ISSN:
0016-7835
Keywords:
Key words Leaching experiments
;
Cation exchange resin
;
Zr
;
Sr
;
Trace element fractionation
;
Zr/Hf
;
Y/Ho
;
Rare earth elements
;
Tetrad effect
;
Metamictization
;
Magmatic-hydrothermal alteration
;
Greisenization
;
S-type granites
;
Variscan granites
;
Tin granites
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract Mineralogical, experimental, geochemical and stable-isotope data give evidence for an aqueous late-stage fluid which develops increasingly from the less to the more highly evolved granites of the Fichtelgebirge (G1–G4). In less-evolved granites (particularly G1) only minor chloritization and sericitization, minor hydration and corrosion of zircons, low leachable fractions of Sr and Zr, the nearly chondritic ratios of Zr/Hf and Y/Ho, and rare-earth-element (REE) patterns lacking the tetrad effect provide evidence of a less-differentiated granitic melt system, poor in complexing agents and water, with insignificant late magmatic fluid–rock interaction. The subsequent low-temperature alteration, which is suggested by oxygen-isotope composition of quartz and biotite, did not affect the whole-rock chemical composition. In the highly evolved granites (particularly G4), albitization, sericitization and fluoritization, ubiquitous hydration and corrosion of zircons, high leachable fractions of Sr and Zr, Zr/Hf and Y/Ho ratios very different from the chondritic ratios, and REE patterns showing a marked tetrad effect point to the presence of a highly specialized fluid system, rich in water and complexing agents, such as fluorine, leading to a marked magmatic–hydrothermal alteration. The oxygen isotopes also indicate alteration by high-temperature fluids which were likely exsolved during the final stage of crystallization.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/PL00014647
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