1

Mineralogy, geochemistry and genesis of The Zafar abad Iron oredeposit based on trace elements and REEs contents of Magnetite mineral

Barati, M1*, Gholipoor, M1. Sameti, M2

1-Bu-Ali Sina University, faculty of sciences, Department of Geology, Iran2- Shahid Chamran university, faculty of earth sciences, department of geology, Iran

Email:barati@basu.ac.ir (Tel: 0811-8253467)

AbstractThe Zafar abad iron ore deposit is located in 12 Km of Divandarreh city and northwestern margin

of Sanandaj-sirjan zone. The deposit is lentoid to tabular shap which occurred in calk schist andcalcareous host-rocks in shear zone. However pyrite and other sulfide minerals are known in thedeposit but, magnetite with massive, cataclastic and replacement textures are the main mineral. Mainelements, minor and trace elements analysis were done by ICP-MS and ICP-AES. According to traceelement ratios of magnetite such as Ni/ (Cr+Mn) vs Ti+V and Ca+Al+Mn vs Ti+V digramsdistinguished that The Zafar abad is Skarn deposit. Comparison between REE patterns of the Zafarabad Magnetite and different type of iron ores indicated that the Zafar abad deposit is similar to Skarntype. Analysis of REEs represented that hydrothermal mineralization fluids were mainly magmaticand during crystallization and differentiation of plutons injected in carbonate rocks as ferruginousfluid and finally caused creation of the Zafar abad iron skarn deposit.

Key words: The Zafar abad, shear zone, Magnetite, REE, magmatic fluids, skarn.

IntroductionThe Zafar abad iron deposit is located in 12 Km of the Divandarreh town with 46˚ 58΄ 22˝E

longitude and 36̊ 01́ 14˝ N latitude. The study area can be accessible by the Divandarreh-Saghezmain road. There are abundant studies about the genesis of iron ores in the Sanandaj-Sirjan Zone(SSZ) whereas formation of them is controversial. There are numerous studies about iron distributionof iron ores in Iran and all over the world but investigation about these elements in magnetite is scarceand mostly studied about magmatic magnetite-apatite mineralization types. Since there isn’t anyscientific study on the Zafar abad iron ore, this study investigate about geochemical behavior of REEsand trace elements in magnetite based on mineralogy, textural and geochemical studies in the Zafarabad iron ore.

MethodologyThis study attempt to be provided an appropriate genetic model for the Zafar abad iron ore based

on field studies, mineralogy and geochemistry of trace elements and REEs. For this purpose fieldstudies carried out after collecting the Zafar abad area. 70 samples were collected from ore body,alteration haloes and country rocks. 20 thin sections, 10 thin-polish sections and 10 polish sectionswere prepared for petrography and mineralogy studies. In order to geochemical analysis 7 magneticsamples prepared for main elements and 12 magnetic samples prepared for ICP-MS and ICP-EASwhich carried out by SGS laboratory, Toronto, Canada.

GeologyThe study area is located in part of the Sanandaj-sirjan zone and rock units consist of marbleized

limestone, calk schist, metasomatic rocks (skarn) and Pliocene-Pleistocene conglomerate (Fig. 1). Theoldest exposed rocks in the area is Precambrian calk schist which folded by tectonic forces. The Zafarabad is formed in calk schist and limestone. Slope and length is similar to its host-rocks.Mineralization mostly occurred in calk schist unit as the footwall of ore body and there is nomineralization in the limestone as the hanging wall. Some parts of calk schist and limestone rocks inthe area are influenced by tectonic forces as ductile deformation. Milonitic rocks and structural fabricsconfirmed the presence of shear zone in the study area. Faulting, shear zone and consequently deepplutons injection caused contact metamorphism in calk schist rocks which is limited to epidote-hornfelse facies and marbleized lime stones. The Zafar abad iron ore is a lentoid magnetite mass with130 meter length and 20-30 meter thickness. Long axis of this lens present with NE-SW length and45˚ slope. This ore body is divided into two types: high grade magnetite and pyrite-rich magnetite.

2

The ore body is exposed in to the surface as the result of its hardness and resistance. The ore bodywhich exposed to the surface changes to the yellow limonite and ruddle.

Fig. 1. geological map of the study area (modified after Irankhah, 1/100000 scale).

PetrographyCalk schistMicroscopic properties of these rocks which became milonitic by tectonic forces represent that

they composed of muscovite, quartz, calcite and plagioclase (Fig.2 A). Muscovites are folded state inmost thin sections (Fig. 2 B). Muscovites which became to micafish also can be observed in thinsections. When the porphyroclasts extracted with monoclinic symmetry are mentioned micafish(Eisbacher,1970., Lister, 1984. Micafish and C-S fabric are well visible in milonitic calk schist of thestudy area (Fig. 2 C and D). C-S fabric is a fabric that C plane is parallel to shear zone margin but Splanes makes angle with shear zone margin (Lister, 1984). It can be visible in thin sections that calciteveins made C planes and muscovite crystals made S fabric. Quartz is one of the other commonminerals which has been recrystalized. There are three mechanisms for recrystalization:

1- Bulging Recrystalization (BLG): if two adjacent crystals have different displacement, theboundary of crystal pervade into that one which has more displacement and formed a newindependence small crystal. This phenomenon mentioned as recrystalization in crystals boundary inlow temperature or lump (Stipp et al., 2002). Raised parts can be independence from the main part ofcrystal and small independence crystals formed in it (Means, 1981., Urai, 1986 ). BLG mostlyoccurred in old crystals margin and triple junction of crystals (Fig 3 a).

2- Subgrain rotation recrystallization (SGR): whenever the subgrain boundary couldn’t be includedas a segment of main mineral, a new grain formed as the result of losing gradual orientation withsubgrain rotation. It is possible to completely replacement of old minerals with subgrains and newcrystal lattices. This phenomenon which mentioned as subgrain rotation recrystallization occurs inhigher temperature than BLG (Fig 3 b).

3- Grain Boundary migration recrystallization in high temperature (GBM): in relatively hightemperatures, mobility in crystal boundary increases which can displace the weaknesses and subgrainsboundary in crystals and eliminate them by Grain Boundary migration (Stipp et al., 2002) (Fig 3 c).

3

Diagnosis of new crystals from old ones is so hard. Crystals have amoebic border in hightemperatures but they are almost without strain (e.g lack of wave blackout and subgrain) (Passchierand Trouw, 1996). Sometimes quartz boundaries are ridged indicated migration of grain boundaries.Influence of shear caused that being lenticular formation in poly crystalline quartz is visible inmicroscopic scale. The other fabrics which are common in quartz are wave darkness, formation ofsubgrains and polycrystalline quartz bonds with irregular boundary appeared along foliation as theresult of dynamic recrystalization (Fig 4 A and B). These micro structures formed as the result ofrecrystalization by GBM (Passchier and Trouw, 1996) and also can indicate the combination betweenSGR and GBM process. Presence of pressure shadow around quartz porphyroclasts and low amountof stress in these segments caused recrystalization of quartz (Fig. 4 C and D). Evidences in aboveindicate tectonic forces on these rocks and locating them in the shear zone.

Fig.2. calk schists in the study area. A. coarse grain plagioclase phenochrysts which transformed into felsicserusite . B. muscovite crystals folding with secondary calcite veins along the fractures. C and D . micamahiwhich formed in milonitic schist in the study area. All of them were studied in XPL state. Q: quartz, Ca: calcite,Mu: muscovite, Pl: plagioclase, Sr: seresite.

Skarn oreThe complex of white rocks which consist of amphibole (tremolite-actinolite), epidote (Zoezithe)

and calcite are visible in the study area (Fig 5 A and B). This complex can be mentioned as amphiboleskarn because of amphibole abundance. Amphiboles are fibrous and elongate, and zoezites areelongate and blue crystals with amphiboles. Fallowing of plutons injection in shear zone, skarnalteration occurred and caused creation of hydrous minerals such as tremolite –actinolite and epidotein the study area. Mentioned step isn’t consideration as regression alteration because tremolite-actinolite and epidote were formed initially and lack of different anhydrous Ca silicates (e.g pyroxeneand garnet) indicates that tremolite-actinolite and epidote aren’t yield of delay alteration of skarnminerals in previous steps. It can be concluded that metamorphism in the study area was progressived,which progressed the forming temperature of minerals such as tremolite-actinolite and epidote.

White crystallized limestoneMicroscopic examination of limestone in the study area distinguished that they formed by

isometric calcites. Deformation Indication is clearly visible in calcites as the result of suitinglimestone in shear zone. Groshing et al (1984) recognized a change in calcite twinning morphologyalong to increasing deformation temperature. Stability of these relations and easy application of themcaused to utilize calcite deformation twinning as a useful geotheremometer.

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Fig. 3. three types of dynamic recrystalization in quartz. A. BLG, B. SGR, C. GBM (Stipp et al., 2002.,Passchier and Trouw, 1996 ).

Fig. 4. A. polycrystalline quartz bands as the result of GBM and SGR dynamic recrystalization along foliation.B. polycrystalline quartz which became lentoid by deformation. C and D. pressure shadow around theplagioclase porphyroclast and quartz crystallization in the study area as the result of low stress. All the sampleswere studied in XPL state. Q: quartz. Pl: plagioclase.

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Fig. 5. A and B . amphiboles of skarn in the study are. All were studied in XPL state. Mt: Magnetite, Ca:calcite, Zo: zoezite, Ter-Act: termolite-actinolite.

According to David et al (2004) investigations about calcite deformation twinning deformationtemperature can be estimated by calcite twining thickness:

1- Thin twinning in calcite formed under 200˚C and predominant heat of 170˚C.2- Thick twinning formed in 200-300˚C.3- Dynamic recrystalization is an important deformation mechanism in calcite in 300˚C (Weber et

al., 2001).In more than 300̊ C lentoid twinning formed which narrowed to the crystal boundaries (Rowe and

Rutter, 1990). Further temperature with dynamic recrystalization caused jagged and saw shape grainsformation (Groshong, 1988). Influence of temperature in deformation by calcite twinning shown inFig. 6. Calcite grains show twinning of first type and second type thin sections of this lithology. Inother words, calcite twinning is thin top wide blade in these thin sections (Fig. 7 A and B). Accordingto twinning deformation temperature can be estimated (Yasaghi, 2009., Burkhard, 1993., Ferrill,1991). According to Fig.7 thickness of calcite twinning will increase parallel to increasingtemperature. Based on mentioned topics deformation temperature in this shear zone estimated about170-300˚C and presence of calcite twinning is the evidence.

Fig. 6. schematic of temperature effect in deformation by calcite twinning (Burkhard, 1993).

Ore microscopyMagnetiteMineralogy of the Zafar abad deposit is simple and magnetite is the main ore mineral. Massive,

catalastic martitization and replacement are the major textures of magnetite (Fig. 8). Martitizationusually occurred in grain margins and along cleavages as an after mineral formation process. It isdone during the Eq (1.1) (Mucke and Cabral, 2005):

(1.1): 2Fe+2Fe+3O4 (magnetite) + 0.5O2 = 3Fe+3O3 (Hematite)

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Fig. 7. A and B mechanical twinning of type 1 and 2 in calcite samples of shear zone in the study area. Allwere studied in XPL state.

In addition, some reactions such as Eq (1.2) can play an important role in creation of themartitization texture.

(1.2): Fe3O4 (magnetite) +2H+ = Fe2O3 (Hematite) + Fe+2 + H2O

The mentioned reaction above isn’t an oxidation-reduction type even it shows transformation ofmagnetite to hematite as the result of Fe+2 leaching in acidic environment (Ohmoto, 2003). Thesereactions can be the principal mechanism for Iron-oxides transition in nature, especially inhydrothermal environments. Ohmoto (2003) expressed that most of magnetite skarn oresdemonstrated a transformation from primary hematite to magnetite and magnetite to secondaryhematite, which may done without presence of oxidizing or reducer. If magnetite to hematiteconversion occurred as the result of oxidation-reduction reactions with presence of pyrite magnetiteoxidized to hematite wholly. When magnetite can be oxidized to hematite, pyrite oxidized with higherintensity than magnetite certainly (Kamei and Ohmoto, 2000). Martitization is visible in the Zafarabad iron ore extremely. Fig (8-C) shows martitization in the Zafar abad deposit. It is clearly visiblethat magnetite changed to hematite but pyrite grains remain intact, while they should be changed intohematite and it could not be construe with Eq (1.1) , therefore it seems that in magnetite to hematitetransformation in the study area Eq (1.2) is involved. In shear zone and relative parts magnetite foundin crushed grains with different sizes. Replacement of pyrite with magnetite from the margins isvisible in some thin sections which caused different types of replacement such as corrosion textureand remain (island and mainland) in pyrite.

HematiteAll of the hematite minerals in the ore body are secondary and formed during erosion and

martitization of magnetite (Fig. 8).PyriteBased on ore microscopy studies 3 different types of pyrite were distinguished in the Zafar abad

deposit. First type of pyrites (Py1) are massive and anhedral and mostly in paragenesis withmagnetite. In most of samples this pyrite influenced by fault activities and shear zone and exhibitedcorrosion state (Fig. 8-F). Second type pyrites (Py2) seems completely euhedral in polish sections(Fig. 8-G). It can be mentioned that Py2 is Py1 which growth in enough space (Klein and Hurlbut,1985). Third type pyrites (Py3) formed during delay sulphide phase in the shape of sulphide veinletswhich crossed the ore body (open space filling texture). It seems that they are the other generation ofpyrites in the study area (Fig. 8-H). First type pyrites are the most abundant pyrites in samples andPy2 and Py3 are the less.

ChalcopyriteChalcopyrite belongs to minor sulphide phases which accompanied magnetite and other sulphide

minerals in low quantities. Texture relations such as open space filling of pyrite by chalcopyriterepresent that this mineral formed after pyrite precipitation (Fig.9-A). Transformation of chalcopyriteto covellite from the margins is visible in some polished sections (Fig.9-B), this transformationusually start from crystal margins (Ramdohr, 1980).

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MalachiteMalachite mostly appearance as open space filling, in the shape of narrow bands accompanied with

magnetite. This mineral is seen light green and exhibited colloform texture in studied polishedsections (Fig. 9 C and D).

Fig. 8. A. magnetite with massive and fine grain texture. B. magnetite with catalastic texture. C. martitization ofmagnetite, D. pyrites which replaced by magnetite, pyrite was replaced by magnetite and remain like an islandwith its primary shape, E. martitization texture in The Zafar abad iron ore, as it can be visible magnetitetransformed to hematite while pyrites remained intact, F. pyrites of first type (Py1) with cataclastic texture, G.pyrites of second type (Py2) beside Py1 which replaced by magnetite relatively, H. pyrite veins of third type(Py3)which acrossed the magnetite. All were studied in PPL state. Mt: magnetite, Py: pyrite, Mar: martitization,Py1: first type of pyrite, Py2:second type of pyrite, Py3: third type of pyrite, Mal: malachite.

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Fig. 9. A. chalcopyrite with filling space of fractures in pyrite texture. B. transformation of chalcopyrite tocovellite from the margins, C and D. malachite with coloform texture. All were studied in XPL state. Cpy:chalcopyrite, mal: malachite, cov: covellite, Py: pyrite, Mt:magnetite.

DiscussionThe most important process to formation an ore body is the influence of source rocks, migration of

mineralized fluids and minerals precipitation. According to textural properties in polished sectionsdefined that pyrite formed at first after that magnetite created as the result of pH and Eh changing anddecreasing the temperature. It can be found mineralized fluid was reduction at first which causedformation of sulphide minerals; afterward a process caused changing state of mineralization solutionsfrom reduction to oxidation. The most probable which can be considered for this state is mixing ofprimary reduction solution with meteoric waters. According the presence of shear zone in the studyarea and Considering that these regions are so appropriate for permeation and influence of meteoricwaters therefore it can be understand that the precipitate decreasing of temperature and probablypressure done as the result of getting fluid to the shallow and sheared and combination with meteoricwaters which associated with decreasing fluid acidity and solubility of iron complexes, causedchanging the state of mineralized solution from reduction to oxidation and Fe-bearing compoundsdeposition in oxide form (magnetite). Mentioned mechanism is one of the most important factors inFe-bearing compounds deposition (Monteiro et al., 2008). Minerals paragenesis of the Zafar abaddeposit represented in table 1.

Table 1: paragenesis table of The Zafar abad iron ore.

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Geochemistry of magnetite oreChemical analysis results of the Zafar abad magnetite ore are shown in table 2. In order to

understand relation between these elements (main and trace elements) and Fe (Fe is considered asTFeo) correlation processing was done among the collected samples from the study area.

Main elementsThe trends of Al2O3, SiO2, CaO and MgO against the Fe indicate that they will decrease by

increasing the quantities of Fe; therefore it can represented a negative correlation between theseelements and Fe. MnO quantity show relatively increases by increasing Fe. Negative correlationbetween Fe, CaO and Al2O3 is due to concentration of them in plagioclase of producer magma of theore body, because crystallization of plagioclase caused decreasing of Ca and Al in magma. The reasonof negative correlation between Fe and MgO is due to lack of mafic minerals with magnetite (Fig. 10).

Geochemistry of trace elementsInvestigation of trace elements in the Zafar abad ore samples indicate that with increasing Fe

quantities V, Co and Mn increase and Cr, Ti and Ni decrease (Fig.12). Since occurrence of Co is seenjust in calcic iron skarn deposits therefore presence of Co represents skarn condition of orebody(Meinert, 1984). Lack of Mn and V independent minerals in orebody demonstrated replacement ofMn+2 by Fe+2 and V+3 by Fe+3, which is corresponding with positive correlation between Fe with Mnand V. correlation between Cr and Fe is negative in magnetite samples of the Zafar abad. Accordingto Pendahel and Friesch (1995) negative correlation between Fe and Cr can be appeared due to themagmatic character of Fe. There is no specified correlation between Fe and Cu in The Zafar abaddeposit. Presence of Cu in this deposit is due to chalcopyrite and covellite minerals in the samples(Fig. 11).

Rare earth elements (REE)Results of REE analysis are exhibited in table 3. In order to construe the REE behavior in the Zafar

abad deposit amounts of ΣREE, (La/Sm)cn, (Eu/Sm), Eu/Eu* and Ce/Ce* were calculated. Spiderdiagrams which drawn after chondrite normalizing (Boynton, 1984) of The Zafar abad ore samples,show a negative uniform slope with negative anomalies of Eu and Ce (lesser than Eu) (Fig. 12). Thisdescending trend is due to enrichment of light rare earth elements (LREE) than the heavy rare earthelements (HREE).Magnetite can included 6.67wt% of Ca, therefore if a big cation like Ca can beentered into magnetite crystal lattice, entering of REE ions which are comparable with Ca by theirionic radius in magnetite is feasible DE Siter (1977). Since LREEs have closer ionic radius to Catherefore locating in magnetite lattice and LREE enrichment is more possible. LREE enrichment inthe Zafar abad deposit is this factor too. There is a separation among LREEs too, it can be found from(La/Sm)cn ratios which dedicate average of 5.91ppm in samples. Three samples exhibited moreseparation than others, in this sense (average 12.53). Eu and Ce show negative anomalies in the studyarea (Eu/Eu*=0.66) and (Ce/Ce*=0.83). Eu in divalent state is similar to Ca therefore replacement Cain calcic plagioclase and then exited from magmatic system by it. Depletion of Eu in magnetite orebody can be related to partial melting from a magma which related to mineralization or related tooxidize condition of environment (Pendahel and Friesch, 1995). Eu negative anomalies occurred asthe result of entering Eu in primary magmatic plagioclase and lack of this mineral with magnetite. TheZafar abad hasn’t any high Ce anomalies. Since Ce+3 can be oxidized to Ce+4easily therefore it causedreducing ionic radius afterward it can be transmitted by hydrolysis and particulates or in presence ofcarbonate ligands in carbonate fluids excite from the environment. Negative anomalies and droppingCe in the Zafar abad samples can be the sign of Ce+3 oxidation to Ce+4 excite of it from environmentand lack of partial presence of it in the magnetite lattice (Appel, 199).

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Table2: main elements (wt %) and trace elements (ppm) quantities in the The Zafar abad magnetite ore by ICP-MS and ICP-AES.

* =Not Applicable

No.Sample D-108 D-109 D-124 D-129 D-132 D2-103 D2-104 D2-105 D2-109 D2-111 D2-115 D2-121

Pos

itio

n

N:3

6˚01

'19"

EO

:46˚

58'2

1"

N:3

6˚01

'32"

EO

:46˚

58'1

9"

N:3

6˚01

'51"

EO

:46˚

58'0

5"

N:3

6˚03

'34"

EO

:46˚

58'5

3"

N:3

6˚01

'18"

EO

:46˚

57'2

0"

N:3

6˚01

'08"

EO

:46˚

57'1

2"

N:3

6˚01

'35"

EO

:46˚

57'1

8"

N:3

6˚01

'11"

EO

:46˚

58'1

2"

N:3

6˚01

'39"

EO

:46˚

58'0

9"

N:3

6˚01

'56"

EO

:46˚

57'0

1"

N:3

6˚01

'07"

EO

:46˚

58'1

3"

N:3

6˚01

'16"

EO

:46˚

58'1

0"

SiO2 N.A* 4.96 N.A 3.44 5.15 N.A 4.15 4.37 N.A N.A 4.01 3.73Al2O3 N.A 0.61 N.A 0.31 0.34 N.A 0.28 0.31 N.A N.A 0.26 0.28TFeO N.A 92.54 N.A 90.35 86.9 N.A 97.15 92.36 N.A N.A 94.86 95.74CaO N.A 0.29 N.A 0.08 2.14 N.A 0.29 0.13 N.A N.A 0.23 0.09MgO N.A 0.29 N.A 0.31 1.87 N.A 1.13 2.34 N.A N.A 0.87 1.31Na2O N.A 0.1 N.A 0.01< 0.01< N.A 0.1< 0.1< N.A N.A 0.1< 0.1<K2O N.A 0.06 N.A 0.01< 0.02 N.A 0.01< 0.01< N.A N.A 0.01< 0.01<TiO2 N.A 0.07 N.A 0.01< 0.01< N.A 0.01< 0.01< N.A N.A 0.01< 0.01<MnO N.A 0.34 N.A 0.36 0.53 N.A 0.63 0.23 N.A N.A 0.28 1.08P2O5 N.A 0.03 N.A 0.02 0.03 N.A 0.01< 0.03 N.A N.A 0.04 0.01<

Cr2O3 N.A 0.01< N.A 0.01< 0.01< N.A 0.01< 0.01< N.A N.A 0.01< 0.01<Cr 28 30 33 30 20 25 20 40 18 15 21 37V 71 79 70 82 66 67 81 70 58 33 93 60

Co 46 24 87 54 47 96 94 38 43 142 101 29Mn 1740 3070 1435 2620 2036 2430 2180 1540 1689 1702 1562 3950Ni 49 22 36 22 65 19 13 52 41 50 47 29Ti 60 50 87 50 73 60 47 82 51 48 60 49Cu 273 123 631 306 103 97 78 41 133 461 63 371Zn 251 320 2140 1080 707 505 548 380 1250 649 389 359

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Fig. 10. correlation between Fe and main oxides in the Zafar abad magnetite ore. A. TFeO vs Al2O3, B.TFeO vs SiO2, C. TFeO vs MnO, D. TFeO vs CaO and E. TFeO vs MgO.

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Fig. 11. correlation between Fe and trace elements in The Zafar abad magnetite ore. A. TFeO vs Cr, B.TFeO vs V, C. TFeO vs Co, D. TFeO vs Ni, E. TFeO vs Ti, F. TFeO vs Mn and G. TFeO vs Cu.

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Table3: REE (ppm) quantities and relative ratios and parameters in the the Zafar abad magnetite ore by ICP-MS and ICP-AES.

Fig. 12. chondrite normalized REE distribution pattern in The Zafar abad magnetite ore (Boynton, 1984).

Comparison among magnetite REE pattern of The Zafar abad deposit with different types ofiron ores:

Comparison of magnetite REE pattern in the Zafar abad with other iron ore types (skarn, sedimentary,hydrothermal and kiruna) carried out in order to investigation about mineralization type in the Zafarabad deposit (Fig.13). Distribution pattern of REE of skarn iron ore in Misi Finland region shown inFig. (13-A), as it is visible there are similarities between this pattern with REE pattern of The Zafarabad deposit, such as Eu negative anomalies, same amount of REE and descending trend are similarto The Zafar abad deposit. The difference is small negative anomaly of Ce in Zafar abad which isn’tvisible in Misi region. According to exhibited distribution REE pattern for both deposits, uniformdescending trend from La to Lu is visible for both of them which is due to the separation of LREEs

D2-121

D2-115

D2-111

D2-109

D2-105

D2-104

D2-103

D-132D-129D-124D-109D-108No.Sample

N:3

6˚0

1'16

"E

O:4

6˚5

8'10

"

N:3

6˚0

1'07

"E

O:4

6˚5

8'13

"

N:3

6˚0

1'56

"E

O:4

6˚5

7'01

"

N:3

6˚0

1'39

"E

O:4

6˚5

8'09

"

N:3

6˚0

1'11

"E

O:4

6˚5

8'12

"

N:3

6˚0

1'35

"E

O:4

6˚5

7'18

"

N:3

6˚0

1'08

"E

O:4

6˚5

7'12

"

N:3

6˚0

1'18

"E

O:4

6˚5

7'20

"

N:3

6˚0

3'34

"E

O:4

6˚5

8'53

"

N:3

6˚0

1'51

"E

O:4

6˚5

8'05

"

N:3

6˚0

1'32

"E

O:4

6˚5

8'19

"

N:3

6˚0

1'19

"E

O:4

6˚5

8'21

"

Pos

itio

n

1.532.101.004.200.701.960.804.701.001.601.301.10La4.801.312.244.800.601.971.836.801.102.002.301.20Ce0.440.30.150.440.140.390.180.610.180.430.350.21Pr1.200.522.001.200.401.710.601.400.601.201.400.70Nd0.200.100.370.20<0.100.310.310.20<0.100.200.300.19Sm

<0.05<0.05<0.05<0.050.060.070.050.060.050.060.070.05Eu0.270.150.320.150.060.350.270.270.240.400.290.34Gd

<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05Tb0.300.270.220.130.070.390.340.290.220.270.280.27Dy

<0.05<0.05<0.05<0.05<0.05<0.050.100.080.050.060.070.09Ho0.170.160.290.100.060.280.120.350.170.160.210.24Er

<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05Tm<0.10<0.100.180.10<0.100.310.230.320.210.190.200.23Yb<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05<0.05Lu8.914.916.7711.322.097.814.83150.24.276.466.824.62REE∑4.4112.001.6112.05-3.641.4813.54-4.602.493.32(La/Sm)n

-----0.650.530.80-0.650.730.61Eu/Eu*1.410.391.390.850.750.541.160.960.620.570.820.60Ce/Ce*

--1.417.652.002.631.473.261.473.873.011.56(Pr/Yb)n

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from HREEs. REE distribution pattern of hydrothermal iron ores shown in Fig. (13-B). Positiveanomaly of Eu and extremely enrichment of LREE than HREE known as index features ofhydrothermal iron ores which identified these deposits from The Zafar abad deposit. Fig. (13-C)exhibited the REE pattern of sedimentary iron ores. Eu positive anomaly and strongly negative Ceanomaly are the main characters of sedimentary iron ores. Positive Eu anomaly in these depositsoccurred as the result of hot and Eu enriched hydrothermal fluids to the oceans (Barret et al., 1988).Strongly negative Ce anomaly is one of the other major features of submarine hydrothermal iron ores(Fryer, 1977). Eu positive anomaly and Ce negative anomaly together in sedimentary iron oresindicate chemical precipitation and with submarine hydrothermal fluids. Lack of such a pattern likethis distinguish the Zafar abad,s from this type. REE distribution pattern of kiruna type iron oredeposits shown in Fig. (13-D). Magnetite ores relate to paleoprotrozoic different types in northernSweden are relatively poor in REE and there is little separation between LREE and HREE inmagnetite of these deposits. One of the main differences between REE distribution pattern of kirunatype iron ores and the Zafar abad is negative Gd anomaly in kiruna type deposits while this negativeanomaly in the Zafar abad deposit is related to Eu. According to Fig. 13 the Zafar abad and of Finlandskarn deposits REE patterns exhibited the most similarities with each other. Common source andgenesis can be suggested with skarn Fe deposits whereas the similarities between the Zafar abad andother types are lower.

Fig. 13. chondrite normalized REE distribution pattern in The Zafar abad magnetite ore. A. magnetite ore inMisi Finlend (Niiranen et al., 2005). B. Hydrothermal iron ore (Tallarico et al., 2005). C. sedimentary iron ore(Oksuz and Koc, 2009 ). D. kiruna type iron ore (Pendahel and Friesch, 1995).

Genesis of the Zafar abad iron deposit by trace elements and REEs geochemistry inmagnetite phases:

Some researchers exhibited diagrams which identified different types of iron deposits based ongeochemistry of iron ores. Lohberg and Horndhal (1983) based on ferrite elements (Fe, Ni,V and Ti)and mentioned ratios, classified Precambrian iron deposits of into 3 groups of apatite iron, Fe-Tibearing deposits and banded iron deposits. Dupuis and Beaudion (2011) offering diagrams in order todistinguished the different iron deposits (Fig. 14). Basis of their segmentation was chemical analysisof magnetite and hematite in Fe-oxide ores. Because magnetite and hematite in all deposits representcompositional differences, which related to ore type and can be a suitable resolving to creationdiscriminate diagrams for different mineralization types. Chemical analysis of magnetite of different

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ores indicated that kiruna type magnetite-apatite ores contain more concentrations of V and Ti thanIOCG, also this type of ores represent low concentration of Al and Mn. Nystrom and Henriquez(1994) suggested that magnetite of apatite-bearing Fe ores are recognized by very low Cr and highcontaining of V. although magnetite with low amount of Ti is one of the characteristics of IOCG oresbut investigations show that it is a common character between IOCG and skarn deposits. Fe-oxideminerals of skarn deposits represent low Ti+V concentration even though they have variableNi/(Cr+Mn) ratios. High concentration of Mn is one of the hydrothermal skarn Fe deposit’s features.Dupuis and Beaudion (2011) exhibited diagrams based on trace elements quantities and Ni/(Cr+Mn)vs Ti+V and Ca+Al+Mn vs Ti+V ratios and according them the Zafar abad Fe deposit is plotted inskarn deposit section (Fig. 14 A and B). According to field studies, microscopic investigations andgeochemical analysis it seems that the Zafar abad iron ore is skarn and Fe-riche fluids in carbonate-rich rocks caused skarn formation and finally concentration of magnetite.

But if the intrusion in the depth was provided the Fe for mineralization or there was another Fesource for mineralization? it is the main question. In other words, if mineralized fluids were magmaticor provided as the result of circulating meteoric waters, leaching Fe from rocks and finallyprecipitating them in carbonate rocks in the study area. Kato (1991) investigated about four depositsin Japan and detected the origin of them which is meteoric or magmatic with usage of Eu/Eu*,Ce/Ce* and (Pr/Yb)cn parameters (Fig 15 a, B and C). In both Ce/Ce* and (Pr/Yb)cn diagrams samplesfrom study area plotted in magmatic waters district but in Eu/Eu* diagram they plotted betweenmagmatic and meteoric waters. It can be concluded according to these diagrams effective fluids in theZafar abad mineralization is a combination of meteoric and magmatic fluids which the meteoricwaters contains smaller segment. This small segment can be due to the meteoric water movementsalong shear zone and then combining with magmatic fluids. The trend of most samples is near tomagmatic fluids and it can indicate that mineralized fluids in the Zafar abad are mainly magmatic. Asthe result responsible mineralization fluid formed during the diffraction and crystallization of deeplyigneous intrusion and injection in carbonate rocks caused to form iron ore. Finally suggested genesismodel for Zafar abd iron deposit represented in Fig. 16.

Fig. 14. position of magnetite samples of The Zafar abad A.in Ni/(Cr+Mn) vs Ti+V. B. in Ca+Al+Mn vs Ti+V(Dupuis and Beaudion, 2011).

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Fig. 15. A, B and C indicator diagrams for detecting magmatic or meteoric mineralization fluids (Kato, 1999.

ConclusionResults of field studies, mineralogy and geochemistry in the Zafar abad deposit indicate that Fe-

oxide deposit formed as the result of magmatic fluid movements along faults and shear zone. Injectionof deeply igneous intrusions in carbonate rocks or carbonate-rich rocks caused metasomatismoccurrence, formation of skarn halos (skarn rocks) and finally deposition of The Zafar abad deposit.Comparison between REE distribution pattern in the Zafar abad and other iron deposit types (skarn,hydrothermal, sedimentary and kiruna) represented that REE distributiin pattern in the Zafar abad issimilar to skarn Fe ores. It can be visible According to Ni/(Cr+Mn) vs Ti+V and Ca+Al+Mn vs Ti+Vthat the Zafar abad is located in skarn region. Analyses of REEs indicate that mineralized fluids weremainly magmatic. Mineralization fluid formed during the diffraction and crystallization of deeplyigneous intrusion and injection in carbonate rocks which was the cover of ore before caused to formedskarn deposit.

Fig. 16. genesis model of The Zafar abad iron ore.

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