geochemical and mineralogical characteristics of fe-ni...
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Geochemical and Mineralogical Characteristics ofFe-Ni Laterite Ore of Sarıçimen (Çaldıran-Van)
Area in Eastern Anatolia, Turkey
ALİ RIZA ÇOLAKOĞLU
Department of Geological Engineering, Yüzüncü Yıl University, TR−65080 Van, Turkey (E-mail: [email protected])
Received 10 March 2008; revised typescript received 24 June 2008; accepted 31 October 2008
Abstract: The Sarıçimen Fe-Ni laterite ore is located 15 km east of Çaldıran County, northeast of Lake Van. This areais situated in the eastern Anatolia accretionary complex of Turkey, close to the Iran boundary. It is the first transportedFe-Ni rich laterite to be described from this area. This paper concentrates on the mineralogical and textural features ofthe ore minerals and the transported Fe-Ni laterite zone. These transported laterites are very inhomogeneous andcontain very abundant zoned chromite grains, which have been altered to magnetite. SEM/probe investigations indicatethat Fe-Ni is depleted in the core chromite and increases in the magnetite rim. A sedimentary transported laterite zoneexhibits a high proportion of silcretes and ferruginous materials and chemically contains 29−61wt% SiO2 and 11.8−48.7wt% Fe2O3. The average contents of Al2O3, TiO2, MnO and P are 4.81, 0.37, 0.32, and 0.03 (all in wt%) respectively. Thehighest Ni value obtained from the transported lateritic ferruginous zone is 1.16 wt%. The Pt and Pd concentrations arelow, ranging from 39 ppb to 6 ppb and 21 ppb to 5 ppb, respectively. The Au value reaches up to 3 ppb. The diversityin chemical compositions of transported laterites is related to fracturing, erosion, corrosion, transportation, quantity ofclastic material with different alteration history and diagenesis.
Key Words: Van, ophiolite, Fe-Ni laterite, eastern Anatolia, Turkey
Sarıçimen (VAN) Fe-Ni Laterit Cevherleşmesinin Jeokimyasal veMineralojik Karakteristikleri, Doğu Anadolu, Türkiye
Özet: Sarıçimen Fe-Ni laterit cevherleşmesi Van Gölü’nün kuzeydoğusunda, Çaldıran İlçesinin 15 km doğusundakonumlanmıştır. Cevherleşme İran sınırına yakın Doğu Anadolu Yığışım Kompleksi içinde yer almaktadır. Bölgededaha önce Fe-Ni laterit türünde bir cevherleşmenin varlığı bilinmemektedir. Cevherleşme oluşum koşulu ve türübakımından da bu bölgede tanımlanmış ilk taşınmış Fe-Ni laterit cevherleşmesidir. Bu çalışmada Fe-Ni laterit zonununve opak minerallerinin mineralojik ve dokusal özellikleri incelenmiştir. Sedimanter karakterde taşınmış Fe-Ni lateritcevherleşmesi çok farklı bileşimlerdeki kırıntılardan ve tane kenarlarından itibaren manyetite dönüşmüş zonlu kromittanelerinden oluşmaktadır. Taramalı elektron mikroskop (SEM/prob) incelemeleri ile zonlu kromitlerin alterasyonusonucu kenarlarından itibaren oluşan manyetitlerde Ni oranının arttığı tespit edilmiştir. Taşınmış ve sedimanter olarakçökelmiş laterit zonu yüksek miktarlarda silisli ve demirli kırıntılar içermektedir. Kimyasal olarak % 29−61 SiO2 ve% 11.8−48.7 arasında Fe2O3 içermektedir. Cevherleşme ortalama olarak % 4.81 Al2O3, % 0.37 TiO2, % 0.32 MnO ve% 0.03 P içermektedir. Demirce zengin taşınmış lateritik zondan alınan örneklerin en yüksek Ni içeriği % 1.16 olarakbelirlenmiştir. Pt ve Pd konsantrasyonları oldukça düşük olup sırasıyla 6−39 ppb ve 5−21 ppb arasında değişmektedir.Au değeri ise en yüksek 3 ppb olarak ölçümlenmiştir. Sedimanter karakterdeki laterit zonunun kimyasal bileşimdekifarklılıklar kırıklanma, erozyon, ayrışma, taşınma, farklı alterasyona maruz kalmış kırıntılı malzemenin miktarına vediyajeneze bağlı olarak gelişmiştir.
Anahtar Sözcükler: Van, ofiyolit, Fe-Ni laterit, doğu Anadolu, Türkiye
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Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol. 18, 2009, pp. 449–464. Copyright ©TÜBİTAKdoi:10.3906/yer-0803-5 First published online 24 March 2009
IntroductionIt is well known that laterites are products of tropicalconditions. The best description for the genesis of Nilaterite deposits has been provided by (Golightly1981). Most of the expansion in nickel productioncapacity over the next ten years will come fromprocessing laterite ores (Dalvi et al. 2004). It isknown that when exposed to prolonged tropicalweathering, ultramafic rocks containing olivine andpyroxene minerals in a variety of geological settings,from Precambrian to Tertiary age, can result in theformation of nickel laterites (Dalvi et al. 2004). Someopinions expressed about the formation time oflateritization processes in Turkey are as follows: (i)present climatic conditions are not conductive tolateritization processes and formation of deposits(Kurter 1979); (ii) in Late Cretaceous andEarly−Middle Miocene times the climate wassuitable for lateritization processes in Turkey(Tüfekçi 1991).
In Turkey, lateritic bauxite deposits arecommoner than the Fe-Ni type lateritic deposits.Research on bauxite deposits in the Central Taurusand Fe-Ni lateritic deposits in western Anatoliasuggests that suitable climatic conditions existed inthe past for the formation of laterites in Turkey.Investigation of lateritic Fe-Ni zones in Turkey hasmostly been carried out in western and centralTurkey. The most investigated sites are the Manisa-Çaldağ, Kütahya, Eskişehir-Mihalıçcık, Bursa-Orhaneli, Adana-Kozan and Sivas-Divriği regions(Figure 1). The first lateritic Fe-Ni deposit to bemined in Turkey was in the Manisa-Çaldağ region,which was originally mined for iron, followingstudies implemented by the General Directorate ofMineral Research and Exploration (MTA) for Ni-Coby Yıldız (1977) and Hirano & Boyalı (1980). The siteis currently operated by the European NickelCompany. A revised feasibility study has beencarried out, which suggests a planned/productionrate of 2.5 Mt/y of ore, averaging 1.13 wt% Ni and0.07 wt% Co, with an expected heap recovery rate of72 wt% of the contained metal over a 20-month leachcycle (Mining Journal 2006). Other recently foundlateritic Fe-Ni deposits in the surrounding area arecurrently operated by the Egemad Company.
Although ophiolites cover a large area in Turkey,few lateritic ore deposits have been discovered. In thepast, the ophiolites in Turkey were explored forchromite deposits rather than lateritic ore deposits.However, in countries with Alpine rocks such asGreece and former-Yugoslavia numerous lateritic Fe-Ni rich mineralization have been extensively studied(e.g., Albandakis 1980; Michailidis 1990; Tashko etal. 1996; Economou-Eliopoulos 1996; Eliopoulos &Economou-Eliopoulos 2000; Skarpelis 2006).Although ophiolite units are common in easternTurkey, limited Ni exploration has been conducted inthe last decades. The Sarıçimen Fe-Ni transportedlaterite deposit, located about 100 km north-northeast of Van city, in eastern Turkey (Figure 1), isthe first lateritic Fe-Ni ore to be described from theophiolitic area of eastern Turkey. This paper presentsa preliminary evaluation of new data about thegeology, mineralogy and petrography of the newlydiscovered transported Fe-Ni laterite in theSarıçimen area. The mineralogical and chemicalcomposition of the laterite and SEM/probeinvestigations are presented and a geodynamicalmodel is proposed for the Sarıçimen area. These dataand the description of this mineralization type willbe a useful guide for future exploration in the region.
Regional GeologyThe area studied lies northeast of Lake Van withinthe eastern ophiolitic belts of Turkey, whichrepresent fragments of Neo-Tethyan oceaniclithosphere (Şengör & Yılmaz 1981). EasternAnatolia is one of the best examples of a continentalcollision zone in the world. It also comprises one ofthe high plateaus of the Alpine belt with an averageelevation of ~2 km (Keskin 2003) and includes theAnatolian-Iranian Plateau (which extends fromeastern Anatolia to eastern Iran) and typically has anelevation about 1.5–2 km in eastern Anatolia. Thebasement of the Anatolian-Iranian Plateau is madeup of a series of micro-continents, accreted to eachother during Late Cretaceous−Early Tertiary time(Şengör 2002). These micro-continents are separatedfrom each other by ophiolite belts and accretionarycomplexes. Eastern Turkey is thus a very complexdomain situated in the Alpine-Himalayan fold-thrust fault belt. The intracontinental convergence
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and N−S-directed compressional-contractionaltectonic regime continued until the end of the LateMiocene and Late Early Pliocene, in places along theBitlis Suture Zone (Koçyiğit et al. 2001). Theseophiolitic zones, which extend into Iran and areknown as the Khoy Ophiolites, are mostly covered byyoung volcanic rocks in Turkey.
Local GeologyThe study area includes a typical ophiolitic mélange.Serpentinite, peridotite, claystone-marl-clayeylimestone, chert, conglomeratic limestone,fossiliferous limestone, conglomeratic chert, Fe-Nilaterite, clast supported conglomerate, porphyriticdiorite, micro-diorite and basalt are identifed unitsin the investigation site (Figure 2). Pelagic sedimentscomposed of claystone, marl and clayey limestonesare the main units in the study area. Limestone,chert, conglomeratic limestone, fossiliferouslimestone, conglomeratic chert blocks varying inshape from roundish to lensoid exist in pelagicsediment matrix (Figure 2). After the pelagicsediments, the most common rock type isserpentinite, which most extensive in the west and
north. The serpentinite contains some preservedharzburgitic peridotite in the north of the mappedarea (Figure 2). Nearby, chrysotile (1−3 cm), calcite(2−5 cm), dolomite (5−20 cm) and opal-chalcedony(10−150 cm) veins and veinlets in the serpentiniteextend to the NW and NE (Figure 2).
The Fe-Ni laterite zone is 650 m long and about10 to 35 m thick in the study area. In hand specimen,the Fe-Ni laterites range from red to purple in colour.The Fe-Ni rich laterite zone is inhomogeneous andshows stratification. The bedding thicknesses changefrom 5 to 30 cm with a dip of 60−80 degrees. Thiszone alternates towards the west and the south withslightly ferruginuous conglomerates and clast-supported conglomerates. These layers are 10−30 cmthick, greenish, and contain serpentinized olivineand pyroxene and yellowish brown colouredlimonite rich stratification (Figure 3A). They havethrust contacts (Figure 2). This mixed iron-richlateritic zone with other conglomeratic zones hasthree different features: (1) fine-grained, massive redsilcrete Fe-Ni laterite sediments contain abundantheterogeneous grains of chromite, magnetite,radiolarite, mafic silicate minerals, chalcedony, redchert: quartz clasts with different dimensions and
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PONTIDES
ANATOLIDES
TAURIDES
BORDER FOLD BELT
Ankara
İstanbul
Edirne
Van
ErzurumBalıkesir
KütahyaEskişehir
Adana
Hatay
SivasErzincan
Troodos
NAFZ
BSZEAFZ
Aegean Graben
System
Black Sea
Mediterranean Sea
Aegean
Sea
Sea of Marmara
Lake Salt
Lake Van
040
80km
ophiolite and ophiolitic mélanges
N
Kars
Bursa
Manisa?
Gre
ece
Iraq
Iran
Armenia
Georgia
Syria
Bulgaria
NAFZ- North Anatolian Fault Zone
EAFZ- Eastern Anatolian Fault ZoneBSZ- Bitlis Suture Zone
Muğla
EastAnatolian
AccretionaryComplex
Study Area
Figure 1. Ophiolite distributions in Turkey (modified from Juteau 1980).
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Explanations
Fe-Ni laterite
iron cementedconglomerateclast supportedconglomerate
claystone-marl-clayey limestone
fossiliferous limestone
serpentinite
peridotite
conglomeratic chert
conglomeratic limestone
opal-chalcedony vein
chert
Late
Cre
taceous-E
ocene
basalt
micro diorite
diorite porphyry
Mio
cene
Plio
cene
Pale
ocene
Eocene
thrust
strike-Slip Fault
normal Fault
200 m
36
43 0003522 4
000
23
37
Figure 2. Geological map of the study area.
shapes are found as clastics (Figure 3A, B); (2) clast-supported conglomerate (1 mm − 1.5 metre blocks)in a less iron-rich matrix with clasts composed ofchert, radiolarite and serpentinized ophiolitefragments of varying sizes and differing degrees ofweathering; (3) a clast-supported conglomeratecontaining abundant fragments of limestone,serpentinized ophiolites and chert (Figure 3C).These clastics confirm that the minerals andcomponents did not form in a primary lateritic crust,but by erosion of the lateritic components and theirtransport in a shallow marine environment near tothe ophiolites.
In the study area, magmatic rocks includemicrodiorite, porphyritic diorite and basalt. Thebasalts stratigraphically overlie the serpentinites and
are the youngest units observed in the study area(Figure 2). Microdiorites found in the southwest ofthe area studied extend eastwards, beyond the maplimit. Some small porphyritic diorites with amaximum dimension of 300 x 400 meters wereobserved in five different locations. One, a dyke-likeintrusion, cuts the lateritic zone. Porphyritic dioritesin this area are first described and reported in thisstudy but are not yet dated. This rock showsmacroscopically typical onion-skin weatheringtexture due to cooling and alteration (Figure 3D).
Petrography and Ore MineralogyThe Fe-Ni laterite zone is mainly composed ofgoethite, magnetite, chromite, silicate minerals
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Ch
Fe
rich
ban
d
Ch
A B
C D
Fe
po
or
ban
d
Lst
Figure 3. All macro-photos (A) iron rich and iron poor bands 5−30 cm in thickness in the Fe Ni laterite zone. Beddingdips at 60º SE (B) chert (Ch) and quartz fragments in reddish ferricrete laterite; (C) clast-supportedconglomerates; abundant limestone with fewer serpentinite and chert fragments; (D) porphyritic dioriteshowing onion skin weathering (hammer is 35 cm long; magnetic pen is 12 cm long).
(serpentinized olivine and pyroxene) clay minerals,chlorite, calcite and talc. In the laterite zone,chalcedony, red chert, quartz, radiolarite andophiolite fragments of varying sizes and shapesdisplaying differing degrees of weatheringcomponents are found as clastic fragments. Amongthese components, creamy-white chalcedony showsa comb texture which is characteristic of open spacefilling (Figure 4A). Some parts containing radiolarite(Figure 4B) and chert are cut by secondary silica(micro-crystalline quartz and chalcedony) veinlets(Figure 4C). Deformation textures observed in chertand chromite grains indicate that tectonic eventsaffected the minerals (Figure 4D).
The main phases in the porphyritic diorite areplagioclase, hornblende ± biotite (Figure 4E), foundin a fine-grained plagioclase-dominated matrix. Theporphyritic microdiorites are finer-grained than theporphyritic diorite and contain plagioclase, biotite ±hornblende. Basalt is macroscopically very fine-grained, petrographically defined as olivine basaltand plagioclase and olivine are the main componentsin the micro-porphyritic matrix; pyroxene is lessabundant (Figure 4F). The textural features of the Fe-rich laterites obtained from both microscopic andmacroscopic observations show that weathered anddecomposed material from ultrabasic rocks wastransported.
Identified opaque minerals in the ore zoneinclude magnetite, chromite, chrome-spinel,hematite, maghemite, goethite, and traces ofmillerite and psilomelane. Some Mn oxide mineralswere observed in the fracture surfaces. Theassociated silicate minerals are quartz, chert,radiolarite, serpentinized olivine, pyroxene, togetherwith small amounts of clay minerals and chlorite.Magnetite is the main opaque mineral. It occurs asabundant euhedral crystals 1−200 microns across.The opaque minerals in the Fe-rich laterite are richin chromite, partly altered to magnetite. Themagnetite alteration of chromites was initiated at therim (Figure 5A, B). Chromite grains with differentdimensions and shapes show different degrees ofalteration. The texture of the laterite indicates thatre-deposition occurred in at least in two stages,(fragments containing chert (Ch) in a magnetite(Ma) matrix are embedded in a later iron and chertmatrix) (Figure 5C, D).
All chromite crystals form euhedral and anhedralcrystals which are altered to magnetite at the rim(Figure 6A). Millerite was observed as inclusionstrapped at the boundary of the magnetite-chromiterims (Figure 6B) or within large magnetite crystals(Figure 6C). Some chromite crystals have beenaltered to hematite (Figure 6D) or directly to ferrianchromite. This ferrian chromite can be identified byits low reflectance grey colour compared to chromite.Chromite shows different modes of zonation. Ideally,optically zoned chromite shows dark chromite core,surrounded by a light-grey ferrian chromite zone,and greyish-white magnetite at the rim. However,mostly the observed zonations are less regular(Figure 6E, F).
Analytical MethodsIn total 12 rock samples were collected to determinemajor oxide and trace element data. Of these 11 arefrom the transported iron rich lateritic zone, and 1from intraclastic limestone (sample no= SC-12).Analyses were determined using the ME-XRF-11method at the CHEMEX Analytical Laboratories inCanada. The major oxide and trace element resultsare given in Table 3. Au, Pt and Pd were analysed byultra trace level methods using ICP-AES, with PGM-ICP23 code number. The detection limits for theseelements are 0.001 ppm for Au, 0.005 ppm for Pt and0.001 ppm for Pd. The SEM/probe investigation wascarried out in the Department of GeologicalEngineering SEM/probe laboratory at HacettepeUniversity, equipped with a Zeiss EVO-50 withBruker-Axs XFlash 3001 SDD-EDS. The XFlash3001 SDD EDS was operated under 15 kVaccelerating voltage, 15 nA probe current for elementanalysis, and 15 kV accelerating voltage and 0.5−1nA probe current for the images.
GeochemistrySEM/probe Investigation No analysis was performed to determine the nickelconcentration in silicate minerals in this study. Thecompositional variation was examined in twodifferent chromite grains which have been altered to
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Chr
Tc Ch
Ch0 0.2mm
Rd
0 1mm
Pl
Ol
0 1mm
B
Pl
Hb
Bi
0 1mm
Pl
ChQz
0 1mm
D
E
Qz
Lim
Lim
0 1mm
F
A
C
Figure 4. (A−D) Cross-polarized transmitted light photomicrographs of the Fe-Ni lateritic ore zone, (E, F) of porphyritic diorite andbasalt. Qz− quartz; Rd− radiolaria; Lim− limonite; Ch− chert; Chr− chromite; Tc− talc; Pl− plagioclase; Hb− hornblende;Bi− biotite; Ol− olivine. (A) Comb texture of quartz in limonitic matrix laterite zone; (B) micro-crystalline quartz cross-cutting radiolarite fragments; (C) red and grey chert cut by micro-crystalline quartz and chalcedony; (D) elongated androtated chert and chromite grains indicating shearing; (E) zoned plagioclase, biotite and hornblende in porphyritic diorite;(F) plagioclase and olivine crystals in olivine basalt.
magnetite at their rims by SEM/probe line scatteredanalysis (Figure 7). Usually, chromite grains showonly a chromite core and magnetite rim but in somethe chromite is surrounded by ferrian chromite andan outer rim of magnetite. Line scattered analysisshowed that the Al has the highest content in the firstchromite core and Mn, Mg and Fe elementsdecreases respectively (Figure 7A). However, the Mncontent of the second chromite core is lower than theFe content, which means that Mn content is variablein the chromite core (Figure 7B−D). The SEM/probeinvestigation indicates that magnetite rim is depletedin Mg, Mn, Al and Cr and is enriched in Fe and Ni(Figure 7).
Mn, Al, Cr, Fe, Ni and Mg analyses wereperformed on different chromite grains that exhibitchromite cores, ferrian chromite and magnetite rims.In total 10 analysis were measured from alteredchromite grains (see Table 1, sample # SC-2). The Nicontent varies between 0.98−2.05 wt% in themagnetite rim containing 70.1−84.4 wt% Fe2O3. TheMn and Al contents vary between 1.53−11.8 wt%and 6.5−16.8 wt% in the chromite core and ferrianchromite respectively. This analysis also shows31−46.8 wt% Cr and 11−24.6 wt% Fe (Table 1). Thedescription of macroscopic colours, magneticsusceptibility and Ni, Fe and Al2O3 wt% values of thesamples taken from the laterite zone are given inTable 2.
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Chr
Chr
Ma
MaMa
Ch
Ch
Chr
Ma
A B
C D
10 m
20 m 20 m
30 m
Figure 5. Back-scattered electron SEM/probe images (A) different sized zoned chromite (Chr) grains altered to magnetite(Ma) at rim; (B) zoned chromite with diversity in alteration degree; (C, D) the texture of laterite indicates that re-deposition occurred in at least two stage (the fragments having with chert (Ch) in magnetite (Ma) matrixembedded in another iron and chert matrix).
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0.1mm
Mil
ChrHe
Ma
B
0.1mm
Chr
Chr
Chr
Ma
0.1mm
0.1mm0.1mm
A
D
E F
Chr Chr
ChrChr
Fcr Fcr
Ch
TcTc
Qz
He
He
He
Ma
Ma
Ma
Qz
0.1mm
Mil
ChrChr
He
Ma
C
Figure 6. Photomicrographs of Fe-Ni ore texture in plane-polarized reflected light. (A) Different size of core chromite (Chr)altered to magnetite at its rim. (Ma) millerite (Mil) was only seen as inclusions in the martitized (He: hematite)magnetite both at rims surrounding to core chromite (B) or (C) within free large magnetite crystals; (D) zonedchromite core crystals are decomposed first to hematite in quartz (Qz) matrix; (E) irregular ferrian chromite zoneshows light grey colours compared to chromite core; (F) dark grey chromite core followed by an irregular light greyferrian chromite zone and a pale grey magnetite rim.
Whole-rock ChemistryThe major oxide and trace element compositions ofthe 12 samples are given in Table 3. While estimatingthe average value of the all samples, sample SC 12 is
omitted since it is intraclastic limestone. Asedimentary transported laterite zone has a highproportion of silcretes and ferruginous materials andchemically contains 29−61 wt% SiO2 and 11.8−48.7
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Cr
Ma
Cr
Mn
Ma
MaMaMa Ma
Ma
Ni
Fe
FeFe
Ma
Fe
Chr
Cr
Ni
Ni
Mn
Chr Chr
Chr
FeNi
MnAl
Mg
m20m20
m20 m20
A A
A A
A B
C D
Figure 7. SEM/probe line scattered analysis in core chromite and altered magnetite rim. (A) Cr, Al, Mn and Mg elements incore chromite depleted in magnetite rim, whereas Fe and Ni increased; (B−D) line scattered analysis in the differentgrains show that Mn content is variable in the chromite core.
wt% Fe2O3. The average content of Al2O3, TiO2, MnOand P are 4.81, 0.37, 0.32, and 0.03 (all in wt%)respectively (Table 3). It is apparent that SiO2 andFe2O3 values reach high values in the Fe-Ni lateritezone. Average Al2O3 and TiO2 values are 4.81 wt%and 0.37 wt%, respectively. The Ni values shownegative correlation with Al2O3 and TiO2 (Figure8A). Al2O3 reaches 8.27 and 12.10 wt% in SC 10 andSC 5 samples, respectively. These samples containlow Ni, Fe and Cr values (Figure 8B). There is apositive correlation between Al2O3 and TiO2 values(r= 0.96) (Figure 8C). However, Fe and Ni show poorcorrelation, r = 0.66 (Figure 8D), possibly because ofthe small number of samples and theinhomogeneous composition of the clastic units. The
Sarıçimen Fe-Ni laterite occurrences in easternTurkey are characterized by significant contents ofchromium, up to 2.52 wt% and manganese rangingfrom 0.12 to 0.6 wt% MnO. Cobalt ranges from 200to 700 ppm in these deposits and zinc rangesbetween 100 and 1100 ppm. The Pt and Pdconcentrations are generally low (ranging from 39ppb to 6 ppb and 21 ppb to 5 ppb, respectively). Nogold anomaly was detected: the Au value reaches upto only 3 ppb in three samples, while the remainingsamples are below detection limit. Typical feedcomposition for various types of operations (Dalvi etal. 2004) are shown in Table 4, and compared withsamples SC1 to SC11 from this study.
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Table 1. SEM/probe analyses: Mn, Al, Cr, Fe, Ni and Mg values in zoned chromite grains (all in wt%).
Samples Description Mn Al Cr Fe Ni Mg
SC-2 min. magnetite rim − − 1.02 70.1 0.98 0.91SC-2 n=6 average magnetite rim − − 1.57 80.4 1.54 0.95SC-2 max. magnetite rim − − 1.61 84.4 2.05 0.98SC-2 ferrian chromite 1.53 16.8 31 17 − 7.9SC-2 ferrian chromite 4.46 10.4 34.2 24.6 − 1.91SC-2 chromite 11.8 6.5 46.8 11 − 5.2SC-2 chromite 8.1 7.3 39.2 13.6 − 6.3
Table 2. Sample descriptions and Ni, Fe and Al2O3 analyses (all in wt%).
Samples Description Ni Fe Al2O3
SC-1 fine-grained, reddish coloured high magnetic susceptibility 0.65 29.60 3.64SC-2 fine-grained, black coloured high magnetic susceptibility 1.16 34.08 4.48SC-3 fine-grained, black coloured high magnetic susceptibility 1.09 30.02 3.74SC-4 fine-grained, reddish to purple coloured, high magnetic 1.03 27.64 3.51SC-5 fine-grained, black coloured, light weight, weak magnetic 0.27 11.79 12.10SC-6 medium-grained, reddish to yellow-brown limonitic zone more
fractures more detritic quartz. weak magnetic 0.59 14.56 4.83SC-7 medium-grained clastics, purple coloured, weak magnetic 0.60 10.36 1.31SC-8 medium-grained clastics, purple coloured, weak magnetic 0.99 24.49 3.43SC-9 medium-grained clastics, purple coloured, weak magnetic 0.71 17.56 3.20SC-10 green-coloured, altered ophiolitic detritics, weak
magnetic susceptibility 0.63 8.26 8.27SC-11 reddish to black coloured, weak magnetic fractures are limonitic 1.00 12.14 4.35SC-12 intraclastic limonitic limestone with quartz and ophiolite clasts 0.14 5.84 4.99
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Table 3. Some major and trace element analyses of Fe-Ni laterites from the Sarıçimen area.
Sample SC-1 SC-2 SC-3 SC-4 SC-5 SC-6 SC-7 SC-8 SC-9 SC-10 SC-11 SC-12
ppbAu 3.00 3.00 <1 <1 <1 1.00 <1 1.00 3.00 <1 1.00 <1 Pt 39.00 39.00 36.00 24.00 6.00 20.00 15.00 39.00 23.00 17.00 37.00 <5Pd 16.00 18.00 21.00 14.00 5.00 8.00 11.00 15.00 6.00 7.00 22.00 2.00
wt%SiO2 36.20 29.00 41.30 44.00 52.40 61.20 54.60 46.70 55.60 54.90 58.50 51.30Al2O3 3.64 4.48 3.74 3.51 12.10 4.83 1.31 3.43 3.20 8.27 4.35 4.99Fe2O3 42.32 48.72 42.92 39.52 16.86 20.81 14.81 35.01 25.11 11.80 17.36 8.35Na2O 0.10 0.23 0.27 0.27 0.01 0.01 0.28 0.85 0.68 <0.001 0.01 <0.001K2O 0.05 0.04 0.08 0.06 2.38 0.10 <0.01 0.05 0.05 0.02 <0.01 0.18V2O5 0.02 0.02 0.02 0.02 <0.001 0.01 <0.001 0.01 0.01 <0.001 0.01 <0.001TiO2 0.05 0.06 0.04 0.06 2.10 0.08 <0.01 0.03 0.03 1.21 0.07 0.38MgO 5.12 8.67 5.49 6.10 6.23 4.40 >10.0 7.71 8.60 >10.0 7.84 5.19MnO 0.33 0.60 0.36 0.40 0.23 0.12 0.27 0.37 0.44 0.36 0.09 0.04CaO 0.18 0.25 0.09 0.25 1.75 0.88 0.58 0.11 0.33 0.79 0.37 >10.0SO3 0.01 0.04 0.04 0.02 0.04 0.05 0.06 0.05 0.04 0.06 0.06 0.10As 0.03 <0.001 <0.001 0.00 <0.001 0.00 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001Ba <0.001 <0.001 <0.001 <0.001 0.00 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001Cl 0.01 <0.001 <0.001 <0.001 0.01 0.00 <0.001 <0.001 0.01 <0.001 <0.001 <0.001Co 0.03 0.07 0.06 0.06 0.02 0.03 0.03 0.05 0.05 0.05 0.05 0.01Cr 1.90 2.52 1.98 1.86 0.30 2.48 0.73 2.09 2.40 0.48 2.52 0.25Cu 0.01 0.01 <0.001 0.00 0.00 <0.001 <0.001 0.00 <0.001 0.38 0.01 <0.001Ni 0.65 1.16 1.09 1.03 0.27 0.59 0.60 0.99 0.71 0.63 1.00 0.14Zn 0.11 0.03 0.02 0.03 <0.001 0.01 <0.001 0.02 0.01 <0.001 0.01 <0.001P 0.02 0.02 0.02 0.04 0.11 <0.002 <0.002 0.01 0.01 0.05 0.00 0.04LOI 2.870 2.870 1.410 1.840 4.670 3.200 3.750 1.550 1.600 6.770 6.350 17.600
r = 0.66
0.00
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Figure 8. (A) Al2O3, TiO2 and Ni pattern in the laterite ore. First axis show Al2O3; second axis shows TiO2 and Ni values; (B) Fe,Ni and Cr pattern in the laterite ore, second axis shows Ni and Cr value; (C) correlations of TiO2 versus Al2O3; (D)correlations of Fe versus Ni (all in wt%).
Geodynamic ModelA model explaining the geodynamic evolution of theregion is presented in Figure 9. Lithological unitsand structural/textural features related to the lateriteore in the study area are similar to those from theEdessa area in northern Greece (Michailidis 1990).In view of the Late Cretaceous−Paleocene oceanclosure in eastern Anatolia (Şengör & Yılmaz 1981),similar geological conditions are likely to havecontrolled the formation of these two ore deposits,although the Sarıçimen laterite ore was formedsomewhat later than the Late Jurassic−EarlyCretaceous Edessa area ores (Boccaletti et al. 1974;Pearce et al. 1984). The geological evolution of thedeposit is as follows: (1) oceanic lithosphere wasobducted in ore-Late Cretaceous time to formophiolitic rocks; (2) subsequently the ophiolites wereexposed to extensive Late Cretaceous weatheringresulting in the formation of a laterite crust; (3) theselaterite crusts were eroded in LateCretaceous−Paleocene time, and the products weredeposited as clastic, and mainly chemical coastalsediments; (4) during Eocene−Miocene time clasticsedimentary laterite in continental stage was affectedby thrusting; (5) porphyritic diorite dykes wereintruded in the Miocene; (6) young, still activestrike-slip sinistral faults are displacing the rocks.
Discussion and ConclusionsThe Sarıçimen transported Fe-Ni laterite ore wasrecently found and is reported for the first time inthe present study, which only investigated the Fe-richzone. Although the number of studies of ophioliticrocks and mineral exploration activities in EasternAnatolia are quite limited, similar types of lateritedeposits are very common and have been well
studied in Alpine-Himalayan belt (e.g., Engin &Aucott 1971; Evans & Frost 1975; Albandakis 1980;Valeton et al. 1987; Michailidis 1990; Eliopoulos &Economou-Eliopoulos 2000; Economou-Eliopoulos,2003; Skarpelis 2006). The multistage deposition ofthe Fe-Ni ores, the redistribution of ore metals, theintense deformation and metamorphism which haveaffected all the Ni laterite deposits of Greece, havealmost totally changed their initial mineralogicalcomposition and texture (Eliopoulos & Economou-Eliopoulos 2000).
Mineralogical and petrographic features indicatethat the Sarıçimen Fe-Ni laterite deposit is atransported ferricrete zone, comprising aconglomerate of ophiolitic fragments, radiolariancherts, ferricrete and silcrete clastic materials. Itsmost characteristic features are optically zonedchromites, containing a chromite core, anintermediate ferrian chromite zone and a magnetiterim. Although there is no agreement about exactlyhow ferrian chromite and magnetite zoning inchromite was produced, all the researchers acceptthat it is an alteration product of chromite. Ferrianchromite was originally defined as intermediate incomposition, colour and reflectance betweenchromite and magnetite by Spangenberg (1943)(Michailidis 1990). Many researchers determinedthat the ferrian chromite formation was related toserpentinization (Peters & Kramers 1974; Takla et al.1976), while others related it to metamorphism afterserpentinization (Engin & Aucott 1971; Groves et al.1977).
The Mn and Al content of the altered chromitesstudied vary greatly. Mn contents range from 1.53 to11.8 wt% and Al contents range from 6.5 to 16.8 wt%in the core chromite and ferrian chromite zones. The
A. R. ÇOLAKOĞLU
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Table 4. Typical feed composition for various types of operations (Dalvi et al. 2004).
Analysis (wt%) SiO2 Ni Co Fe Al Mg Mn
Moa Bay 3.7 1.3 0.15 48 4.5 1.0 0.75SLN 37 2.7 0.07 14 15Cerro Matoso 46 2.9 0.07 14 9P.T. Inco 34 1.8 0.07 18 10Murrin Murrin 42 1.3 0.09 22 2.5 4 0.4This study 48 0.8 0.04 20 2.5 4 0.3
FE-NI LATERITIC ORES OF EASTER ANATOLIA
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Lateritic crust
platformlimestone
peridotitespelagicsediments
dioriteporphyry
continentalcrust
conglomerates
Fe-Ni laterite
Explanations
thrust faults
strike-slip faultsmovement towardobserver
NS Sea level
Pre-Late Cretaceous
Late Cretaceous
Late Cretaceous-Paleocene
Eocene-Miocene
S NSea level
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N
S
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S
N
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NSSea level
Sea level
6
Not to scale
+
+
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+
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.
.
.
.
.
Figure 9. Geodynamic model of the Sarıçimen Fe-Ni laterite ore zone.
interpretation of the chromite alteration and the highMn content of the zoned chromites is attempted onthe basis of the complicated history which they haveundergone from the first origin to their presentposition within the laterite ores (Michailidis 1990).Some Mn oxide minerals observed on the fracturesurfaces and known Mn mineralization in thevicinity may be evidence for the high Mn content inthe Sarıçimen laterite ore, and also confirms that Mncontents of the chromites are not primary.
Nickel content in the laterite zone averages 0.79wt% (n= 11 sample). The SEM/probe investigationindicated that nickel content varies between 0.8−2.05wt% in the magnetite rim of the chromite grains. Ptand Pd contents in the Sarıçimen Fe-Ni lateritesaverage 27 and 13 ppb, respectively. These values arelower than the average contents of Pt and Pd in Fe-Nilaterites (44 and 29 ppb, respectively) of Greece(Economou-Eliopoulos 1996). The average Al2O3and TiO2 contents of most Sarıçimen Fe-Ni lateritesamples (excepting Al2O3 and TiO2 rich samples SC5and SC10) with values of 4.5 wt%, and 0.04 wt%respectively, are similar to those of Greek Fe-Nilaterite deposits in Kostaria, Bitincka and Tsauka(Eliopoulos & Economou-Eliopoulos 2000). Thehigh content of samples SC5 and SC10 may indicatethat some of the clastics represent differentcompositions and degrees of alteration. All thesemineralogical and geochemical data indicate that the
Sarıçimen transported laterite zone was been formedin several stages of geodynamic evolution. The age ofthe porphyritic diorites is accepted as Miocenebecause similar porphyries (Upper Miocene calc-alkaline monzodioritic subvolcanic intrusions) cuttheir Paleocene−Eocene cover in Iran. This suggeststhat these porphyritic diorite intrusions may also beof Miocene age (Khalatbari-Jafari et al. 2004).
Diversity in chemical compositions of thelaterites is related to erosion, fracturation,transportation, corrosion, quantity of clastic materialwith different alteration history and diagenesis.Although this study presents limited data about theFe-rich zones, it is clear that undiscoveredtransported zones such as Ni-rich saprolite, clay andgoethite zones may also be important and this regionneeds to be explored for its economical potential.
AcknowledgementsThe author thanks Prof. Erkan Aydar for his helpwith electron microscope analysis and Üner Çakır,University of Hacettepe, for his comments. Thanksare also due to Sarah Gleeson and Economou-Eliopoulos for linguistic improvement andconstructive criticism, suggestions and comments onan earlier draft of the manuscript. Erdin Bozkurt iskindly thanked for editorial handling. English of thefinal text is edited by John A. Winchester.
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