(Ca,Mg)2Si2O6 clinopyroxenes: A solution model based on nonconvergent site-disorder

Davidson, Paula M.; Grover, John E.; Lindsley, D. H.

doi:10.1007/bf00376737

Cited by 26 publications

(5 citation statements)

References 21 publications

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“…The CaO content of the low-Ca pyroxenes increases with temperature (e.g. Lindsley et al, 1981;Davidson et al, 1982) rising from $1•3 wt % at 15008C to $2•3 wt % at 15508C. The Na 2 O contents of the low-Ca pyroxene increase from 0•1 to 0•3 wt % with increasing temperature and pressure in our experiments.…”

Section: Pyroxenesupporting

confidence: 46%

The Temperature and Pressure Dependence of Nickel Partitioning between Olivine and Silicate Melt

Matzen

Baker

Beckett

et al. 2013

Journal of Petrology

151

110

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We measured Ni partitioning between olivine and melt, D ol=liq Ni , in experiments on mid-ocean ridge basalt (MORB) encapsulated in olivine at pressures from 1atm to 3•0 GPa and temperatures from 1400 to 15508C. We present a series of experiments where the temperature (T) at each pressure (P) was selected so that the liquid composition remained approximately constant over the entire P^T range.This approach allowed us to investigate the effects of Tand P on D ol=liq Ni , independent of substantial changes in liquid composition. Our experiments show that for a liquid with $18 wt % MgO, D ol=liq Ni

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Section: Pyroxenesupporting

confidence: 46%

The Temperature and Pressure Dependence of Nickel Partitioning between Olivine and Silicate Melt

Matzen

Baker

Beckett

et al. 2013

Journal of Petrology

151

110

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“…results (Bolhen & Essene, 1979). It appears that their assumptions of ideal mixing in clinopyroxene and a large reaction enthalpy for reaction ortho-En = clino-En are seriously in error (Davidson et al, 1982;Lindley, 1983). The geothermometers of Kretz (1982), Lindsley (1983) and Davidson & Lindsley (1985) also give overestimates of metamorphic temperature or scattered data for the Jining region.…”

Section: G R a N U L I T E F A C I E S M E T A M O R P H I S M I N mentioning

confidence: 99%

P–T–t paths and tectonic history of an early Precambrian granulite facies terrane, Jining district, south‐east Inner Mongolia, China

Lu¹,

Shiqin²

1993

Journal Metamorphic Geology

106

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The widespread khondalite series of south-east Inner Mongolia consists largely of biotite-sillimanitegarnet gneiss and quartzo-feldspathic gneiss with some marble and mafic granulite layers. It has experienced two metamorphic events at c. 2500 and 1900-2000 Ma.A pre-peak stage of the first metamorphism at T = 600-700" C and P > 6-7 kbar is recognized by the relict amphibolite facies assemblage Ky-Grt-Bt-PI-Qtz and 'protected' inclusions of biotite, hornblende, sodic plagioclase and quartz in garnet or orthopyroxene. The peak stage, with T = c. 800 f 50" C and P 8-10 kbar, is characterized by the widespread granulite facies assemblages Sil-Grt-Bt-Kfs-PI-Qtz in gneiss and Opx-Cpx-PI f Hbl f Grt in granulite. The P-T-t path suggests that the supracrustal sequence was buried in the lower &st by tectonic thickening during Dl-D2. The beginning of the second metamorphism is characterized by further temperature rise to 700°C or more at lower pressure. This stage is manifested by the appearance of cordierite after garnet, fibrolite (Si12) after biotite in gneiss and transformation of Hbll into Opx2 and Cpx2 in granulite. Coronas of symplectitic Opx2 + PI2 surrounding Grtl and Cpxl in mafic granulite are interpreted as products of near-isothermal decompression. The P-T-t path may be related tectonically to waning extension of the crust by the end of the early Proterozoic.

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“…After 1981, more models have been proposed for the En-Di system. Davidson et al (1982) presented a model based on non-convergent site-disorder. The authors reported that the temperatures calculated from the model for coexisting Opx and Cpx fit the experimental data to within 10 °C in most cases.…”

Section: Pyroxenes In the System Cao-mgo-siozmentioning

confidence: 99%

“…In 1984, Brey and Huth published new data for Di-En equilibria at pressures from 4 to 6 GPa and ten^ratures from 1100 °C to 1500 °C. Based on the new data, Brey and Huth (1984) stated that the thermodynamic models of Lindsley et aL (1981), Davidson et al (1982) and Holland et al (1979) all tend to overestimate the influence of pressure and result in overestimation of the temperature at and above 4 GPa. Based on the data of Brey and Huth (1984) and other available data.…”

Section: Pyroxenes In the System Cao-mgo-siozmentioning

confidence: 99%

Experimental determination of phase relations of pyroxenes in the system Na2O-CaO-MgO-Al2O3-SiO2 (NCMAS) at 2.5 GPa and high temperatures

Wang

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Phase relations of clinopyroxene (Cpx) and orthopyroxene (Opx) in the system NajO-CaO-MgO-AljOj-SiO, (NCMAS) were studied experimentally at 2.5 GPa and a range of temperatures from 1000 to 1300 °C using a piston-cylinder apparatus. The compositions of the coexisting Opx and Cpx solid solutions were determined by electron microprobe anzdysis. The results show that Cpx and Opx solid solutions coexist with a large miscibility gap. The concentrations of Mg2Si206 in Cpx increase substantially with increasing temperatures but the content of NaAlSijOg and CaMgSijOg in Opx is very limited. Based on electron microprobe data from this study and the data from previous studies for the three binary systems NaAlSiiOs-MgjSijOs, MgjSijOg-CaMgSijOs, and NaAlSijOg-CaMgSijOa, the ternary diagram of MgjSijOft-NaAlSijO^-CaMgSi206 has been constructed. These results can be used empirically as a geothermometer. However, an attempt to develop a thermodynamic model based on the experimental data failed and the problems are discussed. 10 CHAPTER n. PREVIOUS RELATED STUDIES The NCMAS system includes the following simpler systems; CaO-MgO-SiOi (CMS), CaO-MgO-AfcOj-SiOi (CMAS), NaaO-MgO-AlaCb-SiOj (NMAS) and NazO-CaO-AlzOj-SiQ> (NCAS). Many experimental studies at high pressure and high temperatures in these systems have been done. This chapter is a review of studies related to these systems. 18 3. Pyroxenes in the system Na20-Mg0-Al203-Si0z Pyroxenes in the system NaiO-MgO-AlaOs-SiOj (NMAS) include Jd and En. Until recentfy, experimental investigation of the En-Jd join has been limited despite its in^rtance for the petrogenesis of basalts. At the conditions of the Earth's crust, the En-Jd join is metastable; the stable join is albite-forsterite, which produces the thermal divide responsible for the separation of olivine tholeiite and alkali basalts (Yoder and Willey 1962). At pressures of 2.0-3.0 GPa, Jd forms from albite + forsterite, and the En-Jd join becomes the new thermal divide (Windom and linger 1988). Windom and Boettcher (1981) investigated the Jd-En join at 2.8 GPa. They found that substantial solid solution exists between these two pyroxenes. The con:qx>sitions of coexisting Cpx and Opx on the En-Jd join were first reported by Gasparik (1986). At 6 GPa, 1400 °C , Cpx with the conq)osition EneoJdio was found to coexist with the En88Jdi2 Opx. Pierson and Windom (1986) and Windom and Pierson (1989) briefly reported their experiments on Jd-En join at 25 Kb. However, because of the short run duration and the limitation of the microprobe analysis, the data may not represent the real equilibrium composition. Later, Gasparik (1989) reported his experimental results at pressures from 10 to 16.5 GPa. He found that at above 10 GPa, garnet forms from the Jd-En join. In 1992, Gasparik extended the study of the Jd-En join up to 27 GPa and developed a thermodynamic model for the temperature range 500-2500 °C and the pressure range 0-27 GPa. He concluded that the two major discontinuities in the Earth's mantle at 400 and 670 km depths could cor...

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(Ca,Mg)2Si2O6 clinopyroxenes: A solution model based on nonconvergent site-disorder

Cited by 26 publications

References 21 publications

The Temperature and Pressure Dependence of Nickel Partitioning between Olivine and Silicate Melt

The Temperature and Pressure Dependence of Nickel Partitioning between Olivine and Silicate Melt

P–T–t paths and tectonic history of an early Precambrian granulite facies terrane, Jining district, south‐east Inner Mongolia, China

Experimental determination of phase relations of pyroxenes in the system Na2O-CaO-MgO-Al2O3-SiO2 (NCMAS) at 2.5 GPa and high temperatures

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