60 Türkiye Jeoloji Kurultayi

Exploration for Skarn Deposits

Larry MeinertDepartment of GeologySmith CollegeNorthampton, MA 01063 USAEmail: Lmeinert@smith.edu

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