22-49 zone is an Iron Formation (source of Fe and S)
Porphyries have mafic-rich side (southern) and quartz-rich
side (northern)
strat. bottom strat.
top
Diorite Ores are Iron Formations on lava tops
Minor post-mineral dikes cut through mineralized porphyries
(# 6)
Spinifex lavas form underwater?
1.
Pontiac Province + porphyries :
2686
2.
oblique collision Abitibi D1
3.
hydrothermal alteration – mineralization
4.
D2
5.
Hydrothermal alteration – mineralization
6.
D3
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Core kept at Gov. : 22-429, 22-433, 22- 489,
22- 318
Total of 342 m
LOCAL
SEQUENCE OF EVENTS
Metavolcanics were faulted on top of northern parts of
Pontiac along steep-angle, reverse faults, such as the CTZ
2690 – 2675 Metamorphism of volcanics
max. 2691 – 2682
Sediments ( Kewagama, Cadillac,
Pontiac )
sediments + chert
F2
2682
Lamaque Plug - oblique accretion of oceanic plateau
onto an island arc
2685
Camflo Quartz monzonite
2700
Bourlamaque batholith syn – volcanic
2705 – 2706
Volcanics - oceanic plateau,
flow-tops = diorite ores
ARCHEAN EVENTS
Volcanism ended 2.70
VMS 2.75 - 2.65
BIF : 2.73 Au: 2.73 with D2
Post – Plutonic
: 2.65
Deformation ended, craton stabilized 2.50
Older in the north than in the south by 20 – 30 m.y.
----------------------------------------------------------------- .
OROGENIC
GOLD
DEPOSITS
Archean gold deposits ; 20 % of gold deposits
Excluding the super giants > 2,500 tonnes Au Witwatersrand
> 2,000 tonnes Au Golden Mile, Kalgoorlie
> 1,000 tonnes Au Hollinger – McIntyre, Timmins
Archean Superior + Slave cratons have 220 known deposits
with > 1 tonne Au
14 deposits have > 100 tonnes Au : regarded as “world class” (East Malartic is one)
majority contain
0.44 – 10 M t of ore at grades of 4 -
12 g/t Au
YILGARN
craton: 16 deposits with
> 1 t Au
15 world – class mining camps
