Article Highlights
- The Dresser Formation in the East Pilbara Terrane of Western Australia holds some of the earliest evidence of life on Earth.
- This study used NMR and NEXAFS alongside other analytical methods to study carbonaceous matter (CM) in Archean rocks from the Dresser Formation.
- NMR and NEXAFS revealed a highly aromatic composition with lower aliphatic content, indicating elevated thermal maturity. Raman mapping and analysis further characterized three distinct populations of CM within the rocks.
- Secondary ion mass spectrometry (SIMS) supported a biogenic origin for CM within growth bands and the barite matrix, while CM within quartz veins showed evidence of a later introduction to the system.
The Dresser Formation is a Paleoarchean geologic formation that occurred in the East Pilbara Terrane of the Pilbara Craton of Western Australia. This formation has fascinated scientists and archaeologists for decades because of how it contains some of Earth’s earliest evidence of life on the planet (1). Some of these bits of evidence include stromatolites, microfossils, and fractionated sulfur and carbon isotopes (1).
Nuclear magnetic resonance (NMR) is a spectroscopic technique that is often used to determine the molecular structure at the atomic level of a sample (2). A recent study published in Precambrian Research examined how NMR and near edge X-ray absorption fine structure (NEXAFS) was used to study carbonaceous matter (CM) in Archean rocks found in the Dresser Formation. The findings the research team uncovered reveal what an early Archean habitat looked like and provided a greater understanding into the depositional processes and the influence of microbial life in the region (3).
NMR and NEXAFS was integral for revealing a highly aromatic composition with a lower aliphatic content, indicative of relatively elevated thermal maturity (3). However, apart from NMR and NEXAFS, the research team used a variety of additional analytical techniques for specific steps in their analysis. For example, high-resolution Raman mapping and light microscopy were used to reveal three distinct populations of CM within the ancient rocks (3). The three populations were as follows: a) CM located at the edges of single growth bands of barite crystals; (b) CM embedded within the barite matrix; and (c) CM contained within secondary quartz veins that intersect the black bedded barite (3).
Then, Raman analysis was done to evaluate the metamorphic temperatures of the CM populations. CM within the barite matrix exhibited temperatures consistent with the main metamorphic event in the area around 3.3 billion years ago (3). In contrast, CM within quartz veins showed lower temperatures, suggesting a later introduction to the system (3).
Finally, the research team also used secondary ion mass spectrometry (SIMS) to great effect. The SIMS-based δ13C values of individual CM particles supported a biogenic origin, consistent with stromatolitic microbialites associated with the black bedded barite (3). This evidence led the researchers to conclude that CM within growth bands and the barite matrix is syngenetic, whereas the CM within quartz veins emerged later (3).
As a result, NMR was used to study ancient rocks and uncover more about the mysteries of life on Earth. The success of these chromatographic and spectroscopic techniques in analyzing the CM in Archean rocks underscores the significance of using analytical techniques in geological applications.
References
- Djokic, T.; Van Kranendonk, M. J.; Campbell, K. A.; et al. Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits. Nat. Commun. 2017, 8, 15263.
- Singh, M. K.; Singh, A. Chapter 14 – Nuclear Magnetic Resonance Spectroscopy in Characterization of Polymers and Fibres. 2022, 321–339, Woodhead Publishing. https://doi.org/10.1016/B978-0-12-823986-5.00011-7
- Weimann, L.; Reinhardt, M.; Duda, J.-P.; et al. Carbonaceous matter in ∼ 3.5 Ga black bedded barite from the Dresser Formation (Pilbara Craton, Western Australia) – Insights into organic cycling on the juvenile Earth. Precambrian Res. 2024, 403, 107321. DOI: 10.1016/j.precamres.2024.107321
