CLIMAX MINE MOLYBDENUM
Central Colorado's Climax
Mine is the largest molybdenum mine on Earth. It's located in the
Southern Rocky Mountains, near the northern end of the Rio Grande Rift, a
large, Neogene-aged rift valley on the eastern side of the Colorado Plateau.
Molybdenum (Mo - "moly") mineralization at
the Climax Mine occurred as a series of igneous bodies intruded through
Proterozoic basement rocks (gneisses and granites). Seven intrusive
bodies make up the composite Climax Stock (Oligocene, 24-33 m.y.).
Three of them produced significant moly mineralization in the form of molybdenite-quartz
veins and disseminated molybdenite (MoS2 - molybdenum sulfide).
The rocks of the Climax Stock are alkalic felsic
intrusives. They range from porphyritic alkalic rhyolites to alkalic
aplites to porphyritic alkalic granites. In map view, the igneous bodies
of the Climax Stock form a roughly circular structure. In cross-section
view, each intrusion has an inverted bowl shape.
Published studies on the origin of the Climax
Molybdenum Deposit and other Climax-type moly deposits have concluded that they
form principally in incipient extensional tectonic settings well inland from
shallow-angle subduction zones that have recently ceased.
The 1st sample shown below is a large cut &
polished slab of molybdenum ore from the Climax Mine. Note that the thicker
mineralized veins tend to have quartz (light gray) making up most of the vein
and molybdenite (dark gray) lining the walls of the vein. Compare that
with the thinner veins which are principally composed of ~just
light gray quartz or ~just dark gray molybdenite (such
molybdenite-dominated thin veins are referred to as "moly paint").
The 2nd sample is a closeup of a molybdenite-quartz
Climax Mine molybdenum ore (large cut & polished slab) - multiple
molybdenite-quartz veins intruding porphyritic alkalic granite (Climax Mine,
Old Glory Hole, Fremont Pass, Lake County, central Colorado, USA).
Dark gray = molybdenite (MoS2)
Light gray = quartz (SiO2)
Mottled yellowish = porphyritic alkalic granite host rock (Climax
CSM # 12334, Colorado School of Mines Geology Museum,
Golden, Colorado, USA
Climax Mine molybdenum ore (4.6 cm across at its widest) - molybdenite-quartz
vein from the Climax Mine, Lake County, central Colorado, USA).
Dark silvery gray = molybdenite (MoS2).