The system: Two alkali feldspars-KCl-NaCl-H2O at moderate to high temperatures and low pressures

Lagache, Martine; Weisbrod, Alain

doi:10.1007/bf00371028

Cited by 112 publications

(26 citation statements)

References 16 publications

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“…Superficially this would seem to be a relatively straightforward experimental problem, but consistency between the various solvus determinations has been poor. Recent determinations at I kb using equilibrium reversals by P. Smith and the writer (1974) and by Lagache and Weisbrod (1977) , are in extremely good agreement, and also fit well with the highpressure reversal study of Goldsmith and Newton (1974) ifa linear dependence of the critical temperature on pressure of I6 ~'C/kb is assumed (Parsons, 1978 ). The solvus most widely applied to a number of petrological problems is that obtained by Thompson and Waldbaum (1968) by a thermodynamic treatment of data of Orville 0963) and Luth and Tuttle (I966).…”

Section: Solvus Curvessupporting

confidence: 73%

“…Any effects of nonstoichiometry in the starting materials, as suggested by Luth and Tuttle (i966), and possible effects due to framework ordering during synthesis experiments with excess alkali (Martin, I974) must be disentangled from partial equilibrium effects before they can be accepted as fact. Feldspar solvus diagrams purporting to show sudden breaks due to framework ordering processes (Luth et al, I974;Martin, 1974) should be treated with caution, since neither the writer (Parsons, I978 ), Lagache and Weisbrod (1977) , nor Goldsmith and Newton (J974) have been able to detect effects due to ordering even in relatively long experiments.…”

Section: Solvus Curvesmentioning

confidence: 99%

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Feldspars and fluids in cooling plutons

Parsons

1978

Mineral. mag.

186

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SUMMARY. Alkali feldspars in plutonic igneous rocks vary both in their exsolution textures and in the structural state of their components. The primary factor leading to this diversity is the availability of hydrothermal fluids during their cooling history. In many plutons feldspar variation is related to degree of fractionation as indicated by rock chemistry. The variation reflects build-up of water with magmatic evolution and implies that fluids did not circulate freely in the intrusives in the temperature range of unmixing and ordering. Experimental work bearing on the role of fluids in subsolidus changes in feldspars is reviewed, and points of overlap between crystallographic studies of feldspars and stable isotope studies are discussed. THE factors that control the striking variety of exsolution textures and differences in framework order-disorder in alkali feldspars have been the subject of a number of review articles (e.g. Smith and MacKenzie, I96I;Martin, 1974; Stewart and Wright, I974). The stress in such treatments has been predominantly on thermal history, both with respect to temperature of crystallization and to cooling rate. In this talk, with an eye on petrologists, not feldspar specialists, I wish to concentrate on what is generally agreed to be one of the important subsidiary controls, namelythe presence of aqueous fluids during the cooling of the feldspar from magmatic temperatures, and to suggest that this is pre-eminently the factor that dictates the nature of the feldspar in all but the smallest intrusive igneous bodies provided they have escaped tectonic deformation. I shall show how a few petrographic observations or simple X-ray diffraction measurements may yield a wealth of information about the distribution of fluids during the cooling of a given body of alkali-feldsparbearing rock, and demonstrate that in many ~) Copyright the Mineralogical Society fractionated intrusive complexes 'water' was distributed following a 'magmatic' pattern, building up with progressive fractionation, and remained essentially restricted within the evolving lithological units.The effects of water during ,cooling of igneous bodies is a matter of particular concern at the present time because of the demonstration, by means of stable isotope studies (e.g. Taylor, 1974) of large-scale interactions between plutons and groundwaters. Some of the limited interactions that are demonstrated in the present review contrast strongly with the large-scale, all-pervasive waterrock interactions proposed by Taylor. The crystallographic observations to be described could, under favourable circumstances, be used to limit the thermal range in which water-rock interactions may have occurred, a factor by no means clearly defined in stable-isotope studies.I shall draw a number of examples of feldsparfluid interactions from one small (4 x 3 km stock), very intricate layered syenite pluton, the Klokken intrusion, in the pre-Cambrian Gardar province in South Greenland. The photomicrographs in the following sections illustrate the ran...

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Section: Solvus Curvessupporting

confidence: 73%

Section: Solvus Curvesmentioning

confidence: 99%

Feldspars and fluids in cooling plutons

Parsons

1978

Mineral. mag.

186

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“…Au cours de ces dernières années, de nombreuses recherches ont prouvé que rimmiscibilité à l'état fluide peut être responsable de beaucoup de phénomènes géologiques dans les environnements sédimentaires, métamorphiques et magmatiques, entre autres, les transformations métasomatiques (Weisbrod et Poty, 1975;Weisbrod et al, 1976;Lagache et Weisbrod, 1977;Weisbrod, 1980), l'altération et la concentration des métaux dans les gisements de porphyres cuprifères (Roedder, 1971a et b;Denis, 1974;Moore et Nash, 1974;Chivas et Wilkins, 1977;Etminan, 1977;Eastoe, 1978;Ramboz, 1979;Denis et al, 1980;Le Bel, 1980;Wilson et al, 1980), d'autres types de gisements associés aux activités volcaniques (Spooner, 1980) ou magmatiques acides (Kelly et Turneaure, 1970;Landis et Rye, 1974;Rye et Sawkins, 1974;Leroy, 1978;Bray, 1980;Grant et al, 1980;Ramboz, 1980), les gisements métallifères des formations sédimentaires (Roedder, 1976(Roedder, , 1977a et la mise en place des gisements pétroliers.…”

Section: 331-immiscibilité : Définition Et Contraintesunclassified

Facteurs paramètres dynamique de distribution et genèse des dépôts de columbo-tantalite d Issia centre-ouest de la Côte d Ivoire

Allou

2005

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(1) les trois principaux granites de la région ont été produits par des processus profonds ayant généré une fusion partielle de la croûte, (2) ils ont été formés par cristallisation fractionnée pendant la période syn-à tardi-D2 de l'orogenèse Ébuméenne, et ( Du point de vue de l'évolution supergène, il est montré que les processus naturels superficiels dans les milieux tropicaux humides ne génèrent ni croissance, ni changements chimiques dans les minéraux de Nb-Ta. Toutefois, même si la qualité chimique du minéral est préservée, la qualité physique, quant à elle, se dégrade progressivement des zones éluviales aux zones alluviales sous l'effet des corrosions mécaniques. Columbite-tantalite deposits in humid tropical areas are generally supergene deposits associated with gravel. These deposits have been poorly studied and are mined only by small developers. This is attributed, on one hand to the small scale and the short life of the individual deposits and, on the other hand to the great thickness of the alteration overburden in zones of high concentration.This study has a triple objective: (1) establish a geodynamic model for the Issia columbite-tantalite primary mineralization and associated minerals; (2) define the factors controlling the secondary redistribution of the mineralization in detrital environments through integrating pedo-geomorphologic and geostatistical studies; and (3) determine the mineralogical species of niobium, tantalum and other associated ore minerals.The study area includes three granitic massifs intruding sedimentary rocks: the oriented two-mica granite (Lobo granite), the oriented muscovite granite (Bitapia granite) and the non-oriented, porphyritic muscovite granite (Issia granite). Field observations and whole rock analyses show that: (1) the three main granites of the region are produced by deep seated processes which generated partial melting of the crust; (2) they were formed by fractional crystallization during the syn to late-D2 period of the Ebumean orogenesis; and (3) the Issia type granite was the last to be formed at 2106±78 My. Variographic analyses and kriging give satisfactory results for the columbite-tantalite supergene deposits prospecting. This approach defines prospecting grids for the deposit types in the studied areas and it brings to evidence very weak variation on a small scale and a great continuity of the mineralization following the direction of pegmatites. The kriging results indicate that lognormal kriging is the best tool for estimation of the reserves because this method better minimizes the bias and the variance of estimation. VIThis study has a direct implication for the prospecting of columbite-tantalite detrital deposits in Issia as well as at the global scale. Indeed, it shows that in a columbite-tantalite pegmatite environment located in humid tropical areas, eluvial and colluvial gravels are more favourable to mining than alluvial gravels. Enfin, je remercie tout le personnel du module des sciences de la terre, les professeurs, les techniciens, les é...

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“…5b). This enrichment of K may be linked to experimental studies, which have demonstrated that as temperature declines, the K/Na ratio of the fluid also declines in cases involving fluidalkali feldspar interaction (Orville 1963, Lagache & Weisbrod 1977. Thus, for the case studies herein, the decrepitate data may record the early formation of relatively K-rich fluids and gradual change over time to a more Na-rich fluid as temperature decreases.…”

Section: Implications For Fluid : Rock Interaction and Mineral Potentmentioning

confidence: 67%

Analysis of Evaporate Mounds as a Complement to Fluid-Inclusion Thermometric Data: Case Studies From Granitic Environments in Nova Scotia and Peru

Kontak¹

2004

The Canadian Mineralogist

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The bulk composition of fluid inclusions is generally determined by using the temperature of ice melting (i.e., freezing-point depression of H 2 O-NaCl) and relating this to the ice-melting curve in the two-component system H 2 O-NaCl. In reality, natural systems are more complex. Therefore, the bulk composition is referred to as equivalent wt.% NaCl to account for the presence of other, generally undetermined, cations (e.g., K, Ca, Fe, Mn, Mg). Inferences of a more complex chemical composition are generally made on the basis of the depression of the eutectic temperature for the H 2 O-NaCl system (-21.2°C), the other common solutes being CaCl 2 , MgCl 2 , and FeCl 2 . Such an approach is qualitative at best, and the inherent problem of metastability invites caution. An alternative, relatively simple and cost-effective method among the many analytical methods available, is to artificially decrepitate fluid inclusions and analyze the resulting evaporate mounds with an electron microprobe equipped with an imaging system. To illustrate the potential of the method, three granitic environments, in Nova Scotia and in Peru, were chosen, two mineralized (Sn, Cu, Zn) and one barren (tourmaline pegmatite). Standard fluid-inclusion thermometric data have been integrated with compositions determined from evaporate mounds in the same suite of samples. The following points emerge: (1) the inclusions are invariably multi-component, being dominated by Na-K-Ca, but in consistently different proportion that reflect protracted fluid:rock interaction and mixing of reservoirs; (2) the low first-melting temperatures (i.e., <-50°C) do not unequivocally indicate the presence of CaCl 2 in solution; (3) high concentrations of Fe and Mn are common within the mineralized systems examined, in addition to lesser amounts of Sr, Ba, P and Zn, and (4) the two methods complement each other, together providing a much more comprehensive account of the nature of the fluid and its evolution in space and time.Keywords: fluid inclusions, evaporate mounds, granites, pegmatites, tin mineralization. Nova Scotia, Peru. SOMMAIRELa composition globale de la phase fluide piégée dans les cristaux est généralement établie au moyen de la température de fusion de la glace, c'est-à-dire, l'abaissement du point de congélation de l'eutectique du système H 2 O-NaCl, mis en relation avec la courbe décrivant la fusion de la phase solide dans le système binaire H 2 O-NaCl. En fait, les systèmes naturels sont plus complexes. Pour cette raison, la composition globale du fluide est exprimée en termes d'équivalents de NaCl afin de rendre compte d'autres cations, non déterminés, par exemple K, Ca, Fe, Mn, Mg. Des conclusions à propos de la composition chimique plus complexe sont généralement faites pour rendre compte de l'abaissement de l'eutectique en dessous de -21.2°C, sa valeur dans le système H 2 O-NaCl. Les autres solutés courants sont CaCl 2 , MgCl 2 , et FeCl 2 . Une telle approche est définitivement qualitative, et le problème de métastabilité mérite une att...

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The system: Two alkali feldspars-KCl-NaCl-H2O at moderate to high temperatures and low pressures

Cited by 112 publications

References 16 publications

Feldspars and fluids in cooling plutons

Feldspars and fluids in cooling plutons

Facteurs paramètres dynamique de distribution et genèse des dépôts de columbo-tantalite d Issia centre-ouest de la Côte d Ivoire

Analysis of Evaporate Mounds as a Complement to Fluid-Inclusion Thermometric Data: Case Studies From Granitic Environments in Nova Scotia and Peru

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