Page 15 of the AMEC presentation ."Classic Archaean Greenstone...

Page 15 of the AMEC presentation .

"Classic Archaean Greenstone Komatiite-hosted (Kambalda-type) nickel sulphide deposit"


Kambalda's nickel deposits are believed to have formed approximately 2.7 billion years ago. The deposits were formed in lava channels, created by 'rivers' of lava that extended for many miles. Under the right circumstances, nickel sulphides pooled at the base of these lava flows, forming ribbon-like lenses of sulphides. Over the eons the landscape on which these rivers of lava and their associated pools of sulphides were formed were buried and folded, so that today the sulphide pools are found in a variety of configurations, from vertical (as at Miitel) to flat-lying but gently plunging (as at Otter Juan).

Due to the circumstances of their formation, all of Kambalda's ore deposits share certain characteristics, which aids in their exploration. Most importantly, they all occur on the so-called 'basal contact'. This is the contact between the underlying basalt rock (the surface upon which the lava originally flowed, and into which channels were cut by the flowing lava) and the overlying ultramafic rock (known as Komatiite, which was the actual lava that flowed upon the basalt). It is in incised channels in the basalt, on the contact between the basalt and the overlying Komatiite rock, that all Kambalda's significant ore bodies are found. Thus modern exploration for Kambalda-style nickel deposits focuses on exploring this basal contact.

The original formation of the river-like channels, and the pools of sulphides that developed along them, create another characteristic that is important in their exploration. That is, that nickel sulphide ore bodies tend to be elongated and ribbon-like, and present continuously or intermittently along well-defined 'channel structures' incised in the basal contact. Thus once a sulphide ore body is discovered, and the hosting 'channel structure' defined, then that channel structure can be pursued through exploration, and even where the sulphide ore body ends, further exploration along the channel is likely to discover further 'pools' of sulphides (ore bodies). This characteristic has been widely exploited by Mincor, and has led to important discoveries at Miitel, Mariners, Otter Juan and Carnilya Hill.