Faculty Profiles - NAKAMURA Daisuke

Papers - NAKAMURA Daisuke

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Metamorphic pressure-temperature conditions of garnet granulite from the Eastern Iratsu body in the Sambagawa belt, SW Japan Reviewed

Daisuke NAKAMURA, Mutsuki AOYA, Tomoki OKAMURA

Journal of Mineralogical and Petrological Sciences 120 ( 1 ) n/a - n/a 2025.4

Maximum P-T conditions of felsic granulite occurring in the Zrcadlová Hut’ quarry of the Bohemian Massif, Czech Republic Reviewed

Mio NAITO, Kensuke YAMANE, Daisuke NAKAMURA

Japanese Magazine of Mineralogical and Petrological Sciences 53 ( 1 ) n/a - n/a 2024.4

Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating Reviewed International coauthorship International journal

Yu ITAMI, Daisuke NAKAMURA, Atsushi YASUMOTO, Takao HIRAJIMA, Martin SVOJTKA

Journal of Mineralogical and Petrological Sciences 117 ( 1 ) n/a - n/a 2022.10

Mineralogical heterogeneity of UHP garnet peridotite in the Moldanubian Zone of the Bohemian Massif (Nové Dvory, Czech Republic) Reviewed International coauthorship International journal

Juliah MURIUKI, Daisuke NAKAMURA, Takao HIRAJIMA, Martin SVOJTKA

Journal of Mineralogical and Petrological Sciences 115 ( 1 ) 1 - 20 2020

A rapid and precise quantitative electron probe chemical mapping technique and its application to an ultrahigh-pressure eclogite from the Moldanubian Zone of the Bohemian Massif (Nové Dvory, Czech Republic) Reviewed

A. Yasumoto, K. Yoshida, T. Kuwatani, D. Nakamura, M. Svojtka, T. Hirajima

American Mineralogist 103 1690 - 1698 2018

Amphibole in UHP eclogite from the Sulu region, eastern China Reviewed

Satoshi Yamasaki, Daisuke Nakamura, Takao Hirajima

Journal of Mineralogical and Petrological Sciences 113 135 - 151 2018

Evidence for partial melting of eclogite from the Moldanubian Zone of the Bohemian Massif, Czech Republic Reviewed

Takahiro Miyazaki, Daisuke Nakamura, Akihiro Tamura, Martin Svojtka, Shoji Arai, Takao Hirajima

JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES 111 ( 6 ) 405 - 419 2016.12

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN ASSOC MINERALOGICAL SCIENCES

Eclogites from the Moldanubian Zone of the Bohemian Massif (Czech Republic) have experienced ultrahigh-pressure (UHP) and ultrahigh-temperature (UHT) metamorphic conditions (P > 4.0 GPa, T > 1000 degrees C). One eclogite sample collected from Nove Dvory, eastern part of Czech Republic, contains leucocratic pockets. The mineral assemblage of the melanocratic part of the eclogite is garnet + omphacite + rutile + later-stage minerals (biotite + amphibole + plagioclase). The leucocratic pockets mainly consist of plagioclase and include moderate amounts of garnet and clinopyroxene + small amounts of biotite and amphibole. Garnet and clinopyroxene grains in the leucocratic pockets display faceted shapes whereas those in the melanocratic part show irregular shapes. These are consistent with the idea that garnet and clinopyroxene grains in the leucocratic pockets had been surrounded by melt, as melt can provide free space for the formation of such faceted shapes. The major and trace element composition of garnet grains in the melanocratic part are the same as those in the leucocratic pockets. Clinopyroxene also shows the same major and trace element composition for irregular shape grains in the melanocratic part as faceted grains in the leucocratic pockets. If the melt had originated from the gneiss surrounding the peridotite body with eclogite lenses or layers, the composition of clinopyroxene in the leucocratic pockets would have been completely different from that in the melanocratic part. In addition, the trace element composition of melt estimated from clinopyroxene composition resembles that of Tonalite Trondjhemite - Granodiorite (TTG), which can be produced by partial melting of eclogite. Thus, these observational and analytical data suggest that the leucocratic pockets were originally melt that was internally produced by partial melting of the eclogite.

DOI： 10.2465/jmps.151029c

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Effect of clinopyroxene composition on Fe-Mg distribution coefficient between garnet and clinopyroxene Reviewed

Daisuke Nakamura, Madoka Okada, Takao Hirajima

JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES 110 ( 2 ) 82 - 87 2015.4

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN ASSOC MINERALOGICAL SCIENCES

This study examines the effect of jadeite content (Xjd) in omphacite on Fe-Mg distribution coefficient between garnet and clinopyroxene (K-D) by using natural data obtained from ultrahigh-pressure eclogites of the Sulu region, China. A previous study has already pointed out that a negative correlation between lnK(D) and Xjd and a positive correlation between Fe# [=Fe2+/(Fe2++Mg)] of omphacite and Xjd are present. On the other hand, this study newly recognized that KD decreases with decreasing Ca + Na + K contents in M2 site of omphacite, indicating that excess Fe2+ may be incorporated into M2 site of omphacite with decreasing Ca + Na + K contents and hence total Fe# values of omphacite may become excessively high. Thus, application of garnet-clinopyroxene geothermometer for omphacite with significant amount of jadeite and/or ferrosilite (and enstatite) components may overestimate the peak metamorphic temperatures in some cases. As a first approximation, it is better to avoid the use of omphacite with Ca + Na + K contents significantly lower than 1.0 a.p.f.u. for the application of garnet-clinopyroxene geothermometer.

DOI： 10.2465/jmps.141020

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A new approach to develop the Raman carbonaceous material geothermometer for low-grade metamorphism using peak width Reviewed

Yui Kouketsu, Tomoyuki Mizukami, Hiroshi Mori, Shunsuke Endo, Mutsuki Aoya, Hidetoshi Hara, Daisuke Nakamura, Simon Wallis

ISLAND ARC 23 ( 1 ) 33 - 50 2014.3

Significant cooling during exhumation of UHP eclogite from the Taohang area in the Sulu region of eastern China and its tectonic significance Reviewed

Daisuke Nakamura, Takao Hirajima

ISLAND ARC 19 ( 4 ) 707 - 717 2010.12

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL PUBLISHING, INC

The decompressional pressure-temperature (P-T) path was estimated for ultrahigh-pressure (UHP) eclogite from the Sulu region of eastern China by applying geo-thermobarometers to well-preserved equilibrium mineral pairs. The sample studied is a kyanite-bearing eclogite that was collected from the Taohang area of the Sulu region. Garnet is relatively homogeneous in chemical composition, but omphacite has a clear chemical zoning with decreasing jadeite content from core to rim. Assuming that peak-P equilibrium compositions are preserved in the cores of garnet (Grt) and omphacite (Omp), P-T conditions were calculated to be about 700 degrees C and 3.4 GPa. On the other hand, the jadeite content of omphacite rims varies from 0.35 to 0.46 mol.%. Nevertheless, the variation in Fe/Mg ratios of omphacite rims is very small. Temperatures of 566 +/- 54 degrees C were obtained at 1.5 GPa for garnet rim and omphacite rim pairs. These petrological considerations indicate that temperatures should have significantly declined during the early decompression stage of this eclogite. In other areas of the Sulu region, isothermal decompression paths were proposed, and it was concluded that the UHP rocks were exhumed as a large mass tens of kilometers in thickness to avoid thermal effects from the surrounding materials. However, the newly identified decompression path accompanying the significant cooling may indicate that the Taohang outcrop was located at the margin of the Sulu UHP terrane. Thus, the decompressional P-T path is not unique in the Sulu region and varies depending on the location.

DOI： 10.1111/j.1440-1738.2010.00739.x

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Extending the applicability of the Raman carbonaceous-material geothermometer using data from contact metamorphic rocks Reviewed

M. Aoya, Y. Kouketsu, S. Endo, H. Shimizu, T. Mizukami, D. Nakamura, S. Wallis

JOURNAL OF METAMORPHIC GEOLOGY 28 ( 9 ) 895 - 914 2010.12

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL PUBLISHING, INC

The degree of graphitization of carbonaceous material (CM) has been widely used as an indicator of metamorphic grade. Previous work has demonstrated that peak metamorphic temperature (T) of regional metamorphic rocks can be estimated by an area ratio (R2) of peaks recognized in Raman spectra of CM. The applicability of this method to low-pressure (< 3 kbar) contact metamorphism was tested using Raman spectroscopic analyses of samples from two contact-metamorphic aureoles in Japan (Daimonji and Kasuga areas). A suitable measurement procedure allows the dependence of the geothermometer on sample type (thin section, chip) and incident angle of laser beam relative to the c-axes of CM to be tested. Two important general results are: (i) in addition to standard thin sections, chips are also suitable for spectral analysis; and (ii) the incident angle of the laser beam does not significantly affect the temperature estimation, i.e. spectral measurements for the geothermometer can be carried out irrespective of the crystallographic orientation. A laser wavelength of 532 nm was used in this study compared with 514.5 nm in an independent previous study. A comparison shows that the use of a 532-nm laser results in a slightly, but systematically larger R2 ratio than that of a 514.5-nm laser. Taking this effect into account, our results show that there is a slight but distinct difference between the R2-T correlations shown by contact and regional metamorphic rocks: the former are slightly better-crystallized (have slightly lower R2 values) than the latter at the same temperature. This difference is interpreted as due to the degree of associated deformation. Despite the slight difference, the results of this study coincide within the estimated errors of +/- 50 degrees C with those of the previously proposed Raman CM geothermometer, thus demonstrating the applicability of this method to contact metamorphism. To facilitate more precise temperature estimates in regions of contact metamorphism, a new calibration for analyses using a 532-nm laser is derived. Another important observation is that the R2 ratio of metamorphosed CM in pelitic and psammitic rocks is highly heterogeneous with respect to a single sample. To obtain a reliable temperature estimate, the average R2 value must be determined by using a substantial number of measurements (usually N > 50) that adequately reflects the range of sample heterogeneity. Using this procedure (with 532-nm laser) and adapting our new calibration, the errors of the Raman CM geothermometer for contact metamorphic rocks decrease to similar to +/- 30 degrees C.

DOI： 10.1111/j.1525-1314.2010.00896.x

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Sr-sulphate and associated minerals found from kyanite-bearing eclogite in the Moldanubian Zone of the Bohemian Massif, Czech Republic Reviewed

Daisuke Nakamura, Tomoyuki Kobayashi, Norimasa Shimobayashi, Martin Svojtka, Takao Hirajima

JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES 105 ( 5 ) 251 - 261 2010.10

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN ASSOC MINERALOGICAL SCIENCES

Sr-sulphate, celestine, was newly found in a kyanite-bearing eclogite associated with the Nove Dvory peridotite mass in the Moldanubian Zone of the Bohemian Massif, Czech Republic. Celestine is closely associated with anhydrite, pyrite, pyrrhotite and chalcopyrite, and those minerals occur in the matrix, where fine-grained omphacite aggregate and kelyphites after garnet develop. A common Sr reservoir in eclogite is known to be epidote, but the maximum pressure-temperature (P-T) conditions of the studied eclogite was estimated as about 1050-1150 degrees C, 4.5-4.9 GPa. In such extremely high P-T conditions, epidote should be unstable. In fact, epidote is absent from most of eclogites in the Moldanubian Zone of Czech Republic. These facts suggest that a Sr-reservoir after the epidote-breakdown in subducting eclogite might be celestine, or its high-P polymorph, although the formation stage of celestine in the study sample and maximum stability limits of celestine are not known. Another idea is that celestine in the study sample was formed at relatively shallow levels after the ascent of the eclogite. In this case, omphacite and apatite would have contained significant amount of Sr under the eclogite-facies conditions. Otherwise, metasomatic infiltration of Sr-rich fluids into the eclogite is necessary for the formation of celestine in order to provide sufficient amount of Sr. A Ba-rich alumino-silicate, probably celsian, was also found as a retrograde product around pyrrhotite in kelyphite and in symplectites mainly composed of augite and plagioclase after omphacite. Several grains of biotite are also present along the margin of garnet and in the symplectites after omphacite. In addition, small amounts of muscovite and amphibole are present in the symplectites after omphacite. These findings suggest that metasomatism with Sr- and Ba-rich fluids may have occurred during decompression of the eclogite and may not be indicative of the UHP history of these rocks.

DOI： 10.2465/jmps.090817

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A new formulation of garnet-clinopyroxene geothermometer based on accumulation and statistical analysis of a large experimental data set Reviewed

D. Nakamura

JOURNAL OF METAMORPHIC GEOLOGY 27 ( 7 ) 495 - 508 2009.9

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

Published experimental data including garnet and clinopyroxene as run products were used to develop a new formulation of the garnet-clinopyroxene geothermometer based on 333 garnet-clinopyroxene pairs. Only experiments with graphite capsules were selected because of difficulty in estimating the Fe3+ content of clinopyroxene. For the calibration, a published subregular-solution model was adopted to express the non-ideality of garnet. The magnitude of the Fe-Mg excess interaction parameter for clinopyroxene (W-FeMg(Cpx)), and differences in enthalpy and entropy of the Fe-Mg exchange reaction were regressed from the accumulated experimental data set. As a result, a markedly negative value was obtained for the Fe-Mg excess interaction parameter of clinopyroxene (W-FeMg(Cpx) = - 3843 J mol(-1)). The pressure correction is simply treated as linear, and the difference in volume of the Fe-Mg exchange reaction was calculated from a published thermodynamic data set and fixed to be -120.72 (J kbar(-1) mol(-1)). The regressed and obtained thermometer formulation is as follows: where T = temperature, P = pressure (kbar), A = 0.5 X-grs (X-prp - X-alm - X-sps), B = 0.5 X-grs (X-prp - X-alm + X-sps), C = 0.5 (X-grs + X-sps) (X-prp - X-alm), X-prp = Mg/(Fe2+ + Mn + Mg + Ca)(Grt), X-alm = Fe/(Fe2+ + Mn + Mg + Ca)(Grt), X-sps = Mn/(Fe2+ + Mn + Mg + Ca)(Grt), X-grs = Ca/(Fe2+ + Mn + Mg + Ca)(Grt), X-Mg(Cpx) = Mg/(Al + Fe-total + Mg)(Cpx), X-Fe(Cpx) = Fe2+/(Al + Fe-total + Mg)(Cpx), K-D = (Fe2+/Mg)(Grt)/(Fe2+/Mg)(Cpx), Grt = garnet, Cpx = clinopyroxene. A test of this new formulation to the accumulated data gave results that are concordant with the experimental temperatures over the whole range of the experimental temperatures (800-1820 degrees C), with a standard deviation (1 sigma) of 74 degrees C. Previous formulations of the thermometer are inconsistent with the accumulated data set; they underestimate temperatures by about 100 degrees C at > 1300 degrees C and overestimate by 100-200 degrees C at < 1300 degrees C. In addition, they tend to overestimate temperatures for high-Ca garnet (X-grs approximate to 0.30-0.50). This new formulation has been tested against previous formulations of the thermometer by application to natural eclogites. This gave temperatures some 20-100 degrees C lower than previous formulations.

DOI： 10.1111/j.1525-1314.2009.00828.x

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Experimental evaluation of garnet-clinopyroxene geothermometry as applied to eclogites Reviewed

D Nakamura, T Hirajima

CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 150 ( 6 ) 581 - 588 2005.12

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

This study performed equilibrium experiments in order to evaluate previously proposed formulations of the garnet (Grt)-clinopyroxene (Cpx) thermometer as applied to eclogites. The starting material is fine-grained powder of natural eclogite (< 10 mu m), whose main constituents are Grt (Fe:Mg:Ca similar to 44:28:28), Cpx (Na pfu similar to 0.55-0.60), phengite, quartz and rutile. Experimental conditions are 1,100-1,250 degrees C at 2.5 GPa, and the run duration is 193-334 h. The experimental run products mainly consist of Grt, Cpx, and glass. In a preliminary experiment at 1,000 degrees C for 144 h, Cpx grains are clearly zoned and most Grt grains maintain primary compositions. In the higher T (>= 1,100 degrees C) and longer run (>= 193 h) experiments, Cpx in the run products becomes poorer in Na and higher in Fe/Mg compared with the starting material, and each grain does not show clear chemical zoning. Garnet compositions become poorer in Ca [Ca/(Fe+Mn+Mg+Ca)similar to 0.2-0.25] and lower in Fe/Mg compared with the starting material. The average composition of Cpx and the average of Ca-poor Grt compositions in each run product were used to evaluate previously proposed formulations of the Grt-Cpx thermometer. Temperatures calculated with formulations by Pattison and Newton (1989) and Berman et al. (1995) are much lower than the experimental temperatures, even though these formulations are based on the compositional bracketing-type experiment. One of the reasons for this discrepancy might be uncertainty of solid-solution properties of Al in Cpx, because the value of the excess interaction parameter for Al in the generally low-Al Cpx modeled by Berman et al. (1995) is much higher than those proposed by independent experiments, resulting in the estimated temperatures being significantly lower than the experimental temperatures.

DOI： 10.1007/s00410-005-0023-x

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Very high-pressure (> 4 GPa) eclogite associated with the Moldanubian Zone garnet peridotite (Nove Dvory, Czech Republic) Reviewed

D Nakamura, M Svojtka, K Naemura, T Hirajima

JOURNAL OF METAMORPHIC GEOLOGY 22 ( 6 ) 593 - 603 2004.8

Language：English Publishing type：Research paper (scientific journal) Publisher：BLACKWELL PUBLISHING LTD

Equilibrium pressure-temperature (P-T) conditions were estimated for kyanite-bearing eclogite from Nove Dvory, Czech Republic, by using garnet-clinopyroxene thermometry and garnet-clinopyroxene-kyanite-coesite (or quartz) barometry. The estimated P-T conditions are 1050-1150degreesC, 4.5-4.9 GPa, which are mostly the same as previously estimated values for garnet peridotite from Nove Dvory (similar to1100-1250degreesC, 5-6 GPa). Such very high-P conditions, which correspond to about 150-km depth, have been obtained for some garnet peridotites in the Gfohl Unit of the Bohemian Massif, but pressure conditions of eclogites associated with the garnet peridotites have not been so well constrained. This is the first substantial finding of eclogite that gives such very high-P conditions in the Gfohl Unit of the Bohemian Massif. The Gfohl Unit mainly consists of felsic granulite or migmatitic gneiss, but these rock types do not display high-P (>2.5 GPa) evidence. It is unclear whether both the peridotite body and surrounding felsic rocks in the Gfohl Unit were buried to very deep levels, but at least some garnet peridotites and associated eclogites in the Gfohl Unit have ascended from about 150-km depth.

DOI： 10.1111/j.1525-1314.2004.00536.x

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Variety in mode of occurrence of staurolite and characteristics of chemical composition Reviewed

Daisuke Nakamura

Japanese Magazine of Mineralogical and Petrological Sciences 33 ( 6 ) 233 - 243 2004

Language：English Publishing type：Research paper (scientific journal)

This paper summarizes the variety in the mode of occurrence of staurolite and compiles its compositional features. Staurolite generally occurs in pelitic schists that underwent medium pressure (P) and medium-temperature (T) metamorphism (about 0.5–1.0 GPa, 500–600°C), which is represented by the presence of the staurolite zone in the Barrovian region. However, in not a few cases, staurolite is stable even in eclogite- and granulite-facies conditions, and also in andalusite-stable low-P conditions. Mineral parageneses are important to give a constraint to P-T conditions
i.e. staurolite itself cannot be an indicator for P- T conditions. Especially, the most important point is whether the staurolite-forming environments are SiO2-saturated or not. In the SiO2-undersaturated environments, Mg-rich staurolite [Mg/(Fe+Mg)=0.30] is stable over a wide range of P-T conditions, and is commonly associated with aluminous phases such as spinel and corundum. For example, Mg-rich staurolite is known to be stable even in ultrahigh pressure conditions, which was shown by the synthetic experiments and observation of natural rocks. Also in the granulite-facies rocks, staurolite occurs as inclusions in garnet, cordierite and plagioclase or as a matrix phase associated with spinel and corundum. Stability P-T field of staurolite is not known, but staurolite itself should be stable even in high-T conditions (=700°C). Compilation of natural staurolite compositions revealed that exchange between bivalent and trivalent cations should be considered for formula expression. In addition, comparison of staurolites formed under high-P and medium- or low-P conditions did not show a clear relationship between staurolite compositions and pressures. We cannot give a constraint to pressure conditions only from the staurolite compositions. Geothermometer using Fe-Mg exchange reaction between garnet and staurolite has been proposed, but Fe-Mg distribution coefficients are widely scattered even in the rocks that experienced mostly the same temperature metamorphism. Solid-solution properties of staurolite are still not well known. © 2004, Japan Association of Mineralogical Sciences. All rights reserved.

DOI： 10.2465/gkk.33.233

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Stability of phengite and biotite in eclogites and characteristics of biotite- or orthopyroxene-bearing eclogites Reviewed

D Nakamura

CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 145 ( 5 ) 550 - 567 2003.8

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER-VERLAG

Stability of phengite and biotite in eclogite is discussed using petrological data of natural eclogites, and the observational data are examined by thermodynamic calculations. Generally, phengite is a major K phase in natural eclogite and is stable in wide range of bulk composition. However, in eclogites from several localities of the Caledonides, biotite occurs as a stable eclogite-facies mineral, and is often associated with orthopyroxene. Bulk compositions of such biotite- or orthopyroxene-bearing eclogites are compared with those of eclogites from the Dabie-Sulu region, China, where phengite is a major K phase in eclogite. The biotite- or orthopyroxene-bearing eclogites from the Western Gneiss Region of the Caledonides are rich in MgO (10-15 wt%) and relatively poor in CaO (78 wt%) and Al2O3 (12-16 wt%). The CaO/MgO ratios of the biotite- or orthopyroxene-bearing eclogites are clearly lower than those of eclogites from the Dabie-Sulu region, indicating that MgO-rich and CaO-poor environments should be important for stabilizing of biotite and orthopyroxene in eclogite. Biotite-bearing eclogite from the North-East Greenland Eclogite Province is rich in MgO (approximate to 16 wt%) and CaO (approximate to 15.5 wt%) and extremely poor in Al2O3 (approximate to 8 wt%). To stabilize biotite in eclogite, Al2O3-poor environments are also important. Bulk compositions of these biotite- or orthopyroxene-bearing eclogites are similar to picrite basaltic compositions. To examine these observational data, thermodynamic calculations were carried out in a seven-component system KH2O1.5-Na2O-CaO-FeO-MgO-Al2O3-SiO2, which includes garnet, kyanite, phengite, biotite, quartz, omphacite, orthopyroxene and olivine in conjunction with mass-balance calculations. Firstly, calculations were performed on the average bulk composition of eclogites from the Dabie-Sulu region to lherzolite (KLB-1). The calculation results confirmed that phengite should be stable in eclogite with 'ordinary' basaltic composition, whereas biotite and orthopyroxene should be stable in picrite basaltic compositions (e.g. MgO > 11.0 wt%, CaO < 9.8 wt%, Al2O3 < 15.2 wt% at 700 degreesC, 2.5 GPa). Further calculations in basaltic system confirmed that increase of MgO content and decrease of CaO and Al2O3 contents were important to stabilize biotite and orthopyroxene in eclogite. Thus, mineral assemblage in picrite basalt system should be completely different from that in normal basaltic system.

DOI： 10.1007/s00410-003-0469-7

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Kinetics of decompressional reactions in eclogitic rocks - formation of plagioclase coronas around kyanite Reviewed

D Nakamura

JOURNAL OF METAMORPHIC GEOLOGY 20 ( 3 ) 325 - 333 2002.4

Language：English Publishing type：Research paper (scientific journal) Publisher：BLACKWELL PUBLISHING INC

This paper describes a kinetic study on reaction textures in eclogitic rocks from the Sulu region, eastern China. Some of the eclogitic rocks display a decompressional reaction texture, whereby kyanite grains are surrounded by plagioclase coronas and are never in contact with quartz. The change in mineral parageneses with progress of the reaction was predicted by constructing chemical potential diagrams in a model system. The chemical potential diagrams indicated that the chemical potential of 2Na(2)O+CaO (2mu(Na2O)+mu(CaO)) in intergranular regions between kyanite and quartz should decrease with decreasing pressure, whereas 2mu(Na2O)+mu(CaO) in intergranular regions between garnet and omphacite should increase with decreasing pressure. Thus, upon decompression, an inequality in chemical potential arises in the rock. To reduce this inequality, garnet and omphacite react to produce amphibole and plagioclase and release Na2O and CaO. Then, the released Na2O and CaO components diffuse into the regions between kyanite and quartz grains and react to produce plagioclase between them. This model also indicates that the chemical potential of SiO2 should decrease around kyanite grains during the progress of the decompressional reaction, and Si-undersaturated conditions should have formed around kyanite grains in spite of the presence of quartz in these eclogitic rocks. Thus, spinel or corundum that are not stable in the system with excess quartz can form as a metastable phase, as observed in eclogitic rocks from the study areas. Phase diagrams in the system with excess quartz should be carefully applied for analysis of such reaction textures.

DOI： 10.1046/j.1525-1314.2002.00370.x

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Talc-phengite-albite assemblage in piemontite-quartz schist of the Sanbagawa metamorphic belt, central Shikoku, Japan Reviewed

J. Izadyar, T. Hirajima, D. Nakamura

Island Arc 9 ( 1 ) 145 - 158 2000.3

Granulite-facies overprinting of ultrahigh-pressure metamorphic rocks, northeastern Su-Lu region, eastern China Reviewed International journal

D. Nakamura, T. Hirajima

Journal of Petrology 41 ( 4 ) 563 - 582 2000

Language：English Publishing type：Research paper (scientific journal) Publisher：Oxford University Press

Secondary enstatite is present in ultrahigh-pressure (UHP) metamorphic rocks at two localities of Rongcheng County, in the northeastern Su-Lu region, eastern China. An enstatite-bearing eclogitic rock consists mainly of large grains of garnet and clinopyroxene, and enstatite is present as fine-grained coronas around quartz in the matrix. The enstatite coronas tend to develop near garnet grains, and plagioclase forms between the two minerals. In the second enstatite-bearing eclogite, the assemblage of enstatite + diopside is present as coronas around quartz. Textural relationships indicate that enstatite formed under plagioclase-stable and Si-saturated conditions after the peak-P metamorphism. Several reaction curves constrain the enstatite-forming conditions to be 700-800°C and 0.7-1.2 GPa. Application of thermometers to enstatite coronas also indicates high-T (~700-800°C) conditions. In these rocks, kyanite has been partially replaced by spinel + anorthite symplectites. Similar development of spinel is common in kyanite eclogite from Rongcheng County, suggesting that all share a similar decompressional history. Granulite-facies overprinting of UHP eclogite is probably a common phenomenon in the northeastern Su-Lu region. Equilibrium temperature at the peak-P stage is approximately the same as that recorded at the granulite stage, implying nearly isothermal decompression. Although such an adiabatic path generally requires rapid exhumation of the UHP rocks, the scale of the exhuming body is also important. Calculation of the length scale for thermal conduction indicates that UHP rocks must be greater than ~ 10 km in scale to avoid loss or gain of heat during the exhumation. Individual UHP eclogitic blocks are smaller than required for adiabatic exhumation in Rongcheng County, and hence they probably ascended together with the surrounding orthogneiss.

DOI： 10.1093/petrology/41.4.563

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Winchite from Mt. Hiei contact aureole, Kyoto, Japan Reviewed International journal

T. Hirajima, D. Nakamura, K. Shirahata

Journal of Mineralogical and Petrological Sciences 95 ( 6 ) 107 - 11 2000

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Association of Mineralogical Sciences

Sodic-calcic amphibole closely associated with aegirine-augite was newly found from a sandy hornfels at Mt. Hiei contact aureole, Kyoto, Japan. The amphibole shows a pleochroism of X=colorless, Y=blue and Z=light blue and is winchite with significant amounts of TiO₂ (1.5-2.5 wt.%) and of Mg-Fe-Mn-Li amphibole component at B site (ca. 0.1-0.4 cations for O=23 basis). The chemical composition and the coexisting phases of the winchite in this study are similar to those in the alkaline igneous complex.

DOI： 10.2465/jmps.95.107

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Thermodynamic modelling of sodic pyroxene solid-solution and its application in a garnet-omphacite-kyanite-coesite geothermobarometer for UHP metamorphic rocks Reviewed

D Nakamura, S Banno

CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 130 ( 1 ) 93 - 102 1997.12

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER VERLAG

A garnet-omphacite-kyanite-coesite geothermobarometer is constructed to estimate the peak metamorphic pressure of ultrahigh-pressure (UHP) eclogites. For this we use a quaternary regular solution model for garnet, and propose a new model for sodic pyroxene that assumes double site solid-solution (Na,Ca)(M2)(Al,Fe3+,Fe2+,Mg)(Si2O6)-Si-M1, where cations in the M2- and the M1-sites mix randomly but with intersite interactions, not only between nearest neighboring cations but also between next nearest neighboring cations. In the new model, overall excess interaction parameters are quantitatively deduced from the previous experimental data and critical temperature, and the activity of the jadeite component agrees reasonably with that based on the Landau theory. Furthermore, the relations of the calculated order parameter to temperature and composition are consistent with other experimental works. These facts support the usefulness of the new model. Application of our geothermobarometer to kyanite eclogite gave metamorphic conditions around 3.4 GPa and 800 degrees C for both samples from the ora Maira Massif, Western Alps, and from Rongcheng County, in the Su-Lu region of eastern China.

DOI： 10.1007/s004100050352

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Occurrence and field relationships of ultrahigh-pressure metagranitoid and coesite eclogite in the Su-Lu terrane, eastern China Reviewed

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Journal of Geological Society, London 154 45 - 54 1997

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