نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 52
پرینت

Ferric iron in sapphirine:a Mtissbauers pectroscopisct udy
G. SrerrBN, F. Selrenr
Mineralogisches Institut der Universitdt, Kiel, Germany
rNo G. ArrlrHnupn
Mineralogisches Institut der Universitrit, Marburg, Germany

 

Abstract
Substitution of ferric iron for aluminum in the sapphirine structure extends up to an approximate composition Mg:sf'ei.1etr3Si15 026 at ll50'C, 2 kbar and high oxygen fugacities.T he sapphirinesc oexistw ith Fe3*-bearingc orundum,F e3*-bearings pinelsa nd cordierite. By comparing the hyperfine parameters of 57Fe in sapphirine with those reported for other crystal structures, Fe3* is assigned to the tetrahedral positions in sapphirine.

ادامه مطلب: Ferric iron in sapphirine:a Mtissbauers pectroscopisct udy
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 54
پرینت

Extinction angles for monoclinic amphiboles or pyroxenes: a cautionary note
Ssu-CHuN Sul'2 nuo F. D. Blossl
Department of Geology, University of New Mexico
Albuquerque, New Mexico 87131


Abstract
For monoclinic crystals with b = Y, extinction angles measured relative to a {ll0}cleavagetr acew ill equalt he optic orientationa ngleZ A c (or X A c) only for (010)s ections.Such sections are best recognized from display of a centered optic normal figure and, as long known, are not necessarilyth e sectioni n the [001]z one that exhibitst he maximum extinctiona ngler elative to the {ll0} cleavaget race. Such maximume xtinctiona nglesa re herep rovedt o exceedZ Ac(or X A c) for optic orientationsw hereb

ادامه مطلب: Extinction angles for monoclinic amphiboles or pyroxenes: a cautionary note
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 46
پرینت

Experimental delineation of the Cl = /1 transformation in intermediate plagioclasef eldspars
MrcHeer A. Ca.npBNTER AND J. DesuoNo C. McCoNxBn
Department of Earth Sciences, (Jniversity of Cambridge
Downing Street, Cambridge CB2 3EQ, England


Abstract
The Cl = 11 AySi order/disorder transformation in intermediate plagioclase feldspars has been experimentally bracketed by dry and hydrothermal annealing of natural samples in the composition range An56An6s. It can be represented on the albite-anorthite binary phase diagram by a steep line passing through the points -Anss, lfi)0"C and -An77, 1440"C (where it meets the one atmosphere solidus). The transformation appears to be characterized by a change from long range order (sharp D reflections in electron diffraction patterns) to short range order (diffuse D reflections) over a fairly narrow temperature interval.

ادامه مطلب: Experimental delineation of the Cl = /1 transformation in intermediate plagioclasef eldspars
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 53
پرینت

Enumeration of 4-connected 3-dimensional nets and classification of framework silicates:
linkagesf rom the two (52.8)2(5.822)1D nets
JosBpH V. Smith
Department of the Geophysical Sciences
The University of Chicago, Chicago, Illinois 60637
aNo J. Mrcnepr Br,NNerr
Union Carbide Corporation
Tarrytown, New York 10591

 

Abstract
Two topologically distinct 3-connected 2D nets can be developed from pentagons and octagons, and the centered one can be distorted into an oblique net which is polytypic with the zigzag net. Many infinite series of polytypic 4-connected 3D nets were enumerated by addition of updown linkagest o the 3-connectedn odes,a nd by conversiono f horizontal branches of the two 2D nets into crankshaft and zigzag chains.

ادامه مطلب: Enumeration of 4-connected 3-dimensional nets and classification of framework silicates:...
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 47
پرینت

Entropies of kyanite, andalusite, and sillimanite: additional constraints on the pressure and temperature of the Al2SiOs triple point
Rrcneno A. Rosrp eNo Bnuce S. HrurNcwey
U.S. Geological Survey
959 National Center, Reston, Virginia 22092

Abstract
The low-temperature heat capacities of kyanite (Minas Gerais, Brazil), andalusite (Espirito Santo, Brazil), and sillimanite (Reinbolt Hills, Antarctica) were measured with an automatic, adiabatically shielded calorimeter between approximately l0 and 380 K. At 29E.15K the entropiesa re E2.30-r0.139, 1.39-+0.14a,n d 95.79-ro.l4J /(mol. K) for kyanite, andalusite, and sillimanite, respectively. our values are 1.8, 2.0 and0.4vo smaller than those of Todd (1950).

ادامه مطلب: Entropies of kyanite, andalusite, and sillimanite: additional constraints on the pressure and...
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 55
پرینت

The jeweler's refractometer as a mineralogical tool
C. S. HunrBUl, Jn.
Department of Geological Sciences
Harvard (Jniversity, Cambridge, Massachusetts 02138

Abstract

The jeweler's refractometer ofers a simple method of determining the refractive indices of any mineral having a single polished surface of at least I mm2 to a precision of about 0.fi)2. For some crystallographic orientations of the polished surface of anisotropic crystals, it is necessary to determine the angles the vibration directions of the measured refractive indices make with the polished surface.

ادامه مطلب: The jeweler's refractometer as a mineralogical tool
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 72
پرینت

Sinkankasite, a new phosphate from the Barker pegmatite, South Dakota
DoNero R. Pencon    -    Department of Geological Sciences
University of Michigan, Ann Arbor, Michigan 48109  -   Pere J. DUNN
Department of Mineral Sciences   -   Smithsonian Institution, Washington, D.C. 20560
Wrrrnno L. Rosenrs, THoMAs J. CnMpenrl  -   Museam of Geology
South Dakota School of Mines and Technologl   -    Rapid City, South Dakota 57701
eNo WIlua,u B. SIuruoNs    -    

Department of Earth Sciences
University of New Orleans, New Orleans, Louisiana 70148

Abstract

Sinkankasite, ideally HzMnAl(POa)z(OH) . 6HzO, is a new mineral occurring as an alteration product of triphylite at the Barker pegmatite, Keystone, South Dakota. It is triclinic, spaceg roupP T or Pl, with cell parametersa = 9.58(4,) b :9.79(5), c : 6.88(4)4, a : 108.1(2)p,: gg.6(3)y, :98.7(3)',V :

ادامه مطلب: Sinkankasite, a new phosphate from the Barker pegmatite, South Dakota
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 55
پرینت

Memorial of Earl V. Shannon
1895-1981
PBrn J. DUNN euo Jeur,s A. FBRnetolo
Department of Mineral Sciences
Smithsonian Institution, Washington, D. C. 20560

The death of Earl V. Shannon in Hampton, Virginia on October 23, l98l , marked the passing of one of the more talenteda nd energeticm ineralogistso f the early part of this century. Earl Shannon was born in Idaho on February 16, 1895,a ndr esidedi n Kellogg,I daho for mosto f his youth.

ادامه مطلب: Memorial of Earl V. Shannon
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 57
پرینت

Geochemical evolution of topaz rhyolites from the Thomas Range and Spor Mountain, Utah
Eruc H. CnnrsrrausBNl. Jnuns V. BrruN2. MrcHRnr F. SspnroaN AND Doxnro M. Bunr
Department of Geology, Arizona State University
Tempe, Arizona 85287

Abstract

Two sequences ofrhyolite lava flows and associated pyroclastic deposits are exposed in the Thomas Range (6 m.y.) and at Spor Mountain (21 m.y.) in west-central Utah. Both contain topaz indicative of their F-enrichment (>0.2%) and aluminous nature. The rhyolites are part of the bimodal sequence of basalt and rhyolite typical of the region. Moderate changes in major elements coupled with large variations in trace elements in vitrophyres from the Thomas Range are generally consistent with fractionation of observed phenocrysts.

ادامه مطلب: Geochemical evolution of topaz rhyolites from the Thomas Range and Spor Mountain, Utah
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 52
پرینت

Diffraction study of annealing of metamict samarskite
Luowrc KelLenl
Department of Materials Science and Engineering
School of Engineering and Applied Science
University of California, Los Angeles
Los Angeles, California 90024

Abstract
X-ray difraction of metamict samarskite, heated in air for 15 min above its crystallization temperatureo f 870'C, indicatest hat its premetamicts tructurei s not restored.I nstead,t he heatingr esultsi n the formationo f threes toichiometricp hasesw hich are (Y,RE)(Nb,Ta)o+,FeNbOaa nd UrOs' 1.5Nb2O5B. roadeningo f X-ray line profileso f the crystalliner eaction productsi s analyzeda s stressb roadeningc ausedb y new phasen uclei.

ادامه مطلب: Diffraction study of annealing of metamict samarskite
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 69
پرینت

Davreuxite: a reinvestigation
ANonE-MerHrEU FRaNsorBr
Institut de Mindralogie
Universiti de Liige, Place du Vingt-Aofit, 9
84000 Lidge, Belgium
Kunr Annc,HeM AND KURT SAHL
Institut fiir Mineralogie, Ruhr-Universitrit
Bochum, Postfach 102148, D4630 Bochum l, F. R. Germany

Abstract
Davreuxite from Ottr6, Belgium, occurs as fibrous masses in quartz veins intimatelyassociated with pyrophyllite and kaolinite. These quartz veins cross-cut the low-grade metamorphicm anganese-richro cks of Ordovician age of the Stavelot Massif, and also contain andalusite, ottrelite or chloritoid, sudoite, hematite, pyrophyllite, chlorite.

ادامه مطلب: Davreuxite: a reinvestigation
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 62
پرینت

Crystal structure of ilmenite (FeTiOs) at high temperature and at high pressure
B,q,nny A. WecHsr-Enl ANo Cnenr_rs T. pnewrrr
Department of Earth and Space Sciences
State University of New York
Stony Brook, New York 11794

Abstract
The structures of two single crystals of synthetic ilmenite were refined using X-ray intensity data collected at24,4ffi,600, 800, and 1050'c (l atm) and 0.fi)1, 25.4,34.6, and 46.1 kbar (room temperature). Thermal expansion of the unit cell was nearly isotropic, whereas compression was relatively anisotropic, with cla decreasing linearly with incriasing pressure.

ادامه مطلب: Crystal structure of ilmenite (FeTiOs) at high temperature and at high pressure
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 60
پرینت

Donpeacorite,( MnrMg)MgSi2O61r n€\il orthopyroxenea nd its proposedp hase relations in the system MnSiO3r-MgSiO3-FeSiO3'
Enrcn U. PBrr,nseN.2L ewneNce M. ANovrrz, nNo Enrc J. EsseNn
Department of Geological Sciences
University of Michigan, Ann Arbor, Michigan 48109

Abstract
A Mn-rich orthopyroxene Mgl.alMns.5oCao.orSizOocec, urs in a manganiferousp od in the marble units near Balmat, N. Y. The pyroxene coexists with triodite, tourmaline, ferrian braunite, manganoan dolomite , and hedyphane. Refinement of the crystal structure of the pyroxene (space group Pbca) shows that as expected virtually all of the Mn is located in the M2 site and the general formula is therefore (Mn,Mg)MgSi2O6.

ادامه مطلب: Donpeacorite,( MnrMg)MgSi2O61r n€\il orthopyroxenea nd its proposedp hase relations in the system...
 
نوشته شده توسط سيداحمدخزايي دسته: Geology (زمين شناسي)
نمایش از 12 مرداد 1392 بازدید: 69
پرینت

Crystal structure of germanite, Cu26GeaFeaS32,determined by powder X-ray diffraction
RooNry T. Tr,rreNHoRST AND Cuenlr,s E. ConeA,r6
Department of Geology and Mineralogy
The Ohio State University, Columbus, Ohio 43210

Abstract
The crystal structure of germanite has been refined in space group 218, P43n, to a
weightedR of 3.60Vofr om 66 powder X-ray diffractionr eflections.T he structured eviates only slightly from a body-centered lattice type and is a modification of the sphalerite structure. The cubic cell dimension is 10.5862(5tA. fne ideal chemical formula is Cu26GeaFeaSa3n2a, logoust o the formula proposedf or colusiteb y Orlandi et al. (1981).

ادامه مطلب: Crystal structure of germanite, Cu26GeaFeaS32,determined by powder X-ray diffraction
 

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