For some late weekend musings on Yappsu and the nature of...

For some late weekend musings on Yappsu and the nature of magmatic Ni Cu in Chronoliths...sweet dreams:
GLTAH and DYOR

Compiling some of the information given about Yappsu gives this rough data.

So far there have been 5 holes that have intersected significant mineralization as shown on this long section.  This reveals a zone (that remains open) some 250m long with massive sulphides in the hanging wall (top of zone) and very significant disseminated mineralisation below averaging well over 50m of probable true thickness at what looks to be a very consistent grade.

Hole 79, at least on this section, appears to be an infill hole that continues to verify this continuity and style of mineralisation.  The azimuth (nearly E-W) of 79 is almost at right angles to previous drilling and IMO was drilled to test some geological and perhaps geophysical theories as well as confirming the prior results - more bang for the buck?.


the Yappsu intrusion is a slab-like body, striking east-west and plunging to the west. The massive sulphide mineralisation intersected to date, is interpreted to be hosted within a bulge or flexure of the host intrusion, with the flexure and thus massive sulphide mineralisation striking in a north-westerly direction.
What does this mean?  EW strike OK.
Slab? plunging to the W?? Structural geology was not something I liked so this confuses me a bit.  Dip yes  or plunge anywhere but East or West.  So another question I would have if ever chatting to staff. (C.f Arunta "syncline")
The mineralisation is within the plane of the body/slab so as a flexure within it it plunges NW.

Another feature of the mineralisation is that the massive sulphide zone occurs above the disseminated mineralised zone.  This probably means that the massive sulphides have been structurally concentrated from ?elsewhere because most processes of Ni/Cu mineral formation initially invoke gravity separation from complex processes (mentioned below).

A resource model is beginning to shape up at Yappsu and further drilling will define what is or isn't there. So questions such as those above, while intriguing for me and perhaps other explorationists, are side issues.

For this weekend I have been doing further research on the other deposits mentioned in this week's announcement with special attention to the term "chronolith" that is mentioned in context with Ni Cu deposits.


My initial research was into the Eagle Deposit of Michigan where I made an assumption about the Eagle East deposit being the main section of the mine.  This is definitely not the case although it may be in the future.  The initial discovery hole was into the Eagle deposit much closer to surface where the bonanza came in this hole:

The link to the Eagle deposit report is in this post.  I have extracted most of the geological information from that report into this PDF.

Section 8 is fairly pertinent and gives IMO a good summary of magmatic sulphide deposits and a range of their formative processes.


At Eagle East the exploration apparently lacked any geophysical support but relatively simple geometry and structure allowed for assumptions to be made that led to a discovery within the "chronolith" as described in the report.  I can understand surface geophysics not being effective at the depth of the deposit but wonder why down hole electrical methods were not used to vector towards massive sulphide mineralisation as I expect the WMP team to do.

I still do not fully understand what a "chronolith" is!

These definitions don't help me much ....
I suspect chronolith is a generic term for certain types of intrusives (Lopoliths/Laccoliths/Dykes/Sills etc) where there may be highly variable shapes but the intrusives are in some way connected in time and origin.  Some may be mineralised....
It is used for Yappsu, Nebo-Babel and many other massive sulphide related deposits including the Sudbury meteor impact deposits and Norilsk.



The WMP doesn't show up on this graph (yet) but hopefully will in the future.  There is so much information available it is difficult to know whether to even begin to touch on it.

My search for information on Chronolith Nickel led me to a complete book on the Sudbury Deposits by P. Lightfoot which IMO is worth a look for anyone interested in going beyond basics up to PhD level of Ni/Cu/PGE deposits.  For those interested, on P572 (copyright) there is a pseudo section of Voisey's Bay showing how complex the "chronolith" is with multiple deposits forming in different areas.  I imagine the concepts shown in this image and other sections are ones the WMP team are applying to their work albeit in a different geological setting.