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Cassinga |
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Angola |
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Fe
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Cassinga iron deposit is located on the southern margin of the Angola-Kasai Shield, on the southern part of the Archaean Congo (Zaire) craton. It is 630 km by rail east of the Atlantic Ocean port of Namibe (Mocamedes) in southern Angola (#Location: 14° 40' 43"S, 16° 3' 14"E).
The Angola-Kasai Shield comprises a core of Archaean overlain by Paleo- to Neoproterozoic successions, intruded by Proterozoic granitoids and covered over large areas by mainly Mesozic to Cenozoic cratonic sediments. The succession is as follows, from the base:
i). Mesoarchaean - 3.4 Ga Upper Luanyi gneisses and migmatites, separated by an inferred fault from and the adjacent Kanda Kanda grey tonalites and granodioritic gneisses and alaskite gneisses;
ii). Kasai-Lomami gabbro-norite and the dark, acid, enderbitic-charnockitic assemblage, all of which have been metamorphosed to granulite facies, with a date of 2.8 Ga;
iii). Neoarchaean Dibaya granitic to tonalitic migmatite assemblage and calc-alkaline granites with metamorphic ages of between 2.82 and 2.56 Ga;
iv). Paleoproterozoic Luiza Supergroup - a meta-sedimentary sequence of quartzites, mica schists and iron formations unconformably overlying the Kanda-Kanda gneisses. Both the Luiza Supergroup and Archaean basement were deformed and metamorphosed by the earliest Eburnean event at 2.42 Ga.
iv). Possible Lukoshi metasediments, which with the Archaean basement were deformed and metamorphosed by later Eburnean events between 2.2 and 1.9 Ga and intruded by a post tectonic (2037 ±30 Ma) granodiorite.
v). Lulua Group - a meta-sedimentary and meta-volcanic suite up to 6000 m thick to the north of the Luiza Supergroup as a 170 x 20 km belt, composed predominantly of slates and quartzites which are intercalated with greenstones (1469 ±30 Ma spilitic, pillowed basalt lavas) and intruded by post tectonic 1468 ±30 Ma syenodiorite sills.
vi). Damara-Kaokoveld orogen sediments to the south.
The Cassinga deposits are developed within the iron formations of the early Paleoproterozoic Luiza Supergroup:
Three styles of ore and mineralisation are recognised:
i). Primary banded hematite iron formation containing 40% Fe. Resources of this ore type have not been mined (2000) and amount to approximately 1 Gt.
ii). Supergene enriched hematite ore with 62% Fe, 6% SiO2, 0.1% P. The reserves in 1970 were estimated to have been 11 Mt.
iii). Detrital (canga) ore in 15 different areas around the main deposit, with a grade of around 61% Fe, 0.04% P. The reserves in 1970 were estimated to have been 150 Mt.
Past production comprised 40 Mt of enriched in situ ore @ 50 to 60% Fe between 1957 and 1975, 6.1 Mt of which was mined in 1974. Proved and probable reserves are estimated at 34.2 Mt @ 44% Fe.
The most recent source geological information used to prepare this decription was dated: 2006.
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.
Cassinga
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