Titaniferous magnetite–ilmenite thermometry and titaniferous magnetite–ilmenite–orthopyroxene–quartz oxygen barometry in granulite facies gneisses, Bamble Sector, SE Norway: implications for the role of high-grade CO2-rich fluids during granulite genesis

Harlov, Daniel E.

doi:10.1007/pl00007670

Cited by 41 publications

(24 citation statements)

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“…More recently, such investigations have been expanded to include oxygen buffers such as orthopyroxene–magnetite–quartz and fayalite–magnetite–quartz (Frost et al. , 1988; Harlov, 1992, 2000a; Harlov et al. , 1997).…”

Section: Introductionmentioning

confidence: 87%

“…Orthopyroxene also shows Al contents (1.1 < Al 2 O 3 < 3.7) typical for high‐grade metamorphic rocks (e.g. Harlov, 1992, 2000a). In the CGF, the ferrosilite component in orthopyroxene (0.37 < < 0.48) (Table 2) is very similar to what is seen in the SGF whereas clinopyroxene shows even lower Fe abundances (0.27 < < 0.34) (Table 3).…”

Section: Textures and Mineral Chemistrymentioning

confidence: 99%

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Oxide and sulphide isograds along a Late Archean, deep‐crustal profile in Tamil Nadu, south India

Harlov¹,

Hansen

2005

Journal Metamorphic Geology

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Oxide-sulphide-Fe-Mg-silicate and titanite-ilmenite textures as well as their mineral compositions have been studied in felsic and intermediate orthogneisses across an amphibolite (north) to granulite facies (south) traverse of lower Archean crust, Tamil Nadu, south India. Titanite is limited to the amphibolite facies terrane where it rims ilmenite or occurs as independent grains. Pyrite is widespread throughout the traverse increasing in abundance with increasing metamorphic grade. Pyrrhotite is confined to the highgrade granulites. Ilmenite is widespread throughout the traverse increasing in abundance with increasing metamorphic grade and occurring primarily as hemo-ilmenite in the high-grade granulite facies rocks. Magnetite is widespread throughout the traverse and is commonly associated with ilmenite. It decreases in abundance with increasing metamorphic grade. In the granulite facies zone, reaction rims of magnetite + quartz occur along Fe-Mg silicate grain boundaries. Magnetite also commonly rims or is associated with pyrite. Both types of reaction rims represent an oxidation effect resulting from the partial subsolidus reduction of the hematite component in ilmenite to magnetite. This is confirmed by the presence of composite three oxide grains consisting of hematite, magnetite and ilmenite. Magnetite and magnetite-pyrite micro-veins along silicate grain boundaries formed over a wide range of post-peak metamorphic temperatures and pressures ranging from high-grade SO 2 to low-grade H 2 S-dominated conditions. Oxygen fugacities estimated from the orthopyroxene-magnetite-quartz, orthopyroxenehematite-quartz, and magnetite-hematite buffers average 2.5 log units above QFM. It is proposed that the trends in mineral assemblages, textures and composition are the result of an external, infiltrating concentrated brine containing an oxidizing component such as CaSO 4 during high-grade metamorphism later acted upon by prograde and retrograde mineral reactions that do not involve an externally derived fluid phase.

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Section: Introductionmentioning

confidence: 87%

Section: Textures and Mineral Chemistrymentioning

confidence: 99%

Oxide and sulphide isograds along a Late Archean, deep‐crustal profile in Tamil Nadu, south India

Harlov¹,

Hansen

2005

Journal Metamorphic Geology

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“…Fluid inclusion studies document CO 2 dominated fluids in amphibolite lithologies, and CO 2 + brines in more siliceous gneisses during peak metamorphic conditions (Touret 1971); conclusion that is supported by fluid modelling using the iron-titanium oxygen barometer (Harlov 2000).…”

Section: Geological Settingmentioning

confidence: 72%

Coupled trace element mobilisation and strain softening in quartz during retrograde fluid infiltration in dry granulite protoliths

Sørensen

Larsen

2008

Contrib Mineral Petrol

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This study focuses on the retrograde rheological and chemical evolution of quartz and the behaviour of quartzites during retrograde metamorphism following dry high grade metamorphism at 750°C, 7 kbar. SEM-CL and LA-HR-ICP-MS are applied to document quartz texture and chemistry, respectively. Four generations of quartz were distinguished by SEM-CL; Qz1, Qz2, Qz3 and Qz4. Qz1, brecciated and partly dissolved old grains, is enriched in B, Al and Ti when compared with the other types. Qz2, formed during brecciation and partial dissolution of Qz1, has low Al contents (\50 ppm) but, due to rutile inclusions, variable Ti contents when occurring in amphibolite (210-10 ppm) but more consistent values when occurring in quartzites (peak value 32 ppm). Qz3, dark grey luminescent quartz forming fluid migration channels (fluid pathways), has Ti \ 5 ppm and Al contents below 10 ppm and B \ 1 ppm. Qz4, comprises are group of quartz later than Qz3 filling micron thick cracks and pods with very low luminescent quartz, i.e. darker than Qz3. The textural and chemical evolution of quartz in our study is explained by two major influxes of aqueous fluids during regional uplift and retrogression. They facilitated rehydration and recrystallisation in the otherwise dry high grade quartzites. The first introduction of aqueous fluids was associated with brecciation of the high grade quartz (Qz1) and dissolution/precipitation of quartz (Qz2). Ti in quartz geothermometry (Wark and Watson, Contrib Mineral Petrol 152(6):637-652) gives 626°C in agreement with the retrograde PT-path deduced from phase diagrams. Later fluid influx associated with scapolitisation of amphibolite caused localised recrystallisation (Qz3) and alteration of biotite to muscovite along mm-wide fluid migration channels. During subsequent deformation, Qz3 deformed plastically and recovered by subgrain rotation recrystallisation (SGR), resulting in a reduction of grain size, whereas Qz1 quartz formed micro faults. Qz2 was plastic but did not experience SGR to the same degree as Qz3 quartz. Increased plasticity and recovery rates most likely relate to an increased H 2 O fugacity and the depletion in trace elements of the quartz lattice by promoting strain softening processes dislocation climb and recovery.

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“…Several high-grade terranes exhibit unusually high oxidation states (Griffin et al, 1978;Currie and Gittins, 1988;Harlov, 1992Harlov, , 2000Harlov and Förster, 2002a,b;Harlov et al, 1997). This may result from interaction with brines carrying SO 2 exsolved from underplated magmas (Cameron and Hattori, 1994;Harlov et al, 1997).…”

Section: Brines and Redox Effectsmentioning

confidence: 99%

Brines at high pressure and temperature: Thermodynamic, petrologic and geochemical effects

Manning

Aranovich

2014

Precambrian Research

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a b s t r a c tA number of observations point to the participation of brines in high-grade metamorphic processes. These include findings of alkali and alkaline-earth halides as daughter crystals in fluid inclusions, appreciable concentrations of Cl measured in amphiboles, biotite, scapolite and apatite, and direct observations on high-temperature halides present in the intergranular space in high-grade rocks. This paper reviews some thermodynamic, petrologic and geochemical effects of these brines. Thermodynamic mixing properties of concentrated water-salt fluids at high pressure (P) and temperature (T) differ greatly from those of water-non-polar gas mixtures: the former are characterized by a large negative deviation from ideal solutions, while the latter exhibit positive deviation from ideality. The contrasting behavior has three major petrologic implications. First, compared to mixtures of water and non-polar gases, brines more strongly increase the melting temperature of quartzofeldspathic rocks and more strongly decrease dehydration temperature of water-bearing minerals. This allows a wide P-T window in which subsolidus deep-crustal metasomatism may take place at relatively low H 2 O activity (a H 2 O ) via migrating fluids. In addition, above 2-3 kbar, brine-saturated solidi for simple granite melting show positive dP/dT at constant H 2 O mole fraction (X H 2 O ), favoring ascent of fluid-saturated liquids. Finally, a large miscibility gap exists in H 2 O-CO 2 -salt ternaries at lower crustal conditions, which may concentrate salts in a separate phase and help explain the common observation of CO 2 -rich inclusions in high-grade minerals. We discuss three geochemical consequences of high-grade brines. We report new experimental data on melting of a model granitoid liquid (69 wt% NaAlSi 3 O 8 , 31 wt% SiO 2 ) at 2 kbar in the presence of aqueous NaCl solutions ranging in concentration from a salt mole fraction (X NaCl ) of 0.1-0.3. The results show that Na preferentially partitions into the silicate liquid, enriching the coexisting fluid in HCl. This hydrolysis effect, known previously for granite melts equilibrated with dilute solutions, therefore also extends to more saline brines. Mineral solubilities depend strongly on salt concentration in the coexisting fluid. Below 5 kbar at 700• C, quartz initially salts in with addition of NaCl to H 2 O, reaches a maximum, and then declines; however, it salts out at all X NaCl at higher P. At granulite-facies P-T conditions, the solubilities of other oxide and silicate minerals (corundum, wollastonite, grossular) salt in and then either reach a plateau or salt out slightly at high X NaCl . In contrast, the solubility of Ca-salt minerals increases exponentially with rising X NaCl . The solubility patterns reflect variations in complexing and H 2 O activity in the brine. Partitioning of REE between rock forming minerals and brines, and between felsic melts and brines, differs strongly from that between minerals, melts and water (±non-polar gas). Brines extract REE f...

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Titaniferous magnetite–ilmenite thermometry and titaniferous magnetite–ilmenite–orthopyroxene–quartz oxygen barometry in granulite facies gneisses, Bamble Sector, SE Norway: implications for the role of high-grade CO2-rich fluids during granulite genesis

Cited by 41 publications

References 62 publications

Oxide and sulphide isograds along a Late Archean, deep‐crustal profile in Tamil Nadu, south India

Oxide and sulphide isograds along a Late Archean, deep‐crustal profile in Tamil Nadu, south India

Coupled trace element mobilisation and strain softening in quartz during retrograde fluid infiltration in dry granulite protoliths

Brines at high pressure and temperature: Thermodynamic, petrologic and geochemical effects

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