The philipsbornite-segnitite solid-solution series from Rędziny, eastern metamorphic cover of the Karkonosze granite (SW Poland)
PBN-AR
Instytucja
Wydział Geologii, Geofizyki i Ochrony Środowiska (Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie)
Informacje podstawowe
Główny język publikacji
EN
Czasopismo
Annales Societatis Geologorum Poloniae
ISSN
0208-9068
EISSN
Wydawca
Polish Geological Soc.
Rok publikacji
2016
Numer zeszytu
1
Strony od-do
73--83
Numer tomu
86
Link do pełnego tekstu
Identyfikator DOI
Liczba arkuszy
0.78
Autorzy
Pozostali autorzy
+ 1
Słowa kluczowe
EN
chemical composition
Rędziny
arsenates
oxidation zone
philipsbornite
segnitite
carminite
Streszczenia
Język
EN
Treść
Supergene minerals of the philipsbornite–segnitite series, PbAl3(AsO4)(AsO3OH)(OH)6–PbFe3+3(AsO4) (AsO3OH)(OH)6, accompanied by carminite, PbFe3+2(AsO4)2(OH)2, were found in relics of hydrothermal quartz– chlorite–arsenopyrite veins, associated with subordinate polymetallic ores disseminated in contact zones of a dolomitic marble deposit at Rędziny, Western Sudetes, Poland, and recognized by means of electron microprobe and X-ray and electron-back-scattered diffraction (XRD and EBSD). Philipsbornite and segnitite, as the two minerals of the series, exhibit highly variable compositions, especially in terms of the range of Fe3+ Al3+ substitution at the G site, with a distinct gap between the values of 0.52 and 0.89 for the Fe/(Al+Fe) ratio; substitutions at the D and T sites are less important. In this respect, the minerals are almost identical with philipsbornite and segnitite, known from other localities. The gap might be a consequence of the limited miscibility of the end-members, but also might be attributed to crystallization under the changing and distinctly differing activities of Al3+ and Fe3+. The unit-cell parameters of philipsbornite, a = 7.1245(13) Ο, c = 17.0967(45) Ο, make the mineral comparable with philipsbornites from other occurrences. The EBSD analysis confirmed the rhombohedral structure of both minerals and the space group symmetry R-3m. The minerals crystallized in the sequence: philipsbornite -> segnitite -> carminite, which reflects (i) decreasing acidity in the oxidation zone, due to the leaching of sulphate ions and interaction of the solutions with a nearby dolomite lens, and (ii) varying activities of Al3+, Fe3+ and Pb2+ cations, mobilized by the solutions through interaction with the silicate host containing disseminated arsenopyrite and subordinate sulphides, up to complete Pb2+ depletion.
Cechy publikacji
original article
peer-reviewed
Inne
System-identifier
idp:096580
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