Australian Museum Journal Laumontite and heulandite-clinoptilolite pseudomorphous after Jurassic gastropods from Ponganui, New Zealand

Shortform:
Rodgers and Hudson, 1992, Rec. Aust. Mus., Suppl. 15: 73–81
Author(s):
Rodgers, K. A.; Hudson, N.
Year published:
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 package:
EndNote file
Title page:
Title page (104kb PDF)
Complete work:
Complete work (1681kb PDF)

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.