جستجوی مقالات مرتبط با کلیدواژه "dokhtar zone" در نشریات گروه "زمین شناسی"

The magmatic evolution of the Urumieh-Dokhtar arc is related to the Neo-Tethys subduction and the continental collision between the Arabian and Eurasian plates, which has led to the creation of diverse and different magmatism along different parts of this belt (Shahabpour, 2005; Agard et al., 2011; Richards, 2015; Karimpour et al., 2021).Volcanic rocks, with various lithological compositions located in the central part of the Urumieh-Dokhtar belt, are part of the extensive Eocene activity, Knowing the nature of basic-intermediate volcanic rocks northwest of Nain requires more detailed investigations. For this purpose, the exploration areas of Chakad, Safafoulad, and Mehrando, located northwest of Nain, were selected for further investigations. The main goal of the present paper is to understand the origin and the tectonic of the volcanic rocks of this part of the Urumieh-Dokhtar magmatic belt using their petrography and geochemical characteristics

Regional Geology:

Many outcrops belonging to Tertiary volcanic lavas and pyroclastic deposits are widespread 50 km northwest of Nain, within the central part of the Urumieh-Dokhtar magmatic arc (UDMA). The volcanic units are basic to acidic composition ranging in age from Eocene to Oligocene (Chiu et al., 2013) and pyroclastic rocks including tuff, breccia, and ignimbrite, low in altitude, overlain by a sequence of Quaternary alluvium. In the exploration areas of Chakad, Safafoulad, and Mehrando, the Eocene basic-intermediate volcanic rocks with the combination of basalt, basaltic-andesite and pyroclastic rocks exposed and play as the host rocks for copper mineralization. The youngest igneous units observed in the region are a set of parallel diabase and dolerite dikes as swarms, intruded the volcanic rocks. Based on field observations, silica and carbonate veins with different trends are observed along with copper mineralization in basaltic- andesite and basalt units. This ore mineralization occurs mainly as an oxide (malachite and azurite) accompanies with propylitic alteration and less argillic and silicification along and at the intersection of faults and fractures.

Following the preparation of thin sections and petrographic and mineralogical investigations of these units, 26 volcanic samples have been analyzed by the ICP-MS method for trace and rare earth elements. Petrography The basic-intermediate volcanic rocks of the region are mostly basalt and basaltic-andesite, as well as diabase and dolerite dikes. The studied basalts, mineralogically, dominated by Euhedral to subhedral phenocrysts of plagioclases (30 to 50 vol%) and clinopyroxene phenocrysts, with porphyritic texture. Small amounts of olivine occur as phenocryst and iddingsite basaltic- andesite consists of plagioclase (40 to 60 vol%), and clinopyroxene (15 to 20 vol%) phenocrysts set in a fine-grained to microlithic groundmass. Clinopyroxene and plagioclase with intergranular texture are the dominant minerals in diabase and dolerite. Chlorite, calcite, epidote, and quartz are the main altered minerals of the rocks under study.

Based on the geochemical data, the basic- intermediate volcanic rocks with the combination of basalt and basaltic- andesite have a calc-alkaline nature, consistent with the features of volcanic arcs in the subduction zone of the active continental margin. In the primitive mantle-normalized multi elements diagram, the patterns of basic- intermediate volcanic rocks show enrichment of LILE (e.g., Ba, K, Rb) and depletion of HFSE (e.g., Nb, Ti, Zr) one of the remarkable features of subduction zone- related magmas (Yang and Li, 2008; Kuscu and Geneli, 2010). In the chondrite-normalized REEs diagram, these rocks exhibit LREE enrichment relative to HREEs. Rare earth elements such as La and Sm are not significantly affected by the mineralogical changes of the source rock, so they can provide information on the chemical composition of the total source rock. The volcanic rocks of the region generated by partial melting of 5 to 10% (Aldanmaz et al., 2006) of the enriched garnet- lherzolite mantle at a depth of 90 to 100 km. It seems that the parent magma has been metasomatized under the influence of fluids and sediments derived from the oceanic lithosphere. As the tectonic setting identification diagrams display the studied samples plotted in the range of magmas related to the subduction zone of the active continental margin. The magmatism under discussion, is the result of the subduction of the Neo-Tethys oceanic lithospheric beneath the central Iranian plate which have given rise to great magmatism during the Eocene and following it.

Study area located on N to NW of Rabor city in Kerman province that belong to Uromieh-Dokhtar Magmatic Belt (UDMB). Most of rock lithology in this area including diorite, granodiorite and granite which have been exposed in volcanic sequences. Based on geochemical studies all of rocks in this area classified in two groups: (1) some igneous rocks show adakitic affinity with high SiO2 (61.49–66.78 wt. %), Al2O3 (15.72–17.74 wt. %), Sr (374–602 ppm), Sr/Y (34–53), (La/Yb) N (8.35–16.88) and low Y values. (2) another rock group that distinguished in study area including various granitiods rocks with typical calc-alkaline characteristics that distinct from adakitic types such as: SiO2 (63.07–72.32 wt. %), lower Sr/Y (3.8–13.2) ratio and higher Y (21.7–31.6 ppm) and Yb (2.29–3.26 ppm) contents, and the lowest Sr (119–297 ppm) and (La/Yb)N (3.02–11.13) values relative to adakitic groups, with distinctly negative Eu [(Eu/Eu*)N= (ave. 0.49)] anomalies.The adakitic rocks most probably originated from thickened mafic lower crust (garnet amphibolite) with garnet rutile ± plagioclase as residual minerals in the source corresponding to depths of >50 km, and calc-alkaline rocks were probably generated in shallow depth than adakitic groups in mid-lower crust (dominant amphibolite) correlating to depths of

The study area includes Alam Baghi, Vashaghan, Sar Band and Ghermez Cheshmeh and is located in the northeast of Farmahin and the southwest of Tafresh. Based on the structural subdivisions of Iran, the mentioned area is a part of Central Iran and the Urumieh-Dokhtar magmatic belt (Hajian, 1970).
The studied volcanic rocks consist of trachybasalt, trachyandesite, basaltic andesite, andesite, dacite, rhyodacite, rhyolite, ignimbrite, tuff and tuffit in composition and in terms of age they belong to the middle and upper Eocene. It seems that the volcanic activities are related to folding and faulting in the studied area. On the other hand, in addition to causing orogenic activity, at the middle and upper Eocene (Ghasemi and Talbot, 2006), locally extensional regime has played a main role in volcanic eruption. Similar to this scenario happened in other areas such as Taft and Khizrabad in Central Iran (Zarei Sahamieh et al., 2008). Porphyritic, microlite porphyritic and microlitic are the main textures in these rocks. Mineralogically, they contain plagioclase, clinopyroxene, amphibole, quartz and biotite as the main minerals and zircon, apatite, and opaque minerals as accessories.
The major and trace elements of mineral composition are determined by electron probe micro-analysis (EPMA) using a Cameca SX100 instrument in the Iran Mineral Processing Research Center (IMPRC). Moreover, the whole-rock major and some trace elements analyses for a few samples were obtained by X-ray fluorescence (XRF), using an ARL Advant-XP automated X-ray spectrometer.
Based on EPMA analyses, plagioclase mineral in basaltic andesite and trachybasalt samples range from labradorite to bytownite in andesite and trachyandesite has oligoclase- andesine and in dacite, rhyodacite, rhyolite has an albite-oligoclase composition. In the Wo-En-Fs diagram, all clinopyroxenes show augitic and a lessor amount of clinoenstatite composition and in the Q-J diagram located in the Mg-Fe-Ca (Quad) field and in the 2Tiિ肕 vs. Naɒ diagram (Morimoto et al., 1988) located above on the Fe3=0 line that indicate high oxygen fugacity during crystallization. Microscopic study on these rocks such as oscillatory zoning, resorption rims in plagioclase and the presence of basic inclusions suggest the occurrence of magmatic contamination on the parent magma. The presence of oxidized amfibool rims (in hornbelende as oxy hornbelende) indicate the high temperature of the magma at the time of eruption.
According to the classification diagrams such as total alkaline vs. SiO2 (Irvine and Baragar, 1971) TAS (Le Bas et al., 1986) and tectonic discrimination diagrams (Pearce et al., 1984) samples are plotted in sub-alkaline, basaltic-andesite, andesite, dacite and rhyodacite, subduction and volcanic arc fields, respectively.
The geochemical diagrams such as AFM are used for the identification of magma series and show that the studied rocks are calc-alkaline and A/NK vs. The A/CNK diagram shows the metaluminous to peraluminous nature. Incompatible and LIL elements such as Ba, K and Rb enrichment show that the contamination of magma with continental crust has occurred. The similarity between the REE patterns in all of the collected samples in Alam Baghi, Vashaghan, Sarban and Ghermez Cheshmeh areas suggest the same source for all of the volcanic rocks.
The tectonic setting diagrams show that these rocks belong to the continental margin which has been involved in a subduction zone.
The position of the samples on the major elements vs. SiO2 diagrams indicate that magma differentiation has occurred. Spider diagrams show a positive anomalous in Rb and a negative anomalous in Nb and Ti This phenomenon shows a contamination between the magma and the crustal rocks (Rollinson, 1993). Also, MORB-normalized incompatible element patterns of the Farmahin area show that the parent magma has been contaminated. It appears that assimilation and fractional crystallization (AFC) were the dominant processes in the genesis of the studied volcanic rocks.
As a conclusion and according to field evidence and geochemical characteristics presented in this article, the studied area is composed of lava flows and pyroclastic rocks such as andesite, dacite, rhyodacite, ignimbrite, tuff and tuffits that cross cut by younger dykes and belong to the middle to late Eocene age (middle to upper Lutetien). According to Sm/Yb vs. Sm diagram (Aldanmaz et al., 2000), all the studied samples in terms of composition are similar to enriched mantle-derived melts that are generated by varying degrees of partial melting (10% - 20%) from a spinel lherzolite to spinel-garnet lherzolite source.
Considering the evidences, all rocks in the studied area belong to the subduction zone and the parent magma originated from mantle and was contaminated with continental crust during eruption and rising.
Acknowledgments: The authors wish to thank the Journal Manager and reviewers who critically reviewed the manuscript and made valuable suggestions for its improvement.

The Kohe GorGor sub volcanic units in the GorGor dome is located in the south of Arabshah village between Zarshouran and Agh dare gold mines. These units are part of Kohe Gor Gor volcano-plutonic complex and composed high-level sub volcanic micro dioritic and micro monzonitic plutons. This area is part of volcanic center between Takab and Qara Aghaj cities which refereed as Takab-Qara Aghaj volcanic belt within the northern part of Urmia-Dokhtar magmatic arc. The Kohe GorGor subvolcanic units have metaluminous and calc-alkaline affinity and represent most similarity to I -type granites. The various petrogenesis diagrams indicate a subduction-metasomatized lithospheric mantle source for parent magma of Kohe Gor Gor which during its ascending to upper level and led to produces more evolved rock types that are emplaced at shallow depths. The Kohe Gor Gor subvolcanic units belong to post collision arc setting which emplaced in Takab-Qara Aghaj volcanic belt during late Miocene-early Pliocene coincide with extensive Mio-Pliocene magmatism in NW Iran and SE Turkey. The evolution processes of Takab-Qara Aghaj volcanic belt in the late Miocene-early Pliocene is dominated by Takab core complex exhumation that accompanied with Decompressional melting of metasomatized lithospheric mantle and subsequently production of primary magma and its Ascending to upper level reservoirs and its modification by crustal melting ,assimilation and fractionation processes which finally produce more evolved felsic magmas which outcropped in the form of high-K calcalkaline I-type sub volcanic intrusions in the some part of this belt.

Bondar Hanza porphyry copper deposit occurs 150 km southeast of Kerman, in southern part of the Urmia-Dokhtar zone and in Dehaj-Sardoiyeh zone. This ore deposit has formed in diorite to granodiorite rocks. The present paper deals with the study of fluid inclusion on quartz and hornblende samples as well as the measurement of isotopic ratio of oxygen and hydrogen with the aim to recognize characterization of hydrothermal fluids effective in mineralization. The studied veinlets are divided into five groups. Veinlet I: fluid of high pressure (>300 MPa) and medium to high temperature (250°C-300°C) with salinity of 38-45 Wt%NaCl that includes molybdenum mineralization. This veinlet contains halite and anhydrite and has resulted in potassic and sodic-calcic mineralization in deeper parts of the ore deposit. Veinlet II: high pressure (>300 MPa), high salinity (33-47 Wt%NaCl) and high temperature (250°C-420°C), containing copper and molybdenum mineralization as well as potassic alteration. Veinlet III: high salinity (40-56 Wt%NaCl), high pressure (>300 MPa) and high temperature (200°C-500°C), containing copper mineralization. Veinlet IV: medium to low salinity (6-7 Wt%NaCl), medium temperature (approximately 170°C), low pressure (0/7-0/8 MPa), containing no mineralization. The study performed indicate that the boiling occurred in the initial magma, as a result of pressure and temperature changes and mixing with meteoric waters, caused copper and molybdenum mineralization. Results obtained oxygen and hydrogen isotopic analysis in quartz show δ18O to vary 3.9 to 6.3 per mil. Considering its formation temperature and based on thermometric study (130-400°C), the amount of δ18o in mineralizing fluid is 5.26 to 6.19 per mil, being indicative of magmatic origin of mineralization fluids like the other porphyry copper deposits of Iran and the world. While results of hydrogen analysis existed in fluid inclusions of quartz mineral illustrate a range between -88 to -90 per mil, being indicative of a decrease in the amount of mineralizing fluid deuterium. These values are traceable to the effect of meteoric waters, given the propylithic and sodic alterations accompanied with potassic alteration in mentioned veinlet.

Jebale-Barez granitoid complex is composed of intrusive bodyes included Mijan, Dareh hamzeh, Kerver and Hishin and is located In the southeastern province of Kerman on the lengths of the 57◦ 45 ' east to 58◦ 00' and Northern latitudes 28◦ 30' to 29◦ 00'.The petrologic composition in intrusive bodyes composed of granodiorite, quartzdiorite, granite and alkali-granite. The geochemical variation diagrams of major oxides, the continuous spectrum of rock compositions has been carried out which indicates the crystallization of magmatic differentiation and extensive appendices. The magma nature of these rocks is sub-alkaline-calc-alkaline, which in SiO2-K2O plot they fall into calc-alkaline series with high potassium. Field observations, petrographic and geochemical studies suggest that the rocks in this area have granitoides I type. Studying the geochemical diagrams of the rocks in the studied area indicates that these rocks have been formed in active continental margin tectononic setting. Most of the volcanic arc granites (VAG) are of "pre-collision" and "syn- collision" types. Three magmatic phases occurred in oligomiocene in this area. The first phase of magmatism in this area composed of the quartzdiorite and diorite that makes the main body of Jebale-Barez granitoid complex. Porphyry bodies will penetrate into the main body, after a short period of magmatic fractionation inside the nest of magma. Petrographic composition of the second phase is mainly diorite to tonalite. Oligo-Miocene magmatic final phase (Phase III) occurs in the region after a short time that the lithological composition of the granite to alkali granite. The third group of rocks in the study area the main body mother came magma fractionation. based on the location of Urmia-Dokhtar magmatic belt seems the rocks of this region there came to subducted oceanic crust Neotethyan beneath continental crust of central Iran.

Kahang copper and molybdenum mine is located in Esfahan province and 10 Km far from the east of Zefreh town that is on Urumieh-Dokhtar volcanoplutonic belt. The Kahang region is an alteration and breccia zone. Generally, hydrothermal fluids have affected more than % 90 of rocks of this region. These alteration are related to Copper (Cu) and Molybdenum (Mo) porphyry deposits. Most of the rocks are acidic, semi acidic and sub volcanic. Several kinds of alteration are observable in kahang as propylitic, argilic, silisification and phyllic. The basic oxides were highly decreased in dacite and rhyodacites of exploration area. This is an evidence of argilic alteration effect on the rock units considering that main deposit is not affected by erosion, placed in depth and potassic alteration is not exposed at surface. In study of existing alteration several methods such as remote sensing, studying of thin section and the chemical analysis of samples were used. Another issue that has taken into consideration in this paper is the magma mixing. This subject is confirmed by petrographic evidence such as sieve texture, corroded rims in primary phenocryst quartz, and hydrothermal effects on plagioclases especially in porphyritic andesites. Moreover, the extensive acidic rocks, notable alteration expanse, and also two generations of mineralization reveal assimilation in the studied area. This text has examined the similarities between Kahang and other porphyries in the Urumieh-Dokhtar zone.