MacFlinCor and its application to fluids in Archean lode-gold deposits

Brown, P. E.; Hagemann, Steffen

doi:10.1016/0016-7037(95)00254-w

Cited by 230 publications

(92 citation statements)

References 17 publications

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“…This is designed vertically with the isochore of each inclusion, assuming that the inclusions were not affected by any other processes after imprisonment (Brown and Hagemann, 1995;Hagemann, 1993). The results indicate that the orebody was formed at a minimum average pressure of 4045.2 bar and a maximum of 4494.8 bar (Fig.…”

Section: Arsenopyrite Geothermometer and Pressure Estimation For The mentioning

confidence: 99%

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Metal source and fluid–rock interaction in the Archean BIF-hosted Lamego gold mineralization: Microthermometric and LA-ICP-MS analyses of fluid inclusions in quartz veins, Rio das Velhas greenstone belt, Brazil

Morales

Silva

Lobato

et al. 2016

Ore Geology Reviews

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The Lamego orogenic gold deposit (440,742 Oz gold measured reserves and 2.4 million t measured resources, with an average grade of 5.71 Au g/t and the cut-off grade of 2.15 g/t Au; AGA personal communication, 2014) is located in the 5 km-long trend that includes the world-class Cuiabá deposit. It is hosted in the Neoarchean metavolcano-sedimentary rocks of the Rio das Velhas greenstone belt, Quadrilátero Ferrífero, Brazil. Mineralization is associated mainly with metachertbanded iron formation (BIF) and carbonaceous phyllites in the reclined Lamego fold, in which the Cabeça de Pedra orebody represents the hinge zone. Mineralization is concentrated in silicification zones and their quartz veins, as well as in sulfide minerals, product of BIF sulfidation. Hydrothermal alteration varies according to host rock, with abundant sulfide-carbonate in BIF, and sericite-chlorite in carbonaceous phyllite. Quartz veins classification according to structural relationships and host rocks identified three vein systems. The V1 system, mainly composed of smoky quartz (Qtz I) and pyrite, is extensional and crosscuts the S0 bedding of BIF, and is parallel to the fold axis. The V2 system, of same composition, is represented by veins that are parallel to the S1-2 foliation and S0 bedding. This system is also characterized by silicification zones in the BIF-carbonaceous phyllite contact that has its maximum expression in the hinge zone of folds. The V3 system has milky quartz (Qtz II) veins, which result from the recrystallization of smoky quartz, located mainly in shear zones and faults; these veins form structures en echelon and vein arrays. The most common ore minerals are pyrite, As-pyrite and arsenopyrite. Fluid inclusion-FI trapped in all quartz veins present composition in the H2O-CO2 ± CH4-NaCl system. Fluid evolution can be interpreted in two stages: i) aqueous-carbonic fluid trapped in Qtz I, of low salinity (~ 2% equiv. wt% NaCl), and ii) carbonic-aqueous fluid, of moderate salinity (average 9 % equiv. wt% NaCl) hosted in Qtz II. Both stages are characterized by decrepitation temperatures in the range of 200 to 300°C, and suggest a fluid of metamorphic origin. Applying the arsenopyrite geothermometer, the calculated formation temperature for the Cabeça de Pedra orebody is 300 to 375°C. The vertical intersection of the isochors allows a pressure calculation between 4 to 4.5 kbar. The composition of individual FIs of this orebody, obtained by LA-ICP-MS analyses, compared with results of FIs for the Carvoaria Velha deposit, Córrego do Sítio lineament, highlights a standard composition typical of metamorphic fluids with Na> K> Ca> Mg, which increase or decrease in concentration as a function of salinity in both deposits. Trace elements vary according to fluid-rock reactions, and are directly related to the host rock composition. The comparison of data sets of the two deposits shows that the Cabeça de Pedra FIs have a higher enrichment in Zn, while Cu, As and Sb are richer in Carvoaria Velha, suggesting influence of th...

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Section: Arsenopyrite Geothermometer and Pressure Estimation For The mentioning

confidence: 99%

“…Apparent salinity has been reported in equivalent percentage weight of NaCl. Calculations of salinity and density were made using the MacFlinCor program (Brown and Hagemann, 1995 …”

Section: )mentioning

confidence: 99%

Metal source and fluid–rock interaction in the Archean BIF-hosted Lamego gold mineralization: Microthermometric and LA-ICP-MS analyses of fluid inclusions in quartz veins, Rio das Velhas greenstone belt, Brazil

Morales

Silva

Lobato

et al. 2016

Ore Geology Reviews

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“…For the fluid inclusions of present study, CO 2 densities of 0.95 g/cm 3 for primary inclusions in rutile, 0.76 g/cm 3 for primary inclusions in apatite, 0.68 -0.85 g/ cm 3 for primary inclusions in garnet, and 0.58 -0.79 g/cm 3 for secondary inclusions in garnet were estimated. Iso- chores were calculated for each category of inclusions using the computer program "MacFlinCor" developed by Brown and Hagemann (1995) and the thermodynamic model of Brown and Lamb (1989). The results are shown in Figure 4 together with available P -T path for Kumiloothu locality .…”

Section: Fluid Inclusionsmentioning

confidence: 99%

Carbonic fluid inclusions in ultrahigh-temperature granulite from Kumiloothu in the northern Madurai Block, southern India

Ohyama

Tsunogae

Santosh

2008

Journal of Mineralogical and Petrological Sciences

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We report fluid inclusion data on ultrahigh -temperature (UHT) granulites from Kumiloothu in the northern Madurai Block situated along the Palghat -Cauvery Shear Zone system in southern India. Three categories of fluid inclusions have been observed: primary inclusions in garnet comprising the dominant category, secondary inclusions in garnet, and rare primary inclusions in rutile and apatite enclosed within garnet. The melting temperatures of all the categories of inclusions lie in the narrow range of -57.0 to -56.6 °C, close to the triple point of pure CO 2 . Most of the fluid inclusions homogenize into the liquid phase between a temperature range of +11.3 to +30.3 °C, corresponding to low -CO 2 densities of 0.59 -0.85 g/cm 3. Slightly higher density of 0.95 g/cm 3 was obtained from a primary inclusion in rutile that homogenized at -3.6 °C. The fluid densities, when computed into isochores, indicate lower pressures (~ 6.6 kbar at 1000 °C) than the peak P -T conditions (T >1000 °C at ~ 8 kbar) estimated for this region. The results of this study, together with the primary nature of the inclusions trapped in high -grade minerals, indicates density reversal of peak metamorphic fluid, a common feature for many UHT granulites along the Gondwana suture zone as well as other UHT terranes showing clockwise P -T history.

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“…Isochores were calculated using the computer program MacFlinCor developed by Brown and Hagemann (1995). Aqueous inclusions were assumed to consist entirely of components in the binary H 2 O NaCl system, and carbonic inclusions were assumed to consist of components in the pure CO 2 system.…”

Section: Microthermometrymentioning

confidence: 99%

Fluid inclusions study of Abukuma metamorphic rocks from the Hanazono district, northeast Japan

Ohyama

Tsunogae

2007

Journal of Mineralogical and Petrological Sciences

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A systematic fluid inclusion study on pelitic and granitic gneisses of the Cretaceous Abukuma metamorphic rocks, exposed in the Hanazono district, northeast Japan, identified three categories of fluid inclusions: primary aqueous inclusions in porphyroblastic garnet, primary to pseudosecondary carbonic inclusions in quartz, and secondary aqueous inclusions in quartz. The primary aqueous inclusions in garnet exhibit melting and homogenization temperatures of −2.5 to −0.3 °C and +168.2 to +360.0 °C, respectively. The dominant primary to pseudosecondary fluid inclusions in undeformed quartz display melting temperatures of −64.2 to −56.6 °C, indicating a CO 2 rich composition with additional CH 4 and/or N 2 . The carbonic inclusions can be divided into high density (1.121 1.153 g/cm 3 ) and medium density (0.683 1.111 g/cm 3 ) types. The fluid densities of the latter inclusions, when translated into isochores, indicate entrapment of CO 2 at the peak P T conditions experienced by rocks in the study area (2.8 5.2 kbar at 770 850 °C). In contrast, the isochores of high density category in quartz and aqueous inclusions in garnet do not intersect the expected P T trajectory, yet are consistent with the prograde high pressure condition of the Abukuma metamorphic rocks in the Takanuki district (8 10 kbar at 700 750 °C). Isochores calculated for carbonic inclusions in granitic gneiss intersect the P T path at 2 3 kbar at 650 °C, suggesting that the fluids were captured during the retrograde stage. It is inferred that H 2 O was the dominant fluid species during the prograde stage, while CO 2 was more abundant during the peak to retrograde stages of the Abukuma metamorphic belt. The prograde H 2 O bearing fluid was probably derived from the break down of hydrous minerals. Although the origin of carbonic fluid is not known, the presence of CO 2 rich fluid during peak metamorphism probably lowers the H 2 O activity in the rocks. The isochores computed for secondary aqueous inclusions in quartz give very low P T conditions (300 °C and 1.7 3.5 kbar), suggesting that the fluids are of retrograde origin.

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MacFlinCor and its application to fluids in Archean lode-gold deposits

Cited by 230 publications

References 17 publications

Metal source and fluid–rock interaction in the Archean BIF-hosted Lamego gold mineralization: Microthermometric and LA-ICP-MS analyses of fluid inclusions in quartz veins, Rio das Velhas greenstone belt, Brazil

Metal source and fluid–rock interaction in the Archean BIF-hosted Lamego gold mineralization: Microthermometric and LA-ICP-MS analyses of fluid inclusions in quartz veins, Rio das Velhas greenstone belt, Brazil

Carbonic fluid inclusions in ultrahigh-temperature granulite from Kumiloothu in the northern Madurai Block, southern India

Fluid inclusions study of Abukuma metamorphic rocks from the Hanazono district, northeast Japan

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