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Rare earth element geochemistry of altered pyroclastic rocks in the Hashtjin area of north-west Iran

Nouri Tohid, Tehrani Parvin Najafzadeh, Masoumi Rahim, Christidis Georgios

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URIhttp://purl.tuc.gr/dl/dias/505213E1-879D-45CB-9E8C-CC86F75EC2E2-
Identifierhttps://doi.org/10.1180/clm.2020.21-
Identifierhttps://pubs.geoscienceworld.org/claymin/article-abstract/55/2/150/591962/Rare-earth-element-geochemistry-of-altered-
Languageen-
Extent16 pagesen
TitleRare earth element geochemistry of altered pyroclastic rocks in the Hashtjin area of north-west Iranen
CreatorNouri Tohiden
CreatorTehrani Parvin Najafzadehen
CreatorMasoumi Rahimen
CreatorChristidis Georgiosen
CreatorΧρηστιδης Γεωργιοςel
PublisherCambridge University Pressen
Content SummaryThis study evaluates the rare earth element (REE) geochemistry in altered trachyandesitic ignimbrites, tuff and lava flows in the Hashtjin area by assessing chondrite-normalized REE patterns and Y/Ho geochemical ratios. Modifications in the REE patterns took place along altered fault zones that were affected by hypogene and supergene alterations. The precursor volcanic and pyroclastic rocks contain phenocrysts of plagioclase accompanied by augite, zircon, apatite and pyrite. Based on X-ray diffraction analysis, the main mineral assemblages of the altered units consist of kaolinite as the main clay mineral, SiO2 polymorphs (quartz and cristobalite) and anatase as a minor constituent. The chondrite-normalized REE patterns of argillic samples reveal fractionation of light REEs (LREEs) compared to heavy REEs (HREEs), together with a marked Eu anomaly and a weak W-type tetrad effect related to the weak non-charge radius control (CHARAC) behaviour of REEs and slightly higher Y/Ho and Zr/Hf ratios. The relationship between the Y/Ho and Zr/Hf ratios and recognizable T3 and T4 effects (tetrad effect) suggests that an increasing degree of water–rock interaction occurred during hypogene alteration processes by acidic hydrothermal fluids that were overprinted by supergene alteration. Water–rock interaction and adsorption by Mn-oxides and clay minerals are considered to have played important roles in determining the close to non-CHARAC behaviour of REEs during the argillic alteration of the pyroclastic rocks in the Hashtjin area.en
Type of ItemPeer-Reviewed Journal Publicationen
Type of ItemΔημοσίευση σε Περιοδικό με Κριτέςel
Licensehttp://creativecommons.org/licenses/by/4.0/en
Date of Item2021-07-21-
Date of Publication2020-
SubjectArgillic alterationen
SubjectHashtjinen
SubjectIgnimbriteen
SubjectKaolinizationen
SubjectLanthanide tetrad effecten
SubjectPyroclastic rocksen
SubjectRare earth elements (REEs)en
Bibliographic CitationT. Nouri, P. N. Tehrani, R. Masoumi, and G. E. Christidis, “Rare earth element geochemistry of altered pyroclastic rocks in the Hashtjin area of north-west Iran,” Clay Min., vol. 55, no. 2, pp. 150–165, Jun. 2020. doi: 10.1180/clm.2020.21en

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