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Publication . 2002

Pseudomorphs after evaporitic minerals interbedded with 2.2 Ga stromatolites of the Yerrida basin, Western Australia: Origin and significance

Mohamed El Tabakh; Kathleen Grey; Franco Pirajno; B. Charlotte Schreiber;
Published: 27 Jul 2002 Journal: Geology, volume 27, page 871 (issn: 0091-7613, Copyright policy )
Publisher: Geological Society of America
Abstract
Widespread quartz pseudomorphs after evaporitic minerals are interbedded with stromatolites in 2.2 Ga sedimentary rocks in the Yerrida rift basin of Western Australia. These deposits preserve diverse original crystal morphologies that grew displacively either as individuals or as clusters within stromatolitic horizons and associated fine-grained siliciclastic beds. The stromatolites were deposited in shallow-marine, restricted environments. Although evaporitic minerals are largely replaced by quartz, their crystal shapes include lenticular, rosette, needle, and nodular forms, suggesting that they formed from calcium sulfate–rich brines. Textures suggest that replacement by quartz occurred during early alteration of the sediments. Original calcium sulfate minerals such as gypsum or anhydrite are indicated by the morphologies of the pseudomorphs; this concept is supported by anhydrite inclusions in the quartz crystals that form the pseudomorphs, and this finding indicates that calcium sulfate existed in Early Proterozoic sedimentary environments.
Subjects by Vocabulary

Microsoft Academic Graph classification: Geology Anhydrite chemistry.chemical_compound chemistry Siliciclastic Proterozoic Pseudomorph Rift Quartz Sedimentary rock Geochemistry Gypsum engineering.material engineering

Medical Subject Headings: complex mixtures

Subjects

Geology