Looking for Traces of Ancient Life: Harvard University’s MicroXRF Analysis of Silica Crusts from South Africa

At IXRF Systems, we are always excited to see how our microXRF technology contributes to groundbreaking research. Recently, researchers from Harvard University, led by graduate student David Madrigal-Trejo, using Harvard’s Atlas X microXRF system, unveiled incredible new insights in silica crusts from the 3.3 billion year old Mendon Formation, South Africa—an ancient rock formation that may hold evidence of life thriving after a catastrophic asteroid impact.

Figure 1: Image of the 3.3 billion year old Mendon Formation, South Africa. 

Life After a Massive Impact?

“What’s particularly interesting about these rocks,” explains David Madrigal-Trejo, graduate student at Harvard University, “is that they were deposited right after a giant impact which was way bigger than the one that killed the dinosaurs 65 million years ago. However, these ancient rocks could preserve an early microbial ecosystem that developed soon after the impact event. We seek to understand what are the environmental and biological processes that influenced the deposition of these silica crusts.”

The Atlas X microXRF system played a crucial role in mapping the elemental composition of a silica crust sample, allowing researchers to track geological and biological patterns preserved in the rock. The team focused on tourmaline crystals, as they hypothesized that these could be used to track past environmental conditions where abiotic precipitation of minerals was dominant over potential biological processes. These crystals were highlighted effectively using iron maps generated by the system.

Signs of Ancient Microbial Life?

One of the most fascinating revelations comes from the laminations within the slab.

Figure 2: Select element overlay map of the Mendon Formation, South Africa displayed above in the following order of elements:K, Fe, and Ti

The research team identified distinct differences between layers which might point towards different formation processes:

• Crinkly laminations may indicate periods when life was more active, suggesting bursts of microbial activity.
• Smooth laminations could represent times when sediment deposition was dominantly controlled by abiotic precipitation of minerals as evidenced by an increase in tourmaline abundance.

This evidence supports the idea that an alternation of different processes controlled the growth of the structures.

A Composition Rich in Clues

The silica crusts are composed primarily of silica (SiO₂), characteristic of chert rocks that are abundant during the Archean Eon.

Figure 3: Select element overlay map of the Mendon Formation, South Africa displayed above in the following order of elements: Fe, Ti, Cr, and K

However, the Atlas X system also revealed important elemental variations that provide further insights into the ancient landscape:

• Potassium and chromium-rich rocks at the bottom of the slab indicate the presence of solidified lavas. These volcanic substrates could have served as a foundation for microbial life, offering critical surfaces for colonization and growth.

Advancing Our Understanding of Early Ecosystems

The combination of precise elemental mapping and high-resolution imaging from the Atlas X microXRF system is unlocking an unprecedented view into Earth’s distant past. By analyzing the chemical and structural characteristics of silica crusts from the Mendon Formation, scientists can reconstruct the environmental conditions that supported life in the wake of a giant asteroid impact—an event that pre-dates the emergence of all complex life on Earth.

These findings not only deepen our understanding of early surface environments but also provide a valuable reference for studying planetary surfaces that record a large number of impact events on their ancient surfaces, such as Mars.

Stay tuned for more updates as Harvard University researchers continue to push the boundaries of early Earth science with the help of Atlas X microXRF technology.

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*A special thanks to David Madrigal-Trejo, graduate student at MIT for his contributions to this research and article.