivine, pyroxene, amphibole, micas, feldspar, and quartz. The liquid fraction (melt) is composed of mobile ions of the major elements abundant in the Earth’s crust, including Si, O, Al, K, Ca, Na, Fe, and Mg. In addition, magmas contain a volatile phase dominated by gaseous components, primarily water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2), which strongly influence the physical and chemical evolution of magmatic systems (McDonough and Sun, 1995; Lutgens and Tarbuck, 2015; De Hoog and Savov, 2018). When a silica melt is enriched in boron, it forms borosilicate melt, which can crystal lize into minerals such as tourmaline, containing up to 3 wt% of boron (MacGregor et al., 2013).These melts are geochemically significant because boron behaves as a fluid-mobile and isotopically fractionating element during magmatic differentia tion, crystallization and metasomatism (White, 2015; Sharp, 2017; De Hoog and Savov, 2018). This mobility stems from its nature as a moderately incompatible element, which preferentially partitions into melts and volatiles during processes like magmatic differentiation, crystallization and metasomatism (Sharp, 2017). Therefore, boron is a key element for understanding geological processes and has two isotopes 10B and 11B with average relative abundances of 20% and 80%, respectively, which differ by nearly 10% in relative mass (White, 2015; De Hoog and Savov, 2018). This large mass difference makes boron isotopes powerful tracers for geological processes as crustal recycling, mantle evolution and hy drothermal alteration. The isotopic partition of boron is sensitive to parameters such as temperature, pH, and mineral coordination environment, allowing its use as a geothermometer and proxy for magmatic and fluid evolution (Lutgens and Tarbuck, 2015; White, 2015). Boron also plays an important role in industrial and technological material (Bultman et al., 2010; Huang et al., 2021). Its combination with oxygen forms borosilicate glass characterized by low thermal expansion and high chemical stability, making it important for laboratory applications. For exam ple, Pyrex is a company that manufactures laboratory glassware and kitchenware made from borosilicate glasses due to their exceptional thermal resistance and durability (Ren et al., 2017). In the field of electronics, boron serves as a crucial p-type dopant in silicon that is used in transistors and solar cells (Bultman et al., 2010; Ng and Sze, 2007). In addition, borosilicate glasses possess excellent optical transparency and refractive stability, which make them ideal for optical fibers, precision lenses, and display technologies (Belokoneva, 2005; Mutailipu et al., 2020; Huang et al., 2021).