Publication detail

Contrasting origins of the mixed (NYF + LCT) signature in granitic pegmatites, with examples from the Moldanubian Zone, Czech Republic

NOVÁK, M. ŠKODA, R GADAS, P. KRMÍČEK, L. ČERNÝ, P.

Original Title

Contrasting origins of the mixed (NYF + LCT) signature in granitic pegmatites, with examples from the Moldanubian Zone, Czech Republic

Type

journal article - other

Language

English

Original Abstract

Two granitic pegmatites with mixed (NYF + LCT) signatures from the Moldanubian Zone, Czech Republic, were examined to determine their origin. On the basis of geological setting, paragenesis, geochemical modeling and chemical composition of rocks and minerals, two contrasting modes of origin were discerned. The Li-bearing (lithium micas + elbaite) Kracovice pegmatite, with "amazonite", samarskite and fergusonite, is the product of the strong fractionation of pegmatite-forming melt derived from the orogenic I-type Třebíč pluton. Geological, petrological, compositional and isotopic data from this ultrapotassic melasyenite–melagranite point to mixing of a mantle-derived magma with (leuco)granitic melt from crustal rocks. The granite–pegmatite system of the Třebíč pluton and the mainly Li-bearing Kracovice pegmatite are typical examples of the mixed (NYF + LCT) petrogenetic family. The contaminated elbaite-subtype pegmatite Bližná I, Český Krumlov Unit, with lithium tourmalines (elbaite, liddicoatite, uvite), primary REE minerals [bastnäsite-(Ce), parisite-(Ce), allanite-(Ce)] and Ca(Mg)-rich minerals (diopside, uvite, titanite), gained its mixed signature through a unique pre-emplacement process involving the external contamination with Ca, Mg and REE of an evolved (LCT) pegmatite-forming melt by distal carbonatite-like marbles with an NYF signature. Despite the clearly mixed-signature mineralogy and geochemistry, the Bližná I pegmatite represents a special type of contaminated LCT pegmatite rather than a member of the mixed family.

Keywords

Li-bearing pegmatites; mixed (NYF + LCT) signature; origin; contamination; mixing test; Moldanubian Zone; Czech Republic

Authors

NOVÁK, M.; ŠKODA, R; GADAS, P.; KRMÍČEK, L.; ČERNÝ, P.

RIV year

2012

Released

1. 8. 2012

Publisher

Mineralogical Association of Canada

Location

Kanada

ISBN

0008-4476

Periodical

CANADIAN MINERALOGIST

Year of study

50

Number

4

State

Canada

Pages from

1077

Pages to

1094

Pages count

18

BibTex

@article{BUT96110,
  author="NOVÁK, M. and ŠKODA, R and GADAS, P. and KRMÍČEK, L. and ČERNÝ, P.",
  title="Contrasting origins of the mixed (NYF + LCT) signature in granitic pegmatites, with examples from the Moldanubian Zone, Czech Republic",
  journal="CANADIAN MINERALOGIST",
  year="2012",
  volume="50",
  number="4",
  pages="1077--1094",
  issn="0008-4476"
}