<abstract xmlns="http://www.w3.org/1999/xhtml"> Hydrothermal alteration of the Meiduk porphyry copper deposit, south of the Kerman Cenozoic magmatic arc and southeast of the central Iranian volcano-plutonic belt has resulted in three stages of mineralisation characterised by veins and veinlets. These are, from early to late: (1) quartz + K-feldspar + biotite + pyrite ± chalcopyrite ± pyrrhotite ± magnetite (early potassic alteration and type-A veins); (2) quartz + chalcopyrite + pyrite + bornite + pyrrhotite + K- -feldspar + biotite + magnetite (potassic-sericitic alteration and type-B veins); and (3) quartz + pyrite + chalcopyrite + sericite (sericitic alteration and type-C veins). Most ores were formed during stages 2 and 3. Three main types of fluid inclusions are distinguished based on petrographical, microthermometrical and laser Raman spectroscopy analyses, i.e. type I (three-phase aqueous inclusions), type II (three-phase liquid-carbonic inclusions) and type III (multi-phase solid inclusions). The fluid inclusions in quartz veins of the stages are mainly homogenised at 340-530°C (stage 1), 270-385°C (stage 2) and 214-350°C (stage 3), respectively, with salinities of 3.1-16 wt.% NaCl equivalent, 2.2-43 wt.% NaCl equivalent and 8.2-22.8 wt.% NaCl equivalent, respectively. The estimated trapping pressures are 97.9-123.6 MPa (3.7-4.6 km) in stage 1 and 62.5-86.1 MPa (2.3-3.1 km) in stage 2, respectively. These fluid inclusions are homogenised in different ways at similar temperatures, suggesting that fluid boiling took place in stages 2 and 3. The fluid system evolved from high-temperature, medium-salinity, high-pressure and CO2-rich to low-temperature, low-pressure, high-salinity and CO2-poor, with fluid boiling being the dominating mechanism, followed by input of meteoric water. CO2 escape may have been a factor in increasing activities of NaCl and S2- in the fluids, diminishing the oxidation of the fluids from stage 1 to 3. The result was precipitation of sulphides and trapping of multi-phase solid inclusions in hydrothermal quartz veins.</abstract>

Hydrothermal alteration of the Meiduk porphyry copper deposit, south of the Kerman Cenozoic magmatic arc and southeast of the central Iranian volcano-plutonic belt has resulted in three stages of mineralisation characterised by veins and veinlets. These are, from early to late: (1) quartz + K-feldspar + biotite + pyrite ± chalcopyrite ± pyrrhotite ± magnetite (early potassic alteration and type-A veins); (2) quartz + chalcopyrite + pyrite + bornite + pyrrhotite + K- -feldspar + biotite + magnetite (potassic-sericitic alteration and type-B veins); and (3) quartz + pyrite + chalcopyrite + sericite (sericitic alteration and type-C veins). Most ores were formed during stages 2 and 3. Three main types of fluid inclusions are distinguished based on petrographical, microthermometrical and laser Raman spectroscopy analyses, i.e. type I (three-phase aqueous inclusions), type II (three-phase liquid-carbonic inclusions) and type III (multi-phase solid inclusions). The fluid inclusions in quartz veins of the stages are mainly homogenised at 340-530°C (stage 1), 270-385°C (stage 2) and 214-350°C (stage 3), respectively, with salinities of 3.1-16 wt.% NaCl equivalent, 2.2-43 wt.% NaCl equivalent and 8.2-22.8 wt.% NaCl equivalent, respectively. The estimated trapping pressures are 97.9-123.6 MPa (3.7-4.6 km) in stage 1 and 62.5-86.1 MPa (2.3-3.1 km) in stage 2, respectively. These fluid inclusions are homogenised in different ways at similar temperatures, suggesting that fluid boiling took place in stages 2 and 3. The fluid system evolved from high-temperature, medium-salinity, high-pressure and CO2-rich to low-temperature, low-pressure, high-salinity and CO2-poor, with fluid boiling being the dominating mechanism, followed by input of meteoric water. CO2 escape may have been a factor in increasing activities of NaCl and S2- in the fluids, diminishing the oxidation of the fluids from stage 1 to 3. The result was precipitation of sulphides and trapping of multi-phase solid inclusions in hydrothermal quartz veins.

First report on the occurrence of CO2-bearing fluid inclusions in the Meiduk porphyry copper deposit, Iran: implications for mineralisation processes in a continental collision setting

Department of Earth Sciences, Faculty of Sciences, Shiraz University, Shiraz, Iran

Department of Geology, Faculty of Sciences, Shahid Chamran University, Ahvaz, Iran

National Iranian Copper Industries Company (NICICo.), Sarcheshmeh, Iran

Geologos

First report on the occurrence of CO-bearing fluid inclusions in the Meiduk porphyry copper deposit, Iran: implications for mineralisation processes in a continental collision setting

Hydrothermal alteration of the Meiduk porphyry copper deposit, south of the Kerman Cenozoic magmatic arc and southeast of the central Iranian volcano-plutonic...

First report on the occurrence of CO₂-bearing fluid inclusions in the Meiduk porphyry copper deposit, Iran: implications for mineralisation processes in a continental collision setting

Publié en ligne: 29 janv. 2014

Pages: 301 - 320

DOI: https://doi.org/10.2478/logos-2013-0019

Mots clés
CO2-bearing fluid inclusions, laser Raman spectroscopy, collision, Meiduk porphyry copper deposit, Iran

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