Specific green zonal silica nodules of serpentinite weathering: Unusual products of silicification in laterite-like residuum (Moldanubian Zone, Bohemian Massif)

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00094862%3A_____%2F21%3AN0000061" target="_blank" >RIV/00094862:_____/21:N0000061 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216224:14310/21:00121194

Výsledek na webu

<a href="http://www.geologicacarpathica.com/browse-journal/volumes/72-1/article-970/" target="_blank" >http://www.geologicacarpathica.com/browse-journal/volumes/72-1/article-970/</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.31577/GeolCarp.72.1.5" target="_blank" >10.31577/GeolCarp.72.1.5</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Specific green zonal silica nodules of serpentinite weathering: Unusual products of silicification in laterite-like residuum (Moldanubian Zone, Bohemian Massif)

Popis výsledku v původním jazyce

Massive quartz–chalcedony ± opal nodules (“plasma” in gemology) represent a specific silica variety, which occurs in the laterite-like residues of pre-Miocene paleo-weathering of ultramafites in western Moravia (Moldanubian Zone, Bohemian Massif). These zonal silica nodules (ZSN) tend to have concentric texture with a dark green to green-brown core, pale green margin and a narrow white rim (outer surface zone). The most typical microscopic feature of ZSN is vermiform microstructure particularly in the two outer zones. Individual zones consist of micro- to non-crystalline SiO2 polymorphs with variable contents of H2O (quartz, chalcedony, moganite, opal-C/CT and opal-A). The predominant green colour is due to submicroscopic smectite pigment, while the brownish colour originated from decomposition of smectite to iron oxohydroxides. ZSN formed in subaerial, partially reducing conditions in the lower part of weathering crusts covering serpentinites. The whole process was preceded by component exchange (chloritization) along serpentinite – felsic rocks (granulite, migmatite, pegmatite veins) boundaries. The gradual silica migration and subsequent redistri­bution associated with the removal of aluminium, magnesium and iron led up to the formation of a zonal nodular texture dominated by SiO2 polymorphs. Newly formed minerals in micro-cavities and cracks of ZSN are represented by acces­sory pyrite and sporadic barite. Zonal silica nodules-bearing residues on serpentinites occur only in a narrow area which was originally covered by clay-sandy Miocene sediments of the Carpathian Foredeep in western Moravia. Probably late low-temperature fluid interaction between silicified serpentinite residuum (chlorite – montmorillonite saprolite) and marine sediments may be the main factor controlling formation of ZSN.

Název v anglickém jazyce

Specific green zonal silica nodules of serpentinite weathering: Unusual products of silicification in laterite-like residuum (Moldanubian Zone, Bohemian Massif)

Popis výsledku anglicky

Massive quartz–chalcedony ± opal nodules (“plasma” in gemology) represent a specific silica variety, which occurs in the laterite-like residues of pre-Miocene paleo-weathering of ultramafites in western Moravia (Moldanubian Zone, Bohemian Massif). These zonal silica nodules (ZSN) tend to have concentric texture with a dark green to green-brown core, pale green margin and a narrow white rim (outer surface zone). The most typical microscopic feature of ZSN is vermiform microstructure particularly in the two outer zones. Individual zones consist of micro- to non-crystalline SiO2 polymorphs with variable contents of H2O (quartz, chalcedony, moganite, opal-C/CT and opal-A). The predominant green colour is due to submicroscopic smectite pigment, while the brownish colour originated from decomposition of smectite to iron oxohydroxides. ZSN formed in subaerial, partially reducing conditions in the lower part of weathering crusts covering serpentinites. The whole process was preceded by component exchange (chloritization) along serpentinite – felsic rocks (granulite, migmatite, pegmatite veins) boundaries. The gradual silica migration and subsequent redistri­bution associated with the removal of aluminium, magnesium and iron led up to the formation of a zonal nodular texture dominated by SiO2 polymorphs. Newly formed minerals in micro-cavities and cracks of ZSN are represented by acces­sory pyrite and sporadic barite. Zonal silica nodules-bearing residues on serpentinites occur only in a narrow area which was originally covered by clay-sandy Miocene sediments of the Carpathian Foredeep in western Moravia. Probably late low-temperature fluid interaction between silicified serpentinite residuum (chlorite – montmorillonite saprolite) and marine sediments may be the main factor controlling formation of ZSN.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10504 - Mineralogy

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2021

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Geologica Carpathica

ISSN

1335-0552

e-ISSN

1336-8052

Svazek periodika

72

Číslo periodika v rámci svazku

1

Stát vydavatele periodika

SK - Slovenská republika

Počet stran výsledku

14

Strana od-do

68-81

Kód UT WoS článku

000623235100005

EID výsledku v databázi Scopus

—