فهرست مطالب ژوزه فرانسیسکو سانتوز

On the basis of field studies, mafic-intermediate bodies of Kashmar are subdivided into the old series (often stocks of gabbro, diorite, quartz diorite/monzodiorite) and the new series (quartz monzodiorite swarm dykes). In terms of crosscutting relationships, old series has the age between oldest volcanic units (57 Ma) and Eocene granitoids (40 Ma), but the swarm dykes are attributed to the post Eocene (Oligocene?) in age. Mafic-intermediate bodies with the high-K calc-alkaline to shoshonitic, metaluminous to low peraluminous, LILE/HFSE and LREE enrichment [(La/Yb)N=5.3-6.8] and depletion of HREE characteristics are reminiscent of the arcs in subduction zone. These features accompany with negative anomalies of Eu indicating magma generating at the depth of plagioclase stability and contaminiation of magma to continental crust, which remains during the melting of the garnet rock. Linear trend of the major oxides and trace elements in Harker diagrams indicate in importance of fractional crystallization of magma evolution. Average of initial isotope ratios of 87Sr /86Sr and 143Nd /144Nd (in age 50 Ma) for the old series samples are between 0.7054 /0.7062 and 51262-0.51264 respectively, and the εNdi has a range of 1.08 to 1.42. Average of initial isotope ratios of 87Sr /86Sr and 143Nd /144Nd (in age 30 Ma) for swarm dykes are 0.7056 and 512623 respectively, and the εNdi amount is .059. εNdi positive values and low ISr of all rocks with their TDM (0.6-0.8) implying that they form from partial melting of lithospheric mantle source, which modified to earlier subduction processes melts. Based on the Th/Ta versus Nb/Ta and Nb/Y versus Zr/Y charts, both subduction and rift forming processes were involved in the formation of Kashmar rocks. This feature is compatible with subduction of Sabzevar oceanic crust to the Lut block.

The Khunik area is located in the south of Birjand, Khorasan province, in the eastern margin of Lut block. Tertiary volcanic rocks have andesite to trachy-andesite composition. Dating analyzing by Rb-Sr method on plagioclase and hornblende as well as whole-rock isochron method was performed on pyroxene-hornblende andesite rock unit. On this basis the emplacement age is Upper Paleocene (58±11 Ma). These rocks have initial 87Sr/86Sr and εNd 0.7046-0.7049 and 2.16-3.12, respectively. According to isotopic data, volcanic rocks originated from depleted mantle and have the least crust contamination while it was fractionated. Geochemically, Khunik volcanic rocks have features typical of calk-alkaline to shoshonite and are metaluminous. Enrichment in LILEs and typical negative anomalies of Nb and Ti are evidences that the volcanic rocks formed in a subduction zone and active continental margin. Modeling suggests that these rocks were derived dominantly from 1–5% partial melting of a mainly spinel garnet lherzolite mantle source that is metasomatized by slab-derived fluid.

The Lalezar granitoids crop out within volcanic successions of the Urumieh-Dokhtar Magmatic Assemblage (UDMA). These granitoids have a range from gabbro-diorites to granites in composition. The mineral compositions of the most felsic rocks are characterized by the abundances of Na-plagioclase, quartz, alkali feldspar, biotite and hornblende. In the gabbro-diorite rocks, plagioclase (Ca-rich), hornblende, biotite and clinopyroxene are the most common minerals. Major element geochemical data show that the Lalezar granitoids are mostly metaluminous, although the most felsic members (granites) attain slightly peraluminous compositions and that they have features typical of high-K calc-alkaline rocks. In primitive mantle-normalized trace element spider diagrams, the analysed samples display strong enrichment in LILE compared to HFSE, accompanied by negative anomalies of Nb, Ta and Ti. REE chondrite-normalized plots show moderate LREE enrichment with slight to strong negative Eu anomalies. Rb–Sr geochronological data, mainly dependent on the Sr isotopic composition of biotite, was obtained in two samples and it points to 15-16 Ma. As a probable, age for the emplacement of the studied intrusives. Initial 87Sr/86Sr ratios and ƐNdi values range from 0.70495 to 0.70565 from +3.1 to +1.5 respectively, which fit into a supra-subduction mantle wedge source for the parental melts and indicates that, in general, crustal contribution for magma diversification was not relevant. Geochemical and isotopic evidence reveal that the Lalezar intrusions are cogenetic I-type granitoids which were generated in a continental arc setting, in agreement with models previously presented in the UDMA.

The study area is located in central part of the Khaf- Kashmar-Bardeskan belt which is volcano-plutonic belt at the north of the Dorouneh fault in the north of Lut block. The north of the Lut block is affected by tectonic rotation and subduction processes which occur in the east of Iran (Tirrul et al.، 1983). The magmatism of Lut block begins in Jurassic and continues in Tertiary (Aghanabati، 1995). Karimpour (Karimpour، 2006) pointed out the Khaf-Kashmar-Bardeskan belt has significant potential for IOCG type mineralization such as Kuh-e-Zar، Tannurjeh، and Sangan (Karimpour، 2006; Mazloumi، 2009). The data gathered on the I-type intrusive rocks include their field geology، petrography، U–Pb zircon dating and Sr–Nd isotope and also alteration and mineralization in the study area.

- Preparation of 150 thin sections of rock samples for study of petrography and alteration of the intrusive rocks. - Magnetic susceptibility measuring of intrusive rocks. - U-Pb dating in zircon of I-type intrusive rocks by Laser-Ablation Multi Collector ICP-MS method. - Sr-Nd analysis on 5 samples of I-type intrusive rocks by Multi-Collector Thermal Ionization Mass Spectrometer (TIMS) VG Sector 54 instrument. - Mineralography and paragenetic studies of ore-bearing quartz veins and geochemical analysis for 28 samples. - Production of the geology، alteration and mineralization maps by scale: 1:20000 in GIS.

Oblique subduction in southern America initiated an arc-parallel fault and shear zones in the back of continental magmatic arc (Sillitoe، 2003). Because of this event، pull-apart basins were formed and high-K to shoshonitic calc-alkalineI- and A-type magmatism occur (Sillitoe، 2003). Most important deposits accompany with this magmatism are Au-Cu deposits types and Fe-Skarns (Sillitoe، 2003). We have similar scenario to Neotethys subduction. Khaf-Kashmar-Bardeskan volcano-plutonic belt is located between Neotethys suture and Alborz- Sabzevar Back- arc (Asiabanha and Foden، 2012). We suggest Khaf-Kashmar-Bardeskan volcano-plutonic belt forms at the arc-parallel fault and shear zones in the back of continental magmatic arc. In the basis of all evidences (Shear zone system، high-K to shoshonitic calc-alkaline I- and A-type magmatism، typical alterations related to upper zones of IOCG deposits and IOCG mineralization)، we suggest IOCG (Au-Cu) mineralization in Kashmar.

On the basis of former regional (Muller and Walter، 1983) and local structural studies (this research)، regional compression causes sinistral strike-slip movements of Dorouneh and Taknar faults، shear zone، pull-apart and Riedel fractures (P، R and R'' types) in the study area. These events cause magma intrusion and circulation of hydrothermal fluids. On the basis of geology، geochemistry and magnetic susceptibility measuring of intrusive rocks، several high K to shoshonitic calc-alkaline to alkaline I-type and one A-type intrusive rocks are intruded in Kashmar area. Swarm dykes are the youngest and the agent for alteration and mineralization. U-Pb dating related to quartz monzonite body (preventative sample for I-type intrusive rocks which are older than A-type series) show 40 Ma (Middle Eocene) for this rock group in Kashmar. The mean of initial 87Sr/86Sr and 143Nd/144Nd are 0. 705-0. 707 and 0. 5135-0. 5126 for I-type series، respectively. εNd (i) amounts for I-type series are in negative to positive limit ranges (-1. 65 to 1. 33). These amounts show subduction source with contamination to continental crust. Two type alteration and mineralization occur in Kashmar: 1) primary alterations (advanced argillic+ sericite+ silicification) which are synchronous with sulfide base-metal veins (chalcopyrite+ pyrite± galena± quartz± chloride) and 2) Lateral alterations (carbonatization+ Fe-oxides+ silicification+ epidotization+ chloride+ sericite+ barite) which are synchronous with IOCG veins (specularite+ chalcopyrite+ pyrite± galena± sphalerite± barite± siderite ± etc.). Primary centralized and sulfide base-metal veins in crosscutting points between Dorouneh fault and minor faults. Bahariyeh، Uchpalang and Sarsefidal areas are located in these crosscutting points. Tourmaline (demorterite) ±chloride fill the fractures in the intrusive rocks of southern part of area next to the Dorouneh fault occasionally. Lateral alteration synchronous with IOCG veins occur in Kamarmard area. Geochemical data of all veins show Cu، Pb، Zn anomalies (>1%) in two type veins، Au anomalies (to about 15 ppm) only in IOCG veins، Mn anomalies in two type veins and Ba anomalies in IOCG veins. Alteration and mineralization in the world-class IOCG deposits identified by sodic-calcic and potassic (hydrothermal actinolite and biotite) and magnetite± gold in deep parts (Sillitoe، 2003) and advanced argillic+ pyrite+ sericite+ toulrmaline (demorterite) in shallow parts (Ray and Dick، 2002). Generally، alteration in the study area is similar to shallow parts of world-class IOCG deposits. Tanourjeh is a IOCG deposit next to the northwest of the study area. In Tanourjeh، the gold-bearing magnetite is synchronous to potassic alteration (hydrothermal biotite) and other alterations are advanced argillic، silicification and sericite. These characteristics are similar to deep parts of world-class IOCG deposits. Bahariyeh، Uchpalang and Sarsefidal have similarities to alterations in Tanourjeh. Considering Tanourjeh lie in the lower level rather to Bahariyeh، Uchpalang and Sarsefidal، we believe they erosion surface in Tanourjeh is lower. Kamarmard lies in the highest erosion surface in the study area. Alterations and Mineralization as similar to Kuh e Zar IOCG deposit (specularite+chalcopyrite+gold) which is next to the Kamarmard area in Northeast of study area. In Bahariyeh-Uchpalang areas we can see only one IOCG vein but in Sarsefidal area exist several IOCG vein. Because of current surface in Bahariyeh-Uchpalang areas is lower than Sarsefidal current surface in Sarsefidal is lower than Kamarmard، we believe that IOCG vein in Bahariyeh-Uchpalang area have been eroded. We Believe to two circulation of oxidized Fe-bearing hydrothermal fluid in Kashmar. During the first circulation، Potassic alteration and gold-bearing magnetite bodies in depth and primary alterations with sulfide base-metal veins was formed. At the second circulation، lateral alterations and IOCG veins was formed at the near of paleo-surface.

The dehsalm porphyritic granitoids belong to the Lut Block volcanic-plutonic belt in East - Central Iran. The intrusive rocks range in composition from gabbro - diorite to granite and can be classified as high-K calc alkaline to shoshonitic volcanic arc granites. Elevated contents of Mo, Cu, Au, Pb, Zn occur in silica veins within Bt - Px - Quartz monzonite and Hbl - monzonite. The trend of major oxides on Harker diagrams point to the crystal fractionation of Ca - plagioclase and mafic minerals. Primitive mantle - normalized trace element spider diagram display strong enrichments in LILE such as Rb, Sr, Ba, Zr, Cs and depletions in some high field strength elements (HFSE) e.g. Nb, P and Y. On chondrite - normalized plots, display significant LREE enrichments, high La/Yb = 21.5 31 and the lack of Eu. On the basis of Sr/Y and La/Yb ratios, Dehsalm intrusives cover characteristic features of adakites and (87Sr/86Sr)i and εNdi isotope ratios range from 0.70469 to 0.70505 and from +1.5 to +2.5 respectively, and show that the source is related to the mantle melts contaminated slightly by the crustal materials. They are classified into the magnetite series granitoids and have high mineralization potential for Cu-Mo-Au porphyry type deposits. Two-sidedasymmetric subduction explains all the tectonic and magmatic occurrences and the mineralization of porphyry type deposits within the Lut Block during the Tertiary.