Mineral–microbe interactions in deep-sea hydrothermal systems: a challenge for Raman spectroscopy

Abstract

In deep-sea hydrothermal environments, steep chemical and thermal gradients, rapid and turbulent mixing and biologic processes produce a multitude of diverse mineral phases and foster the growth of a variety of chemosynthetic micro-organisms. Many of these microbial species are associated with specific mineral phases, and the interaction of mineral and microbial processes are of only recently recognized importance in several areas of hydrothermal research. Many submarine hydrothermal mineral phases form during kinetically limited reactions and are either metastable or are only thermodynamically stable under in situ conditions. Laser Raman spectroscopy is well suited to mineral speciation measurements in the deep sea in many ways, and sea-going Raman systems have been built and used to make a variety of in situ measurements. However, the full potential of this technique for hydrothermal science has yet to be realized. In this focused review, we summarize both the need for in situ mineral speciation measurements in hydrothermal research and the development of sea-going Raman systems to date; we describe the rationale for further development of a small, low-cost sea-going Raman system optimized for mineral identification that incorporates a fluorescence-minimizing design; and we present three experimental applications that such a tool would enable.

Raman investigation of the patina layers on Hungarian copper ingots from a fifteenth century shipwreck

“…C 2 O 4 2‐ + Ca 2+ = > CaC 2 O 4 · H 2 O, in dependence on pH of the environment with calcareous sediment usually deposited in shallow water near land, oxalate solubility, and diagenetic recrystallization . Comparison between Raman spectra of oxalate minerals present in natural patinas confirms that except the Cu‐oxalates and Na‐oxalates, a substantial band overlap is consistently reported for both Ca‐polymorphs (whewellite and weddellite), glushinskite and humboldtine, which together with spectral artifacts makes difficult discrimination between these components. In this context and due to Ca, Fe, Mg, and K detected in the patina, the admixture of other oxalate phases besides whewellite cannot be excluded.…”

“…This compound identified in the corrosion layer is also known as the major ore of copper, and its presence can be accompanied by other Cu compounds and secondary minerals depending on environmental conditions . It is also observed as a primary mineral in hydrothermal veins, which results from interaction mechanism between copper, the iron of the soil, and sulfur originating from decomposition of the organic matter in an almost oxygen‐free environment . In the case of ingots immersed together with iron bars for centuries in saline water, the presence of chalcopyrite resulting from a similar mechanism cannot be excluded.…”

Potential Mitigation and Restoration Actions in Ecosystems Impacted by Seabed Mining

“…Despite some modelling attempts of microbial reaction rates in submarine hydrothermal chimneys (LaRowe et al, 2014), there is still a lack of knowledge of the mineralogy of the new structures as well as the microbial turnover over time, especially if exposed to fluid flow. The interaction of mineral and microbial processes is of recognised importance (Breier et al, 2010). There are no previous studies available of this kind.…”

Biomarkers and their Raman spectroscopic signatures: a spectral challenge for analytical astrobiology

“…In a recent special issue of the Philosophical Transactions of the Royal Society, in a year that celebrated its 350th anniversary as the longest running scientific journal, several articles highlighted the role of Raman spectroscopy in the characterization of biosignatures of extremophilic colonization of geological substrates in a range of stressed terrestrial environments [25,30,[36][37][38][39][40][41][42][43][44][45]; these articles in the same issue which address the detection of geological and biogeological spectral markers that are relevant to space missions give a very good appreciation of the spectroscopic requirements that will be essential for the construction of a relevant spectral database [46] for the ExoMars and forthcoming space missions which have a Raman spectrometer aboard their rover vehicles. Some selected examples of the data which can be provided by the Raman spectroscopic interrogation of terrestrial Mars analogue sites will be highlighted.…”