Abstract
A preliminary list of plausible near-surface minerals present during Earth’s Hadean Eon (>4.0 Ga) should be expanded to include: (1) phases that might have formed by precipitation of organic crystals prior to the rise of predation by cellular life; (2) minerals associated with large bolide impacts, especially through the generation of hydrothermal systems in circumferential fracture zones; and (3) local formation of minerals with relatively oxidized transition metals through abiological redox processes, such as photo-oxidation. Additional mineral diversity arises from the occurrence of some mineral species that form more than one ‘natural kind’, each with distinct chemical and morphological characteristics that arise by different paragenetic processes. Rare minerals, for example those containing essential B, Mo, or P, are not necessary for the origins of life. Rather, many common minerals incorporate those and other elements as trace and minor constituents. A rich variety of chemically reactive sites were thus available at the exposed surfaces of common Hadean rock-forming minerals.
Highlights
The paleomineralogy of Earth’s earliest half-billion years, though poorly preserved in the known rock record, is important for understanding key evolutionary episodes, including the rate of planetary differentiation, the initiation of plate tectonics, the rate and nature of continental crust formation, and the origins of life
The varied roles proposed for these minerals include catalysis for synthesis of essential biomolecules; protection of those molecules through surface interactions; molecular selection and concentration of specific subsets of molecules, including chiral selection, from a dilute prebiotic milieu; templating and formation of biopolymers; formation of lipid membranes; and surface redox chemistry that promoted life’s earliest metabolism (e.g., [18,19,20,21])
It has been assumed that mineral species proposed in these origins-of-life scenarios must have been present in the near-surface environment of prebiotic Earth for the scenario to be valid
Summary
The paleomineralogy of Earth’s earliest half-billion years, though poorly preserved in the known rock record, is important for understanding key evolutionary episodes, including the rate of planetary differentiation, the initiation of plate tectonics, the rate and nature of continental crust formation, and the origins of life. It has been assumed that mineral species proposed in these origins-of-life scenarios must have been present in the near-surface environment of prebiotic Earth for the scenario to be valid In this contribution, we first re-examine the list of plausible Hadean minerals proposed by. Significant excursions from that buffered state by several plausible natural processes may have led to the formation of minerals at much higher or lower oxygen fugacities Given these additional modes of mineral formation—parageneses not fully considered among the 420 species tabulated in the preliminary list of Hazen [1]—we catalog scores of additional species that might have occurred on Earth prior to life’s origins. Numerous types of chemically reactive sites have been exposed at the surfaces of Earth’s commonest minerals throughout geological history
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