F. Xia, J. Zhao, B. Etschmann, J. Brugger, C. Garvey, C. Rehm, H. Lemmel, J. Ilavsky, Y. Han, A. Pring:
"Characterization of porosity in sulfide ore minerals: A USANS/SANS study";
American Mineralogist, 99 (2014), S. 2398 - 2404.

Kurzfassung englisch:
Porosity plays a key role in the formation and alteration of sulfide ore minerals, yet our knowledge
of the nature and formation of the residual pores is very limited. Herein, we report the application of
ultra-small-angle neutron scattering and small-angle neutron scattering (USANS/SANS) to assess the
porosity in five natural sulfide minerals (violarite, marcasite, pyrite, chalcopyrite, and bornite) possibly
formed by hydrothermal mineral replacement reactions and two synthetic sulfide minerals (violarite
and marcasite) prepared experimentally by mimicking natural hydrothermal conditions. USANS/
SANS data showed very different pore size distributions for these minerals. Natural violarite and
marcasite tend to possess less pores in the small size range (<100 nm) compared with their synthetic
counterparts. This phenomenon is consistent with a higher degree of pore healing or diagenetic com-
paction experienced by the natural violarite and marcasite. Surprisingly, nanometer-sized (<20 nm)
pores were revealed for a natural pyrite cube from La Rioga, Spain, and the sample has a pore volume
fraction of ~7.7%. Both chalcopyrite and bornite from the massive sulfide assemblage of the Olympic
Dam deposit in Roxby Downs, South Australia, were found to be porous with a similar pore volume
fraction (~15%), but chalcopyrite tends to have a higher proportion of nanometer-size pores centered
at ~4 nm while bornite tends to have a broader pore size distribution. The specific surface area is
generally low for these minerals ranging from 0.94 to 6.28 m 2 /g, and the surfaces are generally rough
as surface fractal behavior was observed for all these minerals. This investigation has demonstrated
that USANS/SANS is a very useful tool for analyzing porosity in ore minerals. We believe that with
this quantified porosity information a deeper understanding of the complex fluid flow behavior within
the porous minerals can be expected.

SANS, USANS, sulfide ore minerals, porosity, mineral replacement reactions

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