فهرست مطالب sara dargahi

The Lar igneous suite (LIS), in southeastern Iran, is part of post collisional alkaline magmatism in Sistan suture zone. Shonkinite and kersantite are the only two high-Mg, K-rich olivine bearing rocks in the LIS. We study major and some compatible trace elements in the Lar shonkinite and kersantite (LSK) olivines to define mantle mineralogy and metasomatic processes. Olivines in shonkinite have higher Fo (83-90), compared with those in kersantite (Fo76-80). Ca and Ni contents in the olivines are relatively low, whereas their Mn and Ti contents are high and variable, respectively. Low Ni contents exhibit olivine crystallization at igneous conditions from a magma originated by partial melting of an olivine-rich mantle source. Geochemical date reveal that magma evolution is responsible for high-Mn and low Fo contents in kersantitic olivines. In contrast, high Mn, Mn/Fe and Fo contents in shonkinitic olivines indicate an existence of Mn-rich and Ca-Si-poor metasomatic agents in the source. So, considering the Middle Oligocene-Miocene post-collision nature of the Lar igneous suite, melts or fluids derived from upwelling asthenosphere in the form of magnesitic-carbonatite melts, had great potential in metasomatism of subcontinental lithospheric mantle. This CO2 and K-rich liquid then reacts with peridotite to produce new mineral assemblages including low-Ca clinopyroxene, olivine and phlogopite. Partial melting of such metasomatized source region was responsible for producing the undersaturated, K-rich shonkinite and kersantite in the LIS.

The Chah-Mesi polymetallic vein-type ore deposit, located 40 km north of Shahre-Babak city and 1.5 km southwest of Miduk porphyry copper deposit, is situated in the Dehaj-Sarduieh belt as a part of the Urumieh–Dokhtar magmatic Arc  (UDMA) (Figure 1).
The main objectives of this research study are to investigate: (1) characterization of multi-element distribution associated with Cu mineralization, in order to demonstrate prediction of elemental concentration applied to identify high-grade ore bodies, (2) evaluating the interrelationships between copper, molybdenum, iron, led, zinc, gold and silver.

Petrography and mineralography of the Chah-Mesi ore deposit were carried out using thin and polished sections. More than 980 chemical analyses of samples collected from 35 boreholes of the National Iranian Copper Industry Company (NICICO) were implemented to evaluate the statistical as well as spatial distribution and dispersion of multi-element halos. Geochemical data processing was performed by applying Excel (2010), SPSS (19), Datamine (Studio3.22.84.0) and Surfer10 (2011) software packages.

The Chah-Mesi ore deposit consists of four main and some minor polymetalic (Cu-Pb-Zn-Ag) quartz-sulfide veins, with NE-SW and N-S trending and 65-80 degree dipping, which intersected the Eocene volcanic and pyroclastic sequences (Figure 2). It seems that mineralization has mainly occurred along these quartz-sulfide veins overlaid by Quaternary alluvium. Based on rock outcrops, the prominent mineralization has been controlled by structural features including faults and fractures that provided proper conditions for reaction of hydrothermal fluids with the host rocks.In the Chah-Mesi ore deposit, silicified veins containing poly-metallic mineralization have predominantly occurred along the main faults and shear zones. The intensity of argillic alteration dramatically decreases outward from the mineralized quartz veins (Figure 3). Propylitic alteration which is composed of calcite and chlorite minerals has extended in the peripheral zones and does not represent a clear relationship with Cu mineralization.The main host rocks in the Chah-Mesi ore deposit consist of basalt to basaltic andesite, with porphyry to glomeroporphyry textures, and to a lesser extent of pyroclastic rocks (Figure 4). The ore bodies are mainly composed of pyrite, chalcopyrite, sphalerite and galena. The ore minerals are accompanied with chalcocite, malachite, covellite, azurite and iron hydroxides that have been formed during supergene and weathering processes (Figure 5). According to field surveys, structural controls have played an important role in the mineralization of the Chah-Mesi ore deposit.

Geochemical investigation in the Chah-Mesi ore deposit, using Pearson correlation coefficient of trace elements (Table 1), indicated the highest correlation coefficient (more than 0.7) between Pb-Zn and Ag-Au elements, due to their similar geochemical affinities during epigenetic mineralization. Other significant correlations were observed between Cu-Ag, Cu-Fe, Cu-Au and Fe-Ag with a correlation coefficient of more than 0.6; while the Mo shows weak correlation with other elements. Based on cluster analysis, the trace elements that are associated with mineralization can be classified into four main clusters of Pb-Zn, Mo, Cu-Fe-Ag and Au (Figure 6). Noteworthy, despite the fact that Mo and Au each separately form their individual clusters, Au still shows some proximities with the Cu-Fe-Ag cluster that indicate their genetic relationship. However, Mo displays the most dissimilarity with other clusters, which indicates the role of different processes in its distribution. The results of this analysis are well in line with correlation coefficients.The geochemical vertical zonality of trace elements in the Chah-Mesi ore deposit were studied using four borehole data from different parts of the ore deposit (Figures 7 and 8). This demonstrated that variation of elements at different depths does not follow a uniform pattern due to differences in the type and amount of ore minerals in the veins.The veins containing lead, zinc and gold mineralization are highly abundant at the shallower levels based on geochemical maps of the Chah-Mesi ore deposit (Figure 9). In contrast, the veins containing copper and silver mineralization have been considerably developed in both shallow and deeper levels. The high degree of Mo at shallow levels seems to occur due to either superimposition of primary geochemical haloes of various veins (Li et al., 1995, 2016) and/or the effect of amount of pyrite, pH, and alkalinity contents of hydrothermal fluids (Leanderson et al., 1987).The average value of different elements in intervals of 50 meters from the shallow (2500 meters) to the deep (2300 meters) levels are determined by existence of maximum abundance of lead, zinc and gold elements at surface levels. However, the highest average abundance of copper occurs in the deepest level. The highest average value of silver is also located in the 2450, 2350, and 2500 meters levels, which is economically valuable (Table 2). Therefore, the continuation of drilling in the southern part of the Chah-Mesi ore deposit into deeper levels is strongly recommended as there may still exist more concentrations of copper and silver there.

Bajgan Complex is a part of Iranian Makran including many kinds of metapelites, metabasites, calcsilicates, amphibolites, marbles, meta volcanosediments, felsic, mafic and ultramafic intrusives. The calcsilicates are divided into amphibole bearing epidote schist, epidote - amphibole schist, epidote – amphibole - garnet schist and carbonate bearing mica schist. Among of all calc silicates the epidote – amphibole - garnet schist shows the highest metamorphic condition and consists of garnet, amphibole, epidote, calcite, quartz, secondary chlorite and minor amount of titanite, apatite, white mica and magnetite. In this study the mineral chemical compositions, temprature, pressure and fluid activity in different metamorphic stages of epidote – amphibole - garnet schist were detected. In according to chemical data, garnet has almandine, grossular, spessartine and pyrope solid solution (Alm 35-50, Grs 23-31, Sps 14.6-36, Prp 2.6-9.8 ; mol%) and shows chemical zoning as almandine and spessartine have an increasing and decreasing trend, respectively, from core to rim. Amphiboles are classified in sodic- calcic group and are Barroisite. Chlorites are kown as Ripidolite and epidotes are classified in Clinozoisite subgroup. Peak metamorphic condition of epidote – amphibole - garnet schist has been estimated about 610° C and 8 kbar and molar fraction of Co2 and H2O have been calculated about 0.32 and 0.68, respectively. The retrograde metamorphic condition are about 525° C, 4.5 kbar and molar fraction of Co2 and H2O have been calculated about 0.31 and 0.69, respectively. The epidote – amphibole - garnet schist followed a ‘clockwise’ P–T path during prograde and retrograde metamorphism.

Khunrang intrusive complex (KIC), as a one of the largest complexes in the southern part of Sanandaj- Sirjan zone, is located in northwest of Jiroft in the Kerman province. The complex is mainly consists of acidic-intermediate felsic rocks of diorite, quartz diorite, tonalite, granodiorite and granite with subordinate amounts of hornblende gabbro and microgabbro as mafic members. General texture of the samples is hypidiomorphic granular; but porphyry texture with microgranular groundmass also occasionally occurs in felsic samples. Mineral chemistry studies on the amphibole crystals in both felsic and mafic parts of KIC show that they are S-Amph type and magnesio-hornblende in composition that formed in a relatively oxidized environment in an active continental margin. Plagioclases have a range of composition from labradorite (An50.4Ab49.0Or0.6) to oligoclase (An26.2Ab73.0Or0.9) with average of andesine (An36.6Ab62.6Or0.8) and bytownite (An89.6Ab10.4Or0.0) to andesine (An35.8Ab56.0Or8.2) with average of labradorite (An56.8Ab41.9Or1.3) for felsic and mafic samples, respectively. Based on geothermobarometry studies on amphiboles and also amphibole-plagioclase pairs, average temperatures of 760-783°C and 691-717 °C with pressure ranges of

The Alishahi rhyodacitic-dacitic columnar joints are outcropped in the Middle-Upper Eocene Razak complex in the southeastern of Urumieh-Dokhtar volcanic belt in the Dehaj-Sarduieh volcano-sedimentary belt. The complex consists of intermittent of pyroclastic rocks, andesite, rhyolite, and rhyodacite-dacitic lava flows. The latter partially shows 5 to 6 unequal sided columnar structure in which entablature and colonnade sections along with stria are clearly visible. The predominant textures are phyritic, hyaloporphiritic, glomeroporphyritic, flow and sieve textures along with perlitic cracks. Mineralogically, the Alishahi rhyodacitic-dacitic rocks consist of plagioclase phenocrysts together with rare microphenocrysts of sanidine, orthoclase, hornblende, pyroxene, biotite and accessory minerals including apatite, titanite and opaques are setting in a cryptocrystalline glassy matrix. The matrix is partly in the verge of devitrification process and conversion to mixture of quartz and alkali feldspars. Geochemically, the Alishahi columnar joints are rhyodacitic-dacitic in composition with calc-alkaline nature. Negative Eu anomaly and decrease in Sr content along with increase in Si amount reveal the significance of plagioclase as a differentiated phase. Enrichment in large lithophile elements and depletion in high field strength elements normalized to primitive mantle such as Ti, Ta, Nb along with their chondrite normalized rare earth elements patterns are pointing to their magma formation in a volcanic arc setting in an active continental margin. The depletion in Nb and Ta could be related to their low solubility in aqueous fluids and melts formed under relatively low pressures in the shallow part of the subduction zone.

The Ghaleh-Ganj dioritic- quartz dioritic massifs, with the age of Paleocene-Eocene, located on the west side of the Makran accretionary prism and Jazmurian depression and the east side of Jiroft fault are part of the intrusives in the Ganj Complex which itself is a part of the Jazmurian ophiolitic belt or Inner Makran. These intrusives rocks show microgranular to granular texture and consist of plagioclase, clinopyroxene, amphibole, biotite, quartz, K-feldspar, titanite, apatite and opaque as primary minerals along with chlorite, calcite, clay minerals, sericite and iron oxides as secondary minerals. Based on mineral chemistry studies, the plagioclases are oligoclase to labradorite in composition and predominantly fall in the field of andesine. Considering the total content of Fe in plagioclases, it seems that they were formed in high fO2 conditions. The existence of disequilibrium textures in plagioclases show variations of PH2O and decompression along with minor loss of temperature during the magma ascent to the surface. Clinopyroxenes display augitic composition and are belonging to a tholeiitic magmatic series and formed in 1133- 1382°C temperature, pressure less than 10 kbars and high fO2 conditions. Amphiboles have magnesiohornblende compositions which are estimated to have been formed at 650- 700°C temperature, less than 1 kb pressure and high fO2 conditions in a supra-subduction tectonomagmatic environment.

Gandom Berian area is a basaltic messa composed of dark flows covering about 480 km2 of the western part of Lut desert in the northeast of Kerman. In this area، the fault system follows a north-south trend and، basaltic lavas have flowed along this trend. It seems that in Gandom Berian area، the activity of Nayband fault has created a tensional tectonic regime leading to the creation of open fractures in the crust which have conducted the flow of magma to the surface. Comparing maps of the lineation index factor of Nayband fault and also the related maps to situation of volcanic cones admit the role of fault in formation of Gandom Berian basaltic magma. The presence of coarse euhedral olivine crystals along with coarse crystals of clinopyroxenes and the absence of magmatic quartz، all reveal a fast deep ascending magma through fractures system and deep faults. The deep fracturing of Nayband fault has prevented the mixing of magma with crustal contamination. The high La/Nb value (with average 1. 7) along with low ratio of Ce/Pb and Pb/Nd indicate low mixing of magma in the studied area. Also، none scattering compatible element plots show negligible magma mixing. Uniformity in crystal size distribution (CSD) plots and its constant slope indicate the low impact of physical processes such as magma mixing in basaltic magma which effects the crystallization of plagioclase microlites during its ascent to the surface. The main cause of steepness in CSD is the rapid quenching of basaltic magma during upwelling which leads to plagioclase fine microliths. The presence of olivine and clinopyroxene phenocrysts indicates that in the primary magma، crystallization had occurred before ascent and eruption. Based on Dy/Yb versus La/Yb plot the Gandom Beryian basalts were formed by 8 to 10% partial melting of a garnet-lehrzolite parental rock. In general، lower partial melting of upper mantle (less than 10%) leads to the creation of alkaline basaltic magma. On the other hand، Gandom Beryian basaltic magma has characteristics similar to a high magnesium parental magma with low degree of evolution.

Plagiogranite intrusive rocks are outcropped in the gabbroic section of the Neyriz ophiolitic sequence in the south east of Shiraz. Petrographically, they are comprised of tonalite, trondhjemite and their contact with surrounding gabbros is either sharp or covered. Predominant textures are hypidiomorphic inequigranular, granophyry and micrographic. Mineralogically, they are consisting of plagioclase, quartz, sodium feldspars as major minerals and less than 10% amphibole ± pyroxene, opaques and rarely titanite and zircon as minor minerals. Geochemical studies show that their magma is sub-alkaline type (calc-alkaline series) and metaluminous. Typologically, plagiogranites have characteristics of oceanic ridge granite (ORG) toward I-type granites. Chonderite normalized REE patterns of Neyriz plagiogranites show depletion in LREEs along with a flat HREE patterns and it seems that they were formed in supra-subduction zone environment by partial melting of mafic rocks which in turn were formed by the anatexis of a previously depleted harzburgitic mantle.