15 research outputs found
The effect of chemical variability and weathering on Raman spectra of enargite and fahlore
Enargite (Cu3AsS4) and tennantite
(Cu12As4S13) are typical As-bearing sulfides in intermediate-
and high-sulfidation epithermal deposits. Trace and major element variations
in enargite and tennantite and their substitution mechanisms are widely
described. However, Raman spectra of the minerals with correlative
quantitative chemical information are rarely documented, especially for
enargite. Therefore, comparative electron and μ-Raman microprobe
analyses were performed on enargite and fahlore grains. These spectra can be
used in the industrial detection and subsequent removal of As-bearing sulfides
prior to ore beneficiation in order to diminish the environmental impact of
the metallurgical technologies.
A simple Sb5+–As5+ substitution in enargite was confirmed by Raman
analyses. Similarly, a complete solid solution series from tetrahedrite to
tennantite (i.e., Sb3+–As3+ substitution) can be correlated with a
gradual evolution in their Raman spectra. In turn, Te4+ occupies the
As3+ and Sb3+ sites in fahlore by the coupled substitution
Te4+ + Cu+ → (As, Sb)3+ + (Cu, Fe, Zn)2+.
Accordingly, Raman bands of goldfieldite (Te-rich member) are strongly
broadened compared with those of tetrahedrite and tennantite.
A secondary phase with high porosity and a fibrous or wormlike texture was
found in enargite in a weathered sample. The chemical composition, Raman
spectrum, and X-ray diffraction signature of the secondary phase resemble
tennantite. A gradual transformation of the primary enargite into this
secondary phase was visualized by comparative electron and Raman microprobe
mapping.</p
Automated mineralogy based on micro-energy-dispersive X-ray fluorescence microscopy (µ-EDXRF) applied to plutonic rock thin sections in comparison to a mineral liberation analyzer
Recent developments in the application of micro-energy-dispersive X-ray fluorescence spectrometry mapping (µ-EDXRF)
have opened up new opportunities for fast geoscientific analyses. Acquiring
spatially resolved spectral and chemical information non-destructively for
large samples of up to 20 cm length provides valuable information for
geoscientific interpretation. Using supervised classification of the
spectral information, mineral distribution maps can be obtained. In this
work, thin sections of plutonic rocks are analyzed by µ-EDXRF and
classified using the supervised classification algorithm spectral angle
mapper (SAM). Based on the mineral distribution maps, it is possible to
obtain quantitative mineral information, i.e., to calculate the modal
mineralogy, search and locate minerals of interest, and perform image
analysis. The results are compared to automated mineralogy obtained from the
mineral liberation analyzer (MLA) of a scanning electron microscope (SEM)
and show good accordance, revealing variation resulting mostly from the
limit of spatial resolution of the µ-EDXRF instrument. Taking into
account the little time needed for sample preparation and measurement, this
method seems suitable for fast sample overviews with valuable chemical,
mineralogical and textural information. Additionally, it enables the
researcher to make better and more targeted decisions for subsequent
analyses
A relapsing localized variant of neutrophilic dermatosis triggered by tissue injury.
Neutrophilc dermatoses (ND) comprises a group of autoinflammatory disorders characterized by a neutrophilic-rich infiltrate in the skin. Based on their frequent overlapping features ND have been classified into three major groups: (1) superficial ND; (2) dermal ND, and (3) deep ND.1,2 ND are often associated with haematological malignancies and chronic inflammatory diseases.1,2 We report a striking localized form of relapsing ND