Kerolite in carbonate-rich speleothems and microbial deposits from basaltic caves, Kauai, Hawaii

作者: Richard J. Léveillé , Fred J. Longstaffe , William S. Fyfe

DOI: 10.1346/000986002320514235

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摘要: The occurrence of kerolite in association with various secondary Ca-Mg carbonate mineral deposits (speleothems) was identified basaltic sea caves on the island Kauai, Hawaii. Kerolite is dominant clay deposits. X-ray diffraction (XRD) peaks are characteristically broadened indicating its extremely poor crystallinity. Few changes were observed XRD patterns this when it subjected to humidity, temperature and ethylene-glycol treatments. crystals appear as flaky masses irregular or jagged edges scanning (SEM) transmission electron microscopy (TEM). Electron probe energy dispersive (EDX) microanalysis show that material dominated by Mg-Si-O, minor amounts Al Ca some samples. chemical composition, thermal analysis TEM observations suggest smaller an amorphous serpentine-like phase mixed kerolite. often only associated poorly mineralized, actively-growing microbial mats these common completely lithified mats. latter commonly have microstromatolitic structures a phase. These features formation at least part result activity. abundant extracellular polymers mat-forming bacteria bind concentrate ions (Mg2+, silica) from solution serve nucleation sites for precipitation. Conditions within also probably lead Mg-Si-gels, Mg-silicate precursors ultimately Evaporation cave solutions may contribute formation.

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