Thus, the probability distribution function for each modeled profile, and therefore the uncertainties given with the best fit ages illustrated in figure 3 of the main text include the. Pressure estimates from four garnetplagioclase barometers show good agreement. T1 ternary feldspar experiments and thermodynamic models. Thermometry using ternary feldspar thermometry gives temperatures estimations at ca. The data is a fairly large set of compositions atoms pfu of coexisting plagioclase and alkali feldspar, calculated at 6 kbar and three temperatures 750, 800 and 850.
Ternaryfeldspar modeling and thermometry mineralogical society. Ternaryfeldspar modeling and thermometry request pdf. The incorporation of k into carich plagioclase and of ca into krich alkali feldspar is more. The basic classification only concerned texture, using the wentworth size scale. A ternary feldsparmixing model based on calorimetric data. Feldspar in felsic orthogneiss as indicator for uht. In subsolvus or two feldspar granites crystallisation occurs at high water pressures resulting in the formation of two types of feldspar as opposed to hypersolvus granites in which crystallization at relatively low water pressures results in the formation of a single feldspar variety.
The relationship between the optical properties, composition and structural state of these feldspars is also discussed and a new set of refractive index curves is presented. Feldspar thermometry in ultrahightemperature metamorphic rocks. Amphibole thermometric data mantle pegmatite dyke and sheeted dyke gave a temperature. Ternary feldspar experiments and thermodynamic models. Feldspar group feldspars are the most abundant minerals in the crust. A thermodynamic model following the approach developed by ghiorso 1984 and fuhrman and lindsley 1988 is applied to these new experimental results. In order to test and verify the regional spread of the uht metamorphism in this terrane, ternary feldspar thermometry on varied rock types metanorite, granulite almg and. Because na and k are extremely mobile by solidstate diffusion, cooling gives rise to multiple forms of unmixing products, 2 e. Ternary feldspar thermometry shows that plagioclase in contact with sillimanite plots along the 750degreesc solvus that reflects nearequilibrium conditions of regional metamorphism. From recent enthalpy and volume measurements in the na,ca and k,ca feldspar binaries, new interaction parameters have been derived and previous ones have been updated. For example, sandstones are commonly composed of quartz, two main types of feldspar, and various types of rock fragments called lithics, as well as other types of grains. The present study considers the remarkable exsolution phenomena in feldspars and pyroxenes and titaniuminquartz thermometry. A classification of salic rocks based on the nature of. With a few exceptions, clays from drainages originating in the piedmont contain plagioclase andor kfeldspar while those from drainages restricted to the coastal plain do not.
Quartz may also contain tiny rounded hercyniterich spinel inclusions. Sanidine and orthoclase are monoclinic or nearly so. The activity expressions of this model permit yet another formulation of the twofeldspar geothermometer that fully takes ternary solution into account. Coexisting feldspars from across 2000 km2 of the granulite facies oaxacan complex, southern mexico exhibit variable amounts of solid solution from nearly. Feldspar thermometry in ultrahightemperature metamorphic. Deepdyve is the easiest way to get instant access to the academic journals you need. In order to test and verify the regional spread of the uht metamorphism in this terrane, ternary feldspar thermometry on varied rock types metanorite, granulite almg and orthogneiss and samples that crop out in different zones of the in ouzzal terrane. Request pdf on researchgate on jan 1, 1988, fuhrman m. Gsa data repository 2015242 geological society of america. How to plot ternary diagrams igneous rock rocks free.
Models of ternary feldspars seck 1971a neues jahrb. Most ternary feldspars have negative excess volumesan important constraint on pressure corrections in geothermometry. Application of the twofeldspar geothermometer to ultrahigh. Coexisting feldspars from across 2,000 km2 of the granulite facies oaxacan complex, southern mexico exhibit variable amounts of solid solution from nearly binary aban and abor to substantially ternary abanor. Excess terms for the anor join and for ternary interaction. A metapelite area in the ne of the belt shows assemblages characteristic of uhtm. Contrasting degrees of recrystallization of carbonaceous.
Comparisons with existing mixing models, which are based on phaseequilibrium experiments, reveal distinct differences. However, our thermodynamic modelling suggests that temperatures probably did not exceed that of the opxin reaction f in fig. The data is a fairly large set of compositions atoms pfu of coexisting plagioclase and alkali feldspar, calculated at 6. Although kfeldspars become perthitic and increasingly ordered toward the. Nov 29, 2019 temperatures of crystallization for all or portions of three thin granitic pegmatite dikes in southern california are derived from feldspar solvus thermometry, with supporting data from the kcs ratio of k feldspar, the extent of alsi order in k feldspar, and the texture of granophyre found along the margins of dikes. Pdf ternary feldspar thermometry in granulites from the. Thermometry and barometry of igneous and metamorphic rocks. The bar at the lower right is 100 g and coarse exsolution of albite in alkali feldspar are common. Exsolved ilmenite ilm granulemagnetite m intergrowth. This tutorial develops a simple example whose goal is graphical inspection ternary feldspar relationships within the caona2ok2oal2o3sio2 system. Dr5 in the gsa data repository1, plagioclase, and alkali feldspar. Although k feldspars become perthitic and increasingly ordered toward the. Thus, an arkose sandstone is a rock of sand sized particles, with a high percentage of those particles being feldspar.
For feldspars monocrystals thermometry, several calibrations are available ex. Ternary diagrams first, we would have to normalise our data to just these three variables. T conditions in excess of 104 800c and greater than 18 kbar obrien, 2000. Ternary feldspar thermometry in granulites from the oaxacan complex, mexico. There are many thermometric models which use feldspar compositions involve twofeldspar and ternary feldspar methods. They also evaluate critically the utility of two feldspar thermometry and provide a calculation procedure for estimating twofeldspar temperatures. Quantification of magmatic and hydrothermal processes in a. They also evaluate critically the utility of two feldspar thermometry and provide a calculation procedure for estimating two feldspar temperatures. New developments in twofeldspar thermometry kielprints. The thermodynamic model of the twofeldspar thermometer has been revised. K shortrange order and implications for twofeldspar thermometry. Assrracr a revised thermodynamic model for ternary feldsparsan extension of the approach of.
Summary diagrams and animation showing crystallization path for composition fo66% an12% q22%. More recent calibrations, including ghiorso 1984, green and usdansky 1986, nekvasil and burnham 1987, fuhrman and lindsley 1988, lindsley and nekvasil 1989 and elkins and grove 1990 offer three. Thus, the probability distribution function for each modeled profile, and therefore the uncertainties given with the best fit ages illustrated in figure 3 of the main text include the propagated uncertainty from the mineral thermometry. Magmatism, metamorphism and associated mineralization in. Pdf ternaryfeldspar modeling and thermometry semantic scholar. Mineral chemistry perspective of nain ophiolite melange. Ternary feldspar thermometry in granulites from the oaxacan complex, mexico article pdf available in contributions to mineralogy and petrology 892. This paper reports the results of 20 experiments in which mixes of two or three feldspars were reacted to produce coexisting plagioclase feldspar pf and alkali feldspar af. Rare eclogitemafic granulite in felsic granulite in blansky. Thus, all these results point to a very steep geothermal gradient well into the uht field.
This ternary diagram has quartz at one apex and plagioclase mostly an to an6 at another. Models of ternary feldspars seck 1971a neues jahrb mineral. Fuhrman and lindsley, 1988, elkins and grove, 1990 on solvcalc software wen and nekvasil, 1994 that allow calculations of. These rocks contain either perthitic, antiperthitic or mesoperthitic parageneses. Status of thermobarometry in granitic batholiths earth. Leucosomes commonly show mesoperthite or krich antiperthite. Based on ternary feldspar solvus models, reintegrated compositions of feldspars from a variety of rock types yield the minimum equilibrium temperatures. Assrracr a revised thermodynamic model for ternary feldspars an extension of the approach of.
This thermometer is more useful than previous twofeldspar thermometers because it l fully accounts for ternary solid solution, 2 indicates whether the two. Revised twofeldspar geothermometry applied to sri lankan. Sean mulcahy made an example of plotting elkin and groves 1990 feldspar data. The compositions of most feldspars can be represented by the ternary system anorthite caal2si2o8albite naalsi3o8orthoclase kalsi3o8.
A ternary feldspar mixing model based on calorimetric data. Estimation of pressure and temperature of intrusive rocks. First occurrence of very low pressure ultrahigh temperatures. Pressure size code to produce the above crayon5ebc4d9f534c6343129417. The systematic variations in textural development indicate that the toki granite cooled effectively from the roof and from the western margin during the deuteric coarsening stage. A revised thermodynamic model for ternary feldsparsan extension of the approach of ghiorso 1984was made possible by a inclusion of. Pyroxene thermometry yielded and estimated temperature which varied between 1100 c and 0 c figure 6 a for the different rock units of nom25. Elkins and grove 1990 new experimental data on coexisting. Full text views reflects the number of pdf downloads, pdfs sent. Precambrian research, 66 1994 3577 351 elsevier science b. Thermometry and barometry of igneous and metamorphic rocks thermometry and barometry of igneous and metamorphic rocks bohlen, s r. Magmatism, metamorphism and associated mineralization in north africa and related areas. Feldspar and oxide thermometry of granulites in the.
Using ternary feldspar thermometry, a minimum temperature limit of the peak metamorphic conditions is calculated to be. Plagioclase within alkali feldspar phenocryst from trachyte near top of monte tabor spine specimen 16. Plagioclase fragments within alkali feldspar phenocryst from zara trachyte specimen l. From recent enthalpy and volume measurements in the na,ca and k,cafeldspar binaries, new interaction parameters have been derived and previous ones have been updated. These were originally ternary feldspars formed at extreme t that underwent exsolution during cooling. Does ternary feldspar constrain the metamorphic conditions of.
Quartz, mica, and amphibole exsolution from majoritic. The activity expressions of this model permit yet another formulation of the two feldspar geothermometer that fully takes ternary solution into account. This metamorphism was essentially defined locally in almg granulites, alfe granulites and quartzites outcropping in the northern part of the in ouzzal terrane iot. Ternary feldspar thermometry in granulites from the. Temperatures of crystallization for all or portions of three thin granitic pegmatite dikes in southern california are derived from feldspar solvus thermometry, with supporting data from the kcs ratio of kfeldspar, the extent of alsi order in kfeldspar, and the texture of granophyre found along the margins of dikes. Results of feldspar thermometry are consistent with diopsideforsterite equilibria in marbles which restrict t720 765 c at p7 kbar. Based on ternary feldspar solvus models, reintegrated compositions of feldspars from a variety of rock types yield the minimum equilibrium temperatures ranging from to.
Peak metamorphic conditions in the oaxacan complex are inferred to have been 73050 c, 71 kbar. It might seem that an unlimited variety of particles could end up in a. The ht rutile group t estimates agree with grtopx and opxcpx thermometry in quartzofeldspathic gneisses. The thermodynamic model of the two feldspar thermometer has been revised. Ti fe oxide needles are also found in quartz, orthopyroxene fig. The t estimates for the lt rutile group are consistent with the kyanite zone overprint. Sep 27, 2005 a key to establishing the igneous origin of the ternary feldspar grains is their preservation in garnet that is either itself igneous, or of a relatively low. But any full rock name must specify both texture and composition. Pdf a ternary feldsparmixing model based on calorimetric. A two feldspar thermometer is presented in which temperature is constrained by equilibria among all three componentsalbite, orthoclase, and anorthitein coexisting ternary feldspars. Entropy parameters have been fitted to the phase equilibrium data of seck 1971 and elkins and grove 1990. N2 this paper reports the results of 20 experiments in which mixes of two or three feldspars were reacted to produce coexisting plagioclase feldspar pf and alkali feldspar af. Lindsley 1988, based on the experimental data by seck.
The olivinebearing migmatite, located at the contact with a mafic intrusion, shows two main assemblages. Certain compositions within this system can only be attained at elevated temperatures, and consequently. First, the compositions of host and exsolution features were measured separately by fegepma. Lecture notes feldspars if quantity is of any significance, the feldspar minerals are the most important minerals for geologists studying the crust of the earth. Deepdyve is the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. A mixing model for high structural state ternary feldspars in the naalsi3o8kalsi3o8caal2si2o8 system is presented based exclusively on calorimetric and volumetric measurements. In order to apply the feldspar thermometer to rocks from the adirondacks the exsolved.
Ternary plots of feldspar compositions along with reintegrated recovered onephase feldspar compositions. Feldspar in felsic orthogneiss as indicator for uht crustal. Feldspar thermometry can be applied either to pair minerals such as plagioclase and k feldspar or to hypersolvus feldspar monocrystals. Ternaryfeldspar modeling and thermometry american mineralogist. The paragenesis and optical properties of some ternary feldspars.
Ternary feldspar thermometry of paleoproterozoic granulites from inouzzal terrane western hoggar, southern algeria by a. Based on ternary feldspar solvus models, reintegrated compositions of feldspars from a variety of rock types yield the minimum equilibrium temperatures ranging from to 1110 c 0. Ternary feldspar thermometry in granulites from the oaxacan. Feldspar thermometry can be applied either to pair minerals such as plagioclase and kfeldspar or to hypersolvus feldspar monocrystals. L and others published ternaryfeldspar modeling and thermometry. In this context, ternary feldspars perthite, per provide a robust alternative, as they are. Elkins and grove 1990 new experimental data on coexisting ternary feldspars and a model for excess free. Threedimensional cooling pattern of a granitic pluton ii. Ternary feldspar thermometry of paleoproterozoic granulites.
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