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At the south of the Bardsir, Kerman province, Iran, the southeastern part of the Urmia-Dokhtar magmatic arc (UDMA), a large number of gabbroic intrusions are intruded into the Eocene lava flows and pyroclastic rocks with the form of small stocks and dykes. In this paper, geochemical variations, magmatic evolutions, and the origin of these intrusions are investigated. The studied intrusions are characterized by fine-grained margins resulting from rapid cooling and flow differentiation. They display porphyritic texture and include coarse-grained clinopyroxene with diopside compositions (Wo = 46.89, En = 40.78, Fs = 12.32), plagioclase with labradorite composition (An = 54.14), and olivine in an intergranular crystalline groundmass. Their whole-rock chemistry proves that the rocks belong to the calc-alkaline series. The abundances of trace elements and REE, depletion of Nb, Ta, Zr, Ti, and Hf, and enrichment of LILE relative to HFSE indicate that these rocks belong to a subduction zone setting. Geochemical characteristics (Sm/Yb and La/Sm ratios) show that the source rock of these intrusions was the lithospheric mantle with spinel lherzolite composition, which initially underwent partial melting (10% to 20%) events and then was metasomatized by fluids derived from the subducting Neo-Tethys lithosphere. [ABSTRACT FROM AUTHOR]

The Khut copper skarn deposit is located at about 50 km northwest of Taft City in Yazd province in the middle part of the Urumieh- Dokhtar magmatic arc. Intrusion of granitoid of Oligocene- Miocene age into carbonate rocks of the Triassic Nayband Formation led to the formation of marble and a calcic skarn. The marble contains high grade Cu mineralization that occurs mainly as open space filling and replacement. Cu-rich sulfide samples from the mineralized marble are also anomalous in Au, Zn, and Pb. In contrast, the calcic skarn is only weakly anomalous in Cu and W. The calcic skarn is divided into garnet skarn and garnet-pyroxene skarn zones. Paragenetic relationships and microthermometric data from fluid inclusions in garnet and calcite indicate that the compositional evolution of skarn minerals occurred in three main stages as follows. (i) The early prograde stage, which is characterized by Mg-rich hedenbergite ( Hd53.7 Di42.3- Hd86.1 Di9.5) with Al-bearing andradite (69.8-99.5 mol% andradite). The temperature in the early prograde skarn varies from 400 to 500°C at 500 bar. (ii) The late prograde stage is manifested by almost pure andradite (96.2-98.4 mol% andradite). Based on the fluid inclusion data from garnet, fluid temperature and salinity in this stage is estimated to vary from 267 to 361°C and from 10.1 to 21.1 wt% NaCl equivalent, respectively. Pyrrhotite precipitation started during this stage. (iii) The retrograde stage occurs in an exoskarn, which consists of an assemblage of ferro-actinolite, quartz, calcite, epidote, chlorite, sphalerite, pyrite, and chalcopyrite that partially replaces earlier mineral assemblages under hydrostatic conditions during fracturing of the early skarn. Fluids in calcite yielded lower temperatures ( T < 260°C) and fluid salinity declined to ∼8 wt% NaCl equivalent. The last stage mineralization in the deposit is supergene weathering/alteration represented by the formation of iron hydroxide, Cu-carbonate, clay minerals, and calcite. Sulfur isotope data of chalcopyrite (δ34 S of +1.4 to +5.2‰) show an igneous sulfur source. Mineralogy and mineral compositions of the prograde assemblage of the Khut skarn are consistent with deposition under intermediately oxidized and slightly lower f S2 conditions at shallow crustal levels compared with those of other typical Fe-bearing Cu- Au skarn systems. [ABSTRACT FROM AUTHOR]

Abstract: The giant Sarcheshmeh porphyry Copper deposit is located 65km southwest of Kerman City, southeastern Iran. Numerous Miocene porphyry stocks and dykes intruded thick sequences of Upper Cretaceous sedimentary and Eocene volcanic rocks. Hypogene and supergene porphyry Cu mineralization occurs within the granodioritic porphyry and host rock sequence, which was extensively altered to a dominantly potassic, phyllic, and argillic assemblage with interstitial to distal propylitic types. Biotite-bearing assemblages occur as both primary phenocrysts and secondary replacements showing variable size, colour, and shape. Fluorine contents (0.22 to 1.33wt.%) and XMg (0.54 to 0.71) in biotites from the potassic and phyllic zones are higher than those of non-mineralized granitoids (F=0.09 to 0.56wt.%, XMg =0.43 to 0.54), whereas their Cl contents (Cl=0.05 to 0.24wt.%) are lower than those of the non-mineralized granitoids (Cl=.0.11 to 0.45). The biotites from the phyllic zone have higher log (fH2O/fHF) and log (fH2O/fHCl) values than those of the potassic zone, as well as the granitoid and andesitic dykes. The log (fHF/fHCl) values determined for the granitoid, potassic and phyllic zones are similar, though more negative than those of the andesitic dykes. The log (fHF/fHCl) values have a similar range for biotite from the granitoid, and potassic and phyllic zones. The halogen fugacity ratios established for fluids associated with the Sarcheshmeh deposit from their F and Cl contents in biotite show that the granitoid, potassic zone and phyllic zone are increasingly affected by meteoric waters. The fluids that circulated in the phyllic zone are predominantly of meteoric origin, possibly overprinting original phyllic zone halogen contents. The Cl intercept values of biotite in the granitoid, and phyllic and potassic are similar to other ore-forming systems and tend to be more Cl-rich than Cl-intercept values of biotites in common igneous rocks. Calculated F/Cl intercept values for biotite in the granitoid and potassic zone are also consistent with many other porphyry copper forming systems. [Copyright &y& Elsevier]

Abstract: Miduk hypogene and supergene porphyry Cu–Mo mineralization occurs within the Miocene porphyritic quartz–diorite and host Eocene plagioclase–hornblende phyric andesitic pyroclastic and flow sequence. Both the host rocks were extensively altered by hydrothermal fluids to dominantly potassic, phyllic, and argillic with interstitial to distal propylitic types. Biotite-bearing assemblages from the proximal potassic zone are dark to light brown and have X phl from 0.56 to 0.68; F contents range from 0.15 to 1.8 wt.% and Cl contents range from 0.19 to 0.28 wt.%. Fluorine contents in the biotite negatively correlate with X phl and X Ti and Cl contents, and positively correlate with X phl and SiO2. Calculated log (fH2O/fHF), log (fH2O/fHCl), and log (fHF/fHCl) values of fluid in equilibrium with these biotites ranging from 5.5 to 6.40, 4.64 to 4.79, and −2.54 to −1.68, respectively. Established halogen fugacity ratio contour lines are transected by the steeper slope of measured values of biotite composition; this suggests the fluid composition, fO2 and fS2 of the fluids, and reaction between wall rock and hydrothermal fluids play a key role in the resultant halogen fugacities recorded in biotite that is critical to interpreting metal complexing behaviour during magmatic-hydrothermal evolution. The intercept values of F [IV(F)] and Cl [IV(Cl)] for biotite from the potassic zone are similar to those of related plutonic rocks and other porphyry Cu deposits; the IV(Cl) tend to be more Cl-rich than comparable values of common igneous rocks. F-rich to F-poor biotite crystals from the Miduk deposit show a narrow range of F/Cl intercept values [IV(F/Cl)] consistent with porphyry Cu ore-forming fluids. [Copyright &y& Elsevier]

Graphical abstract Highlights • Massive and banded magnetite from GGID show distinct elemental compositions. • The banded iron ore is not classified as banded iron formation (BIF). • The massive magnetite does not seem to be formed via purely-magmatic processes. • The massive iron ore has similarities with Kiruna-type ore deposits. • The banded iron ore has similarities with magnesian skarn ore deposits. Abstract Genesis of magnetite from Gol-Gohar iron deposit (GGID) of southeastern Iran is studied with reference to elemental composition. More than 1.2 billion tonnes of magnetite ore at 58% total Fe is hosted by greenschist- to amphibolite-facies metapelites and magnesian marbles. The GGID occurs in the mainly-metamorphic terrain of Sanandaj-Sirjan geological province, with continental-margin tectonic setting. The magnetite-bearing ore is divided into two distinct types of massive and banded; the latter hosted mainly by magnesian marbles. Both subtypes of the ore bodies are associated with mineral assemblages consisting of calcite, dolomite, forsterite, tremolite-actinolite, talc, serpentine, and chlorite. The ore minerals in both subtypes are magnetite, hematite with minor amounts of pyrite, pyrrhotite, and chalcopyrite. Concentrations of temperature-dependent elements, Ti, Al, and Ga in the two subtypes would suggest that temperature of formation was higher for the massive magnetite (with Ti = 626 ppm, Al = 69 ppm and Ga = 56 ppm, on average) and relatively lower for the banded magnetite (with Ti = 60 ppm, Al = 62 ppm and Ga = 4 ppm, on average). The multi-element diagrams, for massive magnetite, show patterns closer to those of magmatic-hydrothermel iron deposits (Kiruna-type), whereas, patterns of the banded magnetite match better with those of skarn deposits, particularly the magnesian skarns. Average concentrations of V (>1000 ppm) and Cr (∼4 ppm) of the massive subtype fall within the range of those of Kiruna-type deposits, and the in average lower concentrations of V (∼10 ppm) and Cr (∼1 ppm) of the banded magnetite match the values of skarn deposits. The average V content of the massive magnetite (1342 ppm) is consistent with the global range of magmatic-hydrothermal magnetite (up to 3880 ppm), but different from global values of purely-magmatic magnetites (up to 6600 ppm). The banded magnetites contain 0.21–25 ppm V, which is only consistent with the lowest values of hydrothermal magnetites. We contend that the massive magnetite was formed by magmatic-hydrothermal processes (i.e., Kiruna type) and the banded magnetites were generated via metasomatic reactions between iron-rich residual magmatic fluids and the magnesian carbonate host rocks (i.e., skarn type). [ABSTRACT FROM AUTHOR]

This work investigates the petrogenesis of the main magmatic rocks of the Jurassic Alvand plutonic complex, located in the northern sector of the Sanandaj-Sirjan Zone of Iran. The Alvand complex is made up of a wide range of rocks spanning gabbro to leucogranites, containing a diversified range of enclaves, from mafic-to felsic- and surmicaceous-type. Here we present new textural characterization together with mineral, whole rock and Sr–Nd isotope chemistry of the main magmatic lithotypes. We integrated this new data with the available ones to understand the petrogenesis of the Alvand magmas and their interaction with the Ediacaran-Cambrian crystalline basement. A legacy of the Peri-Gondwanan crust is evident in Alvand felsic rocks. The whole rock chemistry, the Sr–Nd isotope ratios and assimilation-fractional crystallization numerical models indicate their genesis partly through differentiation via fractional crystallization from the coeval Alvand gabbros coupled with a concurrent and significative mass-addition of material from the Cadomian basement. At a wider scale, this work also provides new insights into the understanding the role of the continental crust in the buildup of transcrustal magmatic systems and therefore to a better comprehension of crust growth process driven by intense magma-crust interaction events. • The magma-crust interaction is explored through field and chemical investigations. • The Jurassic Alvand Complex is as a case study to unravel continental crustal growth. • AFC modelling can quantify the crust role in the chemistry of differentiated melts. [ABSTRACT FROM AUTHOR]

The Horjand area is part of the Kashmar-Kerman tectonic zone in the Central Iranian block, where the oldest continental crust of Iran can be found. Mafic igneous rocks associated with sedimentary units (gypsum, shale, limestone, dolomite and sandstone) belong to the magmatism of the Late Neoproterozoic–Early Cambrian Desu Series. Based on petrographic studies, the mafic igneous rocks comprise medium to coarse gabbro, micro-gabbro and hornblende-gabbro. The rocks mainly consist of plagioclase, olivine, clinopyroxene, biotite, amphibole and Fe-Ti oxides. The gabbroic rocks have a variable compositional range, with SiO 2 (44.6–52.9 wt. %), MgO (2.94–13.83 %), CaO (5.56–15.23 wt. %) and TiO 2 (1.19–2.68 wt. %) contents. Petrographic evidence and geochemical data suggest that fractional crystallization has played an important role in the evolution of the ascending magma of the gabbroic rocks. The chemical composition of the minerals is similar to those of gabbroic rocks that were formed in a non-orogenic environment. The crystallization of clinopyroxene of gabbros mainly occurred under temperatures ranging from 1045 to 1216 °C. The geochemical characteristics and mineral compositions of the gabbros show that the samples predominantly have alkaline to minor tholeiitic affinities. During magma ascent, crustal contamination was minor or absent. Rare earth element modeling demonstrates that the magma of the Horjand gabbros was produced from 10 to 15 percent partial melting of a spinel-garnet lherzolite mantle source. Chondrite-normalized rare earth element (REE) patterns are LREE-enriched with (La/Yb) N of 4.50-12.82. Both normalized REE and trace-element spidergrams are similar to patterns of HIMU-OIB (high mu (μ = U/Pb)-ocean island basalt) or intraplate alkaline magmatic rocks. The gabbros geochemically display an intra-plate tectonomagmatic setting without subduction geochemical characteristics. Based on the available data and mineral chemical composition the development of the Horjand gabbroic rocks could be related to an extensional phase, with upwelling melting of the asthenospheric mantle in the continental rift resulting in alkaline magmatism of Late Neoproterozoic–Early Cambrian age, in the Central Iranian micro-continent. [ABSTRACT FROM AUTHOR]