Translation Gliding Research Articles

The structural evolution of dunite and chromite ore from the Kharcheruz Massif, the Polar Urals

The Kharcheruz block of the Syumkeu ultramafic massif is a southern fragment of the Khadata ophiolitic belt, which closes the ophiolites of the Polar Urals in the north. The block, striking in the latitudinal direction, is sheetlike in shape and primarily composed of dunite with nearly latitudinal zones of chromite mineralization. The dunites are subject to ductile deformation various in intensity, and this variability is displayed in their heterogeneous structure and texture. The following microstructural types are distinguished by the variety and intensity of their deformation: protogranular → mesogranular → porphyroclastic → porphyrolath → mosaic. The petrostructural patterns of olivines pertaining to the above types reflect conditions of ductile deformation. Protogranular dunite is formed as a product of pyroxene decomposition in mantle harzburgite accompanied by annealing recrystallization at a temperature above 1000°C. Mesogranular dunite is formed as a product of high-temperature plastic flow by means of translation sliding in olivine and diffuse creep at a temperature dropping from 1000 to 650°C and at a low rate ( 10–6 s–1). Dunite is deformed by means of syntectonic recrystallization and subordinate translation gliding. Linear zones of disseminated mineralization undergo destruction thereby, with the formation of lenticular chromitite bodies from which ductile olivine is squeezed out with the formation of densely impregnated and massive ores.

Preferred Mineral Orientation by Recrystallization under non-Hydrostatic Stress and Geotectonic Stress in the Upper Mantle

Significant elastic anisotropy of olivine single crystal is well known. The velocity of P waves has a maximum in the direction of crystallographic a-axis (identical to optical-acoustic Z-axis). It is also known that dunite and peridotite which are found at the central core of an orogenic zone have a strong tendency to preferred orientation of olivine. The preferred orientation of olivine and elastic anisotropy of dunite in the tectonic zone of Japan are measured optically and acoustically. The latter is carried out using the ultrasonic wave at high pressures. The direction dependence of P wave velocity is expressed by V, = a + b cos2 8, where the direction of 8 = 0 is found to be nearly equal to the direction of lineation which coincides statistically with the direction of a-axis concentration. Recently the existence of anisotropy of the uppermoFt mantle came to be convincing by analysing the results of seismic refraction profiles at the ocean bottom. The P wave velocity can be expressed empirically as V, = a + b cos2 8 where 0 is the azimuth to the perpendicular to the ridge direction. Here the observed seismic anisotropy is attributed to the regional preferred orientation of constituent minerals of rocks composing the upper mantle. The mechanism to produce preferred orientation is known to be either a recrystallization due to elastic anisotropy of minerals or a non-elastic effect such as gliding. In olivine the translation gliding in (010) plane is known. However, it does not seem that such a pure translation gliding can give rise to the significant preferred lattice orientation under stress. Let the preferred orientation of olivine aggregates be due to recrystallization. The stable mineral orientation is specified by the minimum condition of a certain thermodynamic function 4. It must be consistent with the stress and strain continuities at the grain boundary. According to our theory (1) and (2) 4 is represented by a sum of: (a) A function dependent upon a grain shape (interface configuration between grains) (first order). It plays a significant role in mineral orientation of tectonite. However, it is insensitive to the elastic anisotropy. (b) A linear function of deviatric stress component (second order). (c) A quadratic function of stress component (second order). Terms (b) and (c) are related to the stored energy and potential due to deformation and are dependent upon the stress-strain relation, while (a) is independent of stressstrain relation. The expression of C#J is shown in Table 1. Under high hydrostatic pressures greater than lOkb, term (b) becomes predominant. In the actual mineral aggregates, the grain boundary is not a plane, and the surface integral expression of 4 is necessary. To find the condition C#J = min the variational problem for the relative angle between the axis of anisotropy and the axis of external

Structure of melt flow channels in the mantle

Structural events during the formation of the mantle peridotite section in the Voikar-Syn’ya massif of the Polar Urals are considered. The structural units of the mantle section were formed during several deformation stages. Dunite bodies in restitic peridotites were formed in the course of deformation that completed the formation of large-scale folds of high-temperature plastic flow of mantle material. The final stage of deformation accompanied by migration of melt through harzburgite occurred in the shallow mantle in the setting of suprasubduction spreading related to the ascent of a mantle diapir. The rate of plastic deformation was relatively low. As a result, the intracrystal translation gliding of dislocations in olivine was the main mechanism in both harzburgite and dunite. The paths of focused melt flow are marked by dunite veins and associated pyroxenite and chromitite. It is suggested that stress concentration in fold hinges and their abrupt relaxation with formation of orthogonal network of weakened zones with high permeability was one of the possible mechanisms of the formation of melt conduits. The dispersed melt ascending from a great depth spontaneously migrated toward these zones. The distribution and structure of chromitite bodies reflect multistage formation of dunite, nonstationary dynamics of melt flow through restite, and abrupt variations of local stress fields in the areas adjacent to melt conduits.

807 GaAs ウエハの残留応力と結晶すべりの関係

We have developed equipment to measure optical birefringences in commercial LEC-grown GaAs (100) wafers by using a photoelastic modulator and a polarized laser. A He-Ne infrared laser was utilized as the light source for measurements of strain-induced birefringence in the GaAs wafers. The residual strain and stress components were calculated from the values obtained experimentally. The residual stress profiles have been evaluated to explain the correlation between the residual stress and thermal-stress-induced dislocation. It was found that the optical birefringence equipment developed for this study possessed the needed sensitivity to evaluate residual stress profiles of commercial GaAs (100) wafers. We have discovered the relation between the crystal gliding (translation gliding) and the process-induced stressesat 700℃ on GaAs (100) wafers.

Thermoluminescence as a scalar measure of plastic strain in experimentally and naturally deformed crystalline limestones

A number of studies have indicated that the thermoluminescence (TL) sensitivity of minerals changes with deformation. A new TL peak occurs in the case of calcite. It is currently known that plastic deformation of calcite and crystalline limestones results from intracrystalline twinning and translation gliding and a correlation is established between translation gliding and the new (TL) peak. In this work, experimental deformation under a system of triaxial cylindrical stresses is performed at room temperature. It is shown that loading causing dilatancy does not give rise to the TL peak while loading that results in constant volume plastic deformation favours its development. It is shown that this TL peak grows in proportion to increasing strain and thus can be considered as a marker of the plastic deformation. This TL development is applied to the study of rocks which are naturally deformed and the results are compared to data from tectonic studies. A relationship is established between the intensity of deformation of tectonic origin and the intensity of a particular thermoluminescence peak. This enables us to use thermoluminescence to classify naturally deformed limestones according to their relative plastic deformation.

Kinematics of experimentally produced deformation bands in stibnite

Using videotape techniques, we have observed the kinematic development of a variety of microstructures during experimental deformation of single crystals of stibnite (Sb 2S 3). The crystals were deformed by flexure or uniaxial compression at room P- T conditions in a small strain device attached to the stage of a reflecting microscope. In more than 50 experimental runs, the primary microstructures produced in stibnite were deformation bands, not deformation twins as often reported in the literature. Translation gliding along (010) [001] results in visible slipbands and produces two basic types of deformation bands, each with a variety of subtypes. Kink bands form with φ (angle of internal rotation) ≊70° and perpendicular bands develop with φ≊ 90°. Other optical deformation features seen forming were: breccia fragments, bent and opened cleavages, and microfolds. Four stages could be seen in the kinematic development of deformation bands. During initiation, bands form by nearly instantaneous propagation of a narrow bent zone across the crystal. During later migration, the bands widen at a rate invariably slower than the rate of initiation. Termination of bands occurs when growth is impeded by intersections with grain boundaries or other deformation features. During late modification, previously formed bands with straight boundaries are sheared, bent, and compressed. Unconfined crystals tend to form kinks, whereas the perpendicular bands formed in samples confined in relatively rigid plastic. Naturally deformed stibnites show the same features. Television photomicroscopy has great potential for studying microstructures during deformation.

Seismic anisotropy in the oceanic upper mantle: Evidence from the Bay of Islands Ophiolite Complex

Olivine fabrics in 17 field‐oriented ultramafics and mafics from three widely‐spaced traverses in the Bay of Islands Ophiolite Complex, Newfoundland, display a remarkably uniform symmetry in which the olivine a crystallographic axes are aligned subprependicular to the sheeted dikes and the b and c axes lie within the plane of the sheeted dikes. The ultramafics studied consist entirely of tectonites; any olivine formed at the ridge crest by cumulus processes has since been re‐oriented by translation gliding and/or syntectonic recrystallization. Deformation has extended from the ultramafics into the overlying gabbro, which suggests that in many oceanic regions the deepest levels of layer 3 consist of gabbroic tectonites. Compressional wave velocities computed from these petrofabrics display 5–6% anisotropy in the plane of the Mohorovičić discontinuity, with Vp fast parallel to the direction of spreading inferred from dike orientations. Since this pattern is identical to that observed for the oceanic upper mantle, it is concluded that the Bay of Islands Complex is a segment of oceanic crust and upper mantle. Shear wave velocity contours calculated from the same fabrics indicate that the upper mantle is nearly isotropic in terms of the maximum shear wave velocity, , but that the difference in velocity, ΔVs, between shear waves of orthogonal polarization traveling in the same direction may be sufficiently large parallel to the intersection of the Mohorovičić discontinuity and the sheeted dikes to allow detection of two distinct shear wave arrivals.

Brittle deformation of hornblende in a mylonite: A direct geometrical analogue of ductile deformation by translation gliding : Allison, I; La Tour, T E Can J Earth Sci, V14, N8, August 1977, P1953–1958

Brittle deformation of hornblende in a mylonite: A direct geometrical analogue of ductile deformation by translation gliding : Allison, I; La Tour, T E Can J Earth Sci, V14, N8, August 1977, P1953–1958

Experimental deformation of diopside and websterite

Diopside single-crystals, oriented favorably for twin gliding on both systems: (001) [100] and (100)[001] have been deformed in a Griggs apparatus using talc as pressure medium. The latter mechanism is dominant at temperatures ( T) below 1050° C at strain rates (ϵ) of 10 −3 sec −1, and below 800° C at ϵ ̇ = 10 −6 sec −1 ; at higher temperatures translation gliding on (100)[001] accompanied by syntectonic recrystallization is dominant but other glide systems also operate. Tests at a single set of conditions, T- and ϵ-incremental tests and stress-relaxation experiments have been carried out on websterite (68% CPX, 32% OPX), both in talc (“wet”) and talc-AlSiMag (“dry”) assemblies. Most tests were performed in the high-T regime, where syntectonic recrystallization and “relatively nonselective” glide are dominant. The mean size of recrystallized clinopyroxenes ( D, μ m ) appears to be related to stress (σ, kb) as D = 60σ −0.9 . The mechanical data fit the power law ϵ ̇ = A exp(-Q/RT)σ n , where for the “wet” experiments A = 10 5.9 kb −n sec −1 , Q = 91.2 kcal/mole , n = 5.3; for σ < 3.5 kb n appears to decrease to 3.3. For the “dry” experiments A = 10 2.2, Q = 77.9 , and n = 4.3 for σ < 7.0 kb. Clinopyroxene in the upper mantle occurs as ca. 0–15% mixed phase in peridotites and websterites occur as thin layers. Stresses in these materials will then be near those in the olivine-rich matrix. At ϵ ̇ = 10 −14/ sec , the equivalent viscosity of dry websterite is less than that of dry dunite at depths to 60 km but it increases rapidly at higher pressures; at 240 km it is 10 6 greater than that of dunite. This may account for the low strains and passive behavior observed for clinopyroxene crystals in most peridotites and websterites, that presumably have formed at great depth. Attenuated folds of websterite in peridotite—evidence of more ductile behavior—may then have formed at shallower levels; alternatively they may have formed under “wet” conditions.

Brittle deformation of hornblende in a mylonite: a direct geometrical analogue of ductile deformation by translation gliding

Hornblende in a mylonitic rock from the Grenville front has deformed by fracture and slip on a parting subnormal to the c crystallographic axis. Rotation of the fragments during progressive deformation produced a preferred orientation of poles to the slip plane. When this slip plane had rotated close to the plane of the foliation, slip occurred on a second plane. This process is envisaged as being analogous to translation gliding in crystals.

The Kenna ureilite: an ultramafic rock with evidence for igneous, metamorphic, and shock origin

The Kenna ureilite was found in February, 1972 near the town of Kenna, Roosevelt County, New Mexico U.S.A., weighed 10.9 kg, and measured 26.7 × 14.7 × 14.2 cm; it is the seventh known ureilite. The meteorite is composed of xenoblastic olivine (Fo 79.2), commonly rimmed by forsterite (Fo 99), and pigeonite (En 73Wo 9Fs 18), in a volumetric ratio of 3:1, set in a matrix of three carbon polymorphs (graphite, lonsdaleite, and diamond) plus nickel-iron metal and troilite. Some thin metalliferous veins penetrating silicate grains contain secondary inclusions of melt with high-calcium clinopyroxene (high-Ca, Mg-rich augite to augite), andesine, K-feldspar, chromite, and siliceous CaO- and alkali-rich glasses of variable compositions. Textural, mineralogical and fabric information suggest a complex history for Kenna, involving igneous, metamorphic and shock processes. The rock appears to have originated as an ultramafic cumulate whose texture and structure was modified by adcumulus processes and by solution and redeposition in a weak deviatoric stress field. A strong mineral elongation lineation was produced during this high-temperature phase accompanied by mild plastic deformation of olivine on the system 0kl[100]. Superimposed on this original texture and fabric are processes resulting from light to moderate (50–250 kbar) shock deformation, as manifested by fracturing of the silicates, slip parallel to (001) in olivine, and twin and translation gliding parallel to (100) in the clinopyroxene. Lonsdaleite and diamond probably formed during this shock phase, which may be associated with the break-up of the parent body, but the relative time of introduction of the carbon-rich matrix is still unresolved.

Sulfide deformation studies; III, Experimental deformation of chalcopyrite to 2,000 bars and 500 degrees C

Single crystals and aggregates of natural chalcopyrite were deformed under controlled conditions of temperature (24 degrees to 500 degrees C), confining pressure (500 to 2,000 bars), and strain rate (constant 7.2 X 10 (super -5) sec (super -1) ) in several series of experiments designed to test the deformational properties of this mineral under shallow tectonic conditions.At low temperature, chalcopyrite deforms by cataclasis combined with translation gliding on {112} and {112} . Polysynthetic deformation twinning, also on {112}, begins at 100 degrees C (at 500 bars) and becomes increasingly abundant at higher temperatures with a consequent loss of strength, increase in ductility, and decrease in cataclasis. True kinking is very rare in chalcopyrite. Likewise, no new grains or subgrains were observed in any of these deformation experiments. At room temperature, the strength and ductility of chalcopyrite increase with confining pressure, but at elevated temperatures the effects of confining pressure are greatly subordinate to those of the temperature itself. At the constant strain rate employed, the brittle-ductile transition in chalcopyrite takes place between 1,000 and 1,500 bars confining pressure at room temperature and below 500 bars at 200 degrees C. As temperature increases, the ductility of chalcopyrite is enhanced and its strength is greatly reduced. For example, at 1,000 bars confining pressure the strength drops from nearly 5,000 bars at room temperature to less than 1,000 bars at 500 degrees C. Even further reductions in strength would accompany the slower strain rates that prevail in nature (see Roscoe, 1975).Originally undeformed chalcopyrites were studied by both optical and scanning electron microscopy before and after experimental deformation for unambiguous evidence of deformation features. Chalcopyrite deformed at room temperature shows various types of shear and extension fractures whose orientation reflects the known stress field and whose intensity is strongly controlled by original twin and grain orientations. These cataclastic features persist but become subdued at higher temperatures. No deformation twins were seen in any room temperature run. Abundant {112} slip lines can be seen in crystal faces deformed at 24 degrees C but are not visible in these same faces after polishing and etching. At temperatures of 100 degrees C and higher, chalcopyrite develops polysynthetic {112} deformation twins that are readily distinguished from original {110} and {102} twins of nondeformational origin. Complex patterns and sequences of intragranular features arise where the {112} deformation twinning is superposed on a fabric of original growth twins, lensatic twins, and exsolution intergrowths. These features and their age relations could be clearly observed, and easily applied, in the analysis of naturally deformed sulfide deposits.These and earlier experiments (Clark and Kelly, 1973; Salmon et al., 1974) demonstrate that the relative strengths of chalcopyrite, pyrrhotite, sphalerite, and galena are dependent upon the conditions under which these minerals are deformed. If, under simplified laboratory conditions, these sulfides undergo pronounced changes and even reversals in strength as one variable, temperature, is changed, it is unreasonable to expect any single ranking of strength, mobility, or plasticity to be universally applicable to all naturally deformed sulfide deposits.

Preferred orientation in experimentally deformed dolomite

Fine grained dolomite has been deformed in over twenty compression experiments in a Griggs-type piston-cylinder apparatus at various P and T conditions. Preferred orientation determined quantitatively using X-ray techniques and spherical harmonic analysis of the data is presented in inverse pole-figures of — 2/m symmetry. In most cases specimens display strong preferred orientation which varies mainly as a function of temperature. At all conditions it is very different from calcitic limestone. Although there is no significant grain growth even at 1000 °C the simple c-axes maximum fabric above 700 °C might be the result of recrystallization or translation on c. Below 700 °C, the preferred orientation is much weaker and complex. The primary maximum in the inverse pole-figure is near e, a secondary maximum near a high angle positive rhomb, principal minima are at c and f. This inverse pole-figure is consistent with f-twinning and translation gliding on r (t = a ?), two mechanisms which counteract each other. The latter is a new deformation mechanism for dolomite which we propose in order to explain the pattern of preferred orientation. The minimum at c is less pronounced below 100 ° C suggesting that c-translation may be active, but in these fine-grained aggregates it appears to be less important than is expected from single crystal experiments (Higgs and Handin, 1959), at least at low temperatures.

Strain, fractures, and pressure solution in natural single-layer folds

Research Article| October 01, 1975 Strain, fractures, and pressure solution in natural single-layer folds R. H. GROSHONG, JR. R. H. GROSHONG, JR. 1Cities Service Oil Company, Exploration & Production Research, Box 50408, Tulsa, Oklahoma 74150 Search for other works by this author on: GSW Google Scholar Author and Article Information R. H. GROSHONG, JR. 1Cities Service Oil Company, Exploration & Production Research, Box 50408, Tulsa, Oklahoma 74150 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1975) 86 (10): 1363–1376. https://doi.org/10.1130/0016-7606(1975)86<1363:SFAPSI>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R. H. GROSHONG; Strain, fractures, and pressure solution in natural single-layer folds. GSA Bulletin 1975;; 86 (10): 1363–1376. doi: https://doi.org/10.1130/0016-7606(1975)86<1363:SFAPSI>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Intragranular strain has been measured by the twinned calcite strain-gage technique from the hinges and limbs of three single-layer minor folds with limb dips of 15°, 48°, and 67°. The folds are in unmetamorphosed, Silurian-age limestone beds enclosed in shale, in the Appalachian Valley and Ridge province of central Pennsylvania. In all three folds, the maximum compressive strain axes are subparallel to bedding and tend to plunge toward the inner arcs of the hinges. The principal deviatoric compressive strains in the fold cross sections range from −0.48 ± 0.77 to −4.75 ± 0.78 percent; the largest compressive strains are in the gentlest fold and the smallest ones are in the tightest fold. Syntectonic stylolites are abundant in the folds and approximate a fanning cleavage. Filled extension fractures occur normal to bedding on the outer arc of the hinges of the two tightest folds. Filled fractures on the limbs of the same folds began as extension fractures subparallel to bedding and evolved into throughgoing thrust faults. A significant amount of the folding deformation is evidently accomplished by pressure solution and by displacement on fractures.The folds are interpreted as buckle folds and distinguished from transverse bends and passive folds on the basis of the mechanical contrast between the limestone and enclosing shale beds and the orientation and distribution of the principal strain axes, stylolites, and fractures. The orientations of the principal strain axes are best fit by buckle-fold models. Strain models of pure bending, layer-parallel shear, and shear parallel to the hinge plane are shown to be inadequate by themselves even as first-order approximations.A simple rheological model including intragranular strain (twin and translation gliding, grain boundary adjustments) and pressure solution fits the inferred relationships between these features. The model presumes that intragranular strain has a yield stress, whereas pressure solution does not, and that at high stresses pressure solution is more important than intragranular strain. The model predicts that when conditions are suitable for pressure solution, more of the strain will occur by this mechanism than by twin gliding and related mechanisms. This can explain the overall low values of measured intragranular strain. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Hornblende deformation features

We have plastically deformed hornblende in laboratory compression experiments. (101) twinning is a prominent deformation mechanism in single-crystal tests. The twin system is K 1 = (101), N 1 = (101), K 2 = (100), N 2 = [001]. Translation gliding has also been induced on the system T = (100), t = [001]. Although intragranular plastic deformation effects are not commonly observed in naturally deformed hornblende, we describe features in amphibolite from the southwestern Alps that are similar to those produced experimentally.

Mechanisms of preferred orientations of olivine in tectonite peridotite

Preferred orientations of olivine have been produced by syntectonic recrystallization in dunite samples that have been deformed moderately in a general stress field at high temperatures and pressures: X -olivine maxima ( X = [010]) developed parallel to σ 1 and Z -olivine maxima ( Z = [100]) developed parallel to σ 3 . Similar fabrics are expected to form by mechanical rotation due to translation gliding on (010)[100], but much larger strains are required. The experimental results indicate that the orientation patterns are caused by preferred growth of newly formed nuclei that have low coefficients of resolved shear stress for slip on (010)[100].

Preferred orientation in experimentally deformed limestone

Over sixty syntectonic deformation experiments in uniaxial compression have been done on fine-grained limestones in the stability fields of calcite I, calcite II and aragonite. X-ray techniques and spherical harmonic analysis of the data were used to determine preferred orientation quantitatively, and inverse pole-figures were derived for these axially symmetric specimens. They display in most cases strong preferred orientation which varies as a function of the experimental conditions, mainly temperature and pressure. At temperatures below 350° C recrystallization is lacking and flattened grains indicate that translation, twin gliding and kinking have been the dominant deformation mechanisms. The inverse pole-figure shows a maximum at c with a shoulder towards or a second maximum at e. This is in agreement with preferred orientation observed in experimentally deformed Yule marble and can be explained as the product of dominant twin gliding on e and translation gliding on r (Turner et al., 1956). At high temperatures (900–1000° C) strong grain growth (from 4 to 50 microns) indicates that the fabric recrystallized. Grains are equidimensional and clear with a marble-like texture. The inverse pole-figure shows a single maximum at r, and c-axes are oriented in a small circle around the axis of compression, σ1. Such a pattern of preferred orientation would be expected on thermodynamic grounds assuming that recrystallized grains will be oriented in such a way that the strain energy is a maximum (e.g. MacDonald, 1960). Decrease in confining pressure caused a decrease of the maximum at c and the formation of a secondary maximum at highangle positive rhombs in the inverse pole-figure. This can be interpreted as r translation dominating over e twinning. In all deformation experiments an equilibrium in preferred orientation was reached after 20 percent shortening. The strength of preferred orientation decreased with increasing temperature. Aragonite was produced within its hydrostatic stability field at temperatures above 500° C. Close to the phase boundary, coarse-grained textures showed preferred orientation with poles to (010) parallel to σ1. At higher pressures the fabric is fine-grained and [001] is aligned parallel to σ1. Evidence is given that the phase change from calcite to aragonite in these deformation experiments is a diffusive and not a martensitic transformation.

Deformation und Gef�geregelung von Steinsalz im Temperaturbereich 20?200� c

Cubic specimens of fine-grained artifical polycristalline rock salt were deformed at different principal stresses in the range of 20–200° C. The data from different types of tests are compared by plotting σ1–σ3 against ɛ1, ɛ2, ɛ3. The deformation behavior is highly influenced by the intermediate principal stress σ2. An increase of the intermediate stress from compression (σ1>σ2=σ3) to extension (σ1=σ2>σ3) lowers the rate of deformation. An increase of temperature always gives rise to an increase of deformation rate. Translation gliding on (110) is assumed to be the dominant flow mechanism. Textural changes and development of preferred orientation were investigated by means of the X-ray diffractometer. Intensities were measured for (110), (111), and (100). Compression leads to girdle occupations about the unique principle compressive axis, extension to girdles about the unique principle axis of extension. When all principle stresses are different the polfigures tend to a position intermediate between the two occupations.

Steady-State Flow in Marble at 500° to 800°C

The stress-strain behavior of Yule marble, both parallel and normal to the foliation, has been determined in a series of constant strain-rate extension tests at 5000 bars confining pressure, at temperatures of 500° to 800° C and at strain rates ranging from 10−3 to 10−7/sec. These data correlate well with earlier results at 25° to 500° C and l0−1 to 10−8/sec. Steady-state flow is dominant at 400° C and rates <10−7/sec, at 500° C < 10−4/sec, and at all strain rates at higher temperatures. Transient flow (work hardening) is prevalent at lower temperatures and higher rates. Transmission and reflection microscopy as well as etch-pit studies reveal that translation gliding on r, f and twinning on e are dominant in the transient region, becoming less prominent in the steady-state region at high temperatures. Polygonization by dislocation climb becomes characteristic in the steady-state flow region, along with intergranular and intra-granular recrystallization. Grain boundary sliding is present, but of minor importance. The effect of temperature and strain rate on the mechanical behavior, as well as on the correlation of subgrain formation and recrystallization with steady-state flow, is consistent with a diffusion-controlled process. Comparison of the data with several models for diffusion-controlled flow show poor correlation with the Eyring equation, e = A exp ( −E/RT) sinh (Bσ), but excellent correlation with the Weertman equation, e = C exp ( −E/RT) <σN. The activation energy E and the stress exponent N are nearly identical for both orientations of this highly anisotropic marble, and thus this material becomes nearly isotropic (mechanically) for steady-state flow. On the basis of the empirical-flow equation, extrapolations to representative natural strain rates of 3 × 10−14/sec predict stresses of 103 bars at 250° C, ranging to about 30 bars at 700° C. Work-hardening can be expected at these rates at temperatures <250° C; in this region, this marble is expected to be mechanically anisotropic. Calculated equivalent viscosities at natural strain rates range from 3 × 1022 poises at 25° to 4 × 1020 poises at 700° C.

Textures, structures and fabrics due to solid state flow in some European lherzolites

Structures, textures and fabrics caused by solid state flow in lherzolites are described with special reference to the Lanzo Massif (Italian Alps). Extension and shearing movements have produced a foliation, which, for the case of inhomogeneous deformation is developed in the axial surface of shear folds. High simple shear angles have been estimated. The “b” kinematic direction is evidenced in the field by an enstatite lineation. The flow mechanism responsible for the development of the main subfabric is considered to be translation gliding in olivine and enstatite. Syntectonic and annealing recrystallizations are also present; they commonly result in a distinct subfabric.