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Brines in the Precambrian crystalline bedrock of Finland
158 BRINES IN FINLAND
THE PRECAMBRIAN CRYSTALLINE BEDROCK OF
R.G. BLOMQVIST, P.W. LABERMO, S. HALONEN, S.K. FRAPE, and M. ILMASTI. (Geological Survey of Finland, SF-O2150 Espoo, Finland). During areal mapping of deep groundwater in the Precambrinn c r y s t a l l i n e basement of Finland, saline waters, and in some l o c a l i t i e s , even brines (TDS > 100 g/L), have frequently been found at depths below a couple of hundred metres. The sampling method used is a new one and allows a continuous p r o f i l e of water to be taken, e v e n f r o m small diameter (46 mm) d r i l l holes. The saline waters are hosted by widely d i f f e r e n t geological formations and located in d i f f e r e n t parts of the country. The most saline water encountered so far (TDS: iBO g/L) is located in a massive serpentinite in n mica schist environment in Juukn, eastern Finland. The brine, found in the d r i l l hole at depths from BOO to 1100 m, is of Nn-Cn-CI type. A hole d r i l l e d near the c i t y of Pori in SW Finland penetrates f i a t - l y i n g unmetamorphosed sandstone sequences in a graben formation of Precnmbrian age. The groundwater is of Ca-C1 type with TDS 120 g/L at hole bottom (600 m). A d r i l l hole in Ylivieskn, in the middle of the country, is located in n layered mnfic-ultramafic intrusion. The water at hole bottom is of Ca-Nn-Mg-C1 type with TDS exceeding 50 g/L. The t r i t i u m contents in the saline waters are low. The stable isotope values deviate clearly to the l e f t of the GMWL l i n e (in the holes above: 180dnlta = -11.5, -8 and -l)~o, and 2Hdelta = -20 - -5, -50 -40, -60 - -40~o , respectively). The results are indicative of long-lasting water-rock interaction.
INFLUENCE OF HYDROTHERMAL CONDITIONS OF SYNTHESIS ON PHYSICAL PROPERTIES OF ANORTHITE J. COPREAUX, S.C. DUJON, M. GANDAIS. (Laboratoire de Min~ralogie-Cristallographie, CNRS 09, Universitgs Paris VI et VII, and D~partement de Gdologie de l'Ecole normale supdrieure 24, rue Lhomond, 75005 Paris)
UA
A n o r t h i t c s have been s y n t h e t i z e d u n d e r h y d r o t h e n u a l c o n d i t i o n s a t 700°C lO0 MPa b e t w e e n two h o u r s and three montlls. Starting material is a gel. X-ray dlffraction allows to follow evolution of cell parameters with time from which we infer the evolution of Qod, tLle average AI-Si order parameter. Qod is low (around 0.20) at 2 hours, then increases and reaches a steady state around 0.78 after one week. If order-dlsorder is a trieritical transition, as shown by Carpenter (1988, in NATO ASI aerie C vol. 225, 265-324) in natural plagioclases, it is easy, using Landau theory, to calculate Tc, the temperature of anorthite phase transition between ordered I ~ and disordered C T phases. Tc for synthetic anorthite is 1300°C, very different from the 2040°C value given by Carpenter for natur+11 samples. The Tc value allows us to calculate at 700°C tlm ratio of nucleation rate of the ordered phase to the disordered one. Using 2040°C, this ratio is on the order of 1000. Using 1300°C, this ratio is on the order of I, which i s in good agreement with growth kinetics studied by TEM on our e x p e r i m e n t a l p r o d u c t s . S u c h a Tc v a l u e i m p l i e s that synthetic anorthites would have, at temperature higher than 1300°C, a stability domain for the disordered phase. This is in contradiction with observation on natural non hydrothermal anorthikes (bibl. in Carpenter 1988) where such a domain cannot be reached by heating. Another eventuality is thdt the phase transition in the synthetic anorthites is not tricritical, but second order transition. This is not in agreement with Carpenter's data on the degree of order and on the ordering enthalpy of natural plagioclases. I n any c a s e , t h e s y n t h e t i c h y d r o t h e r m a l a n o r t h i t e would h a v e p h y s i c a l p r o p e r t i e s d i f f e r e n t from t h e n a t u r a l non h y d r o t h e r m a l ones.
WATER IN QUARTZ, POINT DEFECTS, SOLUBILITY, DIFFUSIVITY A N D INFLUENCE O N DUCTILITY. PREDICTION OF THE SOLUBILITY OF ALUMINIUMOXIDES AND HYDROXIDES AT HIGH TEMPERATURE AND PRESSURE. S. CASTET, G . M . ANDERSON, R . E . MESMER and J. SCHOTT (Laboratoire de Min~ra1ogie et Cristallographie, Universit6 Paul-Sabatier, 31062 Toulouse,
France). Knowledge of aluminum hydrolisis constants to high temperature and pressure is a prerequisite to understand aluminum behavior during hydrothermal processes. For this purpose we have used the density model developped by Mesmer (1985) which we demonstrate predicts to good accuracy the influence of temperature and pressure on the thermodynamic properties of aqueous species. Using the revised equation of state for water generated by Tanger and Helgeson (1988) and selected values of the heat capacities and hydrelisis constants of AI3+, AI(OH)2+, AI(OH) + AI(OH)3 and AI(OH)4-at 25°C we have Z ' computed the solubility of gibbsite, boehmite and corundum in their stability range as a function of pH to BO0°C and 5Kb. There is a good agreement between the theoretically calculated and the available experimental values. Moreover it is shown that for the interpretation of existing data on the solubility of corundum-including measurements in concentrated solutions of HCl, KOH, NaOH, NaCI, KCI - it is not necessary to appeal to aqueous species unknown at 25°C such as alkali- or chloride-Al203 complexes. Obviously the pH of the aqueous solution cannot be ignored even when considering aluminum behavior and control in metasomatic processes at high pressures and temperatures.
P. CORDIER mid J.C. D O U K H A N (Laboratoire d~ structure et proprietorsde l'~tat solide U A n~234 USTLFA, 59655 Villeneuve d'Ascq Cedex) Water iskn¢ wn for a number of years to be the major impurity of both naturaland syntheticquartzes.A small amount of water can affect drrunaticaily t[e physical properfie3 of the material quartz and especiallyitsrh eologicalbehavior. This isthe well known hydrolytic weakening pherlomenon. Understanding the mechanism by which water defectsa~,.tupon the ductilityof quartz i.e.upon the dislocation motion r~uires apreciseknowledge ofthermodynamic parameterslike the nature and lhe equilibrium concentrationof water point defects versusT and P. Furthermore, meaningful deformation expertments on well characteril'.edwet quartz material have to be performed in T, P conditionssuch thatthe water contentremains dissolvedin the lattice during the experiment (i.e.does not precipitateas the deformation proceeds). W e have investigatedby Near InfraredSpectroscopy n varietyof syntheticquartl,eswith various water contents. It appears thatwater can be incorporatedeitheras clustersof water molecules or as a point defectssolution.Convenient samples have thusbeen characterizedfor fun.her experi~.entson the solubilityand the diffusivityof water in uartz. W e find a solubilityH/Si of the order of I00 at. at =700°C and P=I200 MPa which drastically decreases is lowered. The diffusion coefficient of water in quartz has been investigatedin thetem~eraturoranue 350- 1000"C. W e find: D (m2s'l)= I0-12exp (-95 kJ m ole'I/RT) Finallywe lind thatwater point defectsassociatedto peaks in the vicinityof450~ cm- 1 ~rongly enhance theglidemotion of dislocations whentheir concenttntionisIowerorequal tothe equilibriumsolubility. For concentra~on above the solubilityor for tiny water inclusions (peak in the vicinityof 5200 cm "I) water precipitationoccurs and an intensedislocationclimb isobserved. These two contrastedbehavior of the dislocationsprobably reflectscontrasted behavior of quartz grainsin crustalrocks depending upon the water content and the mode ofincucporatioaof water inthe consistentrocks.
THE PRECAMBRIAN CRYSTALLINE BEDROCK OF
R.G. BLOMQVIST, P.W. LABERMO, S. HALONEN, S.K. FRAPE, and M. ILMASTI. (Geological Survey of Finland, SF-O2150 Espoo, Finland). During areal mapping of deep groundwater in the Precambrinn c r y s t a l l i n e basement of Finland, saline waters, and in some l o c a l i t i e s , even brines (TDS > 100 g/L), have frequently been found at depths below a couple of hundred metres. The sampling method used is a new one and allows a continuous p r o f i l e of water to be taken, e v e n f r o m small diameter (46 mm) d r i l l holes. The saline waters are hosted by widely d i f f e r e n t geological formations and located in d i f f e r e n t parts of the country. The most saline water encountered so far (TDS: iBO g/L) is located in a massive serpentinite in n mica schist environment in Juukn, eastern Finland. The brine, found in the d r i l l hole at depths from BOO to 1100 m, is of Nn-Cn-CI type. A hole d r i l l e d near the c i t y of Pori in SW Finland penetrates f i a t - l y i n g unmetamorphosed sandstone sequences in a graben formation of Precnmbrian age. The groundwater is of Ca-C1 type with TDS 120 g/L at hole bottom (600 m). A d r i l l hole in Ylivieskn, in the middle of the country, is located in n layered mnfic-ultramafic intrusion. The water at hole bottom is of Ca-Nn-Mg-C1 type with TDS exceeding 50 g/L. The t r i t i u m contents in the saline waters are low. The stable isotope values deviate clearly to the l e f t of the GMWL l i n e (in the holes above: 180dnlta = -11.5, -8 and -l)~o, and 2Hdelta = -20 - -5, -50 -40, -60 - -40~o , respectively). The results are indicative of long-lasting water-rock interaction.
INFLUENCE OF HYDROTHERMAL CONDITIONS OF SYNTHESIS ON PHYSICAL PROPERTIES OF ANORTHITE J. COPREAUX, S.C. DUJON, M. GANDAIS. (Laboratoire de Min~ralogie-Cristallographie, CNRS 09, Universitgs Paris VI et VII, and D~partement de Gdologie de l'Ecole normale supdrieure 24, rue Lhomond, 75005 Paris)
UA
A n o r t h i t c s have been s y n t h e t i z e d u n d e r h y d r o t h e n u a l c o n d i t i o n s a t 700°C lO0 MPa b e t w e e n two h o u r s and three montlls. Starting material is a gel. X-ray dlffraction allows to follow evolution of cell parameters with time from which we infer the evolution of Qod, tLle average AI-Si order parameter. Qod is low (around 0.20) at 2 hours, then increases and reaches a steady state around 0.78 after one week. If order-dlsorder is a trieritical transition, as shown by Carpenter (1988, in NATO ASI aerie C vol. 225, 265-324) in natural plagioclases, it is easy, using Landau theory, to calculate Tc, the temperature of anorthite phase transition between ordered I ~ and disordered C T phases. Tc for synthetic anorthite is 1300°C, very different from the 2040°C value given by Carpenter for natur+11 samples. The Tc value allows us to calculate at 700°C tlm ratio of nucleation rate of the ordered phase to the disordered one. Using 2040°C, this ratio is on the order of 1000. Using 1300°C, this ratio is on the order of I, which i s in good agreement with growth kinetics studied by TEM on our e x p e r i m e n t a l p r o d u c t s . S u c h a Tc v a l u e i m p l i e s that synthetic anorthites would have, at temperature higher than 1300°C, a stability domain for the disordered phase. This is in contradiction with observation on natural non hydrothermal anorthikes (bibl. in Carpenter 1988) where such a domain cannot be reached by heating. Another eventuality is thdt the phase transition in the synthetic anorthites is not tricritical, but second order transition. This is not in agreement with Carpenter's data on the degree of order and on the ordering enthalpy of natural plagioclases. I n any c a s e , t h e s y n t h e t i c h y d r o t h e r m a l a n o r t h i t e would h a v e p h y s i c a l p r o p e r t i e s d i f f e r e n t from t h e n a t u r a l non h y d r o t h e r m a l ones.
WATER IN QUARTZ, POINT DEFECTS, SOLUBILITY, DIFFUSIVITY A N D INFLUENCE O N DUCTILITY. PREDICTION OF THE SOLUBILITY OF ALUMINIUMOXIDES AND HYDROXIDES AT HIGH TEMPERATURE AND PRESSURE. S. CASTET, G . M . ANDERSON, R . E . MESMER and J. SCHOTT (Laboratoire de Min~ra1ogie et Cristallographie, Universit6 Paul-Sabatier, 31062 Toulouse,
France). Knowledge of aluminum hydrolisis constants to high temperature and pressure is a prerequisite to understand aluminum behavior during hydrothermal processes. For this purpose we have used the density model developped by Mesmer (1985) which we demonstrate predicts to good accuracy the influence of temperature and pressure on the thermodynamic properties of aqueous species. Using the revised equation of state for water generated by Tanger and Helgeson (1988) and selected values of the heat capacities and hydrelisis constants of AI3+, AI(OH)2+, AI(OH) + AI(OH)3 and AI(OH)4-at 25°C we have Z ' computed the solubility of gibbsite, boehmite and corundum in their stability range as a function of pH to BO0°C and 5Kb. There is a good agreement between the theoretically calculated and the available experimental values. Moreover it is shown that for the interpretation of existing data on the solubility of corundum-including measurements in concentrated solutions of HCl, KOH, NaOH, NaCI, KCI - it is not necessary to appeal to aqueous species unknown at 25°C such as alkali- or chloride-Al203 complexes. Obviously the pH of the aqueous solution cannot be ignored even when considering aluminum behavior and control in metasomatic processes at high pressures and temperatures.
P. CORDIER mid J.C. D O U K H A N (Laboratoire d~ structure et proprietorsde l'~tat solide U A n~234 USTLFA, 59655 Villeneuve d'Ascq Cedex) Water iskn¢ wn for a number of years to be the major impurity of both naturaland syntheticquartzes.A small amount of water can affect drrunaticaily t[e physical properfie3 of the material quartz and especiallyitsrh eologicalbehavior. This isthe well known hydrolytic weakening pherlomenon. Understanding the mechanism by which water defectsa~,.tupon the ductilityof quartz i.e.upon the dislocation motion r~uires apreciseknowledge ofthermodynamic parameterslike the nature and lhe equilibrium concentrationof water point defects versusT and P. Furthermore, meaningful deformation expertments on well characteril'.edwet quartz material have to be performed in T, P conditionssuch thatthe water contentremains dissolvedin the lattice during the experiment (i.e.does not precipitateas the deformation proceeds). W e have investigatedby Near InfraredSpectroscopy n varietyof syntheticquartl,eswith various water contents. It appears thatwater can be incorporatedeitheras clustersof water molecules or as a point defectssolution.Convenient samples have thusbeen characterizedfor fun.her experi~.entson the solubilityand the diffusivityof water in uartz. W e find a solubilityH/Si of the order of I00 at. at =700°C and P=I200 MPa which drastically decreases is lowered. The diffusion coefficient of water in quartz has been investigatedin thetem~eraturoranue 350- 1000"C. W e find: D (m2s'l)= I0-12exp (-95 kJ m ole'I/RT) Finallywe lind thatwater point defectsassociatedto peaks in the vicinityof450~ cm- 1 ~rongly enhance theglidemotion of dislocations whentheir concenttntionisIowerorequal tothe equilibriumsolubility. For concentra~on above the solubilityor for tiny water inclusions (peak in the vicinityof 5200 cm "I) water precipitationoccurs and an intensedislocationclimb isobserved. These two contrastedbehavior of the dislocationsprobably reflectscontrasted behavior of quartz grainsin crustalrocks depending upon the water content and the mode ofincucporatioaof water inthe consistentrocks.