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    The Broken Hill ore deposit (lead-zinc-silver)
                            (New South Wales, Australia) (abstract)


 
 
Empiricism rules:- The variable template provided by boudinage offers the key to the organising principle for the location of ore deposits worldwide. The application in this example, which illustrates the obvious link between boudinage structure and the setting of the Broken Hill ore body, one of the giant ore deposits of  the world, is still ignored in consensus literature. 


Fig.1.  Boudinage analogue for Broken Hill.    The mirrorred images above provide the answer to what used to be popularly known as the  'Broken Hill Enigma', namely the perplexing reason for the location of the giant ore deposit at Broken Hill:- it is located in the neck of a large-scale boudinage structure.  Simple.   Outcrop-scale analogue on the left, kilometre- scale analogue on the right.  Red circle on the right locates the Main Lode outcrop; the analogous position in outcrop-scale boudinage is on the left.  Inset above shows the location of the main shafts.

 
The web used to have numerous  references to "the Broken Hill Enigma",   but no more since the posting of this page.
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In the face of such an  obvious boudinage comparison it is perhaps difficult to believe from this point in time  that there was ever a question regarding the reason for the location of the giant lead-zinc-silver mine at Broken Hill..   But there was.   Ever since the discovery of the deposit in the late 1800's geologists have puzzled over this huge deposit, contention centering on whether the deposit was syngenetic or epigenetic and consensus coming down on the side of syngenesis (where the deposit is formed by the same climatic and geographical conditions that formed the host rock sequence).

But that 'consensus' ignores the boudinage signature in the figure.  Take the boudinage signature out of the picture, and try to see it  (if you can) through the perspective of it not being there, ..which consensus has done for the last fifty years and continues to do.   You will find no reference to a boudinage signature of the orebody by current researchers despite it not only having been  in the public domain for at least the last two decades (1982, 1994, 1998)  but having been vitually identified in the first comprehensive study of the field published in 1950. 

 

 . . . Boudinage of course is not the whole story as regards the formation of the ore body, but as far as the needs of empirical exploration are concerned it goes a very substantial way in the right direction.

In a boudinage model it is axiomatic that ore bodies are consanguineous with the strata in which they occur.  A syngentic component to the mineralisation is therefore not in question.   What is in question (the "enigma") is why such a large lump of economic mineralisation exists in one spot, and this requires more explanation than syngenesis can provide.  The summation of mineralising conditions is complex, but this is where a boudinage model is so empirically useful - there is no need to be concerned with abstruse or esoteric reasons for ore manufacture if in the end the  location is going to be something as obvious as the structural signature illustrated in the figure.  Emprically it is not difficult to check out such a location once it is identified.   What's more,  the model identifies where not to look, which a syngenetic model does not do.  In syngenesis you look everywhere along the favourable bed.   Which is expensive.
 

 


As far as mineral exploration is concerned the above figure encapsulates all that is relevant to understanding the location of the Broken Hill ore body, and supercedes the plethora of studies directed to this end, which ignore (or - believe it or not - cannot see) the boudinage structure apparent in the map section of the image (right).