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rkiye Jeoloji Kurultayi

Exploration for Skarn Deposits

Larry Meinert Department of Geology Smith College Northampton, MA 01063 USA Email: [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 Igneous Composition Igneous geometry Igneous alteration Metamorphism 63 Mt of 0.95 WO3 calc-alkaline granodiorite to granite c.g. batholith with pegmatite, megacrysts Fresh, minor myrmekite, Ca endoskarn Extensive metamorphic aureole (km) with high T mineral assemblages and reaction skarns (bimetasomatism)

Pine Creek, CA W skarn

Skarn Granodiorite Marble

Sub-calcic garnet Calcic garnet & pyroxene

Sub-calcic garnet veins Scheelite

Depth of Formation - Cu Skarns

• • • • • Tonnage and grade Igneous Composition Igneous geometry Igneous alteration Metamorphism 500 Mt of 0.8% Cu calc-alkaline diorite to quartz monzonite m.g. to porphyritic stocks and dikes K-silicate, sericitic, epidote endoskarn Variable metamorphic aureole (cm to km) lacks high T mineral assemblages

Distal Features - Zn Skarns

• • • • • Tonnage and grade Igneous Composition Igneous geometry Igneous alteration Metamorphism 50 Mt of 10% Zn, 5% Pb, 150 g/t Ag granodiorite to granite to unknown batholith to stocks to dikes to unknown Extensive epidote±garnet endoskarn 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

Tembagapura mine camp housing for ~ 7,000 workers

Tram car carries 50-100 workers at a time up to mine site

Mine site at 4,000 m Usually is in clouds

Tram station at mine site, looking down to mill site in valley

Tram station Original Ertsberg ore body

Tram station

Tram station

Yellow Valley syncline Puncak Jaya 5000 m

Grasberg pit

Marble Endoskarn Diorite

Mt-cp-bn

Mg skarn with olivine, monticellite, vesuvianite

Mg skarn with retrograde serpentine veins

Garnet vein Pyroxene envelope/vein Biotite hornfels

Red-brown garnet Anhydrite Cp Cp Cp Cp Cp

Red-brown garnet Pyroxene

Pyroxene-chalcopyrite skarn

Anhydrite Late Fe-rich pyroxene Distal diopsidic pyroxene

Fluid escape structures in marble

Fluid escape structures Gar P>G Pyx Marble