229
A
Primary
Mineralization
B
C
D
E
Early Cycle
Leaching and
Enrichment
Late Cycle
Leaching and
Enrichment
Supergene
Phyllosilicate
Alteration
Enrichment
Blanket Zones
Felsic Igneous
Host Rocks
Quartz-SericitePyrite Alteration
Overprinting
Base
Level
Quartz-Orthoclase
Biotite Alteration
Disseminated:
Chalcopyrite &
Pyrite
0.16% Cu
Pyrite:
Chalcopyrite
5-10 : 1
Total Sulfides
4-7 wt %
Fracture
Abundance
n > 0.3 cm
Goethite with
minor jarosite
Montmorillonite
+ Kaolinite
Leached
Cap
10 - 50
ft. %
Kaolinite
Partially
Leached
10 - 200
ft. %
Montmorillonite
+ Sericite
Base
Level
Enriched
Blanket
50 - 450
ft. %
Kaolinite
Sericite
Hypogene
Hematite with
minor Jarosite
Jarosite with
minor Goethite
Supergene Sulfide
Enrichment
Leached
Zone
0.02 - 0.12 % Cu.
Enrichment
Zone
0.40 - 1.00 % Cu.
Middle
Blanket
0.20 - 0.40 % Cu.
Nascent
Blanket
0.05 - 0.30 % Cu.
Protore
0.05 - 0.30 % Cu.
Primary
Mineralization
FIGURE 40. Generalized Morenci enrichment profile. Panels A through D are modified
from Titley and Marozas (1995). Panel A shows the characteristic features of hypogene
mineralization that form the bulk geochemistry of the deposit prior to enrichment. Panel
B shows the result of first-cycle enrichment that leaves a relatively thin leached capping
beneath partially leached hypogene mineralization and an overlying leached capping.
Panel C shows the result of second-cycle processes as a result of base level drop that
leaves a hematitic leached capping behind at the site of the former first-cycle blanket and
a thicker and higher grade enriched blanket at depth below. The thicker partially leached
zone is caused by partial oxidation of residual hypogene mineralization or subsequent
destruction of the upper portion of the enriched blanket below and can contain zones with
copper oxides or copper sulfides in places. Typical thickness x %Cu for each zone are
shown in units of ft-% on the left side of the panel. Panel D shows the typical alteration
pattern formed when supergene argillic alteration overprints the quartz-sericite-pyrite
hypogene alteration. Panel E is adapted from Lichtner and Biino (1992) and shows the
downward supergene sulfide zoning in the leached enriched blanket. The enrichment
zone contains chalcocite + djurleite >> covellite or chalcopyrite, the middle blanket
contains covellite +/- chalcocite +/- chalcopyrite, and the nascent blanket contains
chalcopyrite > chalcocite or covellite. This is a generalized vertical sequence, and not
every zone is present or as well developed throughout the enriched blanket. Multiple
cycles and structural displacement, particularly in the axial Chase Creek graben add
significant complications to this generalized sequence.