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The missing sulphur in mattheddleite, sulphur analysis of sulphates, and paragenetic relations at Leadhills, Scotland

E. J. Essene, C. E. Henderson and A. Livingstone
The missing sulphur in mattheddleite, sulphur analysis of sulphates, and paragenetic relations at Leadhills, Scotland
Mineralogical Magazine (June 2006) 70 (3): 265-280

Abstract

Published electron microprobe analyses of mattheddleite, a lead sulpho-silicate apatite from Leadhills, Scotland, have 9-13% IV site deficiencies. However, galena was used as a standard for S, which suggested that low S resulted from a shift in the S-Kalpha peak. Wavelength scans with a PET crystal show that the S-Kalpha peak is shifted down by 0.0026 Aa for sulphates relative to sulphides. Quantitative analyses show a approximately 30% increase of S in mattheddleite using a celestite standard, which fills the IV site, but with Si>S, on average Pb (sub 5) S (sub 1.2) Si (sub 1.8) O (sub 11.7) Cl (sub 0.6) (OH) (sub 0.4) . Direct analysis of oxygen with the electron microprobe implies that the charge imbalance engendered from the inequality of Si and S is compensated with substitution of a vacancy ([]), as in Pb (sub 5) S (sub 1.2) Si (sub 1.8) [O (sub 11.7) [] (sub 0.3) ][Cl (sub 0.6) (OH) (sub 0.4) ] or Pb (sub 5) S (sub 1.2) Si (sub 1.8) [O (sub 11.7) (Cl,OH) (sub 0.3) ][Cl,OH) (sub 0.7) [] (sub 0.3) ]. Calculation of OH as 1-Cl suggests the presence of both OH- and Cl-dominant mattheddleite at Leadhills, but direct analysis of H is needed to confirm the dominance of OH in the channel site. Wavelength-dispersive analyses of S in apatite and other sulphates must be undertaken with sulphate standards: use of sulphide standards yields a negative error on the order of 10-20% in the resultant S concentration. Reactions of mattheddleite with other Pb minerals at Leadhills show that their stability depends on fluid composition as well as pressure and temperature. An X-ray map of Cl shows complex zoning between Cl-poor and Cl-rich mattheddleite, recording rapid changes in the fluid chemistry during late-stage hydrothermal processes at Leadhills.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 70
Serial Issue: 3
Title: The missing sulphur in mattheddleite, sulphur analysis of sulphates, and paragenetic relations at Leadhills, Scotland
Affiliation: University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
Pages: 265-280
Published: 200606
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 71
Accession Number: 2006-081622
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N54°40'00" - N61°00'00", W08°30'00" - W00°45'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200646
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