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Titolo:
AMMONIUM ENRICHMENT ASSOCIATED WITH DIAGENETIC ALTERATION IN TERTIARYPYROCLASTIC ROCKS FROM GREECE
Autore:
HALL A; STAMATAKIS MG; WALSH JN;
Indirizzi:
UNIV LONDON ROYAL HOLLOWAY & BEDFORD NEW COLL,DEPT GEOL EGHAM TW20 0EX SURREY ENGLAND UNIV ATHENS,DEPT GEOL GR-15784 ATHENS GREECE
Titolo Testata:
Chemical geology
fascicolo: 1-4, volume: 118, anno: 1994,
pagine: 173 - 183
SICI:
0009-2541(1994)118:1-4<173:AEAWDA>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
MINERALS; NITROGEN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
31
Recensione:
Indirizzi per estratti:
Citazione:
A. Hall et al., "AMMONIUM ENRICHMENT ASSOCIATED WITH DIAGENETIC ALTERATION IN TERTIARYPYROCLASTIC ROCKS FROM GREECE", Chemical geology, 118(1-4), 1994, pp. 173-183

Abstract

The ammonium ion has been measured in fresh volcanic rocks, in vitrictuffs, and in tuffs which have undergone secondary alteration. The ammonium content of fresh lavas of a wide range of composition is shown to be negligible. In contrast, high concentrations of ammonium are found in pyroclastic rocks that have undergone diagenetic alteration. Data are given for three types of diagenetic alteration, namely (1) hydration, (2) zeolitization, and (3) alteration to secondary K-feldspar. Different levels of ammonium enrichment are associated with each type. Hydrated vitric tuffs from Kozani in northern Greece and Heraklion in Crete contain from 158 to 390 ppm NH4+. Zeolitized ash and lapilli tuffs from Santorini and from Lefkimi, NE Greece are much lower in their ammonium content, ranging from 12 to 56 ppm. Tuffs containing secondary K-feldspar in addition to zeolites, from Metaxades, N.E. Greece, have ammonium contents from 51 to 512 ppm. Measurements of fixed and exchangeable ammonium were used to distinguish between the ammonium held by zeolites and that held by K-feldspars. In the clinoptilolite- and mordenite-bearing tuffs from Santorini and Lefkimi, most of the ammoniumis in cation-exchangeable form and must be held by the zeolites. By contrast, in the feldspar-bearing tuffs from the Metaxades area almost all the ammonium is fixed, and it is inferred to be held mainly by secondary K-feldspar.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 02/07/20 alle ore 18:14:58