Abstract

At two rich fossil localities in Ponganui (eastern Port Waikato), zeolite-facies, mid-Jurassic metasandstones and metasiltstones of Murihiku Supergroup contain high-spired gastropods whose tests have been pseudomorphed by laumontite. Upper whorls of the spires are infilled by heulandite-clinoptilolite and laumontite, accompanied by minor potash-feldspar, quartz and pyrite. Body whorls are infilled by zeolitised rock matrix. Laumontite has low alkali and is closer to the ideal formula than other laumontites reported from metamorphic rocks of New Zealand. Dehydration of laumontite to leonhardite is indicated by x-ray diffraction: a = 14.75, b = 13.13, c = 7.57Angstrom, beta = 111.84°. Thermal analysis of heulandite-clinoptilolite gives ambiguous results consistent with the transitional composition these crystals possess within this mineral series. The crystal chemistry and associations of both zeolites is in accord with genetic models proposed by Boles and Coombs for similar Murihiku metasedimentary zeolites.

 
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Bibliographic Data

Short Form
Rodgers and Hudson, 1992, Rec. Aust. Mus., Suppl. 15: 73–81
Author
K. A. Rodgers; N. Hudson
Year
1992
Title
Laumontite and heulandite-clinoptilolite pseudomorphous after Jurassic gastropods from Ponganui, New Zealand
Serial Title
Records of the Australian Museum, Supplement
Volume
15
Start Page
73
End Page
81
DOI
10.3853/j.0812-7387.15.1992.85
Language
English
Date Published
16 October 1992
Cover Date
16 October 1992
ISBN
ISBN 0-7305-9990-6
ISSN
0812-7387
CODEN
RAMSEZ
Publisher
The Australian Museum
Place Published
Sydney, Australia
Subjects
MINERALOGY; GEOLOGY; MOLLUSCA: GASTROPODA
Digitized
28 July 2009
Reference Number
85
EndNote
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Title Page
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Complete Work
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