SH7424 : Coed-y-Brenin Porphyry Cu-Mo Deposit - Phyllic Zone

taken 7 years ago, near to Ganllwyd, Gwynedd, Great Britain

Coed-y-Brenin Porphyry Cu-Mo Deposit - Phyllic Zone
Coed-y-Brenin Porphyry Cu-Mo Deposit - Phyllic Zone
Porphyry copper deposits are of a major economic importance due to the high tonnage (but often low grades) of copper, molybdenum and gold. This deposit contains 200Mt of ore at 0.3% Cu with some Mo and Au. It would be economic only through opencasting, which I can't see happening any time soon!

A process that made PCDs economic was developed in the area, at Glasdir copper mine SE of here. SH7422 : Glasdir Copper Mine LinkExternal link

Hyrdothermal and magmatic fluids circulate to create alteration zones. The ore is usually hosted in the outer edge of the stock.

Potassic zone, usually a igneous stock (volcanic magma chamber).
Can be rich in secondary orthoclase, quartz, biotite and chlorite/sericite.

Phyllic zone, altered host rocks. In this case volcanics and sediments.
Pyrite rich (10-15%), quartz, sericite, chlorite and illite.

+/- Argillic zone. Varies in size, clay alteration.

Propylitic zone, always present. Lightly altered with pyrite, chlorite, quartz, carbonates and epidote.

This shows the phyllic zone. The pyrite has oxidised to produce the red stained colour.
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SH7424, 8 images   (more nearby search)
Photographer
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Date Taken
Sunday, 31 March, 2013   (more nearby)
Submitted
Wednesday, 3 April, 2013
Geographical Context
Geological interest 
Subject Location
OSGB36: geotagged! SH 7474 2495 [10m precision]
WGS84: 52:48.4505N 3:51.5819W
Camera Location
OSGB36: geotagged! SH 7471 2494
View Direction
East-northeast (about 67 degrees)
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