150
FIGURE 32. Cross Section 10,000 W. Looking west at the Morenci, Western Copper,
Metcalf, Shannon, and Garfield areas. Both panels are illustrated with a 2.5 to1 vertical
to horizontal exaggeration, pre-mine topography, water table as of April 1995, drill holes
for control, and major faults for reference. Panel A shows the Morenci intrusive complex
of stocks and dikes intruding Precambrian granite across the district and the Paleozoic
rocks in the Southside, Shannon and Garfield areas. The sedimentary section has been
faulted against Precambrian granite down to the north across the Garfield fault and down
to the south across the Quartzite fault. Panel B shows the supergene profile by
mineralized zone above hypogene protore at depth with pit limits for reference. Note the
gentle southerly dip of the supergene profile that is coincident with the Chase Creek
gradient and the general conformance of the enriched blanket to pre-mine topography.
The Kingbolt and Quartzite bound the thick enriched blanket faults at the southern end of
the Chase Creek graben. Elsewhere, partial leaching and weak enrichment is evident in
the Western Copper and Garfield areas and in the Younger Granite Porphyry along the
western margin of Metcalf. Relatively high-grade supergene mineralization occurs in the
Shannon area but doesn’t persist to significant depths below the limestones and quartzite.
None-the-less, relatively thick, but weak enrichment in the lower blanket and some
leaching below the Paleozoic rocks attest to vertical movement of fluids through the
weakly reactive skarns above and to lateral flow along the ground water gradient.
151
Cross Section 10,000 West
Looking West
West
S
Western
Copper
Morenci
Copper
Mountain
5000 Fault
Quartzite
Fault
Zone
Current
Pit
Pre-Mine
Topography
Standard
Gulch
Fault
Shannon Fault
Metcalf
Brad
Fault
Garfield
El Paso
Fault
N
Final
Garfield
Pit
Fault
Final
Pit
Tpgy
5000
Kingbolt
Fault
Mm
Dm
Ol
Water Table
4000
20000
10000
A)
Cc
4000
Xg
3000
3000
Explanation
Mine Dump
Eocene Younger Granite Porphyry
Eocene Older Granite Porphyry
Eocene Monzonite Porphyry
Eocene Diabase
Tpm
Mississippian Modoc Limestone
Devonian Morenci Formation
Ordovician Longfellow Limestone
Cambrian Coronado Quartzite
Precambrian Granite
20000
10000
Tpgo
Xg
Fault
Drillhole
Horizontal Scale
2.5 V
0
2500
Feet
5000
1.0 H
B)
FIGURE 32. Cross Section 10, 000 W. Looking west at the Morenci, Western Copper,
Metcalf, Shannon, and Garfield areas. A) Geology. B) Mineralization. See facing page
for description.