Автор(ы):Robin E.Harmer
Издание:PGS Publishing, Linden Park, 2002 г., 10 стр.
Mineralisation of the Phalaborwa complex and the carbonatite connection in iron oxide-Cu-Au-U-REE deposits

The family of Proterozoic iron-oxide copper-gold deposits have as a unifying characteristic mineralisation which is dominated by titanium-poor iron oxides in which the total rare earth elements (REE) are enriched. The REE are typically LREE enriched and are concentrated in apatite and/or discrete REE phases. Carbonatites typically contain low-Ti02 magnetite and apatite as minor phases and are characterised by elevated total REE with extreme enrichment of LREE over HREE. Copper and gold are not, however, commonly associated with carbonatites.

МеткиCarbonatite, Copper, Gold, Iron oxide, Phalaborwa, REE, Uranium
Автор(ы):David I.Groves, Noreen M.Vielreicher, Richard M.Vielreicher
Издание:PGS Publishing, Linden Park, 2002 г., 9 стр.
The Phalaborwa (Palabora) deposit and its potential connections to iron-oxide copper-gold depositsof Olympic Dam type

Phalaborwa is the second largest copper mine in the world and the largest in Africa. The orebody is hosted by the Loolekop pipe within the Phalaborwa Complex, and is also mined for magnetite, apatite, vermiculite with a large array of by-products including gold, silver, phosphate, rare earth elements and uranium. The Phalaborwa Complex intruded Archaean basement at the edge of the Kaapvaal Craton in early Proterozoic times (2060±lMa) and consists of concentrically zoned, multiple intrusions which decrease in age from the margin to the core. The outer parts are predominantly clinopyroxenites, which have been variably metasomatised. Younger pegmatoidal pyroxenites intruded at three centres, including Loolekop, where foskcritc and a banded carbonatite were also emplaced, followed by a transgressive carbonatite that intruded as the last magmatic phase along fracture and shear zones. Economic copper mineralisation is hosted predominantly within the transgressive carbonatite as disseminated grains and veinlets of chalcopyrite, with lesser bornite and cubanite. Magnetite is a primary igneous phase in all rocks and is paragenetically earlier than the copper sulphides. The quality and quantity of magnetite is zoned and its distribution is antithetic to that of copper. Ore fluids are high temperature, highly saline, CO,-rich, magmatic-water dominated brines. The Complex and the mineralisation are interpreted to be products of the interaction of multiple pyroxenitic to carbonatitic magmas and their volatiles, which were ultimately derived from decompression melting of metasomatised mantle during extension at a transition from thick Archaean to thinner post-Archaean lithosphere. The orebody at Loolekop has many features including its age, giant size, pipe-like form, low ore grade, minor and major element associations and ore-fluid properties that are consistent with it being a proximal endmember of the widely recognised iron-oxide copper-gold deposit group. As such it helps explain characteristics such as the pipe-like brecciation as well as the common siting of these deposits at craton edges or other lithospheric boundaries.

ТематикаПолезные ископаемые
Автор(ы):Petrus J.Fourie
Издание:PGS Publishing, Linden Park, 2002 г., 12 стр.
The Vergenoeg fayalite iron oxide fluorite deposit, South Africa: some new aspects

Felsic rocks of the Rooiberg Group, which constitutes the roof of the Bushveld Complex., host the discordant volcanic pipe and associated surrounding pyroclastic and sedimentary rocks, called the Vergenoeg suite. The volcanic pipe is situated at the crossing of strong aerial photo and magnetic lineaments, about in the centre of the four lobes of the Bushveld Complex in the Republic of South Africa.

The Vergenoeg suite constitutes of an uppermost stratiform sedimentary unit, followed by fragmental conformably stratified hematite and hematite-fluorite units. This is followed by a breccia agglomerate and then a basal unit of ignimbrites. A discordant volcanic pipe completes the suite. The Vergenoeg volcanic pipe has a vertical funnel-like shape. At the surface this is about 900 m in diameter, tapering sharply in depth to where it is still open-ended at more than 650 m. Horizontal zoning exists in the pipe, with a hematite-fluorite or gossan cap at surface, followed by a deeper zone of unoxidised magnetite-fluorite, then a magnetite-fayalite transition zone and finally a fayalite zone at the deepest levels. Fluorite, siderite and pyrite veins, dykes and lenses are present throughout all the zones. Contacts between zones are gradual but are sharp with the felsic host rock. Felsite breccias, cemented by fluorite, siderite and pyrite are found at depths.

ТематикаПолезные ископаемые
МеткиFluorite deposit, Iron oxide, Vergenoeg fayalite
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