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Title: Formation of coexisting 1M and 2M polytypes in illite from an active hydrothermal system

Abstract

Polytypes of illite from the Broadlands-Ohaaki geothermal system in New Zealand have been studied with transmission electron microscopy and electron diffraction. The illite is predominantly a one-layer polytype with 1.0-nm interlayer spacing. On the scale of a few millimeters, illite occurs as ordered crystals, disordered crystals, and crystals with regions of ordered and disordered stacking. Some crystals are composed entirely of either the one-layer or the two-layer polytype; others show regions of two-layer stacking in a one-layer host. Long period stacking sequences (3- or 4-layer) are less common and occur as lamellar intergrowths in 1M mica. No morphological differences were observed among the discrete crystals, of 1M{sub d}, 1M, and 2M. Textures indicate that regions with two-layer stacking can be produced from 1M{sub d} mica even though there is a general trend with increasing temperature of 1M{sub d} to 1M to 2M. Experimental data on the rate of transformation of 1M to 2M{sub 1} muscovite combined with estimates of the mole fraction of 2M mica and temperatures of illite crystallization were used to place constraints on the duration of hydrothermal activity in the Broadlands-Ohaaki system.

Authors:
;  [1]
  1. Australian National Univ., Canberra (Australia)
OSTI Identifier:
5639839
Resource Type:
Journal Article
Journal Name:
American Mineralogist; (United States)
Additional Journal Information:
Journal Volume: 75:11-12; Journal ID: ISSN 0003-004X
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GEOTHERMAL SYSTEMS; MINERALOGY; ILLITE; MICROSTRUCTURE; NEW ZEALAND; AGE ESTIMATION; CRYSTAL STRUCTURE; CRYSTAL-PHASE TRANSFORMATIONS; CRYSTALLIZATION; DIMENSIONS; ELECTRON DIFFRACTION; LAYERS; MICA; MORPHOLOGY; MUSCOVITE; SYNTHESIS; TEXTURE; TRANSMISSION ELECTRON MICROSCOPY; AUSTRALASIA; CLAYS; COHERENT SCATTERING; DEVELOPED COUNTRIES; DIFFRACTION; ELECTRON MICROSCOPY; MICROSCOPY; MINERALS; PHASE TRANSFORMATIONS; SCATTERING; SILICATE MINERALS; 152002* - Geothermal Data & Theory- Properties of Minerals & Rocks

Citation Formats

Lonker, S W, and Fitz Gerald, J D. Formation of coexisting 1M and 2M polytypes in illite from an active hydrothermal system. United States: N. p., Web.
Lonker, S W, & Fitz Gerald, J D. Formation of coexisting 1M and 2M polytypes in illite from an active hydrothermal system. United States.
Lonker, S W, and Fitz Gerald, J D. . "Formation of coexisting 1M and 2M polytypes in illite from an active hydrothermal system". United States.
@article{osti_5639839,
title = {Formation of coexisting 1M and 2M polytypes in illite from an active hydrothermal system},
author = {Lonker, S W and Fitz Gerald, J D},
abstractNote = {Polytypes of illite from the Broadlands-Ohaaki geothermal system in New Zealand have been studied with transmission electron microscopy and electron diffraction. The illite is predominantly a one-layer polytype with 1.0-nm interlayer spacing. On the scale of a few millimeters, illite occurs as ordered crystals, disordered crystals, and crystals with regions of ordered and disordered stacking. Some crystals are composed entirely of either the one-layer or the two-layer polytype; others show regions of two-layer stacking in a one-layer host. Long period stacking sequences (3- or 4-layer) are less common and occur as lamellar intergrowths in 1M mica. No morphological differences were observed among the discrete crystals, of 1M{sub d}, 1M, and 2M. Textures indicate that regions with two-layer stacking can be produced from 1M{sub d} mica even though there is a general trend with increasing temperature of 1M{sub d} to 1M to 2M. Experimental data on the rate of transformation of 1M to 2M{sub 1} muscovite combined with estimates of the mole fraction of 2M mica and temperatures of illite crystallization were used to place constraints on the duration of hydrothermal activity in the Broadlands-Ohaaki system.},
doi = {},
journal = {American Mineralogist; (United States)},
issn = {0003-004X},
number = ,
volume = 75:11-12,
place = {United States},
year = {},
month = {}
}