The 2740 Ma Côté Gold Au(-Cu) deposit,

Canada: Example of porphyry-type

magmatic-hydrothermal ore-forming

processes in the Archean

Daniel J. Kontak, Laura Katz, Laurentian University

Benoit Dubé, Geological Survey of Canada

(Thanks to: D. Beilhartz, J. Rogers, V. McNicoll, R. Creaser,

B. Lafrance, J. Smith)

+8 Moz Au (0.9 g/t Au) deposit centred on a 2740 Ma

magmatic-hydrothermal breccia complex!

Introduction

Introduction: Where does Côté Gold fit?

Porphyry, IOCG, syeniteXX

XX

Robert et l 2007; Poulsen et al. 2000

Summary of Work to Date dkontak@laurentian.ca

Kontak, D.J., Creaser, R.A., and Hamilton, M. (2013): Geological and geochemical studies of

the Côté Lake Au(-Cu) deposit Area, Chester Township, northern Ontario. In Results from the

Shining Tree, Chester Township and Matachewan Gold Projects and the Northern Cobalt

Embayment Polymetallic Vein Project. Ontario Geol Survey, Miscellaneous Release Data 294.

Rogers, J.R., Beilhartz, D., Kontak, D.J., Katz, L. Dubé, B., and McNicoll, V. (2013): The Côté

Gold deposit: discovery of a new generation low-grade, multi-million oz gold resource in the

Archean Superior Province, Canada. Program Vol.. NewGenGold 2013, Perth, Australia., 159-174.

Katz, L.R., Kontak, D.J., Dubé, B., and McNicoll, V. (2015): The Archean Côté Gold intrusion-

related Au(-Cu) deposit, Ontario: A large tonnage, low-grade deposit centred on a magmatic-

hydrothermal breccia. In: Targeted Geoscience Initiative 4: Contributions to the Understanding of

Precambrian Lode Gold Deposits and Implications for Exploration, (eds) B. Dubé and P. Mercier-

Langevin; Geological Survey of Canada, Open File 7852, 139-155.

Katz, L.R. (2016): Geology of the Archean Côté Gold Au(-Cu) Intrusion-Related Deposit, Swayze

Greenstone Belt, Ontario, PhD thesis, Laurentian.

Smith, J. (2016): Integrated structural and geochemical study of auriferous sheeted quartz veins

in the 2740 Ma Côté Gold deposit, Swayze Greenstone Belt, Ontario, MSc thesis, Laurentian.

Katz, L.R., Kontak, D.J., Dubé, B., and McNicoll, V. (2016): Geology, Petrology and

Geochronology of the Archean Côté Gold Large-Tonnage, Low-Grade Intrusion-Related Au(-Cu)

Deposit, Swayze Greenstone Belt, Ontario, Canada. Canadian Journal Earth Sciences.

Côté Gold 2740 Ma

Introduction

VMS, syenite, orogenic Au

deposits (<2710 Ma)

Dubé and Gosselin (2007)

Introduction: Site visit Summer 2010Breccia (1-3/g/t) Breccia and stock work

Tonalite breccia

Sheeted fractures/veins

1 km

Introduction – The Discovery!

Historical drill hole

(130m @ 1.3 g/t Au)

zone ofelevated Cu

open

zone ofelevated Cu

open

E09 -02

E09 -02

E10

-04

1.1446.6

1.9971.6

0.6980.16

8.20107.1

1.396.8

1.45178.8

2.4957.3

0.938.8

E10-1

1

0.90107.9

0.6661.6

1.2727.0

E10

-12

E09

-03

E10

-04

0.5253.5

3.363.8

0.7238.9

8.772.10

8.0617.9

E10

-26

0.88292.0

E10

-20

E10

-05

1.3420.1

E10

-30

0-4

6

0.90388.0

E

Section 93+00E – facing SE

Ore envelope

136 m @ 1.2 g/t

Introduction – The Discovery!

What is it?

430000

Nature of the Sheeted Veins (?)

1 km

1

1

2

3

3

2. Quartz-sericite-pyrite-(carb)

Côté Gold 2740 Ma

Regional Geology

Dubé and Gosselin (2007)

Chester Group (2739-2734 Ma): subaqueous volcanics (felsic to

intermediate and mafic) and sediments (clastic and chemical (BIF))

Chester Intrusive Complex (2741 Ma): multiphase, laccolithic shaped,

subvolcanic suite of tonalite-diorite-gabbro

Regional Geological Setting

Facing directions

Mafic to felsic

Regional Geological Setting(Gemmel 2015 OGS)

Tonalites – East CIC

(Berger 20123)

Tonalite

Tonalite

Yeo Fm

Is the tonalite at the Côté

Gold deposit different

that regional tonalite and

if so why???

Côté Gold Deposit Geology2740 Ma Tonalite I (Qtz-Plg (An30))

2740 Ma Diorite (Hbl-Plg (An50))

2740 Ma Magmatic-

hydrothermal biotite breccia

rota

ted

Gold deposit

(+8 Moz Au @ 0.9 g/t)

Breccia type

Fracture type

Côté Gold Deposit Geology

AB

A

B

0.5 mm

Deposit Geology: Tonalite (I, II)

Hornblende diorite (and evolved phases)

Côté Gold Deposit: Diorite

Hbl geobarometry = 1.5 kbar

Whole Rock Geochemistry

Whole Rock GeochemistryC

ho

nd

rite

/Ro

ck

Pri

mit

ive

ma

ntl

e/R

oc

k

Tonalite (I, II)

Diorite suite

Diorite

Breccia (magmatic/hydrothermal)

Côté Gold Deposit: Breccia

top

bottom

Use of logging, petrography and

lithogeochemistry (>500 samples)

Qtz-Plag-Biot/Chl … vs Biot-rich

1 mm

Côté Gold Deposit: Breccia

Gold deposit

(+8 Moz Au @ 0.9 g/t)

Breccia type

(disseminated)

Fracture type

AB

A

B

Nature of Mineralization (ca. 0.9 g/t Au)

Nature of Mineralization (ca. 0.9 g/t Au)

1) Disseminated:

- F gr disseminated in

matrix of diorite breccia

and hydrothermal biotite

breccia

- Altered tonalite/diorite

2) Fracture and vein

controlled

3) Re-Os m,oly ages

(n=4) ca. 2740 MaVG

VGMoly

Nature of Mineralization (ca. 0.9 g/t Au)

Hydrothermal breccia

(Mo-Cu-Ag-Zn-Te-Se-F)

Nature of Mineralization – Miaroles (?)

Alteration Types

Biotite Sericite Sodic(Silica) Epidote

Early Late

Breccia matrix BrecciaTonalite Diorite

Magmatic breccia

Hydrothermal breccia

Alteration Types: Distribution

1 mm 0.5 mm

Biotite Alteration (Biot-Mgt-Apt-Carb-Sulf)

1 mm

Nature of Alteration: Biotite

Nature of Alteration: Biotite (Qtz-Mag-Apt-Carb-Sulf)

Biotite altered tonalite (n=20)

Bast

All

Epid

50 μm 500 μm

Fe

FeT

Mg KP Zn

Cs

Ba

LREE

Li

Te

1 mm

Apt

Apt

F

Nature of Alteration - Biotite

disseminations breccias (Au)

vein

s

Oxidation (?)

Nature of Alteration – Sericite (Qtz-Ser-Carb-Py)

Si Al Fe FeT Mg Ca Na K Ti P Li Rb Cs Sr Ba La Ce Dy Yb Au Cu Zn Te Bi F S C LOI

Sericite altered tonalite (n=19)

Sericite altered diorite (n=5)

K Li

Rb

Cs

Ba

C

LOI

K Li

Rb

Cs

Ba

C

LOI

Au

Cu

F

S

Nature of Alteration – Sodic (Alb-Rt-Tit-Fuch)

- Coincident with breccias

- Cross cuts units and ore zones

- Overprints earlier alteration types

Nature of Alteration - Sodic

Titanite = 2740 Ma CA TIMS age

Nature of Alteration - Sodic

Mass balance:

Tonalite = +Na2O, Sr(?)

Diorite = +SiO2, Al2O3, K2O,

Na2O, Rb, Cs, Ba, LREEs

Albite altered tonalite (n=9)

Albite altered diorite (n=9)

Si Al Fe FeT Mg Ca Na K Ti P Li Rb Cs Sr Ba La Ce Dy Yb Au Cu Zn Te Bi F S C LOI

Si Al Fe FeT Mg Ca Na K Ti P Li Rb Cs Sr Ba La Ce Dy Yb Au Cu Zn Te Bi F S C LOI

Nature of Alteration - Sodic

Episyenites

S Isotopes (Cpy, Moly, Cpy): δ34S = -1.5 to 1.0‰ (avg. 0‰)

δ34SH2S = 0‰

O Isotopes (Qtz veins) δ18O = 9.7 to 11.3‰ (avg. 10.0‰)

δ18OH2O @ 350-400°C = 4-7‰

O Isotopes (Carb veins): δ18O = 7.4 to 8.8‰ (avg. 8.4‰)

δ18OH2O @ 350-400°C = 3-6‰

C Isotopes (Carb.) δ13C = -0.9 to -4.4‰ (avg. -2.0‰)

δ13CH2CO3 @ 350-400°C = -5‰

Suggests mixing of fluid types – magmatic and

seawater (?)

Nature of Fluids (Stable Isotopes)

Summary Côté Gold Deposit Formation

1. Amph-biot alt, breccias 2. Regional veins

3. Sericite (epid) 4. Sodic

MFMF

MF + SWSW + MF

Summary Côté Gold Deposit Formation

Is this a porphyry-type system, if so what are the

implications for metallogeny and exploration?

J. Richard 2011

Diorite-tonalite complex

Fluids (K-Fe-Au)

Côté Au

Melts ??

1 km

Two More Important Points(J. Smith MSc 2016)!

1. Candy Cane

2. South Breccia

1) Origin of the sheeted

quartz-sericite-pyrite

veins/alteration

2) Evidence for upgrading

due to deformation

The Sheeted Veins

London DerryChester

Nebaskwasi

144

Sheeted veins and alteration haloes

pre-date regional deformation

The Sheeted Veins

Lithogeochemical transect records same fluid-

isotopic signature as main Côté deposit!

10 cm

Over Printng Deformation vs Au Grade

Evidence for Au upgrading

due to deformation?