Super Porphyry Cu and Au|
IOCG Deposits - 70 papers|
|All available as eBOOKS|
Remaining HARD COPIES on
sale. No hard copy book more than AUD $44.00 (incl. GST)
|Big discount all books !!!
The Kalia iron deposits are located ~50 km WNW of Faranah, ~20 km north of the Sierra Leone border, and ~300 km ENE of the capital Conakry, which is situated on the Atlantic coast of the Republic of Guinea, West Africa (#Location: 10° 6'N, 11° 4'W).
The Kalia deposits lie within the northern half of the NNW-SSE elongated, 1000 x 600 km Man-Kenema domain (or shield), the southern of the two exposed inliers of the Archaean West African craton. The Man-Kenema domain is bounded to the east by the Palaeoproterozoic (2.21 to 2.07 Ga) Birimian domain, composed of metamorphosed sedimentary, lesser volcanic (mafic to felsic), and plutonic (mainly alkaline granites and granodiorites) rocks. To the west it is truncated by the 3000 km long, late Neoproterozoic Pan African Bassaride and Rokelide Fold Belts along the Atlantic coast if Guinea, Sierra Leone and Liberia, that extend northward, below cover, to Morocco. These include reworked Archaean basement but also Neoproterozoic metasedimentary sequences, including a basal tillite, carbonates and clastic units, and 725 Ma volcano-clastic rocks, all of which were metamorphosed and deformed between 570 and 500 Ma. The craton is overlain to the north by the Phanerozoic cratonic sediments of the vast Taodeni basin, which separates it from the similar Reguibat Shield to the north that hosts major iron deposits in Mauritania.
The Man-Kenema domain represents a long history of repeated volcano-sedimentary deposition, followed by granitic intrusion and metamorphism, divided into 5 phases:
i). Palaeoarchaean basement, occurring as a core of orthogneiss and 3.54 Ga metagabbro, which comprise the Dabola Group. These are overlain by
ii). Leonian-age supra-crustal rocks, comprising 3.24 to 3.03 Ga felsic and mafic volcanic suites, terrigenous sedimentary rocks and iron-quartzites (including BIF) of the Kambui Series which host the Kalia deposits. These rocks have undergone variable grades of metamorphism and are intruded by extensive younger granites;
iii). Liberian age intrusion, granitisation and metamorphism between ~2.91 and 2.80 Ga, including large batholiths of ~2.80 Ga intrusive rocks, mainly large batholiths of plagioclase-phyric granite-gneisses and gneisses, with zones of migmatisation and pegmatites;
iv) Post Liberian extension and deposition of mafic volcanic rocks, banded iron formation and pelitic sediments of the Nimba and Simandou successions, which have a minimum age of 2615 Ma (from a detrital zircon in the Nimba Quartzite). These sequences host the Nimba and Simandou iron deposits in SE Guinea, Cõte d'Ivoire and Liberia;
v). Eburnian deformation, granitic intrusion and metamorphism at ~2.05 Ga, producing NNE-SSW trending upright folds and associated retrograde greenschist facies
The Leonian-Liberian crystalline shield in the district surrounding the deposits, is mainly composed of Archaean granitoids and greenstone formations that constitute the Dabola Series crystalline schists and gneisses, and the Kambui Series greenstone rocks.
The iron deposits are hosted by the Mesoarchaean Kambui Series greenstones that occur as relict inliers, or rafts, in the dominant (~90%) Neoarchaean and Palaeoproterozoic plagioclase-phyric granite-gneisses and gneisses and by Palaeoproterozoic metasomatic and intrusive granites, granodiorites, granite-gneisses and migmatites.
The Dabola series comprises granulite facies plagioclase-phyric gneisses and crystalline schists, occurring as linear relicts within the Palaeoproterozoic granitoids. These gneisses are compositionally similar to tonalite-trondhjemite-granodiorite (TTG) "grey gneisses".
The Kambui Series is represented by fragments of the Mongo-Tinkissou greenstone belt, most commonly composed of amphibole-plagioclase and amphibole crystalline schists and amphibolites, with lesser pyroxene crystalline schists, secondary quartzites, and amphibole-magnetite-quartzites which are less common. This Series is locally subdivided into two suites;
i). the lower Mongo suite, which is up to 4000 m thick, and is represented by altered schists and amphibolites, with thin seam-like bodies of magnetite and cummingtonite-magnetite quartzites in the base of the sequence, overlain by by gneisses, magnetite-quartzites and amphibole schists (Deriugin Ju.N., 2003).
ii). the overlying Timbo suite, which is ~2500 to 3000 m thick and is characterised by a compositionally homogenous biotite-amphibole gneisses, that include bodies of magnetite and amphibole-magnetite-quartzites, and amphibolites.
The relict Dabola and Kambui Series rocks are surrounded by Palaeoproterozoic granite-gneisses, granodiorite-gneisses and migmatites that represent >90% of the district. Small rafts and enclaves of Neoarchaean plagioclase-phyric granite-gneisses, diorite-gneisses, plagioclase-phyric granites, migmatites, pegmatoids and enderbite-charnockite rocks, are also recognised, enveloped within the dominant Palaeoproterozoic granitoids, oriented roughly parallel to the regional tectonic fabric. The Palaeoproterozoic granitoid masses are mainly biotite and biotite-amphibole granite-gneisses, largely a metasomatic migmatite-granitoid complex that has reworked and granitised Meso- to Neoarchaean basement granite-greenstone rocks, almost completely destroying the initial boundaries.
Post-tectonic, batholiths of medium- to coarse-grained Palaeoproterozoic granites are widely distributed in areas where relicts of the Mongo-Tinkissou granite-greenstone belt are preserved. They are rounded in plan-view, and have porphyroblastic, leucocratic and mesocratic textures, and are either biotite- or biotite-amphibole granites. A series of small leucocratic and mesocratic granite intrusions (the Tokunu Complex) are also evident, comprising cores of medium- to coarse-grained varieties, fringed by fine-grained mesocratic granites on their peripheries. Younger, alkaline, metasomatic granites form small massifs, dykes and veins of variable thickness, commonly concentrated within, and on the contact zone of the relict greenstone belt.
Mesozoic dolerites, gabbro-dolerites and microgabbro dykes and sills are intruded throughout the district, within zones of tectonic dislocation with a mostly east-west strike.
Slivers of Kambui Supergroup rocks, with a cumulative strike length of 40 km in two main blocks, comprise the the Mongo-Tinkissou greenstone belt. The WNW-trending western block, containing folded, multiple limbs of the Kalia I BIF has been mapped over an interval of 19 km. This is separated from the Kalia II block, by a ~10 km diameter, roughly circular batholith of post-tectonic Palaeoproterozoic granite. The eastern block containing the Kalia II BIF, again occurring as 2 to 3 tightly folded limbs, is exposed over an interval of 20 km with an overall ENE to NE trend.
The Kalia I block of the greenstone belt is bounded to the south by Palaeoproterozoic granite gneisses, and to the north by biotite granite-gneisses and gneisses. The iron mineralisation occurs as a number of bodies of i). banded magnetite (BIF), ii). amphibole-magnetite schists and iii). talc-magnetite schists, with up to 14 mineralised zones identified in any drill section, each with a true width of up to 300 m. The apparent composite thickness of exposed magnetite mineralisation at Kalia I, varies from 2 to 4.5 km. The rocks of the Kambui Supergroup enclosing the iron mineralisation are represented by a wide spectrum of greenschist facies schists, including chlorite-amphibole, biotite-amphibole, pyroxene-amphibole, garnet-biotite-amphibole, chlorite and chlorite-talc varieties. In addition to the schists, amphibolites of different composition are widely developed. Minor sulphide mineralisation is evident, related to hydrothermal-metasomatic alteration of the BIF and enclosing schist. Bands of talc-rich assemblages, which range from 10 to >50 m in thickness, occur on the southern flank of the deposit. These include actinolite-talc and chlorite-talc schists, containing disseminations of magnetite.
The iron mineralisation and interbedded rocks at Kalia I, occur as steeply dipping monoclines or pseudo-monoclines with a general WNW (280 to 315°) strike, dipping steeply to sub-vertically at 70 to 80°SSW. The monoclinal structure is complicated by abundant small compressional folds and flexures. Granitisation and metasomatic alteration of the greenschist facies Kambui Supergroup rocks are observed near the southern contact with granite-gneisses.
The Kalia II deposit has a similar geology to Kalia I, although more structurally complex. The main folded BIF package, which is 150 to 500 m thick, occurs within the axial core of the greenstone belt. It is intensively faulted and folded, with steep 75° to vertical dips, underlain by a schistose unit, and overlain by schists intruded by metamorphosed gabbro. Individual BIF horizons within the package range from tens of metres to 300 m in thickness, inter-banded with un-mineralised schist zones and amphibolites that are 30 to 150 m thick. The exposed width of the greenstone belt varies from 2.5 to 2.75 km. The enclosing geology is a mirror image of Kalia I. Kalia II is bounded to the south and SE by a large intrusive body of mesocratic granites and granodiorite, possibly of Neoarchaean age. To the NW and west, the greenstone belt is truncated by the large Palaeoproterozoic monzogranite intrusive body that separates Kalia I and II. To the north, extensive alluvium obscures the geology.
The primary magnetite-quartzite banded iron formations occur as well bedded to laminated alternating bands of pale silica and grey magnetite, with weakly undulose banding from millimetric to centimetric scale, and intervals of soft-sediment deformation. Other magnetite bearing lithologies that are differentiated in core logging comprise: i). Magnetite rich rock where gangue minerals are predominantly amphiboles; ii). Magnetite rich rock where gangue minerals are secondary and mafic in origin, often banded; iii). Magnetite-rich schist; iv). Talc schist with accompanying magnetite; v). Rock of ultramafic origins with abundant magnetite; vi). Magnetite amphibolite.
The present surface in the Kalia district comprises an ancient erosion surface, complicated by generally NW-trending ridges and river valleys. The deposit area is almost totally covered by a weathering crust, with only rare outcrops of fresh bedrock. Laterite is developed across both the granites and greenstone assemblages, with iron oxide mineralisation formed directly above the BIF horizons and on the flanks of the ridges. There are three types of oxide iron mineralisation, namely:
Massive hematite-goethite is developed above the primary iron formation horizons, occurring at surface as a dense cap rock, or cuirassed layer, that becomes gradually less cemented with depth. These rocks represent dense and poorly-cemented small-debris and detritus breccias with a sandy and clayey cement, with the amount of matrix clay increasing with depth. Debris of differently oxidised iron mineralisation, and sometimes barren rocks and quartz, occur within the iron mineralised blanket. The size and amount of debris fragments decreases with depth, with the lower boundary defined by the appearance of relict, but oxidised BIF, in which leaching of silica is incomplete. This type of ore is developed over a thickness that varies from 4 to 5, up to >70 m, determined by local geomorphology. The greatest thickness is on ridge crests and plateaux where the erosion rates are low.
Canga iron mineralisation occurs as dense and solid dark-brown and reddish-brown rocks that have been eroded from massive iron oxide and BIF units and redeposited down-slope. The mineralisation is brecciated, cavernous and sometimes massive, containing mainly medium-sized angular and poorly rounded debris, and boulders sometimes of 1.5 to 3 m in diameter. Debris comprises oxidised mineralisation, with a range of composition, including hematite, goethite, magnetite-hematite, BIF and minor greenschist. The breccias are re-cemented with an iron rich matrix to produce a cap-rock like layer. The thickness of canga mineralisation varies from 3 to 18 m, with the greatest thickness typically close to the primary source of the mineralisation.
Pisolite-detrital mineralisation is widely distributed over the Kalia deposits, covering an area of ~20 km2, with the most significant occurrences of detrital fans to the east of Kalia I, and along the southern flanks of Kalia II. This type of mineralisation typically comprises detrital deposits that have been re-cemented with limonite, and to a lesser extent, by a vitreous goethite matrix, and like the massive iron oxide and canga mineralisation, have been cuirassed (cemented) on the surface where they are very dense. The degree of cementation decreases with depth where the matrix becomes sandier. Close to source, the mineralised zones contain debris of BIF, quartz, amphibolites and sometimes greenschist. The amount of gangue debris, which is softer, is broken down and decreases with distance from source. The mineralised debris consists of hematite, goethite and magnetite. Limonite is prevalent in the matrix, and is rarely found as debris. The matrix cement comprises sandy material with hydrous ferric oxides, which is frequently homogenous and dense where the hydrous ferric oxides are best develped. The thickness of mineralisation of this type is extremely variable.
Local geomorphology controls the thickness of massive iron oxide. Much of Kalia II is characterised by steep escarpments with acute ridge crests and little or no massive oxide remaining, although localised plateaux are capped by thin (<10 m) developments of iron oxide. At Kalia I, oxide has been developed over gentler slopes and wider plateau areas.
Published JORC compliant mineral resources (Bellzone Mining plc press release, 20th December, 2012) over a 4 km long x 2 km wide interval at Kalia I, based on 200 000 m of drilling, were:
Direct Shipping Ore at a 50% Fe cut-off
Indicated resource - 9.61 Mt @ 55% Fe, 6.7% SiO2, 6.6% Al2O3, 0.13% P, 0.01% S, 6.9% LOI;
Inferred resource - 77.89 Mt @ 54% Fe, 4.4% SiO2, 5.5% Al2O3, 0.09% P, 0.02% S, 9.3% LOI;
TOTAL resource - 87.50 Mt @ 54% Fe, 4.6% SiO2, 5.6% Al2O3, 0.09% P, 0.02% S, 9.0% LOI;
Oxide and supergene enriched BIF Ore at a 20% Fe cut-off
Indicated resource - 71.99 Mt @ 37.8% Fe, 22.7% SiO2, 12.8% Al2O3, 0.10% P, 0.13% S, 8.2% LOI;
Inferred resource - 750.57 Mt @ 36.7% Fe, 18.4% SiO2, 15.2% Al2O3, 0.08% P, 0.05% S, 10.4% LOI;
TOTAL resource - 822.56 Mt @ 36.8% Fe, 18.7% SiO2, 15.0% Al2O3, 0.08% P, 0.05% S, 10.2% LOI;
Measured resource - 240 Mt @ 27.9% Fe, 45.7% SiO2, 2.8% Al2O3, 0.07% P, 0.83% S, 1.6% LOI;
Indicated resource - 850 Mt @ 27.3% Fe, 46.1% SiO2, 3.1% Al2O3, 0.07% P, 0.96% S, 1.3% LOI;
Inferred resource - 3.540 Gt @ 25.4% Fe, 46.3% SiO2, 4.5% Al2O3, 0.08% P, 0.48% S, 1.4% LOI;
TOTAL resource - 4.630 Gt @ 25.9% Fe, 46.1% SiO2, 4.1% Al2O3, 0.07% P, 0.56% S, 1.4% LOI;
Inferred resource - 1.53 Gt @ 9.6% Fe;
TOTAL Magnetite resource - 6.16 Gt @ 21.9% Fe.
Metallurgical test work shows an average mass recovery of 31.86% giving 1.475 Gt of 68.7% Fe magnetite concentrate product.
In addition to the primary Magnetite ore, DSO, Oxide and Supergene BIF components of the Kalia resource, a low cost, stable, quality fines product of 309.2 Mt @ >58% Fe has been delineated over a strike length of 13 km of the total 39 km of mapped Oxide and BIF within Bellzone's Mining Concession (Bellzone Mining plc release, 2012).
The information in this summary is largely drawn from Titley M (CSA Global UK Ltd), 2010 - Competent Person's Report on the Mining Assets of Bellzone Mining Ltd,
Republic of Guinea, West Africa, 193p, downloaded from the Bellzone plc website, 2013.
The most recent source geological information used to prepare this summary was dated: 2010.
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.
Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.
Top | Search Again | PGC Home | Terms & Conditions