Original paper
Murmanite from Ilímaussaq alkaline complex, South Greenland
Karup-Møller, S.
Neues Jahrbuch für Mineralogie - Abhandlungen Band 155 Heft 1 (1986), p. 67 - 88
14 references
published: Sep 8, 1986
ArtNo. ESP154015501006, Price: 29.00 €
Abstract
Murmanite has been found at three localities within the Ilímaussaq complex in South Greenland. It occurs in altered and sheared lava and gabbro intruded by lujavrite. It is the supergene alteration product after lomonosovite and it always contains small amounts of submicroscopic oriented lomonosovite. Average chemical composition based upon 212 microprobe analyses lead to the following formula: (Na0.88K0.02Mg0.03Ca0.38Fe0.09+2)Σ1.40 (Ti1.63Nb0.14Fe0.03+3Mn0.04)Σ1.84 Si2.00O8.63+0.15Na3PO4+1.87H2O. The mineral is triclinic, a = 5.44 Å, b = 7.06 Å, c = 11.71 Å, α = 93.44°, β = 98.52° and γ = 89.49°. It is characterized by a super structure caused by a doubling of the a and b cell dimensions. Trace element contents, infrared and thermal data are listed. Alteration of murmanite has resulted in a heterogeneous intergrowth of very fine grained ramsayite and a mineral which may possibly be a new species. Microprobe analyses suggest the following empirical formula: (Na2.98K0.14)Σ3.12(Ti2.25Nb0.16Fe0.12Al0.79)Σ3.32 Si4.00O15.65+1.04H2O. It is optically negative, 2V = 70°, np = 1.68 and ng = 1.72, monoclinic C-centered with a = 5.1282(37)Å, b = 8.7200(46)Å, c = 24.375(18)Å and β = 99.50°. Guinier powder data, thermal data and infrared data are listed.
Keywords
Murmanite • Ilímaussaq • Greenland