The research identifies, for the first time in nature, compounds that precede the formation of dolomite and magnesite—minerals whose formation process under certain conditions remains unknown
Researchers from the Department of Mineralogy and Petrology at the University of Granada, the Andalusian Institute of Earth Sciences (CSIC), and the University of Málaga have identified, for the first time in a natural setting, mineral phases that serve as a precursor to the formation of dolomite and magnesite.
The discovery was made in the deposits known as moonmilk in the Nerja Cave (Málaga) and provides new evidence to explain how these minerals form under low-temperature conditions. This work is part of the doctoral thesis of Sarah Bonilla-Correa, a doctoral student at the University of Granada, under the supervision of Professors Encarnación Ruiz-Agudo and María Pilar Asta Andrés.
Dolomite and magnesite are among the most abundant carbonate minerals on Earth and are found in numerous rocks. However, scientists do not yet fully understand how they form at low temperatures. This mystery has given rise to the so-called Dolomite Problem, one of the most well-known debates in geology. The paradox lies in the fact that enormous dolomite formations have formed naturally throughout Earth’s history, while their formation is very difficult to reproduce under similar conditions in the laboratory.
To investigate this process, the team studied deposits of moonmilk, a soft, white material found in some caves and composed mainly of carbonate minerals. Using advanced microscopy and mineralogical analysis techniques, along with experiments conducted at the ALBA synchrotron in Spain and the SOLEIL synchrotron in France, the researchers observed amorphous magnesium carbonate and calcium-magnesium carbonate compounds in nature for the first time.
These amorphous materials can be understood as an intermediate phase: they are not yet crystalline minerals, but they can subsequently transform into them. The results show that, under natural cave conditions, these compounds evolve into magnesite and dolomite.
The finding is significant because it provides direct evidence that the formation of these minerals may follow a different pathway than the traditional one.
Instead of forming directly as crystals from a solution, the process could begin with the emergence of a preliminary amorphous phase that, over time, eventually transforms into a crystalline mineral.
According to the researchers, this observation helps to better understand how dolomite and magnesite form in natural, low-temperature environments and provides new data for solving the Dolomite Problem. The results suggest that the existence of an amorphous precursor could be a fundamental step in the formation of these minerals in nature.
The research was funded by the Ministry of Science, Innovation, and Universities; the Regional Government of Andalusia; the University of Granada; and the Scientific Unit of Excellence UCE-PP2016-05.
Link to the original publication:
https://www.sciencedirect.com/science/article/pii/S0016703726004552
This text has been generated using machine translation and has not been revised. The UGR does not guarantee the accuracy of the translation and accepts no liability for possible errors.
