60 Türkiye Jeoloji Kurultayi Exploration for Skarn Deposits Larry Meinert Department of Geology Smith College Northampton, MA 01063 USA Email: [email protected]
Jan 05, 2016
60 Türkiye Jeoloji Kurultayi
Exploration for Skarn Deposits
Larry MeinertDepartment of GeologySmith CollegeNorthampton, MA 01063 USAEmail: [email protected]
Skarns and Skarn Deposits
1) General processes of skarn formation
2) Mineralogy, petrology, & tectonic setting
3) Examples of major skarn deposits: Antamina - Peru
Ertsberg District - Irian Jaya
Depth of Formation - W Skarns
• Tonnage and grade 63 Mt of 0.95 WO3
• Igneous Composition calc-alkaline granodiorite to granite
• Igneous geometry c.g. batholith with pegmatite, megacrysts
• Igneous alteration Fresh, minor myrmekite, Ca endoskarn
• Metamorphism Extensive metamorphic aureole (km)
with high T mineral assemblages and
reaction skarns (bimetasomatism)
Pine Creek, CAW skarn
Granodiorite
Skarn
Marble
Sub-calcic garnet
Calcic garnet & pyroxene
Scheelite
Sub-calcic garnet veins
Depth of Formation - Cu Skarns
• Tonnage and grade 500 Mt of 0.8% Cu
• Igneous Composition calc-alkaline diorite to quartz monzonite
• Igneous geometry m.g. to porphyritic stocks and dikes
• Igneous alteration K-silicate, sericitic, epidote endoskarn
• Metamorphism Variable metamorphic aureole (cm to
km) lacks high T mineral assemblages
Distal Features - Zn Skarns
• Tonnage and grade 50 Mt of 10% Zn, 5% Pb, 150 g/t Ag
• Igneous Composition granodiorite to granite to unknown
• Igneous geometry batholith to stocks to dikes to unknown
• Igneous alteration Extensive epidote±garnet endoskarn
• Metamorphism Bleaching and recrystallization,
no high T metamorphic aureole
Skarns and Skarn Deposits
1) General processes of skarn formation
2) Mineralogy, petrology, & tectonic setting
3) Examples of major skarn deposits: Antamina - Peru
Ertsberg District - Irian Jaya
Skarns and Skarn Deposits
1) General processes of skarn formation
2) Mineralogy, petrology, & tectonic setting
3) Examples of major skarn deposits: Antamina - Peru
Ertsberg District - Irian Jaya
Skarn deposits of Peru
Antamina Cu-Zn skarn, Peru
1) > 1 billion tons of Cu-Zn resource
2) ~ Barren porphyry intrusive center
3) Abundant endoskarn
4) Classic skarn zonation
Quartz monzonite porphyry
Endoskarn
Porphyry
Green garnet skarn
Garnet
Pyroxene
Garnet
Wollastonite
Marble
Garnet skarn
Calcite ± wollastonite veining
Gray marble
Fluid escape structures
Marble
What if Turkey had as many ore deposits as Peru?
Turkey ore deposit density by analogy with Peru
Ertsberg Cu-Au district, Irian Jaya
1) > 2 billion tons of Cu-Au reserves, largest Cu-Au resource on Earth
2) ~ Mineralized porphyry intrusive centers
3) No endoskarn
4) Classic skarn zonation
Tembagapuramine camp housingfor ~ 7,000 workers
Tram car carries50-100 workersat a time up to mine site
Mine site at 4,000 mUsually is in clouds
Tram station atmine site, lookingdown to mill site
in valley
Tramstation
Original Ertsbergore body
Tramstation
Tramstation
Yellow Valleysyncline
Puncak Jaya5000 m
Grasberg pit
Marble
Diorite
Endoskarn
Mt-cp-bn
Mg skarn with olivine, monticellite, vesuvianite
Mg skarn with retrograde serpentine veins
Biotite hornfels
Garnet vein Pyroxene envelope/vein
Red-brown garnet Anhydrite
Cp
Cp
Cp
Cp
Cp
Red-brown garnet Pyroxene
Pyroxene-chalcopyrite skarn
Distal diopsidic pyroxeneAnhydrite Late Fe-rich pyroxene
Fluid escape structures in marble
Gar P>G Pyx Marble
Fluid escapestructures