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Calculated chemical composition for the garnets from the garnet skarn and pyroxene-garnet skarn sub-zones
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Introduction
The Avan Cu-Fe skarn is located at the southern margin of Qaradagh batholith, about 60 km north of Tabriz. The Skarn-type metasomatic alteration is the result of Qaradagh batholith intrusion into the Upper Cretaceous impure carbonates. The studied area belongs to the Central Iranian structural zone. In regional scale, the studied area...
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The North of Baharieh prospecting area is located central part of Khaf-Kashmar-Bardaskan magmatic belt (KKBMB), east of Kashmar in Khorasan Razavi province. This area includes outcrops of pyroclastic and volcanic rocks, which are intruded by intrusive (syenogranite, granodiorite), and sub-volcanic units (monzodiorite, quartz monzonite, and diorite...
Citations
... Due to the intrusion of numerous Oligocene-Miocene batholiths and associated hypabyssal stocks into the Late Cretaceous volcano-sedimentary rocks, dozens of contact metasomatic skarn deposits are widely distributed throughout the QSMB. Some important examples of mineralized systems include; Anjerd Cu (Hosseinzadeh, 1999), Astamal Fe-LREE (Baghban et al., 2015(Baghban et al., , 2016, Avan Cu (Fe) (Mokhtari et al., 2017), Gowdoul Fe (Cu, Au) (Mahmoudi Nia, 2013), Kamtal Fe (Cu) (Mokhtari et al., 2013), Mazraeh Cu (Au) (Karimzadeh Somarin, 2010), Pahnavar Fe (Mokhtari, 2012), Sungun Cu (Calagari and Hosseinzadeh, 2006), and Zandabad Cu (Mo) (Radmard, 2004). ...
The Brazin iron skarn occurs along the contact zone between Late Cretaceous flysch-type sequences and an
Oligocene-Miocene granodiorite. The prograde skarn stage is identified by the formation of garnet and clinopyroxene,
whereas the retrograde stage is dominated by epidote, scapolite, calcite, and quartz. Metal minerals
include magnetite + pyrite + chalcopyrite ± pyrrhotite. Garnet with andradite-grossularite-almandine solidsolution
is ubiquitous throughout the skarn zones. Two principal types of garnet were identified in the skarn
zones: (I) weakly-altered euhedral coarse-grained isotropic garnet exhibits minor variation in the overall
composition (And25.95–39.41 Grs54.95–62.25 Alm + Sps + Py5.39–13.04); (II) strongly-altered anhedral to subhedral
isotropic to anisotropic garnet shows a wide variation in the overall range of composition (And25.91–55.25
Grs41.37–61.15 Alm + Sps + Py1.48–12.85) in which FeOt increases, whereas Al2O3 decreases rimward.
Clinopyroxene with a salitic-ferrosalitic composition is homogenous, has low to relatively high Fe/(Fe + Mg)
ratios, and is poor in TiO2, MnO, and Na2O. It displays a decrease in the diopside content with increasing distance
from the causative intrusion, whereas the ferrosalite content is enriched near the marble and hornfels fronts.
The fluid system evolves from high temperatures (>580 ◦C), saline fluids (>53 wt% NaCl equivalent) in the
late crystallization stage under lithostatic pressure of ~750 bar at a depth of ~3 km. Fluid in the later retrograde
stage has lower temperatures (<430 ◦C) and salinities (<40 wt% NaCl equivalent). Mixing and dilution between
the initial hydrothermal and external fluids might cause a decrease in fluid temperature and salinity causing the
formation of the magnetite.
... Due to the intrusion of numerous Oligocene-Miocene batholiths and associated hypabyssal stocks into the Late Cretaceous volcano-sedimentary rocks, dozens of contact metasomatic skarn deposits are widely distributed throughout the QSMB. Some important examples of mineralized systems include; Anjerd Cu (Hosseinzadeh, 1999), Astamal Fe-LREE (Baghban et al., 2015(Baghban et al., , 2016, Avan Cu (Fe) (Mokhtari et al., 2017), Gowdoul Fe (Cu, Au) (Mahmoudi Nia, 2013), Kamtal Fe (Cu) (Mokhtari et al., 2013), Mazraeh Cu (Au) (Karimzadeh Somarin, 2010), Pahnavar Fe (Mokhtari, 2012), Sungun Cu (Calagari and Hosseinzadeh, 2006), and Zandabad Cu (Mo) (Radmard, 2004). ...
The Brazin iron skarn occurs along the contact zone between Late Cretaceous flysch-type sequences and an Oligo-Miocene granodiorite. The prograde skarn stage is identified by the formation of garnet and clinopyroxene, whereas the retrograde stage is dominated by epidote, scapolite, calcite, and quartz. Ore minerals include magnetite + pyrite + chalcopyrite ± pyrrhotite. Garnet with andradite-grossularite-almandine solid-solution is ubiquitous throughout the skarn zones. Two principal types of garnet were identified in the skarn zones: (I) weakly-altered euhedral coarse-grained isotropic garnet exhibits minor variation in the overall composition (And 25.95–39.41 Grs 54.95–62.25 Alm+Sps+Py 5.39–13.04 ); (II) strongly-altered anhedral to subhedral isotropic to anisotropic garnet shows a wide variation in the overall range of composition (And 25.91–55.25 Grs 41.37–61.15 Alm+Sps+Py 1.48–12.85 ) in which FeO t increases, whereas Al 2 O 3 decreases rimward.Clinopyroxene with a salitic-ferrosalitic composition is homogenous, has low to relatively high Fe/(Fe + Mg) ratios, and is poor in TiO 2 , MnO, and Na 2 O. It displays a decrease in the diopside content with increasing distance from the causative intrusion, whereas the ferrosalite content is enriched near the marble and hornfels fronts.The fluid system evolves from high temperatures (>580°C), saline fluids (>53 wt% NaCl equivalent) in the late crystallization stage under lithostatic pressure of ~750 bar at a depth of ~3 km. Fluid in the later retrograde stage has lower temperatures (<430°C) and salinities (<40 wt% NaCl equivalent). Mixing and dilution between the initial hydrothermal and external fluids might cause a decrease in fluid temperature and salinity causing the formation of the magnetite.
... ( . ﭘﻬﻨـﻪ اﯾـﻦ ﻣﯿﺰﺑﺎن ﮐﺎﻧـﻪ ﻣﺨﺘﻠـﻒ اﻧﻮاع زاﯾـﯽ ﻣـﺲ ﮐﺎﻧﺴـﺎرﻫﺎي ﻣﺎﻧﻨـﺪ ﻓﻠـﺰي ﻫـﺎي ) ﺳـﻮﻧﮕﻮن ﭘـﻮرﻓﯿﺮي Mehrpartou, 1993;Calagari, 1997;Hezarkhani and Williams-Jones, 1998;Calagari, 2004;Aghazadeh et al., 2015 ،( ـﺠﺪداﻏﯽ ﻣﺴــــ ) Mohammadi, 2004;Fard et al., 2005;Akbarpour, 2005;Zonouzi, 2006 ( ﻫﻔـﺖ ، ) ﭼﺸـﻤﻪ Hassanpour et al., 2011 ( ) ﺳﻮﻧﺎﺟﯿﻞ و Hosseinzadeh, 2008 اﺳـﮑﺎرن ،( ﻣـﺲ ﻫـﺎي اﻧﺠــﺮد و ﺳــﻮﻧﮕﻮن ﻣﺰرﻋــﻪ، ) Mollai, 1993;Karimzadeh Somarin and Moayyed, 2002;Calagari and Hosseinzadeh, 2006;Mollai et al., 2014 ( ـﺎﯾﺮ ذﺧـ و اﭘــﯽ ﻃــﻼي ﺷــﺮف ﺗﺮﻣــﺎل ) آﺑــﺎد Pournik, 2002 ﻣﺴــﺠﺪداﻏﯽ ،( ) Mohammadi, 2004;Fard et al., 2005;Akbarpour, 2005;Zonouzi, 2006 ،( زﮔﻠﯿﮏ -) ﺳـﺎرﯾﻼر Heydarzadeh, 2007;Ebrahimi et al., 2011 ،( )ﻣﯿـﻮه اﻧﺪرﯾﺎن آﺳـﺘﺮﻗﺎن و رود( (Jamali, 1999;Gholami Checheki, 2001;Jamali et al., 2012;Ferdosi et al., 2014;Ferdosi et al., 2016 ،( ـﯽ ﻧﺒـــ ) ـﺎن ﺟـــ Baniadam, 2003 ـﻔﯽ ﺻـــ و ( ـﺎﻧﻠﻮ ﺧـــ -ـﺪوز ﻧﻘـــ ) Ghadimzadeh, 2002 Zvedov et al., 1993;Moritz et al., 2016 اﭘﯽ ﻃﻼي ﮐﺎﻧﺴﺎر ،( ) د ز ﺗﺮﻣﺎل Kozerenko, 2004;Konstantinov et al., 2010 ( ، ـﯽ ﭘﻠـ ـﺎرﻫﺎي ﮐﺎﻧﺴـ ـﺎن، ﮐﺎﻓـ ـﺎل ﻣﺘـ ) ﻣﻬﻤﺎﻧـــﺎ و اﻻوردي Mederer et al., 2014 ارﻣﻨﺴـــﺘﺎن در ( ، آﺳـﺘﺎﻣﺎل ﺷـﻤﺎل آﻫـﻦ اﺳـﮑﺎرن ﮐﺎﻧﺴـﺎرﻫﺎي و ) ﭘﻬﻨـﺎور Mokhtari, 2012;Baghban et al., 2015;Baghban et al., 2016 ( ، اﺳـﮑﺎرن آوان ـﺲ ﻣـ ﻫـﺎي ) ﮐﻤﺘـﺎل و Mokhtari et al., 2013;Mokhtari et al., 2016 و ( ﮐﺎﻧﯽ ﻣـﺲ ﺳـﺎزي -ﻣﻮﻟﯿﺒـﺪن -ﻃـﻼي ﻗـﺮه ) ﭼﯿﻠـﺮ Alavi, 1991 ) آﻗﺎﻧﺒﺎﺗﯽ و ( Aghanabati, 2004 ( اﺳﺖ. ﺷﺪه اﻗﺘﺒﺎس Alavi (1991) and Aghanabati (2004 Debon and Le Fort, 1983 اﺳﺖ. ﺷﺪه اﻗﺘﺒﺎس ( ...
Introduction
The Qarachilar Cu-Mo-Au occurrence is located in the Arasbaran ore zone (AZ), NW Iran, some 70 km north of Tabriz. The AZ is characterized by occurrence of different types of mineralization and hosts many Cu-Mo porphyry (PCD), Cu skarn, and epithermal Au deposits (Jamali et al., 2010; Jamali and Mehrabi, 2015). The main rock unit exposed in the area is Qaradagh batholith (QDB). A variety of porphyry and vein-type Cu–Mo–Au mineralization are associated with QDB. The most pronounced occurrences are in Qarachilar, Qara-Dareh, Zarli-Dareh, Aniq and Pirbolagh. This type of mineralization can be followed in other parts of northwest Iran, such as Masjed-Daghi porphyry Cu–Au deposit and Mivehrood vein-type Au mineralization in the southwest of the QDB, the Sungun PCD and the related skarn in its southeast, and Astamal Fe-skarn deposit in south of the QDB. To date, no detailed study has been undertaken to understand the characteristics of the Qarachilar occurrence and its mineralization type is controversial. The recent work by Simmonds and Moazzen (2015) also did not present information relevant for an understanding of the Qarachilar occurrence. The Re–Os age data obtained in their work were compared with similar events along the Urumieh-Dokhtar magmatic arc (UDMA) and southern Lesser Caucasus in order to elucidate the temporal pattern of mineralization across the whole QDB and the UDMA. The present paper provides an overview of the geological framework, the mineralization characteristics, and the results of geochemistry and fluid inclusion studies of the Qarachilar Cu-Mo-Au occurrence with an application to the ore genesis.
Materials and methods
More than 37 polished thin and thin sections from Qarachilar host rocks and mineralized and altered zones were studied by conventional petrographic and mineralogic methods at the University of Zanjan. In addition, 9 samples from non-altered and altered host rocks and mineralized veins were analyzed by ICP-MS for trace elements and REE at Zarazma Co., Tehran, Iran. Microthermometric data were performed on primary fluid inclusions using the Linkam THMSG-600 heating–freezing stage at Iranian Mineral Processing Research Center (IMPRC), Tehran, Iran.
Results
The rock units exposed in the Qarachilar area are different sets of magmatic phases of QDB including granodiorite-quartz monzodiorite, porphyritic granite, quartz monzonite and acidic-intermediate dikes. Granodiorite-quartz monzodiorite is the dominant phase which host Qarachilar quartz-sulfide veins. Mineralization at Qarachilar occurs as three quartz-sulfide veins. The veins reach up to 700-m in length and average 1-m in width, reaching a maximum of 2-m. They are generally steeply-dipping to the NE at 80°. The reported grades of Mo, Cu and Au range from 20 ppm to 3.6 wt%, 0.7 wt% to 5 wt%, and 0.23 to 37.2 g/t, respectively.
Four stages of mineralization can be distinguished at Qarachilar. Stage-1 is represented by quartz veins (ranging from centimeters up to ≤1-m width) that contain variable amounts of chalcopyrite and pyrite. Stage-2 is marked by <1-mm to 3-cm wide veins of quartz with molybdenite ±pyrite that usually cut Stage-1 mineralization, and, in turn, are cut by Stage-3 veins. The Stage-2 veins usually show a banded appearance. Disseminated texture is also observed in this stage. Molybdenite (0‒5%) occurs as large flakes or aggregates of anhedral, tiny shredded crystals, rosettes, or plates, with variable sizes of 200-μm to 3-mm within the quartz veins-veinlets. Stage-3 is represented by 1 to 10-cm wide Au-bearing Fe-hydroxide quartz veinlets. Stage-4 is represented by individual or sets of late quartz-carbonate veinlets that usually cut previous stages. No sulfide minerals are recognized with Stage-4. The hydrothermal alteration assemblages at Qarachilar from proximal quartz, sericite and carbonate to distal sericite, epidote and calcite (propylitic alteration). Potassic alteration occurs locally in 5-cm-wide, quartz-albite-secondary biotite veins within granodiorite-quartz monzodiorite pluton. The ore minerals is composed of chalcopyrite, pyrite, molybdenite, galena and quartz, calcite and ankerite are present as gangue minerals. Chalcocite, covellite, malachite, azurite, ferimolybdite and goethite formed during the supergene stage. The ore minerals show vein-veinlet, brecciated, disseminated, vug infill, replacement and relict textures.
Comparison of Chondrite normalized (Nakamura, 1974) REE patterns of non-altered and altered host granodiorite-quartz monzodiorite pluton and the mineralized samples at Qarachilar indicate that altered pluton and especially mineralized samples show lower concentrations of REE relative to non-altered plutonic host rocks. This signature indicate mobility of REE by Cl and F-rich magmatic-hydrothermal fluids during alteration and mineralization processes. Homogenization temperatures (Th) of two-phase inclusions within quartz varies from 182-532°C, and salinity from 9.2 to 23.5 wt% NaCl equiv. Three-phase halite-bearing type-1 (Th>Tm-h) and type-2 (Tm-h>Th) inclusions homogenized in the range of 197-530°C and 203-375°C, respectively. They, respectively, have a calculated bulk salinities of 29.5 to 55.1 and 32.4 to 45.6 wt% NaCl equiv. The variation in salinity and Th could be explained by a combination of mixing and boiling of hydrothermal fluids. These processes led to the deposition of Cu, Mo and Au in the veins. Geology, ore mineralogy, textures, geochemistry and microthermometric data of Qarachilar occurrence are comparable with vein-type Cu-Mo-Au mineralization related to Cu-Mo porphyry and intrusion related gold deposits.
... ( . ﭘﻬﻨـﻪ اﯾـﻦ ﻣﯿﺰﺑﺎن ﮐﺎﻧـﻪ ﻣﺨﺘﻠـﻒ اﻧﻮاع زاﯾـﯽ ﻣـﺲ ﮐﺎﻧﺴـﺎرﻫﺎي ﻣﺎﻧﻨـﺪ ﻓﻠـﺰي ﻫـﺎي ) ﺳـﻮﻧﮕﻮن ﭘـﻮرﻓﯿﺮي Mehrpartou, 1993;Calagari, 1997;Hezarkhani and Williams-Jones, 1998;Calagari, 2004;Aghazadeh et al., 2015 ،( ـﺠﺪداﻏﯽ ﻣﺴــــ ) Mohammadi, 2004;Fard et al., 2005;Akbarpour, 2005;Zonouzi, 2006 ( ﻫﻔـﺖ ، ) ﭼﺸـﻤﻪ Hassanpour et al., 2011 ( ) ﺳﻮﻧﺎﺟﯿﻞ و Hosseinzadeh, 2008 اﺳـﮑﺎرن ،( ﻣـﺲ ﻫـﺎي اﻧﺠــﺮد و ﺳــﻮﻧﮕﻮن ﻣﺰرﻋــﻪ، ) Mollai, 1993;Karimzadeh Somarin and Moayyed, 2002;Calagari and Hosseinzadeh, 2006;Mollai et al., 2014 ( ـﺎﯾﺮ ذﺧـ و اﭘــﯽ ﻃــﻼي ﺷــﺮف ﺗﺮﻣــﺎل ) آﺑــﺎد Pournik, 2002 ﻣﺴــﺠﺪداﻏﯽ ،( ) Mohammadi, 2004;Fard et al., 2005;Akbarpour, 2005;Zonouzi, 2006 ،( زﮔﻠﯿﮏ -) ﺳـﺎرﯾﻼر Heydarzadeh, 2007;Ebrahimi et al., 2011 ،( )ﻣﯿـﻮه اﻧﺪرﯾﺎن آﺳـﺘﺮﻗﺎن و رود( (Jamali, 1999;Gholami Checheki, 2001;Jamali et al., 2012;Ferdosi et al., 2014;Ferdosi et al., 2016 ،( ـﯽ ﻧﺒـــ ) ـﺎن ﺟـــ Baniadam, 2003 ـﻔﯽ ﺻـــ و ( ـﺎﻧﻠﻮ ﺧـــ -ـﺪوز ﻧﻘـــ ) Ghadimzadeh, 2002 Zvedov et al., 1993;Moritz et al., 2016 اﭘﯽ ﻃﻼي ﮐﺎﻧﺴﺎر ،( ) د ز ﺗﺮﻣﺎل Kozerenko, 2004;Konstantinov et al., 2010 ( ، ـﯽ ﭘﻠـ ـﺎرﻫﺎي ﮐﺎﻧﺴـ ـﺎن، ﮐﺎﻓـ ـﺎل ﻣﺘـ ) ﻣﻬﻤﺎﻧـــﺎ و اﻻوردي Mederer et al., 2014 ارﻣﻨﺴـــﺘﺎن در ( ، آﺳـﺘﺎﻣﺎل ﺷـﻤﺎل آﻫـﻦ اﺳـﮑﺎرن ﮐﺎﻧﺴـﺎرﻫﺎي و ) ﭘﻬﻨـﺎور Mokhtari, 2012;Baghban et al., 2015;Baghban et al., 2016 ( ، اﺳـﮑﺎرن آوان ـﺲ ﻣـ ﻫـﺎي ) ﮐﻤﺘـﺎل و Mokhtari et al., 2013;Mokhtari et al., 2016 و ( ﮐﺎﻧﯽ ﻣـﺲ ﺳـﺎزي -ﻣﻮﻟﯿﺒـﺪن -ﻃـﻼي ﻗـﺮه ) ﭼﯿﻠـﺮ Alavi, 1991 ) آﻗﺎﻧﺒﺎﺗﯽ و ( Aghanabati, 2004 ( اﺳﺖ. ﺷﺪه اﻗﺘﺒﺎس Alavi (1991) and Aghanabati (2004 Debon and Le Fort, 1983 اﺳﺖ. ﺷﺪه اﻗﺘﺒﺎس ( ...
Qarachilar Cu-Mo-Au mineralization is located within the Qaradagh batholite in the Arasbaran metalogenic zone. This area is a part of southern margin of Lesser Caucasus. Qaradagh batholite at the Qarachilar mineralization area composed of granodiorite-quartz monzodiorite (as the main phase and host rock of mineralization), diorite, quartz monzonitic stocks, apophyses of porphyritic granite and acidic to intermediate dykes. All of the mentioned intrusion phases have calc-alkaline to high-K calc-alkaline nature and classified as metaluminous I-type granites. The porphyritic granite apophyses and dykes, and quartz monzonitic stocks have adakitic nature and can be classified as high silica adakites. In the chondrite and primitive mantle normalized spider diagrams, all intrusion phases demonstrate similar patterns with enrichment in LILE and negative anomalies of HFSE. Chondrite normalized REE patterns in granodiorites-quartz monzodiorites indicate enrichment in LREE and flat trend in MREE and HREE, while porphyritic granites show steep pattern with enrichment in LREE and depletion in HREE. Based on field investigation, petrological, geochemical, tectonomagmatic discrimination diagrams and results from previous studies on the northern part of the Qaradagh batholith in the Armenian Republic, it can be conclude that granodiorite-quartz monzodiorite phase was formed in active continental margin as a result of Neo-Tethyan ocean subduction beneath the Eurasia. The quartz monzonite stocks and porphyritic granites were formed in a post collisional setting from metasomatized lithospheric mantle wedge.
... The results of fry analysis suggest that the distribution of the SCDs at the distances ≤7.5 km follow an N-S trend manifesting localscale controls of skarn mineralization (Fig. 5c). These results are significant because local studies on the SCDs of the Varzaghan district recommended the N-S trending faults to be directly associated with the skarnification (e.g., Mollai et al., 2009;Jamali et al., 2010;Mokhtari et al., 2017). Fry analysis also revealed that the district-scale (i.e., distances > 7.5 km) geological processes, which yielded in the distribution of the SCDs in the Varzaghan district, follow an NW-SE trend ( Fig. 5a and b). ...
Recognition of significant ore-forming processes, which control mineralization, improves the efficiency of mineral prospectivity modeling. In this study, controlling processes of skarn copper mineralization in Varzaghan district, northwestern Iran, were distinguished by a series of spatial and numerical analyses comprising point pattern, fractal, fry and distance distribution methods. The recognized processes were then translated to a set of exploration criteria of the deposits in the area. Based on the accomplished exploration criteria, two data-driven models of skarn copper prospectivity were generated using logistic regression and random forest techniques. The comparison of two generated models demonstrated that the targets derived by the latter technique were more reliable for further exploration than those created by the former one.
