scholarly journals Using mineral equilibria to estimate H2O activities in peridotites from the Western Gneiss Region of Norway

2017 ◽  
Vol 102 (5) ◽  
pp. 1021-1036 ◽  
Author(s):  
Patricia Kang ◽  
William M. Lamb ◽  
Martyn Drury
Keyword(s):  
Physical Properties ◽  
Fluid Pressure ◽  
Fluid Phase ◽  
Stability Field ◽  
Lithostatic Pressure ◽  
Free Fluid ◽  
Western Gneiss Region ◽  
Mineral Equilibria ◽  
Earth’S Mantle ◽  
Absent Condition

Abstract The Earth’s mantle is an important reservoir of H2O, and even a small amount of H2O has a significant influence on the physical properties of mantle rocks. Estimating the amount of H2O in rocks from the Earth’s mantle would, therefore, provide some insights into the physical properties of this volumetrically dominant portion of the Earth. The goal of this study is to use mineral equilibria to determine the activities of H2O (aH2O) in orogenic mantle peridotites from the Western Gneiss Region of Norway. An amphibole dehydration reaction yielded values of aH2O ranging from 0.1 to 0.4 for these samples. Values of fO2 of approximately 1 to 2 log units below the FMQ oxygen buffer were estimated from a fO2-buffering reaction between olivine, orthopyroxene, and spinel for these same samples. These results demonstrate that the presence of amphibole in the mantle does not require elevated values of aH2O (i.e., aH2O≈1) nor relatively oxidizing values of fO2 (i.e., >FMQ). It is possible to estimate a minimum value of aH2O by characterizing fluid speciation in C-O-H system for a given value of oxygen fugacity (fO2). Our results show that the estimates of aH2O obtained from the amphibole dehydration equilibrium are significantly lower than values of aH2O estimated from this combination of fO2 and C-O-H calculations. This suggests that fluid pressure (Pfluid) is less than lithostatic pressure (Plith) and, for metamorphic rocks, implies the absence of a free fluid phase. Fluid absent condition could be generated by amphibole growth during exhumation. If small amounts of H2O were added to these rocks, the formation of amphibole could yield low values of aH2O by consuming all available H2O. On the other hand, if the nominally anhydrous minerals (NAMs) contained significant H2O at conditions outside of the stability field of amphibole they might have served as a reservoir of H2O. In this case, NAMs could supply the OH necessary for amphibole growth once retrograde P-T conditions were consistent with amphibole stability. Thus, amphibole growth may effectively dehydrate coexisting NAMs and enhance the strength of rocks as long as the NAMs controlled the rheology of the rock.

scholarly journals Application of titanium-in-quartz thermobarometry to greenschist facies veins and recrystallized quartzites in the Hsüehshan range, Taiwan

Solid Earth ◽  
2013 ◽  
Vol 4 (1) ◽  
pp. 1-21 ◽  
Author(s):  
S. Kidder ◽  
J.-P. Avouac ◽  
Y.-C. Chan
Keyword(s):  
Grain Size ◽  
Fluid Pressure ◽  
Geothermal Gradient ◽  
Greenschist Facies ◽  
Stability Field ◽  
Lithostatic Pressure ◽  
Vein Quartz ◽  
Pressure Term ◽  
Recrystallized Grain Size ◽  
Ti In Quartz

Abstract. The accuracy, reliability and best practises of Ti-in-quartz thermobarometry (TitaniQ) in greenschist facies rocks have not been established. To address these issues, we measured Ti concentrations in rutile-bearing samples of moderately deformed, partially recrystallized quartzite and vein quartz from the Hsüehshan range, Taiwan. The spread of Ti concentrations of recrystallized grains in quartzite correlates with recrystallized grain size. Recrystallized quartz (grain size ~100–200 μm) that formed during early deformation within the biotite stability field shows a marked increase in intermediate Ti-concentration grains (~1–10 ppm) relative to detrital porphyroclasts (Ti ~0.1–200 ppm). Fine recrystallized quartz (~5% of the samples by area, grain size ~10–20 μm) has a further restricted Ti concentration peaking at 0.8–2 ppm. This trend suggests equilibration of Ti in recrystallized quartz with a matrix phase during deformation and cooling. Unlike previously documented examples, Ti concentration in the quartzite is inversely correlated with blue cathodoluminescence. Deformation was associated with a minimum grain boundary diffusivity of Ti on the order of 10−22m2 s−1. Vein emplacement and quartzite recrystallization are independently shown to have occurred at 250–350 °C and 300–410 °C, respectively, with lithostatic pressure of 3–4 kbar (assuming a geothermal gradient of 25° km−1), and with hydrostatic fluid pressure. Estimates of the accuracy of TitaniQ at these conditions depend on whether lithostatic or fluid pressure is used in the TitaniQ calibration. Using lithostatic pressure and these temperatures, the Thomas et al. (2010) calibration yields Ti concentrations within error of concentrations measured by SIMS. If fluid pressure is instead used, predicted temperatures are ~30–40 °C too low. TitaniQ has potential to yield accurate PT information for vein emplacement and dynamic recrystallization of quartz at temperatures as low as ~250 °C, however clarification of the relevant pressure term and further tests in rutile-present rocks are warranted.

A theoretical approach to analyze pressure equilibria in the interstitium

1990 ◽  
Vol 258 (3) ◽  
pp. F705-F710 ◽  
Author(s):  
M. Gilanyi ◽  
A. G. Kovach
Keyword(s):  
Osmotic Pressure ◽  
Fluid Pressure ◽  
Quantitative Relationship ◽  
Fluid Phase ◽  
Free Fluid ◽  
Transient Effects ◽  
Measuring Devices ◽  
Pressure Term ◽  
Gel Phase ◽  
Osmotic Pressure Difference

Inherent problems concerning the interstitial fluid pressure (IFP) are reinvestigated on theoretical grounds. Analyzing the thermodynamic and mechanical equilibria in the interstitium, it is concluded that IFP includes a pressure term originating from the elastic forces and an osmotic pressure term. A quantitative relationship is established between the IFP and all of the parameters responsible for the changes in the recorded pressure. The theoretical results suggest that, under control conditions, 1) there are no permanently existing free fluid spaces, 2) the gel pressure is atmospheric, and 3) the fluid equilibration techniques measure an osmotic pressure difference between the gel phase and the fluid phase created artificially by any of the pressure measuring devices. The pressure response during acute volume changes is attributed to the changes in the osmotic pressure term, gel volume, and elasticity. Volume and elasticity changes are reflected in the recorded IFP as promptly developing and permanent effects; on the other hand, osmotic processes result in slowly developing and transient effects. The volume-pressure relationship is also analyzed.

scholarly journals Application of titanium-in-quartz thermobarometry to greenschist facies veins and recrystallized quartzites in the Hsüehshan range, Taiwan

2012 ◽  
Vol 4 (1) ◽  
pp. 663-706 ◽  
Author(s):  
S. Kidder ◽  
J.-P. Avouac ◽  
Y.-C. Chan
Keyword(s):  
Grain Size ◽  
Best Practices ◽  
Fluid Pressure ◽  
Greenschist Facies ◽  
Stability Field ◽  
Lithostatic Pressure ◽  
Vein Quartz ◽  
Pressure Term ◽  
Recrystallized Grain Size ◽  
Ti In Quartz

Abstract. The accuracy, reliability and best practices of Ti-in-quartz thermobarometry ("TitaniQ") in greenschist facies rocks have not been established. To address these issues we measured Ti concentrations in rutile-bearing samples of moderately deformed, partially recrystallized quartzite and vein quartz from Taiwan's Hsüehshan range. The spread of Ti concentrations of recrystallized grains in quartzite correlates with recrystallized grain size. Recrystallized quartz (grain size ~300 μm) that formed during early deformation within the biotite stability field shows a marked increase in intermediate Ti-concentration grains (~1–10 ppm) relative to detrital porphyroclasts (Ti ~0.1–200 ppm). Fine recrystallized quartz (~5% of the samples by area, grain size ~10–20 μm) has a further restricted Ti concentration peaking at 0.8–2 ppm. This trend suggests equilibration of Ti in recrystallized quartz with a matrix phase during deformation and cooling. Vein emplacement and quartzite recrystallization are independently shown to have occurred at 250–350 °C and 300–410 °C respectively, lithostatic pressure ~5 kbar, and hydrostatic fluid pressure. Estimates of the accuracy of TitaniQ at these conditions depend on whether lithostatic or fluid pressure is used in the TitaniQ calibration. Using lithostatic pressure, Ti concentrations predicted by the Thomas et al. (2010) TitaniQ calibration are within error of Ti concentrations measured by SIMS. If fluid pressure is used, predicted temperatures are ~30–40 °C too low. TitaniQ has potential to yield accurate PT information for vein emplacement and dynamic recrystallization of quartz at temperatures as low as ~250 °C, however clarification of the relevant pressure term and further tests in rutile-present rocks are warranted.

Subcratonic and tectonic evolution of pyroxenite and eclogite with lamellar inclusions in garnet, Western Gneiss Region, Norway

2021 ◽  
Author(s):  
Dirk Spengler ◽  
Taisia A Alifirova ◽  
Herman L M van Roermund
Keyword(s):  
Stability Field ◽  
Mantle Lithosphere ◽  
Western Gneiss Region ◽  
Data Set ◽  
Entire Area ◽  
Ultra High Pressure ◽  
Planar Structures ◽  
Lamellar Inclusions ◽  
Al2o3 Concentration ◽  
Orogenic Peridotite

Abstract Oriented lamellar inclusions of pyroxene and rutile in mantle garnet often serve as evidence for majoritic and titaniferous precursor garnets, respectively. We investigated ten new such microstructure-bearing samples from six orogenic peridotite bodies in SW Norway, which originated in the E Greenland mantle lithosphere, petrologically and thermobarometrically. All pyroxenite (nine) and eclogite (one) samples have large (mainly porphyroclastic) garnet containing silicate and oxide inclusions with shape-preferred orientation relationship. These inclusions vary – dependent on their size – systematically in shape (acicular to subprismatic), width (∼50 μm to submicron size), spacing (several 100 to ∼10 μm) and phase (pyroxene to Ti-oxide ± pyroxene). Smaller inclusions can fill the space between larger inclusions, which support the idea of consecutive generations. The larger, early formed lamellae occur least frequent and are most poorly preserved. A younger generation of other inclusions decorates healed cracks cutting across cores but not rims of garnet. These inclusions comprise oxides, silicates, carbonates (aragonite, calcite, magnesite) and fluid components (N2, CO2, H2O). The older, homogeneously distributed inclusions comply texturally and stoichiometrically with an origin by exsolution from excess Si- and Ti-bearing garnet. Their microstructural systematic variation demonstrates a similar early evolution of pyroxenite and eclogite. The younger inclusions in planar structures are ascribed to a metasomatic environment that affected the subcratonic lithosphere. The microstructure-bearing garnets equilibrated at ∼3.7 GPa (840 °C) and ∼3.0 GPa (710 °C), at a cratonic geotherm related to 37–38 mW m−2 surface heat flow. Some associated porphyroclastic grains of Mg-rich pyroxene have exsolution lamellae of Ca-rich pyroxene and vice versa that indicate a preceding cooling event. Projected isobaric cooling paths intersect isopleths for excess Si in garnet at ∼1550 °C, if an internally consistent thermodynamic data set in the system Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) is applied (or ∼1600 °C if using CMAS). This temperature may confine the crystallisation of the unexsolved garnets at 100–120 km depths of the E Greenland subcratonic lithosphere. Tectonism is indicated in coastal and hinterland samples by porphyroclastic orthopyroxene with Al2O3 concentrations showing W-shaped profiles. Cores of associated large (>200 μm) recrystallised grains have low Al2O3 contents (0.18–0.23 wt.%). Both characteristics typify relatively short intracrystalline Al diffusion lengths and a prograde metamorphism into the diamond stability field. We assign this event to subduction during the Scandian orogeny. Porphyroclastic orthopyroxene in other samples shows U-shaped Al2O3 concentration profiles paired with long Al diffusion lengths (several 100 μm) that exceed the radius of recrystallised grains. Their cores contain high Al2O3 contents (0.65–1.16 wt.%), consistent with a diffusional overprint that obliterated prograde and peak metamorphic records. Unlike Al2O3, the CaO content in porphyroclastic orthopyroxene cores is uniform suggesting that early exhumation was subparallel to Ca isopleths in pressure–temperature space. The depth of sample origin implies that rock bodies of Scandian ultra-high pressure metamorphism occur in nearly the entire area between Nordfjord and Storfjord and from the coast towards ∼100 km in the hinterland, i.e. in a region much larger than anticipated from crustal eclogite.

Le role de la pression fluide dans les deformations tectoniques

1959 ◽  
Vol S7-I (6) ◽  
pp. 571-573
Author(s):  
Jean Goguel
Keyword(s):  
Lateral Pressure ◽  
Fluid Pressure ◽  
Hydrostatic Equilibrium ◽  
Excess Pressure ◽  
Tectonic Deformation ◽  
Lithostatic Pressure ◽  
Solid Friction

Abstract It has been shown by K. Hubbert and W. W. Rubey that fluid pressure may play an important role in tectonic deformation when it becomes greater than that required for hydrostatic equilibrium. When the impregnating fluid in rock is under such excess pressure, the conditions of solid friction are drastically altered. The limit is reached when fluid pressure becomes equal to lithostatic pressure; rocks could then be displaced freely with respect to one another. Rough calculations show that this limit need not be reached; all overthrusts, whether due to lateral pressure or flow, can take place easily if fluid pressure is 95-98 percent of lithostatic pressure. Possible mechanisms for producing excess pressure are discussed.

A model of unsteady-state transvascular fluid and protein transport in the lung

1984 ◽  
Vol 56 (5) ◽  
pp. 1389-1402 ◽  
Author(s):  
R. J. Roselli ◽  
R. E. Parker ◽  
T. R. Harris
Keyword(s):  
Steady State ◽  
Interstitial Fluid ◽  
Transport Theory ◽  
Fluid Pressure ◽  
Water Volume ◽  
Free Fluid ◽  
Base Line ◽  
Unsteady State ◽  
Total Change ◽  
Organ Systems

Models of steady-state fluid and solute transport in the microcirculation are used primarily to characterize filtration and permeability properties of the transport barrier. Important transient relationships, such as the rate of fluid accumulation in the tissue, cannot be predicted with steady-state models. In this paper we present three simple models of unsteady-state fluid and protein exchange between blood plasma and interstitial fluid. The first treats the interstitium as a homogeneous well-mixed compliant compartment, the second includes an interstitial gel, and the third allows for both gel and free fluid in the interstitium. Because we are primarily interested in lung transvascular exchange we used the multiple-pore model and pore sizes described by Harris and Roselli (J. Appl. Physiol.: Respirat . Environ. Exercise Physiol. 50: 1–14, 1981) to characterize the microvascular barrier. However, the unsteady-state transport theory presented here should apply to other organ systems and can be used with different conceptual models of the blood-lymph barrier. For a step increase in microvascular pressure we found good agreement between theoretical and experimental lymph flow and lymph concentrations in the sheep lung when the following parameter ranges were used: base-line interstitial volume, 150–190 ml; interstitial compliance, 7–10 ml/Torr; initial interstitial fluid pressure, -1 Torr; pressure in initial lymphatics, -5 to -6 Torr; and conductivity of the interstitium and lymphatic barrier, 4.25 X 10(-4) ml X s-1 X Torr-1. Based on these values the model predicts 50% of the total change in interstitial water volume occurs in the first 45 min after a step change in microvascular pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Complex ceramic structures. I. Weberites

2009 ◽  
Vol 65 (3) ◽  
pp. 269-290 ◽  
Author(s):  
Lu Cai ◽  
Juan C. Nino
Keyword(s):  
Physical Properties ◽  
Ionic Radius ◽  
Structural Features ◽  
Stability Field ◽  
Bond Ionicity ◽  
Coordination Environment ◽  
Technological Potential ◽  
Axial Transformation ◽  
First Time ◽  
Selection Of

The weberite structure (A 2 B 2 X 7) is an anion-deficient fluorite-related superstructure. Compared with fluorites, the reduction in the number of anions leads to a decrease in the coordination number of the B cations (VI coordination) with respect to the A cations (VIII coordination), thus allowing the accommodation of diverse cations. As a result, weberite compounds have a broad range of chemical and physical properties and great technological potential. This article summarizes the structural features of weberite and describes the structure in several different ways. This is the first time that the stacking vector and stacking angle are used to represent the weberite structure. This paper also discusses the crystallographic relationship between weberite, fluorite and pyrochlore (another fluorite-related structure). The cation sublattices of weberite and pyrochlore are correlated by an axial transformation. It has been shown that the different coordination environment of anions is due to the alternating layering of the AB 3 and A 3 B close-packed cation layers. A stability field of weberite oxides is proposed in terms of the ratio of ionic radius of cations and relative bond ionicity. In addition, a selection of weberite compounds with interesting properties is discussed.

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