Petrographic and Sr–Nd–Pb–Li isotope characteristics of a complex lamproite intrusion from the Saxo-Thuringian Zone. A unique example of peralkaline mantle-derived melt differentiation

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985831%3A_____%2F20%3A00534163" target="_blank" >RIV/67985831:_____/20:00534163 - isvavai.cz</a>

Alternative codes found

RIV/00216224:14310/20:00117219 RIV/00216305:26110/20:PU137692 RIV/41601670:_____/20:N0000027

Result on the web

<a href="https://www.sciencedirect.com/science/article/pii/S0024493720303728" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0024493720303728</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.lithos.2020.105735" target="_blank" >10.1016/j.lithos.2020.105735</a>

Result language

angličtina

Original language name

Petrographic and Sr–Nd–Pb–Li isotope characteristics of a complex lamproite intrusion from the Saxo-Thuringian Zone. A unique example of peralkaline mantle-derived melt differentiation

Original language description

Variscan orogenic lamproites in the Bohemian Massif predominantly occur as 1 to 2 m wide and petrographicallyuniform dykes along the eastern borders of the Moldanubian and Saxo-Thuringian zones. Variscan orogeniclamproites were derived by preferential melting of subduction-related olivine-free metasomatic vein assem-blages stabilised in the lithospheric mantle. These lamproitic melts may subsequently undergo extensive differ-entiation. In this study, we present thefirst combined petrographic and Sr–Nd–Pb–Li isotope characteristics of acomplex lamproite exposed at ca 100 m long profile near Horní Rokytnice (Czech Republic) in the Saxo-Thuringian Zone. This lamproite is characterised by the primary mineral assemblage of K-amphibole + K-feldspar ± aegirine and quartz that petrographically varies from relatively primitive (fine-grained, mafic) tomore differentiated (medium- to coarse-grained, felsic) pegmatitic lamproite domains. These domains may rep-resent the product of crystallisation of immiscible liquids that had separated from the maficmelt.Theprimitivelamproite zone is characterised by the typomorphic minerals–baotite, benitoite, and henrymeyerite. The moredifferentiated pegmatitic domains are free of aegirine and show replacement of primary red-luminescent (Fe3+-rich) K-feldspar by blue-luminescent (Fe-poor) K-feldspar. Residualfluids rich in Ca, Ti, and HFSE in combinationwith the decreasing peralkalinity of the lamproite system resulted in the local formation of secondary zircon,titanite and quartz at the expense of the primary Ti–Ba–Zr–K lamproitic mineral assemblages. Lamproites fromthe Moldanubian and Saxo-Thuringian zones fall on separate mixing trends in the 87Sr/86Sr(t) - εNd(t) diagram,which indicates that the mantle beneath these two zones had been metasomatised by different crustal material.The scatter in the peralkalinity index vs. δ7Li diagram indicates that the Li isotope composition is not controlledbymixing of two end members metasome and ambient depleted mantle alone, but may also be affected by late-stage magmatic and hydrothermal processes. The compositionally zoned Horní Rokytnice dyke is special as thepetrographically different types show a variation of about 4 δ-units in δ7Li due to dyke-internal processes, suchas fractionation, which increases δ7Li in late-stage lamproitic melts, and post-emplacement interaction withfluids that reduced δ7Li in samples that have lost Li. Post-emplacement alteration also led to the disturbance inthe Pb isotope systematics of the differentiated orogenic lamproite as indicated by variable over-correction of in situ radiogenic Pb ingrowth.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

<a href="/en/project/GX19-29124X" target="_blank" >GX19-29124X: EVOLUTION AND POST-EMPLACEMENT HISTORY OF CARBONATITES: IMPLICATIONS FOR THE MOBILITY AND CONCENTRATION OF CRITICAL METALS</a><br>

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2020

Confidentiality

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

Name of the periodical

Lithos

ISSN

0024-4937

e-ISSN

—

Volume of the periodical

374

Issue of the periodical within the volume

15 November 2020

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

15

Pages from-to

105735

UT code for WoS article

000576647400005

EID of the result in the Scopus database

2-s2.0-85089511607