Dear Prof. Urbina,

yes, there is a transition. We have just finished a work on the mineral deposits of the Patagonian Shelf, Argentina, where a gradaul change perpendicular to the geodynamic evolution of the crustal section can be recognized from epithermal systems of low- to intermediate sulfidation. Another paper is just going to be revised. This paper also shows transitions form low to intermediate sulfidation. It is related to As-bearing borate deposits, some of which are also known from Mexico (Magdalena borate deposit in Sonara Province). It an ultimate end member state of this "catena metallifera". Describing deposits, using pigeonholing is a good and efficient way; I do it by myself (see the Chessboard classification scheme of mineral deposits...). In nature, transitional changes, however, are much more the rule than the exception. This is also valid for economic geology and the wide range of mineral deposits.

Best regards

Harald G. Dill

Dear Prof. Dill,

Thank you very much for your reply. Is it possible that you send me a copy of the work that you did in the Patagonia Shelf, Argentina? I suppose it refers to epithermal deposits in the Santa Cruz province. Your paper certainly would be very useful and helpful for me.

Also, if it's not too much trouble for you, I'd like, if you can, send me the paper on Chessboard classification scheme of mineral deposits.

Best regards,

Nilda E. Urbina

Dear Professor Urbina,

I am sorry to say that I cannot yet send you the papers you requested because they are still in different stages of the publishing process. I can send you a different one from the same area.

With regard to the "Chessboard classidication scheme of mineral deposits....." I have had permanent trouble to upload the over-size file (56 MB) onto the RG server. Please send me a message with your  E mail. I will try and find an alternative way to get the over-size study through to you.

With my best regards

Harald G. Dill

Dear Professor Harald,

I understand. Where and when you believe that your work will be published? I hope you let me know when this happens. With regard to the "Chessboard classification scheme of mineral deposits" please send it to me at the following e-mail [email protected]

Thank you for your kindness!

Nilda Urbina

Dear Professor Urbina,

I will keep you posted on the progress of the paper under review and I will try and find a solution to dispatch to the "Chessboard Classiication scheme..."

Best regards for now.

Harald G. Dill

True intermediate sulphidation epithermal where an ore fluid passes from high to low sulphdiation is quite rare and is characterised by advanced argillic wall rock alteration developed during the high sulphidation event. What is commonly called intermediate sulphidation in the literature is actually low sulphdiation, typically of the carbonate-base metal Au style, with near neutral wall rock alteration. There is a progression within the intrusion-related low sulphidation epithermal ore fluid type from quartz-sulphide Au to carbonate-base metal then bonanza Au .... see the attached paper or www.corbettgeology.com

Greg

Dear Harald,  I'll be waiting for your papers. Thank you for your kindness!           Nilda Urbina

Dear Greg,

thank you very much for your reply! I already made the download of your paper. The problem I have is that, on the surface, the deposit is typically low sulphidation epithermal based on their mineralogy and salinity of fluid inclusions. However, in depth, is enriched in Ag and base metal sulphides and the fluid inclusions are rather higher salinity as is typical for intermediate sulfidation. There are no high sulphidation epithermal mineralization in the area.

Thanks for your concepts!!

Nilda Urbina

As I said any association between intermediate and high sulphidation is quite rare. What you are calling intermediate sulphidation is typical intrusion-related low sulphidation in the earlier Leach and Corbett classification. The Intermediate sulphidation classification as presented in phase diagrams is quite rare in the field and it isn't correct the way the use of the terminology has been expanded. There is a common zonation in these systems from Ag with pyrite sphalerite>galena at depth to a chalcedony dominated assemblages at higher levels, possibly with ginguro. All quite normal as more meteoric waters come in at higher levels and the ore fluids evolve. Have a look at the model presented in figure 9 in the attached paper from the symposium we ran to honour the late Terry Leach. It works better in short course presentations with the rock photos.

Greg

Dear Greg,

I find both papers very interesting! Thank you very much for your time and for sharing your knowledge with me. I did the download of the latest paper and I think the Fig. 9 represents very well what you explain me in the text above. It is also very similar to what occurs in the deposits studied by us. Now, when you say "Earlier Leach and Corbett classification" refers to Special Publication 6 of Society of Economic Geologist (1998)? (I have it). Also, I know some of your other works as epithermal Gold for Explorationists (2002), or that from the Ishihara Symposium (2003), etc.

Anyway, this exchange is helpful and enlightening for me, mainly because I didn´t have these files you sent me. Thank you very much!

Nilda