The Role of Advective Fluid Flow and Diffusion during Localized, Solid-State Dehydration: Söndrum Stenhuggeriet, Halmstad, SW Sweden

Harlov, Daniel E.; Johansson, Leif; Kerkhof, Alfons van den; Förster, Hans‐Jürgen

doi:10.1093/petrology/egi062

Cited by 82 publications

(60 citation statements)

References 90 publications

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“…However, monazite nucleation is strongly dependent on the reactivity properties of fluid and the apatite, and also the amount of REEs available [63,64]. Dissolution-reprecipitation occurs in the interconnected micro-to nano-scale fractures and porosity in the host apatites.…”

Section: Textural and Mineral Chemical Evidencementioning

confidence: 99%

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Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

et al. 2018

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Abstract:The Chadormalu magnetite-apatite deposit in Bafq metallogenic province, Central Iran, is hosted in the late Precambrian-lower Cambrian volcano-sedimentary rocks with sodic, calcic, and potassic alterations characteristic of iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) ore systems. Apatite occurs as scattered irregular veinlets and disseminated grains, respectively, within and in the marginal parts of the main ore-body, as well as apatite-magnetite veins in altered wall rocks. Textural evidence (SEM-BSE images) of these apatites shows primary bright, and secondary dark areas with inclusions of monazite/xenotime. The primary, monazite-free fluorapatite contains higher concentrations of Na, Si, S, and light rare earth elements (LREE). The apatite was altered by hydrothermal events that led to leaching of Na, Si, and REE + Y, and development of the dark apatite. The bright apatite yielded two U-Pb age populations, an older dominant age of 490 ± 21 Ma, similar to other iron deposits in the Bafq district and associated intrusions, and a younger age of 246 ± 17 Ma. The dark apatite yielded a U-Pb age of 437 ± 12 Ma. Our data suggest that hydrothermal magmatic fluids contributed to formation of the primary fluorapatite, and sodic and calcic alterations. The primary apatite reequilibrated with basinal brines in at least two regional extensions and basin developments in Silurian and Triassic in Central Iran.

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Section: Textural and Mineral Chemical Evidencementioning

confidence: 99%

“…The concentration of LREE in the NaCl brines increases with X NaCl , pressure, and temperature, because complexing of REE with Cl − stops complexing with PO 4 3-and F − (e.g., [63,77,78]). …”

Section: Nature Of Fluidsmentioning

confidence: 99%

Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

et al. 2018

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“…However, later evidence of subtle partial melting was found [62], suggesting that the orthopyroxene-bearing assemblages formed under suprasolidus conditions. Although some studies have recorded mineral assemblages with prograde subsolidus orthopyroxene e.g., [63,64], these situations generally involve infiltration of a low H 2 O activity fluid (aH 2 O), such as CO 2 -rich fluids or highly concentrated brines, and occur in rocks that have experienced granulite facies temperatures. An example of this is the formation of fine-grained orthopyroxene-andalusite symplectites under low aH 2 O conditions during retrogression of pelitic granulites, described by Ballèvre, et al [65].…”

Section: Limitations Of the Modellingmentioning

confidence: 99%

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

et al. 2017

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Phase equilibria modelling incorporating melt reintegration offers a methodology to create hypothetical rock compositions that may have existed prior to melt loss, allowing the potential prograde evolution of rocks to be explored. However, melt reintegration modelling relies on assumptions concerning the volume of melt that was lost and is generally restricted by the absence of direct constraints on the pre-anatectic mineral assemblages. Mg-rich granulite in the 514-490 Ma Delamerian Orogen in southern Australia contains spinel-cordierite symplectic intergrowths that surround rare, coarse blocky domains of sillimanite. These sillimanite cores, as well as the widespread presence of andalusite in lower grade areas of the southern Delamerian Orogen, suggest that the subsolidus precursor to the granulite contained andalusite. This provides the opportunity to test if melt reintegration modelling of the granulite predicts subsolidus andalusite.Stepwise down-temperature melt reintegration modelling produces a water-saturated solidus after the addition of 12 mol% melt. When modelled at subsolidus conditions, the resulting rock composition produces andalusite-bearing assemblages with andalusite modes similar to the abundance of the sillimanite-cored spinel-cordierite intergrowths. The modelling results from this case study suggest that melt reintegration modelling is a valid method to recreate prograde subsolidus bulk rock compositions.

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“…Elevated Cl concentrations often measured in magmatic and high-grade metamorphic hydrous minerals such as amphibole, biotite, scapolite and apatite (e.g., Henry, 1988; Mora and Valley, 1989;Nijland et al, 1993;Kullerud, 2000;Faryad, 2002;Xiao et al, 2005;Harlov et al, 2006;Hansen and Harlov, 2007;Hammerli et al, 2014) may also be considered as evidence for chlorine-rich metamorphic fluids. This is because of the strong partitioning of Cl into the fluid phase relative to hydrous minerals (e.g., Munoz, 1981; Sverjensky, 1991, 1992;Kullerud, 1996).…”

Section: Introductionmentioning

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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The Role of Advective Fluid Flow and Diffusion during Localized, Solid-State Dehydration: Söndrum Stenhuggeriet, Halmstad, SW Sweden

Cited by 82 publications

References 90 publications

Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

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

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