In the Kalaybar Hasht-Sar area, in the western part of secondary Palaeo-Tethys suture zone (NW Iran), gabbro intrusion, which is older than Paleocene in age, has cropped out. This gabbro is shoshonitic in composition with has arc type geochemical composition. The rocks show high K2O concentration and enrichment of Rb, Ba, U, Th and Pb and depletion of Ta, Nb, Ti also Hf, Zr on primitive mantle-normalized spider diagrams. The parental magma of gabbro is formed by low partial melting rate (less than 10%) of spinel-garnet lherzolite. According to trace elemental ratios, the gabbro was derived from a source strongly modified by subducted slab fluids. Then crustal contamination caused the LILE enrichment in the magma. Considering accompany of the rocks with Palaeo-Tethys suture zone suit, it seems that gabbro was formed due to subduction of this oceanic crust. Metasomatism above subduction zone is an important process that produced heterogeneous mantle and thus changes in geochemical ratios of the magma.

1-Introduction Corundum (Al2O3) is one of the rare metamorphic minerals that its formation requires particular chemical condition (low SiO2 and high Al2O3) in combination with high temperature (Simonet et al., 2008). Therefore, one of the most critical cases in the study of corundum-bearing rocks is the accurate determination of protolith and metamorphic conditions (Yakymchuk and Szilas, 2018). In the Broujerd area, Berthier et al. (1974) reported the corundum in migmatites for the first time. Despite the many studies in metamorphic rocks, these corundum-bearing rocks never reported in later works, until (Ghaffari, 2010) and then (Papi, 2015) again reported corundum-bearing rocks in the area and both concluded that they are a kind of migmatites, evidence of granulite facies metamorphism. Neither Berthier et al. (1974) nor Gaffari (2010) and Papi (2015) reported albitite rocks that are in direct relations with corundum-bearing rocks. Also differences between whole rock composition in migmatites and corundum-bearing rocks and its possible role in corundum formation, never discussed. 2-Materials and Methods Different samples collected for petrographic studies and finally, five samples had chosen for whole rock analysis (Table 1). Bulk rock compositions of selected samples were determined using an X-ray fluorescence spectrometer at the Zarazma Co., Tehran, Iran. Chemical compositions of minerals were obtained using a JEOL W-EPMA JXA8900-R electron microprobe in the Institute of Earth Sciences, Academia Sinica, Taiwan, at an acceleration voltage of 15 kV, a current of 15 nA, and a beam size of 2 nm. (Droop, 1987). The method used for Recalculation of Fe as Fe3+ and Fe2+. All mineral abbreviations are from (Whitney and Evans, 2010). 3-General geology and field relations Borujerd area located in Sanandaj-Sirjan Zone in the western part of Iran. Intrusive rocks, as main granitoids and rare norite, gabbro, and pegmatites, with NW – SE trend, injected along dominant schistosity in metapelites (Berthier et al., 1974), during middle Jurassic (175-170Ma; (Ahmadi-Khalaji et al., 2007; Mahmoudi et al., 2011). Contact metamorphism developed during magmatism, especially in the northern part of Broujerd batholith. Highest metamorphic grade restricted either to the northern part of granitoids or as large enclaves. Migmatites in Ab-Bakhshan area, show one of the most significant outcrops and located between granitoids and hornfelses. Based on Fig. 1, albitites dikes injected in migmatites. In general, towards albitites, migmatites first start to metasomatized and formed metasomatized-migmatites, then corundum-bearing rocks will appear either in contact or inside albitites. Migmatites are metatexite with the low-melt portion, generally with patchy structure. In petrographic studies, they include relatively uniform mineralogy: quartz, plagioclase and potassium feldspar are main minerals in the leucosomes with granoblastic texture, while biotite, cordierite, andalusite, sillimanites, spinel, and Fe-Ti oxides, are major minerals in mesosome, generally with lepidoblastic or grno-lepidoblastic texture. Their chemical composition (Table 1) with high Al2O3 and SiO2, and low alkali and calcium show that they have the pelitic origin. Metasomatized migmatites in the field are the same as migmatites, but under the microscope, andalusite and sillimanites start to replace by sericites, and biotites with chlorite. Near the corundum-bearing rocks (based on Figure 1) all andalusite and sillimanites completely replaced by sericites, all biotites with chlorites and also, feldspars altered. Comparing to migmatites, they have higher SiO2 and less Al2O3 (Table 1). Corundum-bearing rocks have different mineralogy. They mainly composed of corundum, chlorite, white mica (tin muscovites) and feldspar (albite), with rare rutile, ilmenite, and apatite. Albitites are mainly composed of albite (more than 80%) and quartz, sericites, potassium feldspars as minor minerals. Their chemical composition is entirely different from migmatites, with a low concentration of SiO2 and higher Al2O3 and MgO (Table 1). Albitites are deformed and make dikes and small patches in migmatites. They mainly composed of albite with rare muscovite, quartz, and k-feldspar. Their chemical composition is following high– Na plagioclases (Table 1. Figure 1. Schematic illustration of field relations between migmatites, corundum-bearing rocks and albitites (without scale) Table 1. Major elements analysis of selected samples, based on Figure 1 Sample BM-96. 5 BM-96. 8 BM-96. 9 BM-96. 102 BM-96. 7 SiO2 63. 85 71. 08 43. 25 43. 73 61. 45 Al2O3 17. 35 14. 65 28. 38 26. 55 19. 54 TiO2 0. 82 0. 73 0. 69 0. 48 0. 67 Fe2O3 7. 49 3. 6 4. 57 6. 94 2. 02 MgO 2. 2 1. 95 8. 7 8. 68 2. 75 MnO 0. 16 0. 05 0. 05 0. 07 CaO 0. 64 0. 8 0. 54 0. 92 0. 51 K2O 3. 35 2. 39 5. 48 2. 79 0. 32 Na2O 1. 53 1. 74 1. 82 3. 59 10. 09 P2O5 0. 22 0. 1 0. 06 0. 09 0. 16 LOI 2. 31 2. 91 6. 46 6. 09 2. 48 4-Mineral chemistry Selected mineral analysis from corundum-bearing rocks is represented in Table 2. Corundum crystals in a mica matrix, have a relatively pure chemical composition (Table 2) and their aluminum content is above 1. 99 a. p. f. u, only iron is a unique element that it reaches up to 0. 006 a. p. f. u. Chlorite is one of the most abundant minerals in corundum-bearing rocks, which forms a large part of the rock's matrix. Chlorites usually contain rutile and or ilmenite inclusions. Chlorite are Mg-rich (Mg/Mg+Fe from 0. 75 to 0. 76; Table 2). In white micas, iron and magnesium are low and close to a pure muscovite composition. Feldspars are sodic in chemical composition, in which the XAb is 0. 99 (Table 2). In other words, feldspars are pure albite. Cordierite is a rare mineral between feldspars and chlorites, and due to petrographic similarities, it is difficult to detect under the microscope. They are Mg-rich (Mg/(Mg+Fe)=0. 81; Table 2). Rutile as inclusions in chlorite are relatively pure, and their iron and manganese are deficient (Table 2). Ilmenite is also found in some parts in the chlorite or the rock matrix, and its chemical composition is close to the ideal ilmenite, with little impurities (Table 2). Table 2. Chemical analysis of minerals in corundum-bearing rocks of Broujerd area. Only selected analyzes are provided Mineral Chl Chl Ms Ms Crn Crn Crd Crd Fsp Fsp Rt Ilm Point 1 2 1 2 1 2 1 2 1 2 SiO2 27. 31 27. 29 47. 70 45. 98 0. 02 0. 01 48. 21 48. 18 68. 67 68. 03 0. 42 0. 00 TiO2 0. 05 0. 06 0. 09 0. 00 0. 01 0. 05 0. 00 0. 00 0. 00 0. 00 98. 78 53. 97 Al2O3 21. 50 22. 51 34. 86 37. 72 99. 82 99. 71 33. 04 33. 12 19. 42 19. 41 0. 25 0. 00 Cr2O3 0. 04 0. 15 0. 00 0. 00 0. 06 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 Fe2O3 0. 06 0. 00 0. 00 0. 00 0. 00 0. 00 1. 21 1. 23 0. 00 0. 00 0. 00 0. 00 FeO 13. 34 14. 08 0. 65 0. 33 0. 16 0. 20 4. 35 4. 44 0. 00 0. 00 0. 17 43. 67 MnO 0. 08 0. 06 0. 00 0. 00 0. 01 0. 00 0. 65 0. 61 0. 00 0. 00 0. 00 1. 85 MgO 24. 14 23. 36 1. 22 0. 39 0. 00 0. 00 10. 36 10. 45 0. 00 0. 00 0. 18 0. 10 CaO 0. 00 0. 01 0. 00 0. 60 0. 00 0. 00 0. 00 0. 00 0. 15 0. 09 0. 05 0. 00 Na2O 0. 04 0. 00 0. 61 1. 04 0. 00 0. 00 0. 00 0. 00 11. 23 11. 58 0. 00 0. 00 K2O 0. 00 0. 00 9. 76 9. 22 0. 00 0. 00 0. 00 0. 00 0. 05 0. 04 0. 00 0. 00 Totals 86. 56 87. 52 94. 89 95. 28 100. 08 99. 97 97. 82 98. 03 99. 52 99. 15 99. 85 99. 59 Oxygens 14. 00 14. 00 11. 00 11. 00 3. 00 3. 00 18. 00 18. 00 8. 00 8. 00 2. 00 3. 00 Si 2. 73 2. 70 3. 15 3. 03 0. 00 0. 00 4. 94 4. 92 3. 01 2. 99 0. 00 0. 00 Ti 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 99 1. 02 Al 2. 53 2. 63 2. 72 2. 93 2. 00 2. 00 3. 99 3. 99 1. 00 1. 01 0. 00 0. 00 Cr 0. 00 0. 01 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 Fe3 0. 01 0. 00 0. 00 0. 00 0. 00 0. 00 0. 09 0. 10 0. 00 0. 00 0. 00 0. 00 Fe2 1. 12 1. 17 0. 04 0. 02 0. 00 0. 00 0. 37 0. 38 0. 00 0. 00 0. 00 0. 92 Mn 0. 01 0. 01 0. 00 0. 00 0. 00 0. 00 0. 06 0. 05 0. 00 0. 00 0. 00 0. 04 Mg 3. 60 3. 45 0. 12 0. 04 0. 00 0. 00 1. 58 1. 59 0. 00 0. 00 0. 00 0. 00 Ca 0. 00 0. 00 0. 00 0. 04 0. 00 0. 00 0. 00 0. 00 0. 01 0. 00 0. 00 0. 00 Na 0. 01 0. 00 0. 08 0. 13 0. 00 0. 00 0. 00 0. 00 0. 95 0. 99 0. 00 0. 00 K 0. 00 0. 00 0. 82 0. 78 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 Sum 10. 00 9. 97 6. 93 6. 96 2. 00 2. 00 11. 02 11. 03 4. 97 4. 99 1. 00 1. 98 XMg 0. 76 0. 75 0. 79 0. 79 Mg/(Mg+Fe) 0. 76 0. 75 0. 81 0. 81 Or 0. 31 0. 20 Ab 98. 96 99. 40 An 0. 73 0. 40 5-Phase equilibria in the corundum-bearing rocks Phase equilibria for corundum-bearing rocks were modeled in the system Na2O-K2O-CaO-FeO-MgO-Al2O3-SiO2-H2O-TiO2 (Ti-NCKFMASH) using the THERIAK-DOMINO software v. 03. 01. 12 (Capitani and Petrakakis, 2010) with the internally consistent thermodynamic dataset of (Holland and Powell, 1998). The activity models of (Baldwin et al., 2015) are used for feldspar, those of (White et al., 2002) for corundum, and (Coggon and Holland, 2002) for micas. The water content is taken from the 'loss of ignition' (LOI) during XRF analyses, following (Sarkar and Schenk, 2014), although the effects of variation in the amount of water calculated. The fluid phase is assumed to be pure H2O. The final calculated pseudo section is represented in Figure 2. Figure 2. Calculated pseudosection for corundum-bearing rocks in Broujerd area (Sampled BM-96. 102 in Table 1 and Fig. 1). Gray region is following the mineralogy of corundum-bearing rocks. Dashed red and green lines represent equal values of Mg/Mg+Fe for chlorite and cordierite, respectively and their intersection show 605 ° C-3. 3 kb as T and P, based on the mineral analysis in Table 2 6-Conclusion In the Ab-Bakhshan area, corundum-bearing rocks appeared as small patches, located in albitites or albitite-migmatite contact. Based on calculated pseudosection for migmatites, their composition is not suitable for corundum formation, even in high T. Using whole rock composition of corundum-bearing rocks, T and P estimated as 605 ℃ in 3. 3 Kbar. Field relation between metasomatic rocks (albitites) and corundum-bearing rocks show that metasomatism was effective during corundum formation. The albitites occur most commonly in conjunction with other types of metasomatic rocks including scapolitised metagabbros and Mg-Al-rich lithologies such as orthoamphibole-cordierite schists (Engvik et al., 2014; Engvik et al., 2018). During Na metasomatism and albitite formation, Mg-Al rich fluids generated and cause chemical changes in migmatites, lead to appropriate whole rock composition for corundum formation. Na metasomatism could generate Mg-Al rich rocks, as corundum-bearing rocks of Broujerd area. So Mg-metasomatism and corundum formation either in migmatites or albitites, are consequences of Na-metasomatism in the area or are not evidence of very high T metamorphism.

Arash Syenite is located in central Iran and in Bafq metalogenic province, and has intruded into the Precambrian-Cambrian volcanic-sedimentary sequences. Size and distribution of minerals are not uniform in all parts of the body and vary from chilled margins to the central part of the pluton. Effects of tectonic movements, existence of uncommon textures in plagioclase crystals and the appearance of metasomatic textures are the main evidence for metasomatism. Study of elemental concentration deduced from mass balance calculation reveals the effects of alkaline metasomatism in Arash Syenite. Gain in K2O (and Rb) and Al2O3 with parallel losses in Fe2O3, CaO, Na2O, Ba and Sr are shown. Relative increase in Nb and Zr are due to leaching of mobile cations in this pluton.Decrease in Zr and Nb with parallel increase in SiO2, which is one of the most identical factors for the calc-alkaline differentiation, is remarkable in Arash Syenite. There is a clear change in Y, Th and Nb relative to Zr in this pluton and based on the constant ratio of Zr/Nb, the role of contamination and assimilation of country rock is insignificant in the pertrogenesis of this pluton. Negative anomaly for Nb and TiO2 suggest a subduction-related origin for the Arash Syenite.

The Sargaz granitic intrusion has been emplaced in Sargaz ophiolitic suite, south-east of Sanandaj-Sirjan metamorphic zone, south of Kerman province. The central part of the intrusive body contains pinkish coarse-grained granite, but the fractured northern part, neighboring Chah-Mazraeh fault, has been subjected to pervasive Na-metasomatism and related subsolidus reactions. In the northern altered rocks, the primary magmatic textures have been changed into a new generation of albite along with chlorite, epidote and sericite. Petrographically, in Sargaz altered rocks, albite occurs as overgrowth, crack-filling, vug-filling and interstitial forms. The first form has been replaced the primary plagioclase, and/or alkali feldspars by a coupled dissolution-reprecipitation mechanism, while, the other forms have been crystallized from Na-rich alkali fluids during Nametasomatism. In Sargaz unaltered granites, primary feldspars contain oligoclase (An23.8-An10.6) and K-feldspar (kf70-kf95.9), while, metasomatic feldspars are entirely albite (An8.4-An0.3) without any chemical zonation. Na-metasomatism in these rocks resulted obvious mass changes in rock composition, as the altered rock are enriched in Na, La, Y, Yb, Hf and Th and depleted in K, Fe, Mg, Ca, Sr, Co and Zn. Si, P, Rb, Ti, Al and Zr possibly acted as immobile elements during Na-metasomatism. Evidences in Sargaz intrusion show that alkali Na-rich fluids caused Na-metasomatism as dissolution of primary quartz and then, crystallization of albite. Microcracks facilitated infiltration of fluids. During the metasomatism, enough quartz grains were dissolved, thereby releasing silica for the formation of different forms of new albites, thus, the role of quartz dissolution, is more important than those expected earlier.

Dodehak granitoid stock with tonalite to granodiorite composition is exposed south of Dodehak village, north of Ab-e-Garm (Mahalat) in Urumieh-Dorhtar volcanic belt of Iran. Based on petrography and point analysis (EPMA), plagioclase crystals show normal zoning with graphic texture is present. Samples from SE of the intrusion are different and myrmekite texture is present in the rocks, while graphic texture is absent and plagioclases have lost their zoning. In samples from SE of the area, myrmekite is rim type and plagioclases show cross shape twinning. Based on whole rock XRF analyses, Rb-SiO2 and K2O-Na2O diagrams show nonlinear trends and EPMA analysis indicate that plagioclases are homogeneous albite. Such petrographical and geochemical features are evidence for alkaline metasomatism in SE of the Dodehak intrusion.

The Saghand mining district is a part of Bafq-Saghand metallogenic zone in the Central Iranian geostructural zone which is located in northeast of city of Yazd. This area is known to be more susceptible to mineralization of U and Th radioactive elements, but in fact is that its main importance is for relatively large iron deposits. . .

At the NE of Baraghan, gabbroic to monzonitic sill, known as Karaj Dam sill, intruded into the tuffs. Based on field observations and microscopic studies, the sill is differentiated from margin toward the center. Plagioclase crystals sometimes show zoning, but the zoning is not present in rocks with myrmekite texture from the lower part of the sill. However, twinning is preserved in unzoned crystals. Myrmekite is wart like type. High temperature ferromagnesian minerals are decomposed but plagioclases are mostly remained fresh. Based on whole rock XRF analyses, there are non-linear trend on Rb-SiO2 and K2O-Na2O diagrams. Based on norm calculations, Na2O values decreased and K2O values increased in samples from the contact with country rocks. It could be due to extraction of Na2O from the rocks by fluids. Such textural, mineralogical and geochemical features are evidences for low potasic metasomatism in lower part of Karaj Dam sill. Fluid had influenced on tuffs and caused kaolinitization of K-feldspar, sosuritization of plagioclase and chloritization of ferromagnesian minerals. In the other hand, fluids made chemical re-mobilization of ore minerals and accumulation of secondary copper minerals in the tuffs.

Lherzolite is one of the main units in the Ab-Bid ultramafic complex from Esfandagheh-HadjiAbad coloured mé lange (South of Iran). The complex contains harzburgite, dunite, lherzolite and pyroxenite dykes and the lherzolites mainly occur in the margins. In the field, lherzolites occur as weakly foliated coarse-grained peridotites with shiny pyroxene grains and cut by neumerous pyroxenitic veins. Textural features such as elongation and undoluse extinction of minerals and porphyroclastic grains indicate that the lherzolites were part of the upper mantle and experienced high P-T deformational events. Mineral chemistry data such as Cr# values in spinels (10/33-14/04) and fo contents of olivines (90/49-93/51) from the Ab-Bid lherzolites suggest that these rocks belong to the mantle. Evidences such as CaO (1/18-3/23) and MgO (39/53-43/65) contents of whole rock compositions, Cr# (10/33-14/04) and Mg# (74/20-78) values of spinels, besides textural features and REE normalized patterns show that they have past a complex petrological history. At the first stage, they have partially melted (< 10%) in an abyssal environment, then, they refertilized by ascending melts and enriched in LREE. Tectonomagmatic discrimination diagrams indicate that Ab-Bid lherzolites belong to the abyssal peridotites and their petrogenetic evolutions are similar to those from MOR type peridotites. Our data document the dependence of Esfandagheh-HadjiAbad coloured mé lange to the Neotethyan oceanic lithosphere in the south of Iran.

The Neian epithermal deposit in northwest of the Lut block is located in ~35 km southwest of Bejestan. The studies done on this deposit indicate the development of zonation in altered rocks around the ore-bearing siliceous veins and the existence of silicic (quartz, chalcedony, adularia, calcite, illite, and sericite), silicic-argillic (quartz, adularia, illite, sericite, and pyrite), argillic (illite, quartz, calcite, adularia, sericite, kaolinite, smectite, and chlorite), and propylitic (chlorite, calcite, albite, epidote, quartz, and smectite) alterations as the major alteration zones in this deposit that were formed during the five stages. Th geochemical diagrams, molar elemental ratios, and petrographic consideration illustrate the presence of transitional transformation and mineral conversion arrays during the development of hydrothermal system at Neian. Consideration of these diagrams indicate a wide spread of argillic and silicic and a relatively limited extent propylitic alteration zones in the Neian deposit. These diagrams also show that the mineral arrangements such as plagioclase-illite, plagioclase-adularia, illite-adularia, and plagioclase-smectite were developed during the prograde stages, whereas adularia-illite arrangement was formed during the retrograde (waning) stages of hydrothermal system. Permeability, high water/rock ratio in the host rocks (generated by faulting and the presence of extensive pyroclastic rocks) are the main factors for development of alteration zones and formation of widespread adularia in the area. In addition, considering the mineralogical composition of the deposit, the presence of minerals such as adularia and illite in the central and kaolinite in the peripheral part of the system may suggest that they were formed by the fluids having temperatures > 220oC and <140oC, respectively. The presence of mineral assemblage of quartz, adularia, illite, pyrite, chlorite, and calcite may reflect the involvement of upward flowing Chloride-bearing fluids with pH ranging from almost neutral to moderately alkaline. The contemporaneous formation of calcite, smectite, illite, and kaolinite in peripheral parts of the system was resulted by the reaction of CO2-rich fluids (containing hot vapors) with the host rocks. Increasing of temperature and potassium metasomatism in the central parts of the system caused widespread formation of illite at the first stage of alteration and of adularia-illite at the second (maximum K-metasomatism) during the geothermal activity at Neian. Concurrent with the waning stage of hydrothermal alteration and decreasing of K-metasomatism, illite replaced adularia again. The prevalence of conditions (for a long period of time) suitable for stability of illite may account for the greater abundance and extent of this mineral relative to adularia in the host rocks of Neian deposit.

The crystal-chemistry of the plagioclase, alkali feldspar, biotite, amphibole and whole rock geochemistry of Akapol granitic massif are investigated in this paper. The chemical composition of biotites and amphiboles ploted in the annite-siderophyllite, magnesiohornblende and actinolite fields, respectively. Comparison of the chemical composition of biotites and amphiboles with similar minerals from the California granitic batholith indicate that the monzogranitic unit of Akapol belongs to the strongly contaminated I-type granites. Accordingly, these rocks are highly contaminated and may have derived from upper mantle and/or lower crustal sources. They have experienced magma mixing or are affected by contamination with upper crustal rocks. These results are consistent with the curve like logarithmic diagrams of compatible/incompatible elements; the presence of the sieve, poikilitic and rapakivi textures; the partial absorption of the plagioclase phenocherists; the presence of mafic microgranular enclaves and needle apatite in the samples. Based on this study, two types of plagioclase in monzogranitic unit can be recognized in the monzogranitic unit: the first generation occur in the alkali feldspar phenochrysts and the second generation is in the form of covering crystals in rapakivi and sieve textures which probably formed during magma mixing.