A favorable magmatic signature for a porphyry copper may not indicate tonnage of copper...but there might be a lower bound. Either in copper tonnage, or volume of source rock.
Fertility is not for nothing. Take the following image from my own research project. We have what is considered favorable geochem...and favorable drilling (core) but nobody knows a thing about the size of the source magmatic body. We are right on the edge of a large magnetic anomaly of unknown affinity...and we have a few hundred million tons of inferred resource...but where did it come from...and more importantly...how big is that source...in terms of cubic kilometers.
Note: We have quartz eye phenocrysts, mafic enclaves, polylithic sulfidic breccia fragments, tourmaline breccias, chalcopyrite with sphalerite "copper disease", bornite, a bit of orthoclase and perhaps pyroxene in association with amphibole bearing mafic intrusives close to the same 14my age.
The main issue is "size" of the source "granodiorite" material.
The various source granites at Yerington Nevada that Dilles published on are known...I claim there must be a connection between fertility, as measured petrochemically by whatever means and the size of the source in which it developed.
Pretty little thing isn't it. We do have a lot more work...not reported here. It is in "terra incognito" really. Right on the miocene trend and on the famous Domeyko fault though.
Size....it's a quality of its own...right? Mass balance considerations might lend a clue.
Here is the Yerington geology....my take is that porphyry deposits are as much gas as fluid and only to a minor extent actually magmatic. However, the size of the "source rock" lithology is considered important to most considerations.
Tosdahl seema to say that you don’t get fertility indicators if the magmatic source is “small”. It probably indivates a reservoir of 10x 15 km. And down 4 km if it is Cu Mo…seedahl’s type three?
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