Influence of Different Types of Clay Minerals on the Shape and Form of Silica-Carbonates (Biomorphs) of Ca(II), Ba(II), and Sr(II)

Abstract

The array of atmospheric and chemical conditions that prevailed during the Precambrian era favored the origin of life in our planet. The minerals and rocks that existed in that era catalyzed the synthesis of the first biomolecules. It has been shown that mineral clays possess the best-suited mineral surface to study the polymerization of protobiomolecules because they catalyze the binding of monomers to form peptides and nucleic acids and foster the binding between them. Inorganic structures exist formed by silica-carbonates of calcium, barium, or strontium, called biomorphs, which emulate the morphological structure of diverse organisms. Some of these morphologies resemble several of the microfossils found in the Precambrian cherts. Notwithstanding, it has not been documented yet whether biomorphs are a consequence of the dissolution of clays in alkaline environments (rich in alkaline earth metals) during the initial stages of the Earth, which would favor the hypothesis that the biomorphs or cherts existed since that time. To know whether biomorphs could have been embedded within minerals or in diverse types of clays and contributed to the synthesis of protobiomolecules, we aimed at synthesizing biomorphs in the presence of different clays of natural origin in two synthesis conditions that resemble both the atmosphere of the Precambrian era and that of the current time, regarding the CO2 concentration. Our results revealed that in the condition emulating the Precambrian, polymorphs of calcite, aragonite, and vaterite were formed. The barium and strontium biomorphs adopted the morphology of radiolarians, diatoms, and foraminifers in this same condition, indicating that they could be the first structure of these organisms. Results also revealed that the clays present in the Precambrian together with the prevailing environmental conditions played a preponderant role as catalyzers in the structural morphology, chemical composition, and crystalline habit adopted by the first organisms. Biomorphs could have been the first inorganic structures with a structural order and characteristic shape (preserving biomolecules in their interior when they were formed) that were synthetized in the early era of our planet, but they have not been dated as a fossil registry.