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Mar 2009 - NW/SE Special?

What is so special about NW/SE

No matter where you go in the world, the number of orebodies that we (ERA) have encountered where the feeder structure is or appears to be striking NW/SE or NNW/SSE is simply staggering, especially for gold.

So far this year, Kingsgate at Chatree in Northern Thailand (which we visited in late January 2009), the new mineralisation trend as shown in Figure 1a along the west side of Hill A strikes NNW/SSE (heading for Far Q), and looking back in a SSE direction is in line with KE and D.

Since then, we visited Apex (AXM)’s Wiluna in Northern WA in late February 2009, and observed that the rock units strike NW/SE as does Golden Age, with Calais having formed at the intersection of Golden Age with the East Fault Structure (striking NNE/SSW) in that position. Wiluna in fact could be NW/SE structures feeding into N/S striking structures.

AXM also bought Gidgee for Wilsons and Youanmi. Gidgee’s orebodies run N/S except that the best orebody was Kingfisher, and that strikes NW/SE. Gidgee’s Wilsons’ ore shoots strike...NW/SE. Youanmi’s main structure and main pit strikes.....NW/SE.

Last year, we visited Mineral Deposits’ Sabodala in Senegal, and the feeder structure strikes.......NW/SE, feeding into N/S striking structures. It is not confined to gold mineralisation either, Albidon’s Munali nickel mine in Zambia lies within a major NW/SE striking structure.

We remarked to AXM’s Mark Bennett (when we were onsite at Wiluna) as to why no matter where you are in the world, the orebodies often strike NW/SE feeding into N/S or NE/SW structures. Mark said that he recalled a paper (/thesis?), which showed that the main structures of the earth could be overlain by a lattice of parallelograms (whose sides were orientated NW/SE and NE/SW).

We can recall (quite a few years ago now) a representative of Placer Dome telling us that the key signature that they looked for in aeromag was a reverse (greek, lower case) lambda character. A conventional lambda has a main NW/SE axis with a NE/SW “stub”, whereas a reverse lambda has a main NE/SW axis with a NW/SE “stub”

Granny Smith was a reverse lambda as was Sunrise Dam and apparently Wallaby and Red October too. Kingsgate’s C-H pit is another classic example with the main H pit striking NE/SW intersecting the C pit striking NW/SE.

However, what we (ERA) are increasingly encountering is either reverse lambdas where the main long axis is NW/SE feeding into a NE/SW structure (resembling more a mandarin “ren” or person character). Such as Sino Gold (SGX)’s Jinfeng (previously called Huangchangguo) gold mine in Guizhou Province, China as shown in Figure 1b, with the main F3 structure feeding into the F2.

Such lambda’s can also have the NW/SE structure feeding into a N/S vertical structure. Alternatively, the mineralisation can simply align to NW/SE or NNW/SSE as the dominant feeder such as the west side of A at Chatree, or the Kingsgate’s new Chokdee discovery (about 20km NE of Chatree).

Consequently, what we (ERA) have increasingly become aware of, is that although gold and other fields do have a renowned orientation for their mineralisation, sometimes it does pay to look for those possibly hidden NW/SE structures as they could be the main feeder zones or structures for the field.

Disclosure and Disclaimer : This article has been written by Keith Goode, the Managing Director of Eagle Research Advisory Pty Ltd, (an independent research company) who is an Authorised Representative with Taylor Collison Ltd, and with his associates, may hold interests in some of the stocks mentioned in this article. The opinions expressed in this article should not be taken as investment advice, but are based on observations by the author. The author does not warrant the accuracy or completeness of any information and is not liable for any loss or damage suffered through any reliance on its contents.

Figure 1a. Plan of Kingsgate’s Chatree NorthGDNmar09

  • Written by: Keith Goode
  • Sunday, 01 March 2009

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