Spier C.A., Barros de Oliveira S.-M., Rosi?re C.A., Ardisson J.D. Mineralogy and trace-element geochemistry of the high-grade iron ores of the ?guas Claras Mine and comparison with the Cap?o Xavier and Tamandu? iron ore deposits, Quadril?tero Ferr?fe

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reached the unweathered BIF host rock in depth, allow us

to infer that siliceous itabirite is the protore of high-grade

ores in this mine and dolomitic itabirite is entirely absent,

either in the contact zone between ore and BIF or outside

this area. The evidences of structural control is, however,

very conspicuous in the Tamanduá Mine when compared to

the others. In this deposit, high-grade orebodies are

controlled by the hinge zone of hectometric large folds

and by the presence of igneous dikes as well, while in

Aguas Claras and Capão Xavier, the lithologic control is

more evident.

The weathering front in all mines is quite variable,

ranging from a few centimeters to some hundreds of

meters, and may reach, locally, depths of 500 m and deeper

(Figs. 2a and 5a,b). At the Capão Xavier Mine (Fig. 5a),

however, although weathering reached a similar depth both

in the dolomitic and siliceous itabirites, the final result is

quite different. High-grade iron ore was produced mainly

from the dolomitic itabirite, while low-grade ore was

formed from the siliceous itabirite. Both protores show a

transition zone from the BIF to the iron ore, with an iron

enrichment from the bottom to the top of the weathering

profile that is more gradual in the siliceous itabirite than in

the dolomitic itabirite.

Mineralogical and geochemical constraints on the origin

of the soft and hard ore at the Águas Claras Mine

Spier et al. (2003) advocate a hypogene origin for the hard

ore and a supergene origin for soft ore based on a series of

field relations, such as: (1) the occurrence of hard ores

within unweathered dolomitic itabirite; (2) the disappear-

ance of the soft ore down dip; (3) the late ral and vertical

transition of the soft ore to dolomitic itabirite; (4) the

presence of pockets of dolomitic itabirite within the soft

ore; and (5) the occurrence of slump folds in the soft ore.

The mineralo gical and geochemical data presented in

this study are not conclusive in relation to the assumption

of a hypogene origi n for the Águas Claras hard ore, as this

type of ore is predominantly formed by hematite. Hematite

has a very simple chemical composition and a wide stability

field, thereby restricting its use in metallogenetic studies.

On the other hand, the data clearly indicate a supergene

origin of the soft ore. The petrographic studies show that

the diss olution of the do lomitic bands of the itabirite

generates a highly porous material made of hematite and a

brownish residue. Petrographic and Mössbauer analyses

indicate that hematite was not affected by the meteoric

solutions and that the brownish residue comes from

dolomite weathering and dissolution. The SEM and TEM

analyses revealed the presence of iron and manganese

oxides within the brownish residue, whereas MS indicate

ferrihydrite in its mineralogical composition. These obser-

vations led to the conclusion that the dissolution of

dolomite during weathering produced solutions carrying

and Fe

. Calcium an d magnesium wer e leached out

from the weathering profile, wher eas iron and manganese

precipitated along pores and fracture planes forming Mn

oxides and ferrihydrite. Mass balance calculations of the

transition from dolomitic itabirite to soft ore (Table 6)

corroborate this conclusion.

Ferrihydrite is widespread in surface environments and,

unless stabilized in some way, is transformed into the more

stable goethite or hematite. Due to its metastable nature,

ferrihydrite is only found in environments where its

transformation into more stable oxides is inhibited or

Table 7 Summary of the major features of the Águas Claras, Capão Xavier, and Tamanduá orebodies

Águas Claras Capão Xavier Tamanduá

Protore Dolomitic itabirite Dolomitic and siliceous itabirite Siliceous itabirite

Local

Structure

Homocline with bedding dipping

from 60° to 70°

Eastern limb of the Moeda Syncline

with bedding dipping gently (maximum

angle of 45°)

Eastern limb of the Moeda Syncline.

Second-order fold (Tamanduá Syncline).

Ore types Only high-grade ore High- and low-grade ores High- and low-grade ores

Ore contacts Sharp contact between soft ore

and dolomitic itabirite

Gradual contact between soft ore and

dolomitic itabirite and also between low-

grade ores and siliceous itabirite

Sharp contact between high-grade ores and

siliceous itabirite and gradual contact

between low grade ores and siliceous

itabirite

Ore

resources

360 Mt of high-grade ore.

Predominate soft ore (∼85%)

260 Mt of high-grade ore (90% soft

and 10% hard ores)

281 Mt of high-grade ore (70% soft

and 30% hard ores)

235 Mt of low-grade ore (friable

siliceous itabirite)

390 Mt of low-grade ore (friable

siliceous itabirite)

Constraints

of the high-

grade ores

Soft ore is hosted only within

dolomitic itabirite and limited

to the weathering front

Soft ore is hosted mostly within dolomitic

itabirite and limited to the weathering front

High-grade ores occur mostly within

the Tamanduá Sinclyne and are limited

by mafic dykes

Data for ore resources on 01/01/2006 are from MBR and refer only to resources within the current pit limits.

Miner Deposita (2008) 43:229–254 249

retarded (Cornell and Schwertmann 1996). According to

Cornell (1988), the presence of transition elements such as

Mn can stabilize ferrihydrite. The close association of Mn

oxides with ferrihydri te in the residue of the dolomite

dissolution could, therefore, have been responsible for

inhibiting the transformation of ferrihydrite into hematite

or goethite. Ferrihydrite transforms into hematite at temper-

atures as low as 40°C, and the higher the temperature, the

more complete is the formation of hematite (Schwertmann

et al. 1985 ). Thus, if the soft ore had been produced by the

leaching of dolomite by hypogene solutions, ferrihydrite

would not have been found.

The calculated residual porosity of the soft ore (average

40.5%) from Aguas Claras is close to that visually

estimated on polished thin sections (35–45%), and these

values are very similar to those obtained by Ribeiro (2003)

on samples of weathered siliceous itabirite from the Pico

Mine, which corroborates the assumption of a supergene

origin of the high-grade soft ore.

The petrologic and mineralogical data presented in this

study supports previous works that show magnetite as the

oldest iron oxide of the iron mineral assemblages observed in

BIFs in the Quadrilátero Ferrífero (Rosière et al. 1993;

Rosière and Chemale 2000; Rosière and Rios 2004).

Although relics of magnetite are locally observed either in

hard or in soft ores, this mineral was submitted to a high

degree of martitization. This process occurred before the

genesis of the soft ore, considering the identical hyperfine

parameters of the iron oxides observed at MS analyses of the

dolomitic itabirite (protore) and of the soft ore. This is further

supported by chemical analyses of the dolomitic itabirite,

which reveal Fe

/(Fe

+Fe

) ratios close to 1 (Spier et al.

2007). Petrographic analyses also indicate that recrystalliza-

tion of martite during metamorphism and deformation

(probably during the Transamazonian Orogenesis (2.1–

2.0 Ga)) was responsible for the generation of the hematite

crystals within martite, a ccording to the mechanisms

proposed by Lagoeiro (1998), Hackspacher et al. (2001),

and Rosière et al. (2001) and corroborating the model

proposed by Rosière and Rios (2004) to explain the different

generations of iron oxides in the Quadrilátero Ferrífero.

The very simple chemical composition of the soft ore

and, even more, of the hard ore, both with respect to major

and trace elements, makes the utilization of geochemistry

for understanding the genesis of these ores a difficult task.

The high contents of elements like Na, K, Li, Be, and P in

the iron ores of the eastern side of the QF, typically

associated with granitic fluids, led Cabral et al. (2003) and

Lagoeiro et al. (2004) to sugges t that those ores were

generated or affected by hydrothermal solutions produced

during intrusion of granitic bodies in the country rocks in

the adjacent area of the mine. The very low contents of

those elements in the soft and hard ores of the Águas Claras

Mine, however, do not indicate the participation of granitic

fluids in their genesis.

The difference in the heavy REEY

PAAS

patterns of hard

and soft ore samples (Fig. 12c, Table 5) is ano ther indi-

cation for the distinct origin of these ores. The soft ore

shows a REEY

PAAS

pattern identical to that of the dolomitic

itabirite (protore), even when the porous and massive bands

are separately analyzed (Fig. 12d), indicating that the

REEY

PAAS

pattern has been preserved during weathering

of the dolomitic itabirite. The hard ore sh ows strong

decrease of heavy REE in relation to medium REE (average

Dy/Yb

PAAS

1.17). The different REEY

PAAS

pattern of the

hard and soft ores would not be expected in case they had a

common origin.

The negative Ce

PAAS

anomalies in the hard and soft ores

(Table 5) can result from anomalous La enrichment and are

not necessarily a consequence of anomalous Ce behavior.

According to Bau and Dulski (1996), the combination of

(Ce/Ce*)

shale normalized

<1 and (Pr/Pr*)

shale normalized

>1 indi-

cates a negative (Ce/Ce*)

shale normalized

anomaly. Most hard

and soft ore samples shows (Ce/Ce*)

shale normalized

<1 and

(Pr/Pr*)

shale normalized

≅1 (Electronic supplementary material

Appendix C). This suggests that the negative anomalies of

PAAS

in the samples represent higher La abundances,

instead of an anomalous Ce behavior.

Genesis of the iron ores at the western side

of the Quadrilátro Ferrífero

Most of the iron ore produced in the world results from the

enrichment of Precambrian BIFs, but the processes respon-

sible for this enrichment are still unclear and constitute a

source of debate in the literature (Dalstra et al. 2002;

Kneeshaw and Kepert 2002;Morris2002a,b,c;Hagemann

et al. 2005). Two end-member genetic models have been

proposed: supergene vs hypogene enrichment of a BIF

protore. Supergene iron ores are the most abundant type of

iron ores either in the QF where they represent more than

70% of the 27 Gt of geological resources (Gomes 1986;

MBR and CVRD, internal reports), or in the Hamersley

basin where the martite–goethite ores account for some 90%

or more of the BIF-derived enrichment ores (Harmsworth et

al. 1990; Morris 2002c). Supergene ore arises by the

selective leaching of gangue minerals from the BIF by

groundwater and the residual accumulation of the iron

oxides. Hypogene ores form the richest, high-grade Fe, iron

orebodies. Their genesis is ascribed to the interaction of the

BIFs with a hydrothermal fluid, which dissolved chert

(quartz), leaving pores spaces, which were partly were filled

by a new generation of iron oxides associated with

carbonates, iron silicates and apatite.

The occurrence of the hard high-grad e ores within

unweathered itabirites at the Águas Claras and Tamanduá

250 Miner Deposita (2008) 43:229–254

mines, associated with microthermometric data obtained

from fluid inclusion studies of hematite in high-grade ores

of the Co nceição Mine (Rosière and Rios 2004), are

evidence for the hypogene origin of the hard orebodies at

the Quadrilátero Ferrífero. This type of ore is similar to that

described, for instance, by Taylor et al. (2001), Beukes et

al. (2002), Gued es et al. (2002), and Thorne et al. (2004),

which are interpreted as to have formed by hydrothermal

fluids. An explanation for the origin of the giant soft high-

grade orebodies, such as the Águas Claras, Capão Xavier

and Tamanduá orebodies, is not so straightforward. The

general lack of typical secondary minerals such as goethite

in the ore could indicate leaching of gangue minerals from

BIFs by hypogene solutions; but in some cases, other

arguments such as the mineralogical and geochemical

features of the soft ore at the Águas Claras Mine point to

a supergene origin.

The soft ore at the QF orebodies is generally interlayered

with or surrounds the hard hypogene ore. This relation led

many authors (Guild 1953; Dorr 1965; Beukes et al. 2002;

Rosière and Rios 2004) to propose its hypogene–supergene

modified origi n. Hypogene–sup ergene modified models

comprise an initial hypogene stage with either leaching of

all the chert from the BIF protore leaving pore spaces

(Guild 1953; Dorr 1965) or with metasom atic replacement

of those minerals by carbonates, followed by a supergene

stage that leached the hydrothermal minerals formed in the

previous stage (Beukes et al. 2002). The Águas Claras

Mine was described by Beu kes et al. (2002) as the best

example where the dolomitic itabirite “obviously developed

from the replacement of chert bands in iron-formation”.

The use of hypogene–supergene models proposed by

Beukes et al. (2002), Dalstra and Guedes (2004), and

Rosière and Rios (2004) to explain the genesis of the soft

high-grade ore at the Águas Claras and Capão Xavier mines

presents some issues that need to be addressed. One of

them concerns the origin of the dolomitic itabirite. Beukes

et al. (2002) consi dered the dolomitic itabirite of the Águas

Claras Mine as a product of dolomitization of a chert BIF

by hydrothermal solutions. However, they did not take into

account the regional geological setting where the Cauê

Formation (including quartz and dolomitic itabirite) grades

upward into the dolomite of the Gandarela Formation, a

typical marine sequence hosting stromatolites. The contacts

of the Cauê and the Gandarela Formations are laterally and

vertically intergradational, and dolomitic itabirite occurs

also within the dolomites of the Gandarela Formation (Dorr

1969). It appears more probable that the dolomitic itabirite

represents a carbonate-rich facies of the Cauê Formation

modified by a dolomitization process whi ch occurred

during diagenesis (Spier 2005), instead of the hydrothermal

process of carbonatization of the quartz itabirite . The

marine origin of the dolomitic itabirite is also sugges ted

by the C and O isotopes of dolomite (Spier 2005; Spier et

al. 2007). These isotope values correlate well with those of

the stromatolitic carbonates of the Gandarela Formation of

the Minas Basin (S ial et al.

2000) and also with the

carbonates of the Wittenoom Formation of the Hamersley

Basin (Veizer et al. 1990). Isotope data of the dolomitic

itabirite are quite different from those found in carbonates

of the dolomitized jaspilite of the N4 Mine in Carajás and

in hypogene carbonates of the North Deposit in Tom Price

(Table 8). Depleted δ

C values of hypogene carbonates

from these mines compared with the δ

Cvaluesof

dolomite from the dolomitic itabirite also suggest that this

rock was not formed by hydrothermal alteration of the

siliceous itabirite.

Another contentious issue is the origin of the protore of

the soft high-grade ores. According to the hypogene–

supergene models of Beukes et al. (2002) and Dalstra and

Guedes (2004), the soft high-grade ore could not have

formed from siliceous itabirite. However, thousands of

meters of drill cores from the Tamanduá Mine and other

mines of the region, such as the Capitão do Mato, Pico and

Sapecado (Fig. 1), many of them in unweathered itabirites,

intercepted only siliceous itabirite. Carbonate-rich altered

itabirites have never been observed even in the deepest

levels below the water table in these mines. Therefore, it is

Table 8 The C and O isotopic composition of carbonate samples from Águas Claras, Mount Tom Price, and Carajás

Mine Alteration zone δ

O(‰ PDB) δ

C(‰ PDB)

Range Avg Range Avg

Águas Claras

(n=45) −12.4 to −8.5 −10.5 −2.5 to −0.8 −1.7

North Deposit (Tom Price)

Magnetite–siderite–iron silicate (n=17) −17.3 to −11.8 −14.2 −10.6 to −6.3 −8.8

Hematite–ankerite–magnetite (n=17) −16.1 to −13.5 −16.0 −7.5 to −0.9 −4.9

Carajás

(n=25) −24.0 to −10.0 N.A. −6.0 to −3.0 −5.0

N.A. Not available

Spier et al. (2006)

Thorne et al. (2004)

Sial et al. (2000)

Miner Deposita (2008) 43:229–254 251

reasonable to believe that the soft high-grade ores at those

mines originated from the siliceous itabirite and that a

carbonate-rich protore is not a necessary condition to form

high-grade iron orebodies.

Despite the contention about the origin of the dolomitic

itabirite, it is unquestionable that the original composition

of the itabiritic protore played a major role in the genesis of

high- and low-grade soft ores in the QF, the dolomitic

itabirite being the more favorable rock to form large high-

grade deposits due to the higher solubility of dolomite

when compared to quartz. In fact, although the majority of

the iron ore resources in the QF come from siliceous

itabirite protore, the richest soft orebodies derive from

dolomitic itabirite. This is clearly verified at the Águas

Claras and Capão Xavier mines where the high-grade ores

were formed only from the dolomitic itabirite.

The occurrence of bauxite deposits formed from

Tertiary kaolinitic sediments locally blanketing the high-

and low-grade ores of the Capão Xavier Mine is strong

evidence that the chemical weathering in the region was

intense. Weathering was enough to leach dolomite from

the protores of the Águas Claras and Capão Xavier

deposits, but was not able to form large volumes of soft

high-grade ores from siliceous itabirite in either mine.

On the other hand, at the Tamanduá Mine, siliceous

itabirite was the protore of the huge soft high-grade

orebody. It is unlikely that the soft ore could have been

formed by supergene leaching from siliceous itabirite in

this mine, unless mineralization was additionally con-

trolled by the presence of metavolcanic or mafic dykes,

which acted as impermeable barriers for meteoric waters.

This hypothesis needs to be considered, although there is

a significant a mount of field relation s, such as the

contrasting great depths of the soft ore in the hinge

zone of the Tamanduá Syncline; the complex interfinger-

ing between hard, medium, and soft ores; and the

gradation from massive to porous hard ore types, which

all suggest that all those ores were mostly formed by

hypogene fluids t hat generated th e hard ore, thus,

representing different stages of alteration.

Conclusions

The soft- and hard high-grade ores at the Águas Claras

Mine have a very simple mineralogical and chemical

composition. Both ores consist essentially of pure and

well-crystallized hematite. Gangue minerals are rare, con-

sisting of dolomit e, sericite, chlorite, and apatite in the hard

and soft ores, and Mn oxides and ferrihydrite in the soft

ore, where they are concentrated within the porous bands.

Hard and soft ores consist almost entirely of Fe

, with

higher amount of impurities, especially MnO, in the soft

ore. Both hard and soft ores are depleted in trace elements.

The soft ore preserves the REEY

PAAS

pattern of the

dolomitic itabirite, suggesting that weathering promoted a

residual enrichment in REE without fractionation.

The high-grade ores at the Águas Claras Mine have a

dual origin, involving hypogene and supergene processes.

The occurrence of the hard, massive high-grade ore within

unweathered dolomitic itabirite is evidence of its hypogene

origin. Despite the contentions about the origin of the

dolomitic itabirite, the formation of ferrihy drite and Mn

oxides during dissolution of dolomite of the dolomitic

itabirite indicates the supergene origin of the soft ore. The

calculation of the mass balance in the transition from

dolomitic itabirite to soft ore corroborates this conclusion,

given that the alteration process takes place with strict

conservation of the iron mass.

The original composition of the itabiritic protore plays a

major role in the genesis of high- and low-grade soft ores in

the QF. Under the same weathering and structural con-

ditions, the dolomitic itabirite is more favorable to form

large hig h-grade deposits than siliceous itabirite. Field

relations at the Águas Claras and Capão Xavier deposits

suggest that it is not possible to form huge supergene soft

high-grade deposits through the weathering of siliceous

itabirite alone, unless additional factors were available,

such as the presence of impermeable barriers, which would

play an important role in trapping met eoric fluids.

The formation of a huge tonnag e of soft high-grade ore

within the siliceous itabirite in the Tamanduá Deposit and

the close association between hard, medium, and soft ores,

suggest, on the other hand, that all the ore types were

formed during the same hypogene process that generated

the hard ore, representing just different stages of alteration.

The presence of a carbonate-rich protore is therefore not a

necessary condition to the genesis of large high-grade

orebodies, as suggested by Beu kes et al. (2002) and by

Dalstra and Guedes (2004).

The diversity of geological and structural contexts where

high-grade iron ores occur in the Quadrilátero Ferrífero

suggests the local predom inance of hypogene or supergene

processes in each particular orebody.

Acknowledgments This paper is an integral part of the senior

author’s Ph.D. thesis presented at the Geoscience Institute of the

University of São Paulo (USP). This research project was possible

thanks to the grant issued by the Comissão de Aperfeiçoamento de

Pessoal de Nível Superior (CAPES) to C.A.S (grant BEX2189/02-0).

C.A.S also thank Minerações Brasileiras Reunidas (MBR) for

releasing him of his usual activities as a mine geologist during the

period of his stay at the University of Queensland. We are grateful to

the staff of the Center of Microscopy and Microanalysis of the

University of Queensland (CMM), particularly Ron Rasch, Grahem

Auchterfolie, and Kim Sewell, for their assistance. We are also very

grateful to Nivaldo Lúcio Speziali for his help with the determination

of the unit cell parameters of hematite. Steffen Hagemann, Hilke

252 Miner Deposita (2008) 43:229–254

Dalstra, Jens Gutzmer, and Warren Thorne are thanked for their

detailed and insightful review comments.

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Appendix 1 List of the samples, location and analytical procedures

Hand specimens samples

Sample Coordinates (m) Type Petrography MEV XRD Rietveld Mössbauer

Chemical

analyses

MBR

Chemical

analyses

ACTLAB

East North Altitude

MAC2 1589 -511 1050 HO X X X X

MAC3A 2272 -753 939 PB X X X X

MAC12 2300 -720 920 SO X X X

MAC14 2464 -610 920 SO X X X

MAC14A 2464 -610 969 MB X X

MAC14B 2464 -610 969 PB X X

MAC15 1965 -529 917 PB X X

MAC17A 2270 -735 931 SO X X X X

MAC18A 2308 -717 928 SO X X X

MAC19A 2483 -655 978 SO X X X X

MAC20A 1943 -500 929 SO X X X X

MAC44 1930 -530 899 HO X X X

MAC54A 1859 -623 908 SO X X X X

MAC55A 1847 -572 914 SO X X

MAC56A 1883 -578 908 SO X X

MAC57A 2181 -543 925 SO X X X

MAC58A 2235 -560 925 SO X X

MAC59A 2413 -636 954 SO X X X X

MAC59H 2413 -636 954 MB X X

MAC59I 2413 -636 954 PB X X

MAC60A 2930 -450 1210 SO X X X X

MAC62 1230 -410 1229 HO X X X X

MAC67 2289 -579 918 HO X X X X X X

MAC68 1862 -499 965 HO X X X X X

MAC69A 2320 -568 918 SO X X

MAC77A 2356 -642 920 SO X X

MAC84 2380 -670 922 HO X X X

MAC97 1980 -500 932 HO X X X X X X X

MAC105A 1400 -425 1167 HO X X X X X

MAC105B 1400 -425 1167 HO X X X

MAC107 2350 -650 928 PB X X X

MAC112 1300 -410 1210 HO X X

MAC115 1350 -420 1208 HO X X X

MAC126A 2425 -603 957 MB X X X X

MAC126B 2425 -603 957 PB X X X X

MAC127A 2423 -625 956 MB X X X X X

MAC127B 2423 -625 956 PB X X X X X

MAC128A 2418 -649 951 MB X X X X

MAC128B 2418 -649 951 PB X X X X

MAC129A 2459 -594 966 MB X X X X

MAC129B 2459 -594 966 PB X X X X

HO= hard ore; SO=soft ore; PB=porous band of the soft ore; MB=massive band of the soft ore

Appendix 1 (Continued)

Drill core samples

Sample Depth along the

drill hole (m)

Type Petrography MEV XRD Density Mössbauer Chemical

analyses

MBR

Chemical

analyses

ACTLAB

FSD08-99 2.20 SO X X

FSD08-99 4.80 SO X

FSD08-99 7.30 SO X

FSD08-99 12.50 SO X

FSD08-99 13.20 SO X

FSD08-99 14.70 SO X X

FSD08-99 14.80 SO X X

FSD08-99 16.80 SO X X

FSD08-99 17.00 SO X X

FSD08-99 19.00 SO X X

FSD09-99 3.50 SO X X

FSD09-99 4.10 SO X

FSD09-99 8.60 SO X X

FSD09-99 10.50 SO X X

FSD09-99 12.50 SO X X

FSD09-99 13.50 SO X X

FSD09-99 19.70 SO X X

FSD09-99 20.90 SO X X

FSD09-99 24.70 SO X

FSD09-99 27.70 SO X

FSD09-99 28.70 SO X X

FSD11-99 2.50 SO X X X X

FSD11-99 4.80 SO X X X

FSD11-99 5.50 SO X X

FSD11-99 5.70 SO X X

FSD11-99 5.80 SO X X

FSD11-99 6.50 SO X X

FSD11-99 6.80 SO X X

FSD11-99 7.00 SO X X

FSD11-99 7.10 SO X X

FSD11-99 8.30 SO X X

FSD11-99 8.50 SO X X

FSD11-99 8.60 SO X X

FSD11-99 8.90 SO X X

FSD11-99 9.20 SO X X

FSD11-99 12.40 SO X X X

FSD11-99 13.40 SO X X

FSD11-99 20.40 SO X

FSD11-99 22.80 SO X X

FSD11-99 25.50 SO X X

FSD11-99 25.70 SO X X X

FSD11-99 26.30 SO X X

FSD11-99 26.50 SO X X

FSD11-99 26.70 SO X X

FSD11-99 28.30 SO X X

HO= hard ore; SO=soft ore; PB=porous band of the soft ore; MB=massive band of the soft ore

Appendix 2 Major and trace element composition of the hard and soft ores

Sample MAC2 MAC44 MAC67 MAC68 MAC84 MAC97 MAC105A MAC105B MAC115 PZ55AM7 MAC17A

Ore Type Wt% HO HO HO HO HO HO HO HO HO HO SO

SiO

0.48 0.24 0.93 0.71 0.36 1.32 0.57 0.77 0.89 0.99 0.42

0.12 0.14 0.20 0.25 0.02 0.91 0.16 0.13 0.41 0.21 0.24

97.46 96.40 95.11 98.19 98.58 95.00 97.86 97.94 97.51 94.44 98.38

TOT

99.46 99.40 96.00 98.96 98.84 95.00 98.40 98.50 98.00 94.44 98.49

FeO 1.80 2.70 0.80 0.69 0.23 na 0.49 0.50 0.44 na 0.10

MnO 0.021 0.034 0.019 0.010 0.049 0.005 0.008 0.005 0.018 0.093 0.492

MgO <0.03 0.08 0.59 0.05 0.05 1.20 0.04 0.14 0.23 0.27 0.06

CaO 0.03 0.16 0.89 0.04 0.29 0.26 0.16 0.35 0.34 1.41 <0.03

O <0.01 <0.01 0.01 0.37 <0.01 0.22 <0.01 <0.01 <0.01 <0.01 <0.01

O <0.01 0.06 0.06 0.06 0.08 <0.01 0.05 0.05 0.14 <0.01 <0.01

TiO

0.009 0.018 0.017 0.006 0.017 0.033 0.012 0.007 0.030 0.024 0.009

0.06 0.12 0.18 0.03 0.22 0.17 0.14 0.18 0.017 0.18 <0.03

LOI 0.27 0.24 1.39 0.13 0.43 0.89 0.28 0.32 0.21 1.17 0.54

Total 100.34 100.21 100.20 100.54 100.34 100.02 99.78 100.41 100.40 98.80 100.26

ppm

Ba 15.3 4.4 10.9 37.2 9.9 3.7 8.2 6.0 24.0 <3.0 21.7

Sr 7.8 <2.0 7.6 2.3 8.4 2.1 8.8 8.7 9.3 5.6 9.3

Y 7.6 6.2 4.6 2.2 4.6 3.5 6.1 5.8 5.2 4.1 12.7

Sc <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0

Zr 3.3 2.4 4.0 4.5 7.8 7.9 6.7 2.5 4.1 15.1 4.3

Be <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0

V 132.0 32.0 10.0 24.0 17.0 29.7 17.2 13.1 36.3 45.0 30.0

Ni <20.0 20.3 <20.0 <20.0 <20.0 45.0 <20.0 <20.0 <20.0 <20.0 31.6

Cu 15.1 <5.0 <5.0 22.0 <5.0 <5.0 <5.0 13.6 13.6 10.2 <5.0

Zn 31.1 <30.0 <30.0 <30.0 <30.0 <30.0 <30.0 <30.0 <30.0 <30.0 40.6

Ga <1.0 <1.0 <1.0 <1.0 <1.0 1.2 <1.0 <1.0 <1.0 <1.0 1.1

Ge 4.7 5.9 6.0 4.1 3.4 4.8 3.7 3.2 2.8 4.9 3.8

Rb 1.2 <1.0 <1.0 1.9 <1.0 <1.0 <1.0 <1.0 1.1 <1.0 <1.0

Nb <0.2 <0.2 <0.2 0.7 <0.2 1.0 0.6 0.7 0.8 <0.2 <0.2

Mo 3.4 3.2 <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 2.4

Ag 3.8 1.3 1.0 <0.5 0.8 <0.5 <0.5 <0.5 <0.5 <0.5 1.3

In <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Sn <1.0 <1.0 3.6 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0

Cs <0.1 <0.1 0.2 <0.1 <0.1 0.1 <0.1 <0.1 <0.1 <0.1 <0.1

∑REE

10.0 7.5 6.6 3.2 6.1 6.9 8.7 8.1 8.3 5.2 18.2

Hf <0.1 <0.1 <0.1 <0.1 0.1 0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Tl <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Pb 29.0 13.2 <5.0 <5.0 21.8 <5.0 <5.0 <5.0 <5.0 <5.0 10.6

Bi <0.1 <0.1 <0.1 0.1 <0.1 0.1 <0.1 0.1 <0.1 <0.1 <0.1

Th 0.15 0.11 0.16 0.05 0.15 0.44 0.22 0.30 0.45 0.1 0.3

U 12.3 3.8 0.6 2.6 4.8 8.4 2.6 2.3 3.7 3.6 3.2

Au <2.0 <2.0 <2.0 <2.0 <2.0 <2.0 10.0 na na <2.0 18.0

As 12.6 23.1 6.3 15.8 12.6 19.8 8.8 <5.0 5.1 17.3 9.8

Br <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 na na <0.5 <0.5

Cr 71.0 202.0 170.0 36.0 52.0 23.0 29.0 <20.0 25.0 65.0 192.0

Ir <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 <5.0 na na <5.0 <5.0

Sb 6.2 4.6 2.1 4.1 6.9 4.4 3.7 2.0 2.2 4.1 2.2

Sc 1.0 0.6 0.4 0.1 0.5 0.7 0.5 na na 0.3 1.0

Se <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 <3.0 na na <3.0 <3.0

Fe# 0.980 0.970 0.991 0.992 0.997 na 0.994 0.994 0.995 na 0.999

HO = hard ore; SO = Soft ore; MB = Massive band of the soft ore; PB = Porous band. Fe

TOT

expressed as Fe

. Fe# =

(Fe

/(Fe

), na = not analyzed

Appendix 2 (Continued)

Sample MAC20A MAC60A FSD8/

4.8m

FSD8/

7.30m

FSD8/

12.50m

FSD8/

14.70m

FSD8/

16.8m

FSD8/

19.0m

FSD9/

3.50m

FSD9/

8.60m

FSD9/

24.70m

Ore

Type

Wt%

SO SO SO SO SO SO SO SO SO SO SO

SiO

0.24 0.18 2.05 1.14 1.95 0.93 1.62 1.08 1.41 1.02 2.85

0.18 0.33 1.26 0.33 0.63 0.33 0.57 0.33 0.69 0.45 2.1

97.43 97.90 90.49 95.31 93.21 95.52 93.09 94.68 93.48 95.46 89.19

TOT

97.59 98.07 90.55 95.37 93.27 95.58 93.15 94.74 93.54 95.52 89.25

FeO 0.14 0.15 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05

MnO 0.53 0.73 1.39 0.71 1.20 0.73 1.59 1.24 1.09 0.85 2.14

MgO 0.06 0.06 0.75 0.30 0.69 0.24 0.39 0.27 0.36 0.36 0.36

CaO 0.06 <0.03 0.39 0.15 0.21 0.12 0.18 0.15 0.15 0.12 0.18

O <0.01 <0.01 0.39 0.36 0.45 0.33 0.45 0.39 0.39 0.42 0.36

O <0.01 <0.01 0.03 0.24 0.30 <0.01 0.21 0.09 0.09 <0.01 <0.01

TiO

0.009 0.009 0.155 0.024 0.048 0.021 0.045 0.021 0.045 0.045 0.156

0.06 0.06 0.28 0.03 0.06 0.03 0.06 0.03 0.03 0.005 0.09

LOI 0.60 0.78 1.82 0.60 1.26 0.72 1.44 0.99 1.08 0.84 2.31

Total 99.33 100.25 98.55 99.27 100.08 98.97 99.75 99.36 98.91 99.45 99.72

ppm

Ba 79.3 161.0 53.8 78.9 11.4 30.6 43.7 28.9 28.2 6.7 49.8

Sr 4.0 4.4 34.1 10.9 33.7 15.0 35.5 29.5 26.6 24.5 34.8

Y 33.7 5.5 32.2 26.3 14.6 20.7 37.7 30.8 13.3 9.1 31.7

Sc <3.0 <3.0 4.0 0.5 3.0 0.5 0.5 0.5 0.5 0.5 0.5

Zr 4.2 3.5 26.1 15.2 14.9 11.2 28.6 11.3 15.0 18.4 33.2

Be <3.0 <3.0 4.0 0.5 3.0 3.0 6.0 6.0 3.0 0.5 3.0

V 94.0 34.0 69.9 72.2 138.4 87.5 93.3 74.7 99.4 84.1 56.1

Ni <20.0 <20.0 59.8 12.5 20.1 18.3 30.5 27.5 35.0 9.1 65.0

Cu 45.3 <5.0 22.0 14.5 7.7 14.7 34.1 24.8 10.0 6.8 8.8

Zn <30.0 <30.0 6.0 0.5 0.5 0.5 45.1 29.5 0.5 0.5 109.8

Ga <1.0 <1.0 1.7 0.5 1.1 0.5 1.2 0.5 1.8 1.1 2.4

Ge 3.8 3.5 2.4 0.7 4.1 3.0 3.0 0.7 2.2 3.4 2.7

Rb 4.2 <1.0 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Nb <0.2 <0.2 1.2 0.4 0.5 0.4 0.5 0.3 0.4 0.4 1.6

Mo 2.9 <2.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

Ag 1.3 1.1 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

In <0.1 <0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

Sn <1.0 6.3 1.6 0.5 1.1 0.5 1.1 0.5 0.5 0.5 1.2

Cs 0.4 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

∑REE

29.3 24.1 46.0 29.4 21.8 24.9 39.3 28.7 14.3 14.7 41.1

Hf <0.1 <0.1 0.5 0.1 0.2 0.1 0.2 0.1 0.2 0.1 0.6

Tl <0.1 <0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Pb 7.8 12.6 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

Bi <0.1 <0.1 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

Th 0.1 0.2 1.2 0.2 0.4 0.1 0.6 0.2 0.4 0.4 1.5

U 4.2 6.9 6.2 7.2 3.5 4.5 3.6 2.9 3.7 3.0 5.9

Au <2.0 <2.0 1.0 5.5 1.0 1.0 1.0 1.0 1.0 1.0 1.0

As 19.5 11.5 28.4 16.6 18.7 11.7 15.8 14.8 22.0 18.5 22.9

Br <0.5 <0.5 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3

Cr 148.0 29.0 50.0 18.0 32.0 29.0 40.0 38.0 74.0 42.0 80.0

Ir <5.0 <5.0 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5

Sb 3.7 5.6 5.0 6.1 3.4 3.5 3.9 3.6 4.4 3.5 3.4

Sc 0.5 2.3 3.5 0.8 1.1 0.5 1.1 0.7 1.2 1.1 3.3

Se <3.0 <3.0 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

Fe# 0.998 0.998 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

HO = hard ore; SO = Soft ore; MB = Massive band of the soft ore; PB = Porous band. Fe

TOT

expressed as Fe

. Fe# =

(Fe

/(Fe

), na = not analyzed