STUDY OF Cu-Pb- MINERALS ON VOLCANO "MOUNTAIN 1004" (KAMCHATKA) IN WIDE INTERVALE OF TEMPERATURES
Chebotareva N.V., Semenova T.F.
Russia, 199034 Saint Petersburg, Universitetskaya nab. 7/9, St. Petersburg State University, dept. of crystallography.
Keywords: minerals, structure of minerals,
high-temperature X-ray powder diffraction method
Relicts of old fumarole activity which took place more than 2000 years ago were discovered at the cindery cone of mountain 1004 in the axial zone of the Tolbachinsky dale (Central Kamchatka). Minerals of Cu and Pb found there are represented by antlerite Cu3(SO4)(OH)4, atacamite Cu2Cl(OH)3, PbCu(SO4)(OH)2. Antlerite and linarite are typical for the oxidation zones of Cu and Pb ores and have not been found on fumarole fields. The all minerals were formed during the final low-temperature stage of posteruptive process.
Antlerite, linarite, atacamite were identified by the X-ray powder diffraction method. Minerals are analogous to standards of PDF. That confirms the chemical analyses data on the absence isomorphous impurities in these minerals.
Linarite, antlerite and atacamite were studied by high-temperature X-ray powder diffraction method. Fields of their temperature stability and thermal deformations of their structures have been determined.
Linarite PbCu(SO4)(OH)2 is stable up to the temperature 263±12 oC, then it begins to destruct with the formation of anglesite Pb(SO4), chalcokianite Cu(SO4) and tenorite CuO. The temperature dependences of the parametrs of monoclinic cell are discribed by polynomes: a=9.689+0.320x10-3t Å, b=5.650+0.066x10-3t Å, c=4.681+0.130x10-3t Å, bo =102.6+2x10-3t.
Antlerite Cu3(SO4)(OH)4 is stable up to the temperature 425±15 oC, then it begins to destruct with the formation of dolerophanite Cu2O(SO4) and tenorite CuO. The temperature dependences of the ortorombic cell parametrs are discribed by polynomes: a=8.244+0.210x10-3t Å, b=12.00-0.042x10-3t+0.496x10-6t2 Å, c=6.047+0.10x10-3t Å.
Atacamite Cu2Cl(OH)3 begins to destruct by temperature 250±15 0C with the formation of melanothallite Cu2OCl2 and tenorite CuO. The dependences of the ortorombic cell parametrs from the temperature are discribed by polynomes: a=6.030+0.120x10-3t Å, b=9.105+0.180x10-3t Å, c=6.870+0.011x10-3t Å.
The products of thermal destruct of antlerite and atacamite are oxyde (tenorite CuO) and minerals with "addition" oxygen (dolerophanite Cu2O(SO4) and melanothallite Cu2OCl2), which is in tetrahedra from four Cu+. That connects, probably, with the presence of the tetrahedras [OHCu3] in the structures of antlerite and atacamite.