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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEĹ-BOLYAI
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Rezumat: Secondary phosphates rarely have been found in the Palaeozoic argillites of the Uppony Mts. They occur in the fissure-fillings of brecciated or clastic argillite, mainly in near-surface positions in the surroundings of Dédestapolcsány and Nekézseny (Elsholtz et al., 1974). The geochemical investigations of these argillites revealed some uranium enrichment, which shows good correlation with phosphorous. During the new mineralogical investigation of the Dédestapolcsány phosphate-rich area, a hydrous copper-vanadate, volborthite (Cu3V2O7(OH)2.2H2O), was found for the first time in the Carpathians.
Volborthite found in the fissures shows yellow-brown, yellow-green, olive-green, and dark green colours. The common appearance includes: powdery scattering, micro-crusts, porous masses, globular and stalagtite-like aggregates (up to 13 mm). According to SEM studies these aggregates consist of 1030 m long oriented grown needles, which built up lamellae. The largest lamellae are up to 0.30.6 mm.
According to XRD patterns and the appearance of volborthite, we can distinguish at least two varieties, which crystallized differently. The yellowish varieties are the least crystallized, while the greenish varieties are the most crystallized phases. The d values show excellent agreement with JCPDS 26-1119 file, however, intensities with exception of 100 reflexion are smaller. Unit cell data are: a = 10.604 Ĺ; b = 5.879 Ĺ; c = 7.202 Ĺ; = 94.81.
Three chemical analyses carried out with CAMECA CAMEBAX SX50 electron microprobe operated at 25 kV and 0.1 mA. Average of the three analytical results is as follows (in weight %): CuO: 40.97; V2O5: 25.14; P2O5: 0.64; Al2O3:1.14; Cl: 0.41. ... |
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