1. A crystallographic study of crystalline casts and pseudomorphs from the 3.5 Ga dresser formation, Pilbara Craton (Australia)
- Author
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Arnaud Mazurier, A. El Albani, M. J. Van Kranendonk, Carlos J. Garrido, Electra Kotopoulou, Juan-Manuel García-Ruiz, Fermín Otálora, European Commission, Ministerio de Economía y Competitividad (España), Laboratorio de Estudios Cristalográficos - LEC (Armilla, Spain), Universidad de Granada (UGR), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), School of Biological, Earth and Environmental Sciences [Sydney] (BEES), and University of New South Wales [Sydney] (UNSW)
- Subjects
010504 meteorology & atmospheric sciences ,Pilbara Craton ,Archean ,engineering.material ,010502 geochemistry & geophysics ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Crystal ,Precambrian ,chemistry.chemical_compound ,Crystal morphology ,[SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Mineral ,Aragonite ,Research Papers ,Crystallography ,Calcium carbonate ,chemistry ,precambrian ,engineering ,Pseudomorph ,Pseudomorphs ,X-ray tomography ,Geology - Abstract
Crystallographic methods are used to identify the primary mineral phase of pseudomorphs of crystals embedded in 3.48 Ga bedded carbonate-chert rocks from the Dresser Formation, Pilbara Craton, Australia. This identification provides valuable information on the chemical environments at the onset of life on Earth., Crystallography has a long history of providing knowledge and methods for applications in other disciplines. The identification of minerals using X-ray diffraction is one of the most important contributions of crystallography to earth sciences. However, when the crystal itself has been dissolved, replaced or deeply modified during the geological history of the rocks, diffraction information is not available. Instead, the morphology of the crystal cast provides the only crystallographic information on the original mineral phase and the environment of crystal growth. This article reports an investigation of crystal pseudomorphs and crystal casts found in a carbonate-chert facies from the 3.48 Ga-old Dresser Formation (Pilbara Craton, Australia), considered to host some of the oldest remnants of life. A combination of X-ray microtomography, energy-dispersive X-ray spectroscopy and crystallographic methods has been used to reveal the original phases of these Archean pseudomorphs. It is found with a high degree of confidence that the original crystals forming in Archean times were hollow aragonite, the high-temperature polymorphs of calcium carbonate, rather than other possible alternatives such as gypsum (CaSO4·2H20) and nahcolite (NaHCO3). The methodology used is described in detail.
- Published
- 2018