1. Anezka Radkova, Heather Jamieson
Application of synchrotron radiation-based techniques on study of mine waste mineralogy
Anezka Radkova, Heather Jamieson
AESRC, 2015

2. Outline
Introduction to synchrotron related analytical techniques - µXRF, µXAFS, µXRD
Why is the study of tailings mineralogy important?
Arsenic (As) rich tailings Nova Scotia
Antimony (Sb) secondary minerals in tetrahedrite rich waste rock: Slovakia
Conclusions

3. Synchrotron light source
High brilliance (many orders of magnitude more than with X-rays produced in conventional X-ray tubes)
Highly focused light
Tunable energy

4. Experimental techniques: 1) µXRF (X-ray fluorescence spectroscopy) spot analyses and mapping
Characteristic X-ray emission lines
Determining elemental compositions 
 Resolving elements distribution
Micro-focusing techniques - studies of the spatial element distribution on a micrometric scale (chemical zoning and impurity distributions)
Combination with other techniques: XRD, XANES, EXAFS
elemental analysis can be combined with other microanalysis techniques  μ-XRF - selecting sample areas before applying other microanalysis techniques
Secondary oxides mixture
50 µm
SbLa
FeKa
CuKa
AsKa
BiLa Sb Fe Cu As Bi

5. Experimental techniques: 1) microXRD
Structural information of crystalline compounds - high brilliance enable to detect nanoparticulate crystals
Detection of low-abundance crystalline phases
Environmental materials characterization as a heterogeneous multi-phase systems of generally poor crystallinity

6. Experimental techniques: 1) XAFS (X-ray absorption spectroscopy) and µXAFS
XANES
Oxidation state
Coordination chemistry
2.32Å
2.46Å
3.43 Å
2.90 Å
Fe2O3
EXAFS
Quantitative Local Structure.
information on the atoms organisation and chemical bonding around an absorbing atom
XANES = X-ray Absorption Near-Edge Spectroscopy
EXAFS = Extended X-ray Absorption Fine-Structure
Pacheco and Bargar, 2011

7. Application of mine waste mineralogy study: What questions can we answer?
What is the dominant form of contaminant of interest?
Is the contaminant present in toxic or bioaccessible form? Molecular- level speciation of trace environmental contaminants are necessary for understanding their behavior.
Will the contaminant remain stable or is it likely to get mobilized?
Prediction of contaminant behaviour when selecting the remediation technique for particular site

8. ARSENIC BIOACCESSIBILITY IN THE NOVA SCOTIA GOLD MINING DISTRICTS
Arsenic-bearing gold ore mining – As rich tailings
Close distance to residential areas, at times used for racing off-road vehicles
Inhalation or ingestion of As-bearing tailings- risk to human health
In case of some samples no As phases confirmed by field observation or conventional XRD, even though most of these samples contain As concentrations in the wt% range (>10,000 ppm)
Photo: Catherine Craigen
Walker et al., 2009

9. Ferric arsenates (scorodite, amorphous Fe arsenate, kaňkite)
Heterogenous near surface tailings containing arsenopyrite and its oxidation products:
Ferric arsenates (scorodite, amorphous Fe arsenate, kaňkite)
Ca-Fe arsenates (yukonite and an amorphous form)
Remediation challenge: mix of oxidized and reduced As species
BIOACESSIBILITY
Walker et al., 2009

10. Behavior of antimony during the weathering of the tetrahedrite-tennantite [Cu12(Sb,As)4S13] minerals in abandoned waste rock piles
Photo: Martin Chovan

11. A B C
Sb hosts: Mixture of nanocrysctalline romeite group mineral with pyrochlore structure and tripuhyite (FeSbO4), lower wt% of Sb in amorphous phases
Amorphous phases
tetrahedrite
BSE
Amorphous phases
high
Tripuhyite and pyrochlore
low

12. Metals and metalloids distribution in tetrahedrite oxidation products
wt%

14. Conclusions
Synchrotron techniques effective for mine tailings and waste rock mineralogy study:
XRF – identification chemical associations
XRD – identification mineral species
XAFS – information about structural form and oxidation state of metals at molecular level
bulk XANES – proportions of metal species
these methods can be effectively used to characterize host minerals of contaminants such as As and Sb in mine waste
identification of mine waste compounds helps to predict further behaviour of contaminants

15. Acknowledgements EMPA assistance: Brian Joy
APS assistance: Robert Gordon, Zoe Finfrock
EMPA assistance: Brian Joy