Astrophyllite–alkali amphibole rhyolite, an evidence of early Permian A-type alkaline volcanism in the western Mongolian Altai
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F16%3A00000126" target="_blank" >RIV/00025798:_____/16:00000126 - isvavai.cz</a>
Result on the web
<a href="http://www.jgeosci.org" target="_blank" >http://www.jgeosci.org</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.3190/jgeosci.205" target="_blank" >10.3190/jgeosci.205</a>
Alternative languages
Result language
angličtina
Original language name
Astrophyllite–alkali amphibole rhyolite, an evidence of early Permian A-type alkaline volcanism in the western Mongolian Altai
Original language description
A dyke of alkali rhyolite intrudes the Tsetseg and Zuun Nuruu volcanosedimentary sequence of Ordovician–Silurian age (Hovd Zone, Central Asian Orogenic Belt) at the Botgon Bag, Mankhan Soum, Hovd District in Western Mongolia. The rock consists of quartz and K-feldspar phenocrysts set in fine-grained groundmass composed of quartz, K-feldspar, albite, blue alkali amphibole (riebeckite–arfvedsonite containing up to 1.94 wt. % ZrO2), tiny brown radial astrophyllite, annite and accessory zircon, ilmenite, fluorite, monazite, hematite, chevkinite and bastnäsite. Astrophyllite has unusual, highly ferroan composition and occurs as two sharply bound zones of astrophyllite I and II with the average empirical formulae: (K1.71 Na0.01Rb0.08Cs0.01) (Na0.93Ca0.07) (Fe2+6.52Mn0.31Zn0.06) (Ti0.84Zr0.50Nb0.55) Si7.68Al0.32 O26 (OH)3.78 F0.66 (astrophyllite I, Zr-Nb-rich); (K1.52Rb0.07) (Na0.81Ca0.19) (Fe2+6.31 Mn0.28Zn0.06) (Ti1.28Nb0.30Zr0.28) Si7.68Al0.32 O26 (OH)2.85 F0.67 (astrophyllite II). Geochemically, the rhyolite corresponds to strongly fractionated silicic alkaline A-type (ferroan) magmatic rock with 75.5–75.9 wt. % SiO2, 4.4 wt. % K2O, 3.9–4.3 wt. % Na2O and 1.98–2.23 wt. % Fe2O3t, poor in CaO (0.26–0.37 wt. %), MgO (0.01–0.11 wt. %), and P2O5 (0.01 wt. %). The rock is enriched in Zr, Nb, Ta, Ga, Sn, Y, Rb, Cs, U and Th, depleted in V, Sr, Ba, Sc, and exhibits a pronounced negative Eu anomaly, (Eu/Eu* = 0.03–0.05). The conventional whole-rock K–Ar geochronology yielded an age of 299.9 ± 9.1 Ma (1σ), which indicates latest Carboniferous or early Permian extension associated with the A-type alkaline volcanic activity.
Czech name
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Czech description
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Classification
Type
J<sub>x</sub> - Unclassified - Peer-reviewed scientific article (Jimp, Jsc and Jost)
CEP classification
DB - Geology and mineralogy
OECD FORD branch
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Result continuities
Project
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Continuities
V - Vyzkumna aktivita podporovana z jinych verejnych zdroju
Others
Publication year
2016
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Journal of Geosciences
ISSN
1802-6222
e-ISSN
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Volume of the periodical
61
Issue of the periodical within the volume
jaro
Country of publishing house
CZ - CZECH REPUBLIC
Number of pages
11
Pages from-to
93-103
UT code for WoS article
000372458600006
EID of the result in the Scopus database
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