Conversion of smectite to ammonium illite in the hydrothermal system of Harghita Bai, Romania: SEM and TEM investigations

• Type: Article in International Scientific Journal
• Date: 1999

Authors

Bobos, I (Author) Other; Ghergari, L (Author) Other

Journal

The Journal is awaiting validation by the Administrative Services.

Title: GEOLOGICA CARPATHICA

Vol. 50

Pages: 379-387

ISSN: 0016-7738

Indexing

ISI Web of Knowledge - 13 Citations

Scopus - 15 Citations

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Authenticus ID: P-001-362

Abstract (EN): Random and ordered mixed-layer smectite-ammonium illite (NH4-I/S) were identified by XRD analysis in the fossil hydrothermal system of Harghita Bai (Eastern Carpathians, Romania). Morphologies of NH4-I/S were stud led by SEM and TEM. SEM image of random NH,YS displays a cellular or cornflake texture. Ordered NH4-I/S (R = 1) exhibits a scalloped morphology with curled edges. Ribbon crystals of illite rise from the surfaces of plate aggregates. Two generations of NH4-I are distinguished: one developed from a smectite precursor and another from a kaolinite precursor. Hairy illite and illite pseudomorphs after book-like aggregates of kaolinite are present. TEM images show the evolution of morphology from flake to lath habit during the smectite to illite conversion. Particles with veil characteristics and flake particles are observed in random mixed-layered NH4-I/S. Diffuse lath shaped illite developed on the previous morphology in the expandability range 70-20 %S is observed. Euhedral lath shaped illite is present in NH4-I/S, below 10 %S. The reaction of smectite-to-illite is continuous, leading to lath shaped illite.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9