Title: Cu isotope ratio variations in the Dikulushi Cu-Ag deposit, DRC: of primary origin or induced by supergene reworking?
Authors: Haest, Maarten ×
Muchez, Philippe
Petit, Jérôme
Vanhaecke, Frank #
Issue Date: Nov-2009
Publisher: Economic Geology Pub. Co.
Series Title: Economic Geology and the Bulletin of the Society of Economic Geologists vol:104 issue:7 pages:1055-1064
Abstract: This study investigates Cu isotope ratio variations in the high-grade, vein-type Cu-Ag deposit of Dikulushi,
Democratic Republic of Congo. The Dikulushi deposit consists of a Cu-Pb-Zn-Fe mineralization, comprising
sphalerite, chalcopyrite, bornite, and chalcocite that precipitated under reducing conditions. This mineralization
was partly remobilized in more oxidizing conditions into a Cu-Ag mineralization phase, which is dominated
by Ag-rich chalcocite. The upper part of the deposit is strongly reworked by weathering. Sulfides from the two
types of mineralization and Cu carbonates/-silicates from the weathering zone display significant Cu isotope
ratio variations. Chalcopyrite and chalcocite from the Cu-Pb-Zn-Fe and Cu-Ag mineralization types are characterized
by variable low Cu isotope compositions (0.00 to –2.3‰ δ65Cu). The Cu isotope composition for
some chalcocite from the Cu-Ag mineralization deviates to lower δ65Cu values relative to that of chalcocite
from the Cu-Pb-Zn-Fe mineralization. This deviation is likely related to remobilization of the Cu-Pb-Zn-Fe
mineralization in an oxidizing environment. The isotopic composition of Cu in chalcocite from both mineralization
types becomes higher toward the center of the orebody and as a function of depth. This variation could
be related to physicochemical changes in the precipitation environment as a consequence of interaction of the
reduced mineralizing brine with the oxidized host rock or might have been induced by supergene processes
afterward. The supergene mineralization is composed of malachite, azurite, and chrysocolla that are enriched
in 65Cu (1.37–2.65‰ δ65Cu).
ISSN: 0361-0128
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Division of Geology
× corresponding author
# (joint) last author

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