Calculating phase diagrams involving solid solutions via non-linear equations, with examples using THERMOCALC   总被引：33，自引：1，他引：32  

R POWELL  T. HOLLAND  & B. WORLEY 《Journal of Metamorphic Geology》1998,16(4):577-588

Phase diagrams involving solid solutions are calculated by solving sets of non-linear equations. In calculating P–T  projections and compatibility diagrams, the equations used for each equilibrium are the equilibrium relationships for an independent set of reactions between the end-members of the phases in the equilibrium. Invariant points and univariant lines in P–T  projections can be calculated directly, as can coordinates in compatibility diagrams. In calculating P–T  and T–x / P–x pseudosections – diagrams drawn for particular bulk compositions – the equilibrium relationship equations are augmented by mass balance equations. Lines in pseudosections, where the mode of one phase in the lower variance equilibrium is zero, and points, where the modes of two phases are zero, can then be calculated directly. The software, THERMOCALC, allows the calculation of these and a range of other types of phase diagram. Examples of phase diagrams and phase diagram movies, with instructions for their production, along with the THERMOCALC input and output files, and the Mathematica^TM functions for assembling them, are presented in this paper, partly in hard copy and partly on the JMG web sites (http://www.gly.bris.ac.uk/www/jmg/jmg.html, or equivalent Australian or USA sites).
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Mineralogical studies of pyropes in kimberlites from China     

董振信 《中国地球化学学报》1998,17(1):29-43

Based on the measurements of refractive index,specific gravity,unit cell parameter,and mineral chemistry and infrared absorption spectrum analyses of pyropes in kimberlites from China,systematic studies of the Physical properties and compositional variations of pyropes of different colors and diverse paragenetic types,within and between kimberlite provinces have been undertaken,The origin of pyropes in the Kimberlites and the depth of their formation have been discussed.Pyropes of the purple series are different from those of the orange series in physical and chemical properties,for exaple,pyropes of the puple series are higher in α0,RI,SG,Cr2O3,MgO,Cr/(Cr Al),Mg/(Mg Fe),and Mg/(Mg Ca),and lower in Al2O3,Fe2O3 FeO than those of the orange series.The classification of garnets in kimberlites from china by the Dawson and Stephens‘ method(1975) has been undertaken and clearly demonstrates that pyropes of diamond-rich kimberlites contain much more groups than those of diamond-poor,especially diamond-free kimberlites.The higher in α0,RI,SG,Cr2O(3.Cr/(Cr Al),knorringite and Cr-component the pyropes are ,the richer in diamond the kimberlites will be.The infrared absorption spectrum patterns of pyropes change with their chemical composition regularly,as reflected in the shape and position of infrared absorption peaks.Two absortpion bands at 862-901 cm^-1 will grade into degeneration from splitting and the absorption band positions of pyropes shift toward lower frequency with increasing Cr2O3 content and Cr/(Cr Al) ratio of pyropes,LREE contents of orange pyrope megacrysts are similar to those of porple pyrope macrocrysts,but the former is higher in HREE than the latter,showing their different chondrite-normalized patterns.The formation pressures of pyropes calculated by Cr-component,Ca-component,knorringite molecules of pyropes show that some pyropes of the purple series in diamondiferous kimberlites fall into the diamond stability field.but all pyropes of diamond-free kimberlites lie outside the diamond stability field.The megacrysts were formed through early crystallization of kimberlites magma at high pressure condition,the majority of the purple pyrope macrocrysts have been derived from disaggregated xenoliths but the minoirty of them appear to be fragments of the discrete megacryst pyropes,or phenocrysts.  相似文献   

The Discovery of Diamond from the Zhimafang Pyrope Peridotite of the Sulu UHP Metamorphic Zone, East China, and Its Geological Implications     

PAN Mingbao  ZHANG Qinglong  LU Huafu  CHEN Huogen  CHEN Shoujuand ZHU ShipengDepartment of Earth Sciences  Nanjing University  Nanjing  Jiangsu Jiangsu Institute of Geological Survey  Zhujiang Ro  Nanjing  Jiangsu  E-mail: andypans@.com Hao Ziguo  Zhu Xiling 《《地质学报》英文版》2003,77(3):332-337

From Donghai County of Jiangsu Province to Rongcheng County of Shandong Province on the southern border of the Sulu orogen, there exposes an ultramafic belt, accompanied with an ultrahigh-pressure metamorphic zone. It can be further divided into the Xugou belt (the northern belt), and the Maobei-Gangshang belt (the southern belt). One grain of diamond has been discovered from the Zhimafang pyrope peridotite in the southern belt using the heavy mineral method. The diamond grain is 2.13 mm × 1.42 mm × 0.83 mm in size and weighs 9.4 mg. The occurrence of the diamond suggests that the Zhimafang pyrope peridotite xenolith is derived from the lithospheric upper mantle. The tectonic emplacement mechanism of the pyrope peridotite xenoliths in granite-gneisses is obviously different from those in kimberlite. The Sulu orogen was located on the active continental margin of the Sino-Korean craton in the Neoproterozoic. The relatively cold and water-bearing oceanic crustal tholeiite slab subducted beneath the lith  相似文献   

Mineral inclusions in diamonds from the Sputnik kimberlite pipe, Yakutia   总被引：9，自引：0，他引：9  

N. V. Sobolev  F. V. Kaminsky  W. L. Griffin  E. S. Yefimova  T. T. Win  C. G. Ryan  A. I. Botkunov 《Lithos》1997,39(3-4):135-157

The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO₂ content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m² conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle.  相似文献   

Metamorphic charnockite in contact aureoles around intrusive enderbite from Natal, South Africa     

Alfons M. van den Kerkhof  Geoffrey H. Grantham 《Contributions to Mineralogy and Petrology》1999,137(1-2):115-132

In the Port Edward area of southern Kwa-Zulu Natal, South Africa, charnockitic aureoles up to 10 m in width in the normally garnetiferous Nicholson's Point Granite, are developed adjacent to intrusive contacts with the Port Edward Enderbite and anhydrous pegmatitic veins. Mineralogical differences between the country rock and charnockitic aureole suggest that the dehydration reaction Bt + Qtz → Opx + Kfs + H₂O and the reaction of Grt + Qtz → Opx + Pl were responsible for the charnockitization. The compositions of fluid inclusions show systematic variation with: (1) the Port Edward Enderbite being dominated by CO₂ and N₂ fluid inclusions; (2) the non-charnockitized granite by saline aqueous inclusions with 18–23 EqWt% NaCl; (3) the charnockitic aureoles by low-salinity and pure water inclusions (<7 EqWt% NaCl); (4) the pegmatites by aqueous inclusions of various salinity with minor CO₂. As a result of the thermal event the homogenization temperatures of the inclusions in charnockite show a much larger range (up to 390 °C) compared to the fluid inclusions in granite (mostly <250 °C). Contrary to fluid-controlled charnockitization (brines, CO₂) which may have taken place along shear zones away from the intrusive body, the present “proximal” charnockitized granite formed directly at the contact with enderbite. The inclusions indicate contact metamorphism induced by the intrusion of “dry” enderbitic magma into “wet” granite resulting in local dehydration. This was confirmed by cathodoluminescence microscopy showing textures indicative for the local reduction of structural water in the charnockite quartz. Two-pyroxene thermometry on the Port Edward Enderbite suggests intrusion at temperatures of ∼1000–1050 °C into country rock with temperature of <700 °C. The temperature of aureole formation must have been between ∼700 °C (breakdown of pyrite to form pyrrhotite) and ∼1000 °C. Charnockitization was probably controlled largely by heat related to anhydrous intrusions causing dehydration reactions and resulting in the release and subsequent trapping of dehydration fluids. The salinity of the metamorphic fluid in the contact zones is supposed to have been higher at an early stage of contact metamorphism, but it has lost its salt content by K-metasomatic reactions and/or the preferential migration of the saline fluids out of the contact zones towards the enderbite. The low water activity inhibited the localized melting of the granite. Mineral thermobarometry suggests that after charnockite aureole genesis, an isobaric cooling path was followed during which reequilibration of most of the aqueous inclusions occurred. Received: 8 November 1998 / Accepted: 21 June 1999  相似文献   

Elasticity of pyrope and majorite-pyrope solid solutions to high temperatures     

Stanislav V. Sinogeikin  Jay D. Bass 《Earth and Planetary Science Letters》2002,203(1):549-555

Majorite-garnet solid solutions are major mineral phases in the Earth’s upper mantle and transition zone. Here we present the first Brillouin scattering measurements of the elasticity of majorite (Mj, Mg₄Si₄O₁₂)-pyrope (Py, Mg₃Al₂Si₃O₁₂) solid solutions (Mj₅₀Py₅₀ and Mj₈₀Py₂₀) and single-crystal elasticity of pure synthetic pyrope at temperatures up to 800°C. The temperature derivatives of the adiabatic bulk (K_S) and shear (μ) moduli for all compositions along the Mj-Py join are the same within the experimental uncertainties (−∂K_S/∂T=14.0-14.5(20) MPa/K, −∂μ/∂T=8.3-9.2(10) MPa/K). The temperature dependence of the acoustic velocities for Mj-Py solid solutions is about half that of other major transition zone minerals. This implies that temperature variations in the transition zone, inferred from lateral velocity heterogeneity, can be significantly underestimated if the properties of majoritic garnet are not taken into account.  相似文献   

Ab Initio Molecular Dynamic Simulation on the Elasticity of Mg_3Al_2Si_3O_(12) Pyrope     

Donald J Weidner  John Brodholt  Dario Alfè  G David Price 《中国地质大学学报(英文版)》2011,(2)

We calculated thermo-elastic properties of pyrope(Mg3Al2Si3O12) at mantle pressures and temperatures using Ab initio molecular dynamic simulation.A third-order Birch-Murnaghan equation at a reference temperature of 2 000 K fits the calculations with bulk modulus,K0=159.5 GPa,K0'=4.3,V0=785.89 A3,Grüneisen parameter,γ0=1.15,q=0.80,Anderson Grüneisen parameter δT=3.76 and thermal expansion,α0=2.93×10-5 K-1.Referenced to room temperature,where V0=750.80 A3,γ0 and α0 become 1.11 and 2.47×10-5 K-1.The elastic pr...  相似文献   

镁铝榴石的化学成分分类及其在金刚石找矿中的指示意义     

黄进初 《矿物岩石》1990,10(1):12-18

镁铝榴石是找寻金刚石的一种重要的指示矿物。本文应用了聚类分析方法，以镁铝榴石中的钙组分、铬组分、镁组分和镁组分（铁铝榴石）4种成分参数作变量，将56个样品分为6类，讨论了每一类样品的化学成分特点，确定了它们的标型意义，并应用多元判别分析得出了划分这6类和对未知样品进行判别归类的一组判别函数。  相似文献   

湖南桃源理公港地区含金刚石沉凝灰岩的发现及其找矿意义     

杨献忠  蔡逸涛  康丛轩  黄光昭  李帅  向华 《中国地质调查》2014,6(6):56-62

湖南桃源理公港地区白垩纪红盆内的灰绿色和紫红色沉积夹层曾选获过金刚石。以灰绿色岩石为研究对象,通过薄片鉴定和电子探针分析来确定岩石名称和岩石中石榴石和云母的属性。显微镜下,灰绿色岩石呈凝灰结构,由约45%的晶屑、35%的岩屑和20%的玻屑组成,为较典型的沉凝灰岩,并非前人所述的金伯利岩。沉凝灰岩中的石榴石和云母分别为G10型镁铝榴石和金云母,镁铝榴石和金云母的成分与辽宁、山东及南非典型岩管含金刚石金伯利岩中的镁铝榴石及金云母的成分基本一致,暗示其来源于含金刚石的金伯利岩。沉凝灰岩的特征表明,其来源地不会太远,这为在附近找寻火山机构奠定了基础; 金伯利质岩屑、G10型镁铝榴石和金云母的发现,为在周边寻找原生金伯利岩提供了重要信息。  相似文献   

贵州施秉下翁哨地区镁铝榴石和铬尖晶石自然重砂罕见特高异常查证     

杨光忠  李永刚  罗邦良  石庆鹏  黄应均  夏瑞 《地质通报》2019,38(1):36-43

综合利用以往资料发现,贵州施秉下翁哨地区存在特高浓度镁铝榴石、铬尖晶石等自然重砂异常,且长期未能解释其来源及金刚石找矿指示问题。由于资料形成于"文革"时期,有人怀疑其可靠性,通过针对性的野外调查和采样分析,佐证了该异常的客观存在和以往资料的可靠性。镁铝榴石和铬尖晶石自然重砂含量水平实属罕见,异常区分布于高出现代河床200m的斜坡上部,残积于古河道砂砾石冲积层(?)中,矿物学分析未见重砂矿物明显的搬运磨蚀痕迹,电子探针分析分属于G9镁铝榴石和S5铬尖晶石,应主要来源于石榴和尖晶二辉橄榄岩,系载体母岩——钾镁煌斑岩就近风化残积的结果。  相似文献