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Mineralogy of the near-surface expression of Au-As-Cu mineralization in an arid environment

Published online by Cambridge University Press:  05 July 2018

R. Bogoch ,
M. Shirav ,
A. Gilat  and
L. Halicz
R. Bogoch
Affiliation:
Geological Survey of Israel, 30 Malkhei Israel St., Jerusalem 95501, Israel
M. Shirav
Affiliation:
Geological Survey of Israel, 30 Malkhei Israel St., Jerusalem 95501, Israel
A. Gilat
Affiliation:
Geological Survey of Israel, 30 Malkhei Israel St., Jerusalem 95501, Israel
L. Halicz
Affiliation:
Geological Survey of Israel, 30 Malkhei Israel St., Jerusalem 95501, Israel
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Abstract

In the arid, Late Precambrian terrain of southern Israel, a complex suite of minerals and amorphous species were deposited in host gneiss from fluids under near-neutral conditions within 1 m of the surface. The morphology of secondary gold appears to relate to its host mineral (skeletal-dendritic with quartz; multi-faceted crystals with arsenates; spherical droplets with iron oxide). The gold is very fine-grained, and was most likely complexed as a thiosulphate.

Three amorphous phases are present (iron oxide, chrysocolla, Cu-Mn-(Fe-As) silicate). At least in part, gold and baryte appear to have crystallized out of a metal-Fe-oxide gel. Other minerals, including apatite, anglesite, and conichalcite, may have grown from appropriate crystallites present in the gel.

The conichalcite occurs mainly as bladed to acicular radial spherulites. In the presence of lead, a solid solution phase between duftite and conichalcite (‘Pb-conichalcite’) was formed.

Keywords

secondary Au-As-Cu mineralsconichalcitegoldarid environment
Type
Mineralogy
Information
Mineralogical Magazine , Volume 58 , Issue 391 , June 1994 , pp. 315 - 323
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1994

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