Geology,geochemistry,fluid inclusions and O-H stable isotope constraints on genesis of the Lake Siah Fe-oxide±apatite deposit,NE Bafq,Central Iran

The Lake Siah iron±apatite deposit is situated in the Bafq Mining District(BMD),Central Iran.The iron±apatite orebodies are hosted by a succession of rhyolite,rhyolitie tuff,trachyandesite,and andesite of Lower Cambrian age.The host rock has undergone wide-spread alteration and mineralization stages including Na(albite-quartz),followed by Na-Ca(albite-calcite--am-phibole-magnetite±quartz±epidote),magnetite-ap-atite,K(biotite±K-feldspar),hydrolytic(sericite-quartz),and argillic(kaolinite--montmorillonite±dickite),respec-tively.Electron microprobe analyses(EPMA)from mag-netite and hematite show significant variations of trace elements.Based on Ni/Cr+Mn and Ca+Al+Mn ver-sus Ti+V diagrams,the majority of magnetite samples belong to Kiruna-type deposits.At least,three generations of fluid inclusions,including solid-bearing(L+V+S)(Type I),liquid-rich(L+V)(Type II-A),vapor-rich(L+V)(Type II-B),and liquid or vapor mono-phase(Type II),are recognized in quartz and apatite.The solid-bearing fluid inclusions in quartz completely homogenized at temperatures of 150 to>530℃with salinities of 30--58 wt%NaCl equiv.Liquid-rich fluid inclusions in apatite homogenized to a liquid phase at 175--210℃,whereas the vapor-rich fuid inclusions homogenized to a vapor at 335-350°C.Oxygen isotope analysis was carried out on quartz and magnetite.The hydrogen and oxygen isotopic compositions of quartz(8"Onuid values of 7.57-11.04%)show that with progress in time the ore-forming solutions gradually evolved from a magmatic to meteoric-dominated source.

Petrology of the Plutonic Rocks at the XIV Iron-Oxide Prospect, Bafq Mining District, Central Iran

The XIV iron-oxide prospect in the northern part of the Bafq mining district is hosted by intrusive rocks and demonstrates similar characteristics with Kiruna mineralization. The plutonic complex of the XIV prospect is composed of two major types of intrusive rocks, including: 1) a granitic intrusive body which is itself composed of two types;a pale-pink leucogranite and a white-gray aplite, as well as 2) a gabbrodiorite intrusive body. Geochemically, these rocks are tholeitic-calcalkaline and metaluminous in nature. Geochemical characteristics of the plutonic rocks of the study area support a non-orogenic continental setting.

Fe-Ti Oxide Mineralization in the XV Intrusion,Bafq Mining District,Central Iran:Insights from Mineralogy,Mineral Chemistry and S Isotopic Data

The mafic-ultramafic intrusion in the XV anomaly area,contains magmatic Fe-Ti oxides±(p)ore,is located in the Bafq mining district in the Central Iran.It consists of cumulate and layered Fe-Ti-bearing gabbros and pyroxenites.The mineral assemblages include clinopyroxene,Fe-Ti oxides,plagioclase,amphibole,apatite and sulfides(pyrite and chalcopyrite).The Fe-Ti oxides mainly consist of magnetite-titanomagnetite and ilmenite,which occurred as disseminated,intergrowth,lamellae(trellis and sandwich textures)and inclusions.Magnetite in the gabbroic rocks is from the near end-member of Fe_(3)O_(4)(<1 wt.%TiO_(2))to titanomagnetite containing up to 8 wt.%TiO_(2)(about3.73 wt.%to 26.84 wt.%Ulvospinel(X_(Usp))).Magnetite in pyroxenite rocks is characterized with TiO_(2)range from 0.46 wt.%to 3.14 wt.%(X_(Usp)varied from 1.76 wt.%to 10.46 wt.%).The abundances of V_(2)O_(3)range from 0.03 wt.%to 1.29 wt.%and 0.24 wt.%to 1.00 wt.%for gabbro and pyroxenite,respectively.X_(Usp)contents of magnetite show insignificant correlations with Al_(2)O_(3)and MgO.The average XIlmin the ilmenite of gabbro is 92%,whereas it is 90.37%in the pyroxenite rocks.The MgO and V_(2)O_(3)contents show a slightly positive correlation with TiO_(2)in ilmenite.The composition of clinopyroxenes in gabbro and pyroxenite rocks fall in the diopside to augite field with Mg#ranging from 67 to 98 and 74 to 96,respectively.In both rock types,amphiboles are mainly pargasite and rarely actinolite.Plagioclase in pyroxenite rocks is clustered in the labradorite to andesine fields with a compositional ranges of An46-69and in gabboic rocks fall in two fields with compositional ranges of albite with An0.65-5.95and labradorite with An50-63.Theδ34S isotopic values cover a limited range from+3.15‰to+4.10‰V-CDT consistent with magmatic origin.Fe-Ti mineralization is formed in two stages,minor inclusions of Fe-Ti oxide minerals in the pyroxene and plagioclase crystallized in the early magmatic stage,whereas interstitial oxides formed by fractional crystallization processes that accumulated by gravitational settling in the later stage as intercumulus phase.Gravitational settling process is supported by the observation of decreasing the amount of Fe-Ti oxides from Fe-Ti oxide-rich pyroxenite to weak mineralized gabbro(base to top).The high contents of H2O,phosphorate and high initial Ti-Fe in parental magma are the crucial factors controlling the Fe-Ti oxides enrichment and mineralization.

The Relationship between Fe Mineralization and Magnetic Basement Faults using Multifractal Modeling in the Esfordi and Behabad Areas(BMD), Central Iran

Multifractal modeling is a mathematical method for the separation of a high potential mineralized background from a non-mineralized background. The Concentration-Distance to Fault structures(C-DF) fractal model and the distribution of the known iron(Fe) deposits/mines seen in the Esfordi and Behabad 1:100,000 sheets from the Bafq region of central Iran are used to distinguish Fe mineralization based on their distance to magnetic basement structures and surface faults, separately, using airborne geophysical data and field surveys. Application of the C-DF fractal model for the classification of Fe mineralizations in the Esfordi and Behabad areas reveals that the main ones show a correlation with their distance from magnetic basement structures. Accordingly, the distances of Fe mineralizations with grades of Fe higher than 55%(43% < Fe ≤ 60%) are located at a distance of less than 1 km, whereas for surfacial faults with grades of 43% ≤ Fe ≤ 60%, the distances are 3162< DF ≤ 4365 m from the faults. Thus, there is a positive relationship between Fe mineralization and magnetic basement structures. Also, the proximity evidence of Precambrian high-grade Fe mineralization related to magnetic basement structures indicates syn-rifting tectonic events. Finally, this C-DF fractal model can be used for exploration of magmatic and hydrothermal ore deposits.