Geology & GeoMetallurgy

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Identification Of Minerals From A Potential IOCG Formation (4 replies)

6 years ago
Chifita 6 years ago

I recently came across such a mineralisation from an area with a lot of Hematite-Magnetite and just on the peripheral zones of the Lufilian Arc in Kasempa District of Zambia. I carried out a research which indicated that it was acicular malachite! I need help on what this mineral is.
6 years ago
David 6 years ago

It appears your colours are way off on the first two photos as I'm seeing a lot of blue tint to your specimens.

With that said, I'm not sure you have malachite. To me, some of the crystals I'm seeing look dubiously like dioptase, a secondary copper silicate mineral and not uncommon in the oxidized zones of some copper deposits. I've included a paper below on the Lufilian IOCG that talks briefly about the presence of dioptase in the arc.

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6 years ago
(unknown) 6 years ago

in Chile several drills in a IOCG deposit could show us copper oxides and malachita in the first mineral horizons like the copper leaching. But the characteristic in that kind of deposit to me was the mineral association formed for hematite (specular) with calcocite (chacolcite) in levels under the copper oxides. For another hand, the veins in or at the border mineralization were full of albite o feldespar K (white).

5 years ago
Robert 5 years ago
1 like by Bob Mathias

Look through the four papers below as they provide coverage of minerals observed with IOCG deposits. Links to the papers are provided.

  1. Corriveau, L., Iron oxide copper-gold (-Ag-Nb-P-REE-U) deposits: a Canadian perspective


2. Groves, D.I., et al., Iron Oxide Copper-Gold (IOCG) Deposits through Earth History: Implications for Origin, Lithospheric Setting, and Distinction from Other Epigenetic Iron Oxide Deposits, Econ. Geol., vol. 105, 2010, 641-654.


3. Hunt, J.A., et al., A Review of Iron Oxide Copper-Gold Deposits, with Focus on the Wernecke Breccias, Yukon, Canada, as an Example of a Non-Magmatic End Member and Implications for IOCG Genesis and Classification, Exploration and Mining Geology, Vol. 16, Nos. 3–4, p. 209–232, 2007.


4. Williams, P.J., Iron oxide copper-gold deposits: geology, space-time distribution, and possible modes of origin, Econ. Geol., Economic Geology 100th Anniversary Volume, 2005, 371-405.

5 years ago
Mathias 5 years ago

Regarding the weird looking malachite, this mineral is readily soluble in weak acids. So it should reacht with hydrochloric acid. Did you test that?

Regarding the other material. Frankly, I don't know. The images are not the best in my opinion and I do not like uneducated guessing. But the sample is fairly large so there is sufficient material both for a decent thin-section, polished section, and/or X-ray diffraction analysis. All 3 should be able provide a definitiv ID of the material. It would also verify without any doubt if you truly have malachite. XRD would probably be the fastest method.

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