Geology & GeoMetallurgy

Geology & GeoMetallurgy 2017-03-23T09:44:23+00:00
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Geo-chemical signature of copper deposits (5 replies)

OberstGruppen
1 year ago
OberstGruppen 1 year ago

I'm working on Exploration of Copper Strata bound Deposits "Manto Type Cu-Ag", and well I want to know about the Geo-chemical signature of this type of deposits?

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

It seems that manto deposits, especially Chilean ones, are quite variable and rich in terms of geochemical information. This is true for accessory elements (see for instance Sn, Sinclair, British Columbia) and for alteration patterns.

Alteration patterns may be controlled by underlying lithology and by hydro-geothermal factors as much as by ore genesis processes. I would suggest using extensively multi-element analyses (ICP, ICP/MS, XRF) at the reconnaissance stage.

Beware, this felsic magma is one of the richest in dissolved sulphide. Subsequently one of the most prone to ARD. I mean not only mining drainage (AMD), but also naturally acid drainage (ARD sensustricto). I already tested pristine mountain creeks with pH 4-5.

OberstGruppen
1 year ago
OberstGruppen 1 year ago

Indeed all the lithology is Cretacic Volcano-Sedimentary sequences, lava flows and breccias andesitic composition. The mineralization is mainly copper sulphides (Bn-Cpy-Cc- and Sulphides Cu-Ag) and appear as a dissemination - patches and veins, but the alteration, as Fernando said, is K-Fdp, Si, Ep, Cl, Prenhite also baritine, but in the most of cases they are affected by regional metamorphism. So the alteration guide sometimes appear or not. And the Mineral controls are Structural mainly and lithology because the mineral host rock on Vesicular andesitic lavas and volcanic breccias.

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

Metamorphic-metasomatic minerals are a class in their own, because they reflect the specific geochemistry of alteration minerals and zones, but "cooked" by contact or regional metamorphism.

A few examples:

Andalusite, corundum and diasporas on advanced argillic zones (cationic deficit > Al silicates or oxides)
Chloritoid on Fe-chlorite prophylactic zones
Gahnite on zinc-rich aureoles.

Many epidotes belong to this class. These minerals are fantastic exploration guides for clever geologists!

OberstGruppen
1 year ago
OberstGruppen 1 year ago

Thanks a lot for the tips. I'm on surface exploration at the moment, so your help are welcome! Now I work having in mind these entire mineral to describe much better the alteration of the zone, any news soon.

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

I have an old paper on meta-advanced argillic minerals, if you like.

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