DOCSLIB.ORG

Am73 524.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Am73 524.Pdf American Mineralogist, Volume 73, pages524-533, 1988 High-pressure-high-temperaturemelting experimentson a SiOr-poor aphanitic kimberlite from the Wesseltonmine, Kimberley, South Africa Ar,.q.ND. Encan Department of Geology, University of Western Ontario, London, Ontario N6A 5B7, Canada M,q.roro Anrvrl Geological Institute, Yokohama National University, Yokohama 240, Iapan DrlNe K. Bl.r.owrN Department of Geology, Acadia University, Wolfville, Nova Scotia BOP 1X0, Canada Dlvro R. Bnr,r, Department of Geological and Planetary Sciences,California Institute of Technology,Pasadena, California 9 I 125, U.S.A SrvroN R. Snre, E. Mrcrrnrr, W. SxrNNnn Anglo American ResearchLaboratories, Johannesburg, South Africa Eow.qno C. Welxpn Department of Geology, University of Western Ontario, London, Ontario N6A 5B7, Canada Ansrn-lcr Phaserelations in a SiOr-poor aphanitic Group I kimberlite from the Wesseltonmine, 'C. South Africa, were determined at 10-40 kbar and 1000-1525 Experiments were done first with no additional HrO or COr, equivalent to the initial amounts in the rock of 6.20 wto/oHrO and 4.77 wto/oCOr, and secondwith sufficient CO, added to bring the total to 10.34 wto/oCOr. These amounts are equivalent to a mole fraction of CO, (X""r) of 0.24 and 0.52, respectively.Oxygen fugacities are difficult to predict but were likely less than the MW and greaterthan the IW buffer assemblages.All experimentsare suprasolidusand apparently vapor absent.In addition to liquid, runs at X.or:0.24 produced the following assemblageswith decreasingpressure from 40 to 10 kbar and temperaturesfrom 1400 to 1000 "C: olivine, olivine * spinel, olivine * spinel * clinopyroxene + calcite + perov- skite,and olivine * spinel + monticellite + calcite + perovskite.At Xcor:0.52, runs at 20-35 kbar produced olivine * spinel, olivine A clinopyroxene * spinel, and olivine + clinopyroxene + spinel + calcite. Above 35 kbar, the latter assemblageis replaced by olivine * clinopyroxene + dolomite. Comparison of the compositions of the minerals in the rock with those produced in the experiments indicates good agreement except for spinelsthat are highly oxidized in the experimental products relative to those in the rock. The run assemblagesare comparable with the minerals in the aphanitic kimberlite except for clinopyroxene,which is absentin the rock, and ilmenite, apalite,and phlogopite, which are presentin the rock but not in the experimental runs. Basedon the X.or:0.24 exper- iments, the inferred P-T path of ascent of the aphanitic kimberlite magma above about 40-km depth may have exceededthe temperature(1250-1300'C) at which clinopyroxene is stable for this composition. The antipathy of clinopyroxene and monticellite in the X.or:0.24 experiments may be used to explain the incompatibility of these minerals in kimberlite and suggeststhat monticellite need not be a product associatedwith crustal processes. The aphanitic Wesseltonkimberlite has lower SiO, and MgO and higher CaO than other Group I kimberlites and, when plotted on the CMS system,lies on the CaO-rich side of the olivine-clinopyroxene join whereasmore SiOr-rich Group I kimberlites fall close to this join. These compositional differencesmay account for the absenceof orthopyroxene in any of the experimental assemblagesand possibly for the fact that calcite is the only carbonatemineral below 35 kbar and occurs only at high Xco, conditions. Most Group I kimberlite compositions are representedby the model carbonatedlherzolite system (oliv- ine-clinopyroxene-orthopyroxene-dolomite)for which a pseudo-eutecticmelting relation- ship involving enstatite may occur. The absenceof orthopyroxene in the present experi- ments doesnot precludethe more SiOr-undersaturatedWesselton kimberlite magma from 0003-004x/88/0506-0524$02.00 524 EDGAR ET AL.: MELTING OF APHANITIC K]MBERLITE 525 being the product of crystal fractionation at mantle depths of a more SiOr-rich kimberlite magma derived by partial melting of a carbonatedlherzolite source.However, the absence of orthopyroxene in the experiments does indicate that the aphanitic kimberlite magma could have evolved from a source devoid of orthopyroxene and with calcite as the car- bonate phase.The present experiments suggestthat the aphanitic Wesseltonkimberlite is not an evolved speciesbut may representa primitive kimberlite magma. IxrnooucrroN berlite, olivine microphenocrystsoccur in a matrix con- il- Experimental studies under pressureand temperature sisting of variable amounts of calcite, monticellite, perovskite, rare conditions compatible with crystallization and differen- menite, spinel, apatite, serpentine,and phlogopite tiation of kimberlite magmasare valuable in understand- phlogopite. Olivine and xenocrystsand xeno- The ing the evolution of kimberlites (Mitchell, 1986).The only liths of country rock occur only in trace amounts. (Table available studiesusing actual kimberlites are those of Eg- aphanitic kimberlite used in this study 1; analyses gler and Wendlandt (1979) on a modified Lesotho kim- l, 2) has lower SiOr, MgO, and KrO and higher TiOr, berlite composition with 0-l I wto/oHrO and that of Ito AlrOr, and CaO than the mean value for macrocrystic I et al. (1968) on an anhydrous kimberlite from the Du- kimberlites from the same locality and from Group toitspan mine. Most experimentalwork pertinent to kim- kimberlites generally (Table l; analyses3, 4). This com- berlites has involved determination of the role of peri- position also differs considerablyfrom that usedby Eggler dotite, particularly lherzolite and harzburgite with and Wendlandt (1979) in their experiments. orthopyroxene as an essentialmineral, and/or the signif- ExpnnrmnNTAL coNDITToNS AND TECHNIQUES icance of CO, in their genesis,using simplified model periodotite systems (cf. Eggler and Wendlandt, 1979; Experimentswere done under two setsof COr/HrOratios. In Wyllie, 1979, 1980; Olafssonand Eggler,1983; Brey et the first setof experiments,between 10 and 40 kbar,no HrO or al., 1984;'Huang and Wyllie, 1984). Experiments on the CO, other than that in the rock itself was used.These experi- crystallization and evolution of kimberlite magmas are hampered wide by the variation in kimberlite composi- TneLe1. Compositionsof aphanitic,macrocrystic, and average tions and hencethe difficulty in identifying compositions Grouplkimberlites that may be reasonablyrepresentative of primitive kim- berlite magma. 1 2 (n:7) 3 (n: 17) 4 (n: 44\ This paper describessuprasolidus, apparently vapor- sio, 25.60 24.46(22.80-26.00)31.5s(28.90J4.50) 30.26 absent experimentsbetween l0 and 40 kbar on a Group Tio, 3.35 3.11(2.53J.48) 2.OO(1.73-2.32) 1.91 Alro3 3.31 3.58(3.00J.90) 2.57('t.704.45) 2.87 I aphanitic kimberlite from the Wesselton mine, Kim- FerOnn 10.30 9.74(9.06-10.20) 9.01(8.5&-9.46) 8.63 berley, South Africa. The scarcity of xenoliths and xeno- MnO 0.21 0.19(0.15-0.22) 0.15(0.12-0.19) 0.16 crysts, the fine-grained nature of this kimberlite, and its Mgo 27.20 25.94(2326-29.10)31.30(27.10-33.40) 29.62 CaO 15.30 15.07(12.70-16.7018.14(6.40-9.59) 10.13 low SiO, content relative to other kimberlites suggestthat Naro 0.28 0.26(0.10-0.80) 0.35(0.05-0.60) 0.39 the aphanitic kimberlite at Wesselton may represent a KrO 0.70 0.68(0.13-1.23) 1.29(O.4U2.321 1.31 primitive, DA 1.83 1.74(1.45-2.56) 1.00(0.4il1 .58) 1.48 closeto although not necessarilyprimary, kim- 4.77 6.92(3.45-10.86)4.26(1.45-5.97) 5.24 berlite magma composition. If this assumption is correct, Hro* 6.20 7.56(4.92-9.39) 7.71(3.96-10.09) 7.64 then the experiments can be used to determine possible Total 99.05 99.25 99.33 99.64 crystallization paths during ascentof the aphanitic Wes- Trace elements(ppm) F 2500 2225 1784 1917 selton kimberlite from depths correspondingto 40 kbar cr 800 to those correspondingto l0 kbar by comparing the poly- s-671 271 367 baric-polythermal mineral assemblagesobtained in the v-170 105 123 Cr 2410 2007 1291 1517 experimentswith those inferred from the petrography of Co 87 110 94 the rock. Such experimentsalso indicate potential genetic Ni 810 729 1233 1061 relationships between extremely SiOr-undersaturated Cu 105 60 oo Zn 111 88 86 aphanitic varieties of kimberlite, such as the one used in Rb 20 60 78 77 this study, and the more common, relatively SiOr-en- Sr 1180 1256 905 1186 Y1026 12 16 riched macrocrystickimberlites, such as the macrocrystic Zr 580 502 258 318 Wesseltonkimberlite. Nb 250 284 146 171 Ba 1000 1578 1198 1399 Nofe.'Columns are (1) aphanitickimberlite used in this study (after Shee, PBrnocnLpHy AND cHEMrsrRy oF GRoup I 1986, and by X-ray fluorescencetechniques by X-ray Assay Laboratories, KIMBERLITES,I.TWNSSTITON Don Mills, Ontario); (2) mean and ranges of 7 aphanitic kimberlitesfrom Wesselton (after Shee, 1986); (3) mean and ranges of 17 macrocrystic Shee(1984, 1986)described the geology,petrography, kimberlites from Wesselton (after Shee, 1986); (a) mean of 44 Group I classification, and chemistry of the hypabyssal facies kimberlitesfrom Wesselton,DeBeers, Benfontein, Dutoitspan (after Shee, Group I kimberlites at Wesselton.In the aphanitic kim- 1986). 526 EDGAR ET AL.: MELTING OFAPHANITIC KIMBERLITE ments representthe minimum HrO + CO2 prior to crystalliza- chargesat previous run conditions and reducing or increasing tion, and the results assumethat loss of these volatiles during the temperatureby 25'C. In all cases,these runs produced the ascentwas minimal and that neither HrO nor CO, was added sameassemblages as the runs done on the low- or high-temper- by secondaryprocesses. Probably someloss ofvolatiles occurred ature side ofthe liquidus (Table 2). during ascent,and the presenceof serpentinein the groundmass Products of the experimentsconsisted of combinations of ol- suggeststhat some of the volatiles may not be of magmatic or- ivine, spinel, monticellite, clinopyroxene, perovskite, calcite, and igin.
Load more

Recommended publications
  • Influence of Temperature and Water Content on Microstructure Evolution
    Contributions to Mineralogy and Petrology (2018) 173:5 https://doi.org/10.1007/s00410-017-1429-y ORIGINAL PAPER Synthesis of monticellite–forsterite and merwinite–forsterite symplectites in the CaO–MgO–SiO2 model system: influence of temperature and water content on microstructure evolution P. Remmert1 · W. Heinrich1 · B. Wunder1 · L. Morales1 · R. Wirth1 · D. Rhede1 · R. Abart2 Received: 17 September 2017 / Accepted: 28 November 2017 / Published online: 21 December 2017 © The Author(s) 2018. This article is an open access publication Abstract Homogeneous single crystals of synthetic monticellite with the composition Ca0.88Mg1.12SiO4 (Mtc I) were annealed in a ◦ piston-cylinder apparatus at temperatures between 1000 and 1200 C , pressures of 1.0–1.4 GPa, for run durations from 10 min to 24 h and applying bulk water contents ranging from 0.0 to 0.5 wt% of the total charge. At these conditions, Mtc I breaks down to a fine-grained, symplectic intergrowth. Thereby, two types of symplectites are produced: a first symplectite type (Sy I) is represented by an aggregate of rod-shaped forsterite immersed in a matrix of monticellite with end-member composition (Mtc II), and a second symplectite type (Sy II) takes the form of a lamellar merwinite–forsterite intergrowth. Both symplectites may form simultaneously, where the formation of Sy I is favoured by the presence of water. Sy I is meta- stable with respect to Sy II and is successively replaced by the latter. For both symplectite types, the characteristic spacing of the symplectite phases is independent of run duration and is only weeakly influenced by the water content, but it is strongly ◦ ◦ ◦ temperature dependent.
    [Show full text]
  • Magnesioferrite-Olivine Rock and Monticellite-Bearing Dunite from the Iwanai-Dake Alpine-Type Peridotite Mass in the Kamuikotan Structural Belt, Hokkaido, Japan
    J. Japan. Assoc. Min, Petr. Econ. Geol. 77, 23-31. 1982 Magnesioferrite-olivine rock and monticellite-bearing dunite from the Iwanai-dake alpine-type peridotite mass in the Kamuikotan structural belt, Hokkaido, Japan JITSUYA NAGATA Department of Earth Sciences, Kanazawa University, Kanazawa 920, Japan Magnesioferrite, monticellite, perovskite and calcium brittle mica occur in the alpine- type Iwanai-dake peridotite mass in the Kamuikotan structural belt, Hokkaido. These minerals were not primary phases, but were produced through metasomatic processes at a later stage of the granulite facies equilibration. Introduction Magnesioferrite, monticellite, perovskite and calcium brittle mica were found in the Iwanai-dake peridotite mass, an alpine-type intrusion in Hokkaido. As these minerals have not been described in alpine-type peri dotite, their modes of occurrence, chemis tries and paragenetic relations will be described in this paper. The Iwani-dake mass (Fig. 1) is intrud- ed in the Kamuikotan structural belt which is a melange zone consisting of high-pressure metamorphic rocks, low-pressure metamor Fig. 1. Locality of the Iwanai-dake peridotite phic rocks derived from an ophiolitic suite, mass, Hokkaido. and ultramafic rocks (Banno et al., 1978; Asahina and Komatsu, 1979). The Iwanai- ing to Arai (1978), equilibrium temperature dake mass is composed largely of dunite and of ultramafic rocks is estimated to 600 to harzburgite and is almost free from ser 700°C using the olivine-Ca-rich clinopyroxene pentinization (Bamba, 1955; Kato, 1978; geothermometer and olivine-spinel geother Niida and Kato, 1978; Arai, 1978). Gener mometer. ally, dunite and harzburgite form layered structures. Small amounts of chromitite Mode of occurrence, petrography and are also present.
    [Show full text]
  • List of Abbreviations
    List of Abbreviations Ab albite Cbz chabazite Fa fayalite Acm acmite Cc chalcocite Fac ferroactinolite Act actinolite Ccl chrysocolla Fcp ferrocarpholite Adr andradite Ccn cancrinite Fed ferroedenite Agt aegirine-augite Ccp chalcopyrite Flt fluorite Ak akermanite Cel celadonite Fo forsterite Alm almandine Cen clinoenstatite Fpa ferropargasite Aln allanite Cfs clinoferrosilite Fs ferrosilite ( ortho) Als aluminosilicate Chl chlorite Fst fassite Am amphibole Chn chondrodite Fts ferrotscher- An anorthite Chr chromite makite And andalusite Chu clinohumite Gbs gibbsite Anh anhydrite Cld chloritoid Ged gedrite Ank ankerite Cls celestite Gh gehlenite Anl analcite Cp carpholite Gln glaucophane Ann annite Cpx Ca clinopyroxene Glt glauconite Ant anatase Crd cordierite Gn galena Ap apatite ern carnegieite Gp gypsum Apo apophyllite Crn corundum Gr graphite Apy arsenopyrite Crs cristroballite Grs grossular Arf arfvedsonite Cs coesite Grt garnet Arg aragonite Cst cassiterite Gru grunerite Atg antigorite Ctl chrysotile Gt goethite Ath anthophyllite Cum cummingtonite Hbl hornblende Aug augite Cv covellite He hercynite Ax axinite Czo clinozoisite Hd hedenbergite Bhm boehmite Dg diginite Hem hematite Bn bornite Di diopside Hl halite Brc brucite Dia diamond Hs hastingsite Brk brookite Dol dolomite Hu humite Brl beryl Drv dravite Hul heulandite Brt barite Dsp diaspore Hyn haiiyne Bst bustamite Eck eckermannite Ill illite Bt biotite Ed edenite Ilm ilmenite Cal calcite Elb elbaite Jd jadeite Cam Ca clinoamphi- En enstatite ( ortho) Jh johannsenite bole Ep epidote
    [Show full text]
  • Kirschsteinite Cafe Sio4 C 2001 Mineral Data Publishing, Version 1.2 ° Crystal Data: Orthorhombic
    2+ Kirschsteinite CaFe SiO4 c 2001 Mineral Data Publishing, version 1.2 ° Crystal Data: Orthorhombic. Point Group: 2=m 2=m 2=m: In crystals, to 0.5 mm; as skeletal rims on other minerals; crystalline massive. Physical Properties: Hardness = n.d. D(meas.) = 3.434 D(calc.) = 3.596 Optical Properties: Transparent. Color: Pale green; colorless in thin section. Optical Class: Biaxial ({). Orientation: X = b; Y = c; Z = a. ® = 1.660{1.689 ¯ = 1.720 ° = 1.694{1.728 2V(meas.) = 51(1)± 2V(calc.) = 53±{61± Cell Data: Space Group: [P bnm] (by analogy to the olivine group). a = 4.859 b = 11.132 c = 6.420 Z = 4 X-ray Powder Pattern: Mt. Shaheru, Congo. 2.949 (100), 2.680 (85), 2.604 (80), 3.658 (70), 1.830 (60), 2.414 (40), 5.569 (35) Chemistry: (1) (2) SiO2 32.71 31.96 TiO2 0.23 Al2O3 0.26 Fe2O3 0.66 FeO 29.34 38.21 MnO 1.65 MgO 4.95 CaO 29.30 29.83 Na2O 0.34 K2O 0.36 + H2O 0.25 H2O¡ 0.06 P2O5 0.07 Total 100.18 100.00 (1) Mt. Shaheru, Congo. (2) CaFeSiO4: Polymorphism & Series: Forms a series with monticellite. Occurrence: In melilite-nephelinite lava (Mt. Shaheru, Congo); in calcareous skarn (Tazheran massif, Russia). Association: Melilite, nepheline, clinopyroxene, kalsilite, gÄotzenite, combeite, sodalite, magnetite, perovskite, apatite, \hornblende," biotite (Mt. Shaheru, Congo); titanian augite, wollastonite, melilite, garnet, calcite, cuspidine, diopside, perovskite, troilite, graphite (Tazheran massif, Russia). Distribution: On Mt. Shaheru, the extinct southern cone of Mt. Nyiragongo, Kivu Province, Congo (Zaire).
    [Show full text]
  • Diopside Camgsi2o6 C 2001 Mineral Data Publishing, Version 1.2 ° Crystal Data: Monoclinic
    Diopside CaMgSi2O6 c 2001 Mineral Data Publishing, version 1.2 ° Crystal Data: Monoclinic. Point Group: 2=m: As prismatic crystals with nearly square cross sections, to 50 cm; granular, columnar, lamellar massive. Twinning: Simple or multiple twins on 100 or 010 , common. f g f g Physical Properties: Cleavage: Distinct on 110 , (110) (110) 87±; partings on 100 and probably 010 . Fracture: Uneven to conchofidal.g Tenaci^ty: Britt»le. Hardness = 5f.5{6.g5 D(meas.) = 3.f22{3g.38 D(calc.) = 3.278 Optical Properties: Transparent to opaque. Color: Colorless, white, yellow, pale to dark green, black; colorless in thin section. Streak: White, gray, gray-green. Luster: Vitreous or dull. Optical Class: Biaxial (+). Orientation: Y = b; Z c = 38± on (010); X a = 22±. ^ ¡ ^ ¡ Dispersion: r > v; weak to moderate. ® = 1.664 ¯ = 1.672 ° = 1.694 2V(meas.) = 59± Cell Data: Space Group: C2=c: a = 9.746 b = 8.899 c = 5.251 ¯ = 105:63± Z = 4 X-ray Powder Pattern: Schwartzenstein, Austria. (ICDD 11-654). 2.991 (100), 2.528 (40), 2.893 (30), 2.518 (30), 3.23 (25), 2.952 (25), 1.625 (25) Chemistry: (1) (2) (1) (2) (1) (2) SiO2 54.66 54.09 FeO 0.07 1.47 K2O 0.15 + TiO2 0.28 MnO 0.02 0.09 H2O 0.22 0.22 Al2O3 0.07 1.57 MgO 18.78 16.96 H2O¡ 0.08 Fe2O3 0.68 0.74 CaO 25.85 21.10 rem: 0.49 Cr2O3 2.03 Na2O 1.37 Total 100.35 100.64 3+ (1) Juva, Finland; corresponds to Ca1:00(Mg1:01Fe0:02)§=1:03Si1:98O6: (2) Dutoitspan mine, 2+ Kimberley, Cape Province, South Africa; corresponds to (Ca0:82Na0:05Fe0:04Mg0:04K0:01)§=0:96 3+ (Mg0:88Cr0:06Al0:03Fe0:02Ti0:01)§=1:00(Si1:96Al0:04)§=2:00O6: Polymorphism & Series: Forms two series, with hedenbergite, and with johannsenite.
    [Show full text]
  • CRYSTAL STRUCTURES of NATURAL OLIVINES J. D. Brnmt
    THE AMERICAN MINERALOGISI', VOL 53, MAY_JUNE, 1968 CRYSTAL STRUCTURES OF NATURAL OLIVINES J. D. Brnmt, G.V. Grnns2,P. B. MoonE, ANDJ. V. SurrH, Departmentof the GeophysicalSciences, (Jn'ittersity of Chicago Chicago,Illinois 60637,U.S.A. Ansrnncr Atomic parameters were obtained by 3D least-squares X-ray difiraction analysis of forsterite (Mgo go,Feo1s), plutonic hyalosiderite (Mgo u:u,Feonso,Mrio ooo,CzIo oor), dike hortonolite (Mgo as,Feoas,Mno or,Cao or), and fayalite (Feo gz,Mgoor,Mns ,r). The closeness in value of the isotropic temperature factors calculated for the M sites indicates substitutional disorder of the Mg and Fe atoms in all four structures. Poiyhedra distortions are closely similar in all four structures showing that they depend on the struc- ture type rather than on the Mg, Fe substitution. Simple electrostatic rules allied with papk- ing considerations permit qualitative explanation of the structural distortions. The M(l) octahedron has six short shared edges to give a distorted and elongated trigonal antiprism. The M(2) octahedron has a triangle of three short shared edges. Metal-oxygen distances tend to compensate e.g., the longest Si-O distance and the shortest (MS,Fe)-O distance go to the same oxygen. INrnorucrroN The type structure of olivine was determined by Bragg and Brown (1926) on a forsterite crystal with composition Mgo noFeo.ro.Three- dimensionalrefinement of another forsterite crystal by Belov, Belova, Andrianova, and Smirnova (1951) yielded Si-O and M-O distancesfar outside the usual ranges for silicates. More recently Hanke a\d Zemarn (1963) determined the atomic parameters of forsterite from a two-di- mensionalanalysis, and Born (1964) followed this by showing that the observedposition ol M(2) falls on the maximum of the total attractive plus repulsiveenergy for half-ionizedatoms.
    [Show full text]
  • Monticellite Marble at Cascade Mountain. Adirondack Mountains. New York
    AmericanMineralogist, Volume 63, pages 991-999, 1978 Monticellitemarble at CascadeMountain. Adirondack Mountains. New York Rosrnr J. Tnecyl Departmentof GeologicalSciences, Haruard Uniuersity Camb ridge, M assachuset ts 02 I 38 Howeno W. JerneeNo Pernn RosrNsoN Departmentof Geology,Uniuersity of Massachusetts A mherst,M assachuset ts 0I 003 Abstract An Adirondackmarble contains the assemblagecalcite-diopside-forsterite-monticellite, with traceamounts of zincianspinel, titanian andradite, idocrase, and sphalerite. Microprobe analysesindicate that the monticelliteand forsterite both haveMg/(Mg+ Fe)greater than 0.9, and that monticelliteis more iron-richthan coexistingforsterite. Monticellite host grains containrare microscopic exsolution lamellae of forsterite,a featurenoted in only oneother terrestrialmonticellite occurrence. Diopside is stronglyzoned and containsup to 6 weight percentAlrOr and substantial ferric iron, indicating a fassaiticcharacter typical ofcalc-silicate clinopyroxenes. Distributionof Feand Mg amongthe major silicate minerals indicates that the monticellite- producingreaction must be an Fe-Mg continuousreaction combining the end-member reactlon, MgrSiOn* CaMgSirO.* 2 CaCO, : 3 CaMgSiO4+ 2CO2 with two Fe-Mg exchangeequilibria: 2 CaMgSiOn* Fe2SiO.: 2 CaFeSiO,* Mg,SiOn CaMgSirO.* CaFeSiO.: CaFeSirOu* CaMgSiO. Calculationssuggest that Fe doesnot lower the reactiontemperature significantly. The occurrenceof monticellite-freemarble in the sameoutcrops and variablemineral composi- tions in the calcite-diopside-forsterite-monticelliteassemblage
    [Show full text]
  • Petrographic Investigation of Smithing Slag of the Hellenistic to Byzantine City of Sagalassos (SW-Turkey)K
    American Mineralogist, Volume 101, pages 1072–1083, 2016 Petrographic investigation of smithing slag of the Hellenistic to Byzantine city of Sagalassos (SW-Turkey)k KIM EEKELERS1,*, PATRICK DEGRYSE1, AND PHILIPPE MUCHEZ1 1Earth and Environmental Science, Katholieke Universiteit Leuven, Celestijnenlaan 200E, 3001 Heverlee, Belgium ABSTRACT The frequent occurrence of iron slag in excavation layers of the Hellenistic to Byzantine city of Sagalassos (SW Turkey), indicates continuous iron working from the 1st to 7th century A.D. The slag samples are identified as smithing hearth bottoms and are found in dump fills, building foundations, and road constructions. Although several smelting sites are present in the 1800 km2 large territory of the city, the chemical signature of the smelting slag does not correspond to the characteristics of the smithing slag found in the city itself. The smithing slag does offer insight in the smithing techniques applied, which in turn provides information about the objects produced and production chain or “chaîne opératoire” followed for iron production in Sagalassos. Textural and mineralogical analyses reveal two main smithing techniques that were applied throughout the 1st to 7th century A.D. The most commonly applied smithing technique is used for the production of simple bulk materials, like hammers or anvils. Microscopic textures in the slag show mainly mechanical deformation at relatively high temperatures. The second, more sophisticated smithing technique shows the blacksmith treated the iron at different temperatures. The presence of high-lime contents indicates the use of a flux and/ or a protective agent against oxidation. This technique was applied to make more complex objects or objects with cutting edges.
    [Show full text]
  • Crystal Structure and Some Thermodynamic Properties of Ca7mgsi4o16-Bredigite
    crystals Article Crystal Structure and Some Thermodynamic Properties of Ca7MgSi4O16-Bredigite Xinjian Bao 1,2 , Mingyue He 3, Zhigang Zhang 4 and Xi Liu 1,2,* 1 Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education of China, Beijing 100871, China; [email protected] 2 School of Earth and Space Sciences, Peking University, Beijing 100871, China 3 School of Gemmology, China University of Geosciences (Beijing), Beijing 100083, China; [email protected] 4 Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; [email protected] * Correspondence: [email protected] Abstract: Bredigite with the composition Ca7MgSi4O16 (Ca7MgSi4O16-Bre) has been synthesized by a solid-state reaction method at 1.2 GPa and 1373 K for 7 days, and its structure has been determined by single-crystal X-ray diffraction data. Following a relevant genealogy analysis in the literature, we have refined the structure into two space groups, Pnnm and Pnn2, and found that Ca7MgSi4O16-Bre belongs to the space group Pnnm, which can be essentially derived from the space group Pnn2 via an atomic coordinate transformation (with an average deviation of 0.039 Å only). Furthermore, some thermodynamic properties of the Ca7MgSi4O16-Bre have been obtained in this study. Using first-principles simulations based on density functional theory, the isothermal bulk modulus has been determined as 90.6(4) GPa with a pressure derivative of 5.7(1). Using density functional perturbation technique, the phonon dispersions and vibrational density of the states (VDoS) have been calculated.
    [Show full text]
  • Synthesis of Monticellite–Forsterite and Merwinite–Forsterite
    Originally published as: Remmert, P., Heinrich, W., Wunder, B., Morales, L. F., Wirth, R., Rhede, D., Abart, R. (2018): Synthesis of monticellite–forsterite and merwinite–forsterite symplectites in the CaO–MgO–SiO2 model system: influence of temperature and water content on microstructure evolution. ‐ Contributions to Mineralogy and Petrology, 173. DOI: http://doi.org/10.1007/s00410‐017‐1429‐y Contributions to Mineralogy and Petrology (2018) 173:5 https://doi.org/10.1007/s00410-017-1429-y ORIGINAL PAPER Synthesis of monticellite–forsterite and merwinite–forsterite symplectites in the CaO–MgO–SiO2 model system: influence of temperature and water content on microstructure evolution P. Remmert1 · W. Heinrich1 · B. Wunder1 · L. Morales1 · R. Wirth1 · D. Rhede1 · R. Abart2 Received: 17 September 2017 / Accepted: 28 November 2017 © The Author(s) 2017. This article is an open access publication Abstract Homogeneous single crystals of synthetic monticellite with the composition Ca0.88Mg1.12SiO4 (Mtc I) were annealed in a ◦ piston-cylinder apparatus at temperatures between 1000 and 1200 C , pressures of 1.0–1.4 GPa, for run durations from 10 min to 24 h and applying bulk water contents ranging from 0.0 to 0.5 wt% of the total charge. At these conditions, Mtc I breaks down to a fine-grained, symplectic intergrowth. Thereby, two types of symplectites are produced: a first symplectite type (Sy I) is represented by an aggregate of rod-shaped forsterite immersed in a matrix of monticellite with end-member composition (Mtc II), and a second symplectite type (Sy II) takes the form of a lamellar merwinite–forsterite intergrowth.
    [Show full text]
  • The Mineralogical Magazine
    THE MINERALOGICAL MAGAZINE AND JOUI~NAL OF THE MINERALOGICAL SOCIETY No. 214 September, 1951 Vol. XXIX The zoned contact-skarns of the Broadford area, Skye: a study of boron-fluorine metasomatism in dolomites. (With Plates XVIII-XXIV.) By C. E. TILLEY, Ph.D., F.R.S. Department of Mineralogy and Petrology, University of Cambridge. [Read in part June 24, 1948.] CONTENTS 1. Review of the progressive 5. Paragenesis of the skarn zones 644 metamorphism in the aureole 6. Productsoflimemetasomatism 652 of the Beinn an Dubhaich granite ............ 621 7. Contrasts of lime and iron- magnesia metasoma~ism in the 2. The skarn zones ...... 624 skarn successions ...... 658 3. Skarn successions associated 8. Comparison with the skarn with chert nodules ('sponge zones of other regions ...... 659 forms') ............ 632 Tables of mineral and rock analyses ......... 661 4. Mineralogy of the skarn zones 634 References ......... 663 1. REVIEW OF THE PROGRESSIVE METAMORPHISM IN THE AUREOLE OF THE BEIN~ AN DUBI~AIC~ GRA~IT~. N a preliminary note on the dolomite contaet-skarns of the Broadford I area, Skye (Tilley, 1948, a), a brief account was given of the constitu- tion and environment of these multizoned assemblages at the contact of the Durness limestone succession with the Tertiary Beinn an Dubhaich granite. 1 No detailed survey of the numerous parageneses was then attempted, and it is the purpose of the present paper to fill this gap and to discuss the genetic problems of these skarn assemblages. 1 The history of the discovery of these sk~rns and the exploratory work carried out during the 1939-45 war on some of the magnetite ore prospects has been indi- cated in the paper to which reference is now made.
    [Show full text]
  • Thermoluminescence Properties of Olivine
    2011 International Nuclear Atlantic Conference - INAC 2011 Belo Horizonte,MG, Brazil, October 24-28, 2011 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: 978-85-99141-04-5 THERMOLUMINESCENCE PROPERTIES OF OLIVINE Shigueo Watanabe1, Nilo F. Cano1,2, Luciana C. Matsushima2 Glauco Veneziane2 José 3 Roberto B. Paião 1 Instituto de Física, Universidade de São Paulo Rua do Matão, 187- travessa “R” 05508-090 – São Paulo-SP [email protected] 2 Instituto de Pesquisas Energéticas e Nucleares (IPEN / CNEN - SP) Av. Professor Lineu Prestes 2242 05508-000 São Paulo, SP [email protected] 3 Universidade São Judas Tadeu Rua Taquari, 546 – Mooca 03166-000 – São Paulo, SP ABSTRACT Green and black varieties of olivine of chemical formula, (Mg, Fe)2SiO4, obtained from Luiz Menezes Minerals in Belo Horizonte, MG, have been investigated as to some of their thermoluminescence (TL) properties. The X ray fluorescence analysis indicated that the black sample contains in weight %, SiO4 (44), MgO (33), Fe2O3 (11), Al2O3 (7), Cr2O3 (0.87), MnO (0.17) and other oxides in smaller amount; the green sample, in the same order of oxides, and in w%: 41, 39, 15, 3, 0.07, 0.21. The glow curve of green olivine presented a weak peak at about 150 °C, a stronger at 210 °C, a very intense at 350 °C and less intense at 430 °C, whereas the black one presented small peak at 150 °C, a stronger 200 °C and very broad peak around 350 °C. The optical spectrum of green olivine presented a strong UV absorption, violet and blue light absorption that decreases (in absorbance) gradually up to 500 nm, being minimum the absorbance from 500 to 600 nm (green color of the sample), an absorption band is observed peaking at around 1100 nm, decreasing from 250 nm up to 2500 nm.
    [Show full text]