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Pahtohavare

Norbotten, Sweden

Main commodities: Cu Au
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The Pahtohavare Cu-Au deposit is hosted within the Palaeoproterozoic Central Lapland greenstone belt approximately 15 km southwest of Kiruna, in the Norrbotten region of northern Sweden.

The host 2200 to 2130 Ma host Kittilä greenstone, a volcaniclastic unit in the Viscaria Formation of the Kiruna greenstone belt, comprises mafic volcanic rocks with pillow lavas, mafic sills and albitised rocks, which include tuffites, black schists and mafic sills, together with carbonates and the mineralised zones (Lindblom et al. 1996).

The mineralisation is dominantly stratabound, with several east-west trending, copper-, zinc-, and uranium-dominated ore bodies within a sequence of greywacke, phyllite, black schist, mafic tuffite and lava, and chert (Lindblom et al. 1996).

The deposit consists of four separate ore bodies. The Eastern body is a stratabound Cu-deposit that occurs as thin intercalations in the host tuffite. This is a small uneconomic deposit. More significant deposits are the three transgressive epigenetic occurrences in a tectonically disturbed environment. The Central, South and Southeast ores are gold-bearing Cu-deposits, hosted in zones of fine-grained albitised rocks within tuffite, black schist and mafic sills. Graphite horizons in the albite-altered black schist have been replaced completely in the most intensely mineralised sections. Albite-altered zones are symmetrically surrounded by barren biotite-scapolite-altered rocks. Scapolite (marialite) occurs as porphyroblasts and irregular veinlets or networks. Coarse-grained carbonate veins are common, both in ores and in surrounding altered rocks. Quartz veins have a similar occurrence, but are found mainly as irregular masses within ores. Pyrite, chalcopyrite and gold are the main ore minerals and are found in albitised rocks as impregnations, veinlets and breccia fillings with carbonate and quartz (Lindblom et al. 1996).

The Pahtohavare area has been folded in response to shearing along a sequence of large WNW-trending faults or shear zones, which have produced favorable permeability zones for epigenetic solutions (Bergman 1993). Ore bodies have been emplaced in completely deformed host rocks.

Mineralisation occurs as impregnations, epigenetic quartz-rich breccias and fracture fillings in a complex tectonic environment. The epigenetic ores are predominantly pyrite and chalcopyrite, with locally significant pyrrhotite, and minor amounts of associated sphalerite, galena, molybdenite, cobaltite, linneaite, pentlandite, mackinawite, millerite, native gold, hessite, melonite, altaite, tellurobismuthite, rutile and ilmenite have also been found (Halenius 1985,1986,1989). Tellurides and native gold occur as inclusions in sulphides and quartz. Fluid inclusions indicate an early formation of quartz and pyrite at temperatures initially near 500°C and a pressure of 2 to 2.4 kbar from a supersaturated aqueous solution of magmatic origin. In addition to halite cubes, daughter minerals of sylvite, calcite, hematite and graphite are found. The main stage of chalcopyrite and gold deposition is characterised by aqueous fluids of variable salinity (up to 30 wt.% NaCl including CaCl2), at temperatures below 350°C and pressures between 1 and 2 kbar (Lindblom et al. 1996).

Production from this mine between 1990 and 1997 is reported as:
   1.7 Mt with recovered grades of 1.9% Cu and 0.9 g/t Au.

An associated gold resource is understood to contain 4.3 Mt @ 2.6 g/t Au.

The most recent source geological information used to prepare this summary was dated: 2004.     Record last updated: 2/11/2012
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
 References to this deposit in the PGC Literature Collection:
Frietsch R, Tuisku P, Martinsson O and Perdahl J-A,  1997 - Early proterozoic Cu-(Au) and Fe ore deposits associated with regional Na-Cl metasomatism in northern Fennoscandia : in    Ore Geology Reviews   v12 pp 1-34
Lindblom S, Broman C, Martinsson O,  1996 - Magmatic-hydrothermal fluids in the Pahtohavare Cu-Au deposit in greenstone at Kiruna, Sweden: in    Mineralium Deposita   v31 pp. 307-318


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