I did ask the same question during one of our postgraduate group discussion when I was studying at Hokkaido University, Japan from 2007 to 2010.
Some of the group members gave their individual opinion but I never even researched on it to understand it myself. I was actually researching on a massive sulfide deposit at that time.
The question came about because I come from an island country (Papua New Guinea) with similar geological setting as Japan and both countries are located along the Pacific Ring of Fire. PNG has a number of porphyry deposits whereas Japan has none.
The contributions from a number of experts in "Thematic Article, Resource Geology, Vol 68" have given more insights into the geological factors why porphyry type deposits were geologically denied to evolved in Japan.
Many thanks to those authors.
Regards,
Shadrach
Interesting question that brings out the whole setup of porphyry type deposits.
I would say there will be such deposits in Japan in the future many millions of years from now.
Right now there is not enough space for intrusions to get hydrothermally altered and mineralized "in place" surrounded by thick continental crust.
The porphyry copper deposits are probably just very deep and still need to be eroded.
I think that 2 of the papers from the Thematic Issue of Resource Geology that you mention have addressed this issue quite well. The potential reasons for a lack of porphyry deposits are laid out by Richard Sillitoe, and he makes some good arguments as to why they are not likely in Japan even in "hidden" settings. On the other hand, the potential for undiscovered porphyry deposits in Japan is well-supported by Arribas and Mizuta.
I will cite the papers here for others to reference:
Sillitoe, R.H., 2018, Why No Porphyry Copper Deposits in Japan and South Korea? Resource Geology, 68, 107-125.
Arribas, A. and Mizuta, T., 2018, Potential for Porphyry Copper Deposits in Northern Tohoku (or the Exploration Potential for Base and Precious Metal Deposits in Japan 2020). Resource Geology, 68, 144-163.
Yes, Joshua Ehlich is correct, there is a difference of opinion. In the same issue we argued that many of the present (active) volcanic-hydrothermal systems in Japan have characteristics consistent with a deeper porphyry system, although whether or not the magmas are sufficiently Cu-rich to form an ore deposit is still a question, as discussed in the same issue by Hattori. The paper mentioned above by Arribas and Mizuta is included here, which stresses the right setting but a shallow level of erosion.
Thank you all for your comments and sharing of articles (JH). Much appreciated.
My apologies for excluding your paper Jeff! It was not intentional, I simply did not have access to it before. In particular, I think Figure 6 from your study does an excellent job of conceptually supporting your arguments.
Regards,
Josh
Thanks for sharing the articles and comments. I believe in the second view where the deposits occur at depth.
porphyry comes within the evolution of magmatic arcs along convergent plate margins where subduction of oceanic crust and arc-type magmatism generates hydrous, oxidized upper crustal granitoids genetically related to ores.
Porphyry copper deposits are formed on arc islands, not Japan on the arc island. Alteration zones are also low in Japan, but generally porphyry copper deposits in Japan cannot be denied.
I asked Dills this question. He dodged it. I think it is because the crust is too thin and too soft. Poor sealing. That's my take. You get massive sulfides where the crust is thin. The intrusions just don't stop at the 4km boundary and "cook". The break between plastic and brittle failure is probably indistinct. That's my guess.
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