J 2023

Chemical composition of tourmalines from the Manjaka pegmatite and its exocontact, Sahatany Valley, Madagascar

GADAS, Petr; Milan NOVÁK; Michaela VAŠINOVÁ GALIOVÁ a Federico PEZZOTTA

Základní údaje

Originální název

Chemical composition of tourmalines from the Manjaka pegmatite and its exocontact, Sahatany Valley, Madagascar

Autoři

GADAS, Petr; Milan NOVÁK; Michaela VAŠINOVÁ GALIOVÁ a Federico PEZZOTTA

Vydání

Journal of Geosciences, Praha, Česká geologická společnost, 2023, 1802-6222

Další údaje

Jazyk

angličtina

Typ výsledku

Článek v odborném periodiku

Obor

10504 Mineralogy

Stát vydavatele

Česká republika

Utajení

není předmětem státního či obchodního tajemství

Odkazy

Impakt faktor

Impact factor: 1.100

Kód RIV

RIV/00216224:14310/23:00134385

Organizační jednotka

Přírodovědecká fakulta

DOI

UT WoS

001125566400004

EID Scopus

2-s2.0-85179681666

Klíčová slova anglicky

Tourmaline; granitic pegmatite; exocontact; mobility of elements; Manjaka; Madagascar

Štítky

Příznaky

Mezinárodní význam, Recenzováno
Změněno: 23. 1. 2024 09:05, Mgr. Marie Novosadová Šípková, DiS.

Anotace

V originále

Chemical compositions and mineral assemblages of tourmalines from the elbaite-subtype Manjaka pegmatite in the Sahatany Valley, central Madagascar, and its exocontact were examined using EPMA and LA-ICP-MS. Several textural, compositional and paragenetic types of tourmalines were recognized in the individual pegmatite units and in the zones located towards the host rock in the order: wall pegmatite unit -> border pegmatite unit -> contact zone -> recrystallization zone; the latter zone evidently originated after the host Mg-rich calc-silicate rock (Di+Tr+Qz>Pl+Kfs>Phl+ Dol>Cal). Zoned prismatic crystals from the border unit evolved from the core Tur Ia (dravite < Fe-rich elbaite), Tur Ib (Mn,Fe-rich to Mn-rich fluor-elbaite > elbaite), to the crystal rims Tur II (elbaite > darrellhenryite) via the substitutions: (1) 2(Y)R(2+) = (LiAl)-Li-Y, (2) (MnF)-Mn-Y-F-W = (Fe2+WOH)-Fe-Y, (3) Li-Y(0.5) (OH)-O-W = Al-Y(0.5) O-W, and (4) (LiT)-Li-Y (AlOH3)-O-W = (AlT)-Al-Y (SiO3)-O-W . The contact zone, similar to 2 mm thick, contains abundant Tur IV (Li,Fe,Al-enriched dravite > oxy-dravite), and the recrystallization zone, similar to 1.5 cm thick, common Tur V (fluor-uvite > dravite > fluor-dravite, magnesio-lucchesiite, uvite) via the substitutions: (1) 2(Y)R(2+) = (LiAl)-Li-Y and (5) (R2+WOH)-R-Y = (AlO)-Al-Y-O-W,(6) (NaOH)-Na-X-O-W = (CaO)-Ca-X-O-W and (7) Na-X(Y) Al = (CaR2+)-Ca-X-R-Y. The chemical compositions of the individual types of tourmalines suggest that the mobility of elements between calc-silicate rock and pegmatite was low. Only weak influx of Mg, V and Cr into pegmatite and Li and Al from the pegmatite to the host rock - recrystallization zone, respectively, were observed. The existence of thin B-rich contact zone with dominant Tur IV suggests low influx of B into the host rock in early magmatic stage. High contents of F in Tur V from the recrystallization zone were very likely triggered by influx of B,F-enriched residual pegmatite fluids. Very high a(B2O3), but low a(H2O) and a(F) in the pegmatite melt constrained very low degree of external contamination of the pegmatite. Compositional evolution in tourmalines from Manjaka was compared with the pegmatites and their exocontact at Stoffhutte, Koralpe, Austria, and Blizna I, Moldanubian Zone, Czech Republic.

Návaznosti

GA19-05198S, projekt VaV
Název: Greisenizace a albitizace - geologické procesy s potenciálem koncentrovat některé kritické suroviny pro moderní technologie (Akronym: GREISEN)
Investor: Grantová agentura ČR, Greisenizace a albitizace - geologické procesy s potenciálem koncentrovat některé kritické suroviny pro moderní technologie