Hidden Worlds Within Diamonds: How Tiny Inclusions Reveal Earth's Secrets
"Unlocking the mysteries of diamond formation through the study of nanometer-sized olivine inclusions and their preferred orientations."
Diamonds, prized for their beauty and durability, also serve as time capsules, preserving tiny inclusions that offer invaluable insights into Earth's deep mantle. These inclusions, often composed of minerals and fluids, provide a snapshot of the extreme conditions under which diamonds crystallize. The study of these inclusions has become a cornerstone of modern geology, helping scientists unravel the complexities of our planet’s history.
One particularly intriguing aspect is the orientation of minerals within these inclusions. Do these minerals align randomly, or do they exhibit preferred crystallographic orientations? Understanding these orientations can shed light on the formation processes and the environmental factors at play during diamond genesis. Recent research has focused on nanometer-sized inclusions, pushing the boundaries of analytical techniques and revealing previously unseen details.
This article delves into a groundbreaking study that examines the orientation of olivine, a common mineral, within nanometer-sized fluid inclusions found in Aykhal diamonds. By employing advanced transmission electron microscopy (TEM), researchers have uncovered fascinating patterns in olivine orientations, challenging existing theories and opening new avenues for understanding diamond formation and the Earth's deep carbon cycle.
What Can Olivine Inclusions Tell Us About Diamond Formation?
The study focuses on Aykhal diamonds, known for their unique geological context within the Siberian craton. Researchers analyzed healed internal cleavages—essentially tiny fractures—at the core of diamond samples. These cleavages are decorated with ultrapotassic fluid/melt inclusion pockets, containing nanosized graphite, phlogopite, and olivine. The research team found that olivine inclusions are either rounded, surrounded by ample fluid, or facetted, molded by the diamond's {111} faces with only a thin film of fluid between them.
- Pronounced crystallographic texture: Olivines grouped within specific diamond domains exhibit similar orientations.
- Frequent parallelism: Specific low-energy faces of olivine and the surrounding diamond tend to align, indicating preferred crystallographic relationships.
Implications and Future Directions
These findings have significant implications for our understanding of diamond formation. The study demonstrates that the crystallographic orientations of olivine inclusions in diamond are not random but are influenced by interfacial energetics and the presence of a fluid phase. This control allows olivine crystals precipitating from parental fluids to settle and attach to low-energy facets on the diamond surface, resulting in distinct, non-random orientations. The results challenge traditional topotaxy or epitaxy concepts observed in oxide/silicate mineral pairs and suggest a process more akin to Van der Waals heteroepitaxy in artificial systems. Future research should explore the variability of these orientations across different diamond types and geological settings to refine our models of diamond genesis and the Earth's deep carbon cycle.