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The Jaguar sulphide nickel deposit, is located in the southwestern section of the Carajás Mineral Province, ~150 km WSW of Parauapebas, and ~90 km SW and ~110 km west of the Salobo and Sossego IOCG deposits respectively.
It lies between the Onça and Puma lateritic nickel deposits that are hosted by Neoarchaean layered mafic-ultramafic complexes that are each <10 km to the NE and south respectively.
The deposit lies within the Carajás IOCG Province and the Archaean Carajás Domain, close to the contact with the Rio Maria Archaean Domain to the south. It is also close to the intersection of the major, broad, east-west Canaã and NE-SW McCandless fault systems. For detail of the geological setting of the Carajás Domain, see the Carajás IOCG Province record.
Geological units mapped in the area of the Jaguar deposit include:
• Banded felsic gneiss and migmatite basement rocks of the late Mesoarchaean Xingu Complex.
• Large plutons of massive to weakly foliated medium-grained granitic rocks, including granite and granodiorite, likely to be part of the Neoarchean Plaquê Suite (Leite, 2001);
• A volcanic-sedimentary sequence, mainly composed of mafic and felsic metavolcanic rocks, which regional mapping shows to belong to a greenstone belt of the older Andorinhas Supergroup (Vasquez et al., 2008). However, on the basis of a 2.74 Ga U-Pb zircon date from a felsic metavolcanic within the sequence (Vale internal report quoted by Ferreira Filho et al., 2021) this sequence is alternatively interpreted to belong to the 2.76 to 2.73 Ga Itacaiúnas Supergroup. The most prominent geomorphologic feature of this unit is an arcuate ridge that is up to 300 m higher than the surrounding terrane. This ridge is composed of banded iron formations of the Serra Arqueada iron ore deposit.
• Mafic and ultramafic intrusions, which include the Serra da OnÇa and Serra do Puma Complexes (Macambira and Ferreira Filho, 2002; Ferreira Filho et al., 2007; Rosa, 2014). These host the large Onça and Puma lateritic nickel deposits as described in the link above. These layered complexes may also be intruded into the weakly foliated granitic intrusions of similar age and may in part be intrusive equivalents of the mafic volcanism of the Itacaiúnas Supergroup. The Serra do Puma Complex follows the major McCandless fault zone, while the The Serra da Onça Complex is elongated along the Canaã fault trend (Ferreira Filho et al., 2007; Rosa, 2014).
• Younger dolerite dykes that are 3 to 5 m thick and are part of a regional swarm. These dykes are not affected by the widespread hydrothermal alteration that has variably altered granitic intrusions, layered complexes, volcanic-sedimentary rocks and gneiss-migmatite of the Xingu Complex.
Robust magnetic anomalies reflect the Serra da OnÇa and Serra do Puma layered intrusions to the NE and SW of Jaguar and the banded iron formation of the Serra Arqueada to the south.
The Jaguar deposit comprises a 3 km long, WNW trending corridor of discontinuous lens-shaped sub-vertical bodies enveloped by hydrothermally altered rocks. Mineralised outcrops are rare, as the deposit occurs in a flat terrane with rare outcrops in contrast to the steep elongated ridges of the Serra do Puma Complex to the north and Serra Arqueada deposit in the south. Mineralisation lies within a complex collage of Xingu Complex gneissic rocks, fragments of layered mafic-ultramafic rocks of the western Serra do Puma Complex, granitic intrusions and felsic subvolcanics rocks on the northern portion of the Itacaiúnas Supergroup volcanic-sedimentary sequence. Zones of mineralisation ore predominantly found close to the contact between the felsic subvolcanic rocks to the south and the Xingu granitic-gneissic rocks to the north. The lens-shaped mineralised bodies are up to 2 km long with widths varying up to 80 m, and are concordant with the WNW regional structural trend. The mineralised have gradational contacts with the wall rocks, characterised by the increasing abundance of hydrothermal minerals toward the mineralised centres.
The host felsic subvolcanic rocks to the south are massive, dark grey and porphyritic, with abundant euhedral to subhedral phenocrysts of albite and blue quartz set within a very fine-grained matrix of quartz and albite, with subordinate biotite and amphibole. The primary mineralogy suggests a dacitic composition. Albite phenocrysts occur as tabular crystals up to 4 mm long and may locally constitute >50 vol.% of the rock. In contrast phenocrysts of K feldspar are less abundant. Quartz phenocrysts are up to 5 mm across and exhibit corrosion embayments typical of volcanic to subvolcanic rocks. Accessory minerals include apatite, magnetite, ilmenite, allanite and titanite, with subordinate biotite, chlorite and amphibole, which become progressively more abundant towards mineralisation, commonly occurring within weakly foliated and magnetic rocks, the result of weak hydrothermal alteration of the igneous protolith.
In the northern section of the deposit, the host to the Ni sulphide mineralisation is a massive granitic rocks with a predominantly tonalitic composition. The area occupied by these rocks have previously been mapped as gneissic-migmatitic lithologies of the Xingu Complex, and hence may be more extensive that originally expected. They are light grey, medium to coarse-grained and massive, composed of quartz, plagioclase, biotite and minor K feldspar, with magnetite, as well as carbonate veins. Biotite and chlorite alteration of the igneous protoliths becomes more abundant in altered rocks close to the mineralisation, where an incipient to strong foliation is developed.
In addition, crosscutting relationships suggest two distinct sets of mafic dykes are also host and country rocks respectively. The older of the two are a dark grey and moderately magnetic dolerite, composed of coarse-grained plagioclase and clinopyroxene phenocrysts set in a fine-grained intergranular matrix. Its primary igneous assemblage is variably altered to fine-grained biotite, chlorite, epidote and amphibole. The second set are also dolerites, and are dark grey, isotropic and moderately magnetic. They crosscut the Ni mineralisation, its host rocks, and the older dolerite dykes, and have a pristine igneous mineralogy, an ophitic or subophitic texture, and chilled margins at the contact with host rocks and the older dolerite dykes.
Alteration and Mineralisation
Three main alteration assemblages have been recognised in association with the Jaguar deposit, with the highest grade nickel sulphide mineralisation being associated with the youngest. The type and intensity of alteration and mineralisation vary throughout the deposit, although these assemblages define a consistent paragenetic sequence, as follows:
• Biotite-chlorite, which represents an early alteration phase varying from minor to moderate (~30 vol.%) replacement of the host felsic subvolcanic or granitic rocks, grading up to pervasive alteration masses. It mainly comprise a fine-grained intergrowth of biotite and chlorite forming fine-grained biotite and chlorite lamellae that typically define mylonitic foliated bands, alternating with fine-grained quartz- and plagioclase-rich bands. The mylonitic foliation envelops quartz phenocryst relicts in altered felsic subvolcanic rocks are exhibit pressure shadows. In highly altered and sheared zones, phenocrysts of albite and quartz are typically fractured, and become completely replaced by the alteration assemblage. In weakly altered rocks, white mica (sericite) commonly replaces relict albite of the host rocks. Locally, intra-foliation folds occur, with crenulation cleavage defined mostly by chlorite. Whilst biotite and chlorite are commonly associated, the relative abundance of biotite and chlorite in these alteration zones is highly variable, forming alternating bands up to tens of centimetres in thickness. Chlorite occurs in equilibrium with biotite as chlorite I in the chlorite-biotite assemblage, but is also observed replacing biotite as chlorite II associated with talc and quartz.
• Amphibole-biotite, which is less common, occurs as discontinuous lenses associated with zones of both of other two alteration types. The principal amphibole is fine-grained actinolite, although medium-to coarse-grained hornblende is also observed. This alteration assemblage occurs as massive to foliated bodies and may represent a late replacement of the biotite-chlorite assemblage. As the mineralised zone is approached, amphibole-biotite alteration crosscuts the mylonitic fabric defined by the early biotite-chlorite alteration.
• Magnetite-apatite, which occurs as structurally controlled zones that host the highest ore grade mineralisation, and commonly crosscuts and overprints both the biotite-chlorite and amphibole-biotite assemblages. It comprises medium-grained, subhedral, apatite and magnetite with associated fine-grained granular quartz. Amphibole (actinolite/hornblende) and biotite may be associated with magnetite-apatite-quartz alteration, although these minerals are typically less abundant than in other two alteration assemblages. Fluorine and P2O5 are particularly enriched in the magnetite-quartz-apatite alteration zones.
Mineralisation occurs as two closely associated styles that form multiple steeply dipping, generally WNW-ESE trending bodies that range from a few tens are up to 100 m in thickness, have vertical extents of ~100 up to 450 m and strike lengths of <300 to 1750 m:
Type I, the most abundant, is predominantly contained within biotite-chlorite alteration zones but mostly comprises low grade mineralisation. It comprises sulphide bearing veins and veinlets that are either foliation parallel, or are controlled by discordant fractures, or occur as zones of disseminated sulphides. The contacts between sulphide veins and the host biotite-chlorite altered wall rocks is commonly marked by the alteration of biotite to form chlorite- and talc-rich selvages.
Type II is closely associated with the magnetite-apatite-quartz alteration, and includes the highest nickel grades, but is less abundant than Type I. It occurs as breccia bodies, composed of irregular clasts of extensively altered host rocks within a sulphide-, magnetite- and apatite-rich matrix. Mineralised breccias form up to 80 m thick zones parallel to, or crosscutting, biotite-chlorite alteration zones. The breccias are predominantly clast-supported, although matrix-supported varieties are also recognised.
These two distinct styles of mineralisation do not form readily differentiated blocks, but are irregularly developed and closely associated, with zones of one type commonly grading into the other. The sulphide assemblage in both is mainly composed of pyrite and millerite, with variable but generally minor pentlandite, chalcopyrite, pyrrhotite and sphalerite. Pyrite predominantly occurs as euhedral to subhedral crystals but may form irregular anhedral aggregates. Millerite is present as very fine-grained intergranular networks enclosing pyrite grains or aggregates, and is locally partially altered to violarite. Chalcopyrite was formed as very fine-grained crystals, commonly associated with pyrite, but is also enclosed within silicates. The sulphide mineralisation is closely associated with magnetite and apatite, commonly enveloping euhedral to subhedral magnetite or magnetite-apatite aggregates. Magnetite crystals also surround some sulphide grains or aggregates. Small grains and aggregates of magnetite, pentlandite, pyrrhotite and chalcopyrite are enclosed in pyrite crystals. The predominant sulphide assemblage, which comprises fine-grained millerite- and pyrite-rich aggregates, is possibly the product of alteration of an original pentlandite-pyrrhotite assemblage, which is now mainly preserved as inclusions within large pyrite crystals. Pentlandite occurs as coarse blocky aggregates surrounded by an intergranular matrix of pyrrhotite. Pentlandite is more abundant in Type II mineralisation and may be moderately altered to violarite along grain boundaries and grain partings. Sphalerite also occurs within the sulphide-rich matrix and commonly exhibits aligned fine-grained inclusions of chalcopyrite.
The Jaguar deposit has many of the characteristics of iron-oxide-copper-gold (IOCG) mineralisation, and is located within the Carajás Mineral Province, one of the World's premier IOCG districts. Ferreira Filho et al. (2021) suggests this indicates Jaguar and the major Carajás IOCG deposits all belong to a common regional hydrothermal system. Other deposits in the district, such as GT-34 and Castanha, have been previously proposed to be the Nickel-rich members of the IOCG family of deposits. The same authors also suggest the close association between nickel sulphide mineralisation and magnetite-apatite-rich breccias at Jaguar may be interpreted to suggest its association with the iron-oxide-apatite (IOA) stage of the regional IOCG hydrothermal system. It must be appreciated that the deposit also lies within a district that includes significant layered mafic complexes, over which large lateritic nickel deposits have been exploited, as at OnÇa and Puma, detailed above. These layered complexes are located within a few kilometres of Jaguar, and hence may have been leached of nickel by the highly corrosive, hydrofluoric acid bearing hydrothermal fluids associated with the regional mineral system. The presence of hydrofluoric acid is indicated by the abundance of fluorine associated with the alteration accompanying the higher grade Ni mineralisation.
JORC compliant Mineral Resources as at 1 December 2021, using a within pit limits cut-off grade of 0.3% Ni; and below pit limits cut-off grade 0.7% Ni (Centaurus Metals Limited website, viewed December, 2021) were:
Indicated Resource - 0.9 Mt @ 0.86% Ni, 0.07% Cu, 0.0225% Co, 0.45% Zn;
Inferred Resource - 1.0 Mt @ 0.77% Ni, 0.08% Cu, 0.0251% Co, 0.24% Zn;
Indicated Resource - 42.4 Mt @ 0.92% Ni, 0.06% Cu, 0.0260% Co, 0.41% Zn;
Inferred Resource - 36.3 Mt @ 0.90% Ni, 0.07% Cu, 0.0252% Co, 0.31% Zn;
TOTAL Indicated Resource - 43.4 Mt @ 0.92% Ni, 0.06% Cu, 0.0259% Co, 0.41% Zn;
TOTAL Inferred Resource - 37.2 Mt @ 0.90% Ni, 0.07% Cu, 0.0251% Co, 0.31% Zn;
TOTAL Mineral Resource - 80.6 Mt @ 0.90% Ni, 0.06% Cu, 0.0256% Co, 0.36% Zn.
The information and most of the interpretations in this summary are drawn from Ferreira Filho et al. (2021) cited below.
The most recent source geological information used to prepare this summary was dated: 2021.
This description is a summary from published sources, the chief of which are listed below.
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Ferreira Filho, C.F., Oliveira, M.M.F., Mansur, E.T. and Rosa, W.D., 2021 - The Jaguar hydrothermal nickel sulfide deposit: Evidence for a nickel-rich member of IOCG-type deposits in the Carajas Mineral Province, Brazil: in J. of South American Earth Sciences v.111, 23p. doi.org/10.1016/j.jsames.2021.103501.|
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