What are melt inclusions?
Investigating mineral-hosted melt inclusions and glassy rinds to further comprehend how the Earth works. They also help us to invetigate the cycle of water into the deep Earth.
Melt inclusions represent tiny parcels of melt that was trapped during mineral (such as olivine) growth. Because minerals form at high pressure and temperature, melt inclusions recorded the conditions of melt formation at such depth and they preserved high-pressure and high-temperature composition, including their water content. Upon ascent, mineral-hosted melt inclusions preserve the original composition of the melt that they captured, because they are protected by their host mineral. The best example to illustrate this concept is a closed coke can that preserves all the flavors and the gas of the coke. Thus, investigating mineral-hosted melt inclusions provides unique insights into magma formation and geological processes (such as the deep water cycle) because they preserved a reliable record of the original melt (and its water content) that formed at greater depths.
In contrast, glassy rinds are melts that quenched during submarine eruption. Thus, glassy rinds capture the composition of the melt at much shallower depths. In addition, because melts tend to degas upon eruption, glassy rinds do not always preserve their water content. For example, when you open your coke can, some of the gas escapes and the coke degasses, losing some of its volatiles (including water vapor). Thus, glassy rinds are useful to investigate magma formation and the deep water cycle, but they are not as reliable as melt inclusions because they may not have preserved their original melt composition and their water content.