The chemistry, structural parameters, polytypism, optical properties and Rb-Sr isotopes were examined in II to 60 samples of biotite, muscovite and lepidolite from the pegmatites at Rozna (the type locality of lepidolite; 323 +/- 4Ma) and Dobra Voda (306 +/- 9Ma) in western Moravia. At both localities, early endocontact biotite is followed inwards by muscovite and lepidolite, which is concentrated in and around the core. At Rozna, a 1M lepidolite follows after 2M(1) muscovite but all later generations of lepidolite are 2M(2), close to Tri(50) Ply(50) and in part associated with muscovite 2M(1). At Dobra Voda, all lepidolite types are 1M and free of muscovite, and the late varieties approximate Tri(30) Ply(70). At both localities, a trend of increasing mu HF is indicated during the progress of mica crystallization, culminating in precipitation of topaz. Polytypism of lepidolite is not correlatable with any compositional or growth feature, or their combination. Throughout the mica crystallization, Rb/Cs decreases but K/Rb becomes reversed after an initial decrease. Boron is partitioned preferentially into muscovite (up to 1.10 wt. % B2O3) but Be, Zn, Mn and Sc are enhanced in lepidolite. A slight increase in Fe, Ba and Cl in the last generation of lepidolite might be possibly due to mixing of residual pegmatite fluids with metamorphic pore solutions.
GEOCHEMICAL AND STRUCTURAL EVOLUTION OF MICAS IN THE ROZNA AND DOBRA-VODA PEGMATITES, CZECH-REPUBLIC
L Ottolini;
1995
Abstract
The chemistry, structural parameters, polytypism, optical properties and Rb-Sr isotopes were examined in II to 60 samples of biotite, muscovite and lepidolite from the pegmatites at Rozna (the type locality of lepidolite; 323 +/- 4Ma) and Dobra Voda (306 +/- 9Ma) in western Moravia. At both localities, early endocontact biotite is followed inwards by muscovite and lepidolite, which is concentrated in and around the core. At Rozna, a 1M lepidolite follows after 2M(1) muscovite but all later generations of lepidolite are 2M(2), close to Tri(50) Ply(50) and in part associated with muscovite 2M(1). At Dobra Voda, all lepidolite types are 1M and free of muscovite, and the late varieties approximate Tri(30) Ply(70). At both localities, a trend of increasing mu HF is indicated during the progress of mica crystallization, culminating in precipitation of topaz. Polytypism of lepidolite is not correlatable with any compositional or growth feature, or their combination. Throughout the mica crystallization, Rb/Cs decreases but K/Rb becomes reversed after an initial decrease. Boron is partitioned preferentially into muscovite (up to 1.10 wt. % B2O3) but Be, Zn, Mn and Sc are enhanced in lepidolite. A slight increase in Fe, Ba and Cl in the last generation of lepidolite might be possibly due to mixing of residual pegmatite fluids with metamorphic pore solutions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
