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An international research team has achieved a major breakthrough in manganese research after discovering that the growth of three-dimensional manganese dendrites occurs through the accretion of manganese oxide nanoparticles.
In a paper published in the journal Geology, the scientists explain that understanding the dynamics of the growth of three-dimensional mineral dendrites is important for various fields of science—physics, geology, material sciences and even the study of extraterrestrial environments. Thus, not only are they gaining valuable insights into the history of rocks and minerals, but the knowledge can also be used in industry, for example, in the production of synthetic materials with new properties.
According to the group, unlike the metallic or crystalline dendrites that form from supercooled melts, mineral dendrites are a result of unstable aqueous growth processes driven by fluid motion and chemical concentration gradients. Manganese dendrites, in particular, are known to develop as two-dimensional structures on rock surfaces. However, until now, the growth processes of three-dimensional dendrites remained largely enigmatic.
To gain insights into the 3D version of the dendrites, the team led by Zhaoliang Hou from the University of Vienna used a numerical model developed by Dawid Wos, from the University of Warsaw, and focused on natural dendrites formed in clinoptilolite-tuffs (zeolites), a type of compacted, porous volcanic tuff.
“By combining high-resolution X-ray and electron-based imaging techniques with numerical modelling, we were able to unlock the secrets hidden within these intricate mineral formations,” Wos said in a media statement.
The researchers discovered that the growth of dendrites occurred through the accretion of Mn oxide nanoparticles to the elongating structures.
“These nanoparticles formed when Mn-rich fluids mixed with oxygenated pore-water, leading to the development of complex dendritic structures. Remarkably, the geometry of these dendrites recorded the hydrogeochemical history of the rock, including the concentration of ions, the volume of infiltrating fluid, and the number of fluid pulses,” Hou said. “In essence, these 3D dendrites can serve as geological fingerprints, preserving a record of past environmental conditions.”
The study also highlighted a non-classical crystallization pathway in which dendrite growth proceeds through the formation, diffusion, and attachment of Mn oxide nanoparticles. This pathway challenges traditional views of crystal growth and emphasizes the significance of particle attachment processes in the natural world. It further aligns with the growing recognition of this mechanism as a vital and widespread type of crystal growth.
Hou and Wos noted that by deciphering the complex processes behind their formation, scientists gain valuable insights into the history of rocks and minerals. Furthermore, this research paves the way for further investigations into similar dendritic formations, such as gold/electrum dendrites.
“The study of 3D Mn dendrites has unveiled a captivating world of non-classical crystallization pathways and the hidden stories recorded within geological structures. By combining advanced imaging techniques and numerical modelling, scientists have taken a significant step forward in unravelling the mysteries of these intricate mineral formations,” Piotr Szymczak, co-author of the study, said. “As we delve deeper into the secrets of crystal growth, we open doors to a better understanding of earth’s history and the fascinating mechanisms at play in the natural world.”
