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Journal articles on the topic 'Calcite twins'

Author: Grafiati

Published: 25 May 2024

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1

Lacombe, Olivier, Camille Parlangeau, Nicolas E. Beaudoin, and Khalid Amrouch. "Calcite Twin Formation, Measurement and Use as Stress–Strain Indicators: A Review of Progress over the Last Decade." Geosciences 11, no. 11 (October 28, 2021): 445. http://dx.doi.org/10.3390/geosciences11110445.

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Mechanical twins are common microstructures in deformed calcite. Calcite twins have been used for a long time as indicators of stress/strain orientations and magnitudes. Developments during the last decade point toward significant improvements of existing techniques as well as new applications of calcite twin analysis in tectonic studies. This review summarises the recent progress in the understanding of twin formation, including nucleation and growth of twins, and discusses the concept of CRSS and its dependence on several factors such as strain, temperature and grain size. Classical and recent calcite twin measurement techniques are also presented and their pros and cons are discussed. The newly proposed inversion techniques allowing for the use of calcite twins as indicators of orientations and/or magnitudes of stress and strain are summarized. Benefits for tectonic studies are illustrated through the presentation of several applications, from the scale of the individual tectonic structure to the continental scale. The classical use of calcite twin morphology (e.g., thickness) as a straightforward geothermometer is critically discussed in the light of recent observations that thick twins do not always reflect deformation temperature above 170–200 °C. This review also presents how the age of twinning events in natural rocks can be constrained while individual twins cannot be dated yet. Finally, the review addresses the recent technical and conceptual progress in calcite twinning paleopiezometry, together with the promising combination of this paleopiezometer with mechanical analysis of fractures or stylolite roughness.

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2

Parlangeau, Camille, Alexandre Dimanov, Olivier Lacombe, Simon Hallais, and Jean-Marc Daniel. "Uniaxial compression of calcite single crystals at room temperature: insights into twinning activation and development." Solid Earth 10, no. 1 (February 7, 2019): 307–16. http://dx.doi.org/10.5194/se-10-307-2019.

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Abstract. E-twinning is a common plastic deformation mechanism in calcite deformed at low temperature. Strain rate, temperature and confining pressure have negligible effects on twinning activation which is mainly dependent on differential stress. The critical resolved shear stress (CRSS) required for twinning activation is dependent on grain size and strain hardening. This CRSS value may obey the Hall–Petch relation, but due to sparse experimental data its actual evolution with grain size and strain still remains a matter of debate. In order to provide additional constraints on twinning activation and development, new mechanical tests were carried out at room temperature on unconfined single crystals of calcite, with different sizes and crystallographic orientations. Uniaxial deformation was performed at a controlled displacement rate, while the sample surface was monitored using optical microscopy and a high-resolution CCD (charge-coupled device) camera. The retrieved macroscopic stress–strain behavior of the crystals was correlated with the surface observations of the deformation process. Results show (1) the onset of crystal plasticity with the activation of the first isolated mechanical twins during the strain hardening stage, and (2) the densification and thickening of twin lamellae during the steady-state flow stress stage. Such thickening of twin lamellae at room temperature emphasizes that calcite twin morphology is not controlled solely by temperature. The different values for the CRSS obtained for the activation of isolated twins and for the onset of twin densification and thickening raises questions regarding the appropriate value to be considered when using calcite twin data for stress inversion purposes.

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3

Schuster, Roman, Gerlinde Habler, Erhard Schafler, and Rainer Abart. "Intragranular deformation mechanisms in calcite deformed by high-pressure torsion at room temperature." Mineralogy and Petrology 114, no. 2 (January 7, 2020): 105–18. http://dx.doi.org/10.1007/s00710-019-00690-y.

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AbstractPolycrystalline calcite was deformed to high strain at room-temperature and confining pressures of 1–4 GPa using high-pressure torsion. The high confining pressure suppresses brittle failure and allows for shear strains >100. The post-deformation microstructures show inter- and intragranular cataclastic deformation and a high density of mechanical e$$ \left\{01\overline{1}8\right\} $$011¯8 twins and deformation lamellae in highly strained porphyroclasts. The morphologies of the twins resemble twin morphologies that are typically associated with substantially higher deformation temperatures. Porphyroclasts oriented unfavorably for twinning frequently exhibit two types of deformation lamellae with characteristic crystallographic orientation relationships associated with calcite twins. The misorientation of the first deformation lamella type with respect to the host corresponds to the combination of one r$$ \left\{10\overline{1}4\right\} $$101¯4 twin operation and one specific f$$ \left\{01\overline{1}2\right\} $$011¯2 or e$$ \left\{01\overline{1}8\right\} $$011¯8 twin operation. Boundary sections of this lamella type often split into two separated segments, where one segment corresponds to an incoherent r$$ \left\{10\overline{1}4\right\} $$101¯4 twin boundary and the other to an f$$ \left\{01\overline{1}2\right\} $$011¯2 or e$$ \left\{01\overline{1}8\right\} $$011¯8 twin boundary. The misorientation of the second type of deformation lamellae corresponds to the combination of specific r$$ \left\{10\overline{1}4\right\} $$101¯4 and f$$ \left\{01\overline{1}2\right\} $$011¯2 twin operations. The boundary segments of this lamella type may also split into the constituent twin boundaries. Our results show that brittle failure can effectively be suppressed during room-temperature deformation of calcite to high strains if confining pressures in the GPa range are applied. At these conditions, the combination of successive twin operations produces hitherto unknown deformation lamellae.

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4

Mirijam, Vrabec, Rogan Šmuc Nastja, and Vrabec Marko. "Calcite deformation twins in Pohorje marbles." Geologija 61, no. 1 (July 20, 2018): 73–84. http://dx.doi.org/10.5474/geologija.2018.005.

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5

Németh, Péter. "Diffraction Features from (101¯4) Calcite Twins Mimicking Crystallographic Ordering." Minerals 11, no. 7 (July 4, 2021): 720. http://dx.doi.org/10.3390/min11070720.

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During phase transitions the ordering of cations and/or anions along specific crystallographic directions can take place. As a result, extra reflections may occur in diffraction patterns, which can indicate cell doubling and the reduction of the crystallographic symmetry. However, similar features may also arise from twinning. Here the nanostructures of a glendonite, a calcite (CaCO3) pseudomorph after ikaite (CaCO3·6H2O), from Victoria Cave (Russia) were studied using transmission electron microscopy (TEM). This paper demonstrates the occurrence of extra reflections at positions halfway between the Bragg reflections of calcite in 0kl electron diffraction patterns and the doubling of d104 spacings (corresponding to 2∙3.03 Å) in high-resolution TEM images. Interestingly, these diffraction features match with the so-called carbonate c-type reflections, which are associated with Mg and Ca ordering, a phenomenon that cannot occur in pure calcite. TEM and crystallographic analysis suggests that, in fact, (101¯4) calcite twins and the orientation change of CO3 groups across the twin interface are responsible for the extra reflections.

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6

Rutter, Ernest, David Wallis, and Kamil Kosiorek. "Application of Electron Backscatter Diffraction to Calcite-Twinning Paleopiezometry." Geosciences 12, no. 6 (May 25, 2022): 222. http://dx.doi.org/10.3390/geosciences12060222.

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Electron backscatter diffraction (EBSD) was used to determine the orientation of mechanically twinned grains in Carrara marble experimentally deformed to a small strain (≤4%) at room temperature and at a moderate confining pressure (225 MPa). The thicknesses of deformation twins were mostly too small to permit determination of their orientation by EBSD but it proved possible to measure their orientations by calculating possible twin orientations from host grain orientation, then comparing calculated traces to the observed twin traces. The validity of the Turner & Weiss method for principal stress orientations was confirmed, particularly when based on calculation of resolved shear stress. Methods of paleopiezometry based on twinned volume fraction were rejected but a practical approach is explored based on twin density. However, although twin density correlates positively with resolved shear stress, there is intrinsic variability due to unconstrained variables such as non-uniform availability of twin nucleation sites around grain boundaries that imposes a limit on the achievable accuracy of this approach.

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7

Lacombe, Olivier. "Calcite Deformation Twins: From Crystal Plasticity to Applications in Geosciences." Geosciences 12, no. 7 (July 17, 2022): 280. http://dx.doi.org/10.3390/geosciences12070280.

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8

Côté, A. S., R. Darkins, and D. M. Duffy. "Deformation twinning and the role of amino acids and magnesium in calcite hardness from molecular simulation." Physical Chemistry Chemical Physics 17, no. 31 (2015): 20178–84. http://dx.doi.org/10.1039/c5cp03370e.

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We employ classical molecular dynamics to calculate elastic properties and to model the nucleation and propagation of deformation twins in calcite, both as a pure crystal and with magnesium and aspartate inclusions.

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9

González-Casado, José M., and Carmen Garcı́a-Cuevas. "Calcite twins from microveins as indicators of deformation history." Journal of Structural Geology 21, no. 7 (July 1999): 875–89. http://dx.doi.org/10.1016/s0191-8141(99)00081-4.

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10

Kang, Seong-Seung, Jun-Mo Kim, and Bo-An Jang. "Paleostress fields from calcite twins in the Pyeongan Supergroup, South Korea." Island Arc 14, no. 2 (June 2005): 137–49. http://dx.doi.org/10.1111/j.1440-1738.2005.00462.x.

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11

Vattuone, Maria E., Carlos O. Latorre, and Pablo R. Leal. "Mineralogy and paragenesis of Ca-dachiardite in Cretaceous zeolitized volcanic rocks, Esquel, Chubut, Argentinian Patagonia." Andean Geology 33, no. 1 (June 30, 2010): 161. http://dx.doi.org/10.5027/andgeov33n1-a07.

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Ca-dachiardite is present in Cretaceous volcanic breccias affected by very low grade metamorphism. The cement of the breccia shows quartz, Ca-dachiardite, mordenite, cristobalite, calcite and siderite, while in the clasts there are pectolite, prehnite, yugawaralite, Ca-dachiardite, albite, adularia, interestratified smectite/chlorite (S/C), quartz and cristobalite. Most Ca-dachiardites are found in the cement of the breccia. It occurs principally as fibrous tubes of parallel or lightly divergent bladed and tabular crystals, arranged in concentrical layers with length along 'b' and the fibers; the crystals are flattened on {001} and rarely on {100}. It shows cyclic twins in cross section normal to the length and multiple twins parallel to {001}, but single crystals are also present. The optical character shows: a=b; g:c= 43°; 2Va=55°/60°; strong dispersion r>v. The structural formulae is: Ca1.54-1.72 K0.82-0.98 Na0 (Al3.65-3.98 Si19.95-20.25 O48) 13H2O ; TSi= 0.83-0.85; R2+/(R+ + R2+)=0.61/0.68; DEC=Ca and K. The strong diffraction lines are: 3.460 Å; 3.190 Å and 1.870 Å; a0 =18.679Å; b0=7.488 Å; c0 10.267 Å; b=107°86'. The secondary mineralogical succession deposited according with the decrease in temperature and Xco2, could be: calcite (step I); pectolite, prehnite, quartz, yugawaralite, Ca-dachiardite, S/C, adularia, albite (step II, zeolite facies); mordenite and cristobalite (step III) and then, siderite and calcite (step IV). The metamorphic assemblages suggests that the crystallization conditions of Ca-dachiardite would be 200-220°C at pressures smaller than 0.5 kb, from high aSi and aCa fluids.

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12

Zheng, Jian, Yehua Shan, and Simin Hu. "Paleostress Analysis from Calcite Twins at the Longshan Dome (Central Hunan, South China): Mesozoic Mega-Fold Superimposition in the Reworked Continent." Geosciences 11, no. 11 (November 5, 2021): 456. http://dx.doi.org/10.3390/geosciences11110456.

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It is generally accepted that during the Mesozoic NE−NNE-trending folds overprinted E−W-trending folds to form the Longshan dome in the central South China continent, although the interference map does not tell the relative ages of the fold sets. In an effort to deepen our understanding of the process of reworking the continent, paleostress analysis using calcite twins was carried out in this study to verify or falsify this model. Ten limestone samples were collected from Upper-Paleozoic limestones on the flanks of the dome and were measured using the universal stage for calcite e-twins. E-twins in the samples are divisible into two kinds, thick (≥1 μm) and thin (<1 μm), indicative of relatively higher and lower deformation temperatures, respectively. Stress estimates obtained using the improved version of Shan et al.’s (2019) method were grouped into two layer-parallel shortening (LPS) subsets and three non-LPS subsets. These subsets comprise four tectonic regimes: NWW−SEE compression (LPS1 and non-LPS1), NNE−SSW compression (LPS2 and non-LPS2), NW−SE extension (non-LPS3a) and NNE−SSW extension (non-LPS3b). They were further arranged in a temperature-decreasing order to establish a complex deformation sequence of the study area. In the sequence NE−NNE-trending folds have an older age than E−W-trending folds, something different from the model. The approximately N−S regional compression responsible for the former folds should have a profound effect on the intensely deformed continent, something ignored in earlier work.

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13

MAHER, HARMON D., KEI OGATA, and ALVAR BRAATHEN. "Cone-in-cone and beef mineralization associated with Triassic growth basin faulting and shallow shale diagenesis, Edgeøya, Svalbard." Geological Magazine 154, no. 2 (February 11, 2016): 201–16. http://dx.doi.org/10.1017/s0016756815000886.

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AbstractCone-in-cone (CIC) and beef (BF) carbonate lenses ornament detachment zone faults underlying Triassic growth basins on Edgeøya. Field relationships place CIC and BF growth as during early diagenesis and a transition from hydroplastic to a later brittle-style of faulting that is marked by coarser calcite veining. Deformation is constrained to have occurred at <300 m depth. Multiple models exist for CIC formation. For the Edgeøya example, textural analysis of thin-sections suggests that small tensile fractures and carbonate shell fragments nucleated development of calcite aggregates with CIC and BF morphology within unconsolidated to poorly consolidated sediment to form asymmetric antitaxial tensile aggregates subparallel to bedding and fault surfaces. The conical forms result from differential growth on stepped, cleavage-parallel faces of fibres facing host sediment, with preferential inclusion incorporation at inner corners. The preferred directions of calcite growth are attributed to local stresses and seepage flow associated with pore pressure gradients. Substantial framboidal pyrite in the sediments represents an early phase of microbially driven sulphate reduction, which may have induced calcite mineralization. The transition to brittle-style faulting was marked by development of deformation twins in CIC/BF fibres, and a transition to coarse, blocky calcite growth in relay arrays of steeply oriented microveins. This indicates local fault-related stresses substantially changed during shallow diagenesis and lithification, an evolution attributed to changing pore pressures, seepage forces and material moduli. Calcite mineralizations at Edgeøya track the very significant changes in mechanical properties and stress states that occur during synlithification deformation at very shallow crustal levels.

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14

Lacombe, O., and P. Laurent. "Determination of principal stress magnitudes using calcite twins and rock mechanics data." Tectonophysics 202, no. 1 (February 1992): 83–93. http://dx.doi.org/10.1016/0040-1951(92)90456-g.

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15

Craddock, John P., Uwe Ring, and O. Adrian Pfiffner. "Deformation of the European Plate (58-0 Ma): Evidence from Calcite Twinning Strains." Geosciences 12, no. 6 (June 20, 2022): 254. http://dx.doi.org/10.3390/geosciences12060254.

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We present a data set of calcite twinning strain results (n = 209 samples; 9919 measured calcite twins) from the internal Alpine nappes northwestward across the Alps and Alpine foreland to the older extensional margin along the Atlantic coast in Ireland. Along the coast of Northern Ireland, Cretaceous chalks and Tertiary basalts are cross-cut by calcite veins and offset by calcite-filled normal and strike-slip faults. Both Irish sample suites (n = 16 with four U-Pb vein calcite ages between 70–42 Ma) record a sub-horizontal SW-NE shortening strain with vertical extension and no strain overprint. This sub-horizontal shortening is parallel to the margin of the opening of the Atlantic Ocean (~58 Ma), and this penetrative fabric is only observed ~100 km inboard of the margin to the southeast. The younger, collisional Alpine orogen (~40 Ma) imparted a stress–strain regime dominated by SE-NW sub-horizontal shortening ~1200 km northwest from the Alps preserved in Mesozoic limestones and calcite veins (n = 32) in France, Germany and Britain. This layer-parallel shortening strain (−3.4%, 5% negative expected values) is preserved across the foreland in the plane of Alpine thrust shortening (SE-NW) along with numerous outcrop-scale contractional structures (i.e., folds, thrust faults). Calcite veins were observed in the Alpine foreland in numerous orientations and include both a SE-NW layer-parallel shortening fabric (n = 11) and a sub-vertical NE-SW vein-parallel shortening fabric (n = 4). Alpine foreland strains are compared with twinning strains from the frontal Jura Mountains (n = 9; layer-parallel shortening), the Molasse basin (n = 26; layer-parallel and layer-normal shortening), Pre-Alp nappes (n = 39; layer-parallel and layer-normal shortening), Helvetic and Penninic nappes (Penninic klippe; n = 46; layer-parallel and layer-normal shortening plus four striated U-Pb calcite vein ages ~24 Ma) and calcsilicates from the internal Tauern window (n = 4; layer-normal shortening). We provide a chronology of the stress–strain history of the European plate from 58 Ma through the Alpine orogen.

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16

Jang, Bo-An, Cheong-Bin Kim, and Seong-Seung Kang. "Paleostress from calcite twins of limestone and its tectonic implication in South Korea." Geosystem Engineering 15, no. 3 (July 12, 2012): 157–70. http://dx.doi.org/10.1080/12269328.2012.702092.

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17

Rybacki, E., B. Evans, C. Janssen, R. Wirth, and G. Dresen. "Influence of stress, temperature, and strain on calcite twins constrained by deformation experiments." Tectonophysics 601 (August 2013): 20–36. http://dx.doi.org/10.1016/j.tecto.2013.04.021.

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18

Pfänder, Jörg, Blanka Sperner, and Lothar Ratschbacher. "Strain from calcite twins: the TWIST program and its application in the deformation analysis of Southern Germany." Zeitschrift der Deutschen Geologischen Gesellschaft 149, no. 3 (December 17, 1998): 345–58. http://dx.doi.org/10.1127/zdgg/149/1998/345.

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19

Lacombe, O. "Calcite Twins, a Tool for Tectonic Studies in Thrust Belts and Stable Orogenic Forelands." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 65, no. 6 (October 6, 2010): 809–38. http://dx.doi.org/10.2516/ogst/2009088.

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20

Laurent, Philippe, Christophe Tourneret, and Olivier Laborde. "Determining deviatoric stress tensors from calcite twins: Applications to monophased synthetic and natural polycrystals." Tectonics 9, no. 3 (June 1990): 379–89. http://dx.doi.org/10.1029/tc009i003p00379.

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21

González-Casado, José M., and Carmen Garcı́a-Cuevas. "Strain analysis from calcite e-twins in the Cameros basin, NW Iberian Chain, Spain." Journal of Structural Geology 24, no. 11 (November 2002): 1777–88. http://dx.doi.org/10.1016/s0191-8141(01)00166-3.

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22

Ferrill, David A. "Critical re-evaluation of differential stress estimates from calcite twins in coarse-grained limestone." Tectonophysics 285, no. 1-2 (February 1998): 77–86. http://dx.doi.org/10.1016/s0040-1951(97)00190-x.

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23

Kim, Jun-Mo, Bo-An Jang, Yuzo Obara, and Seong-Seung Kang. "Paleostress reconstructions based on calcite twins in the Joseon Supergroup, northeastern Ogcheon Belt (South Korea)." Island Arc 17, no. 1 (December 10, 2007): 57–69. http://dx.doi.org/10.1111/j.1440-1738.2007.00598.x.

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24

Vitale, S., J. C. White, A. Iannace, and S. Mazzoli. "Ductile strain partitioning in micritic limestones, Calabria, Italy: the roles and mechanisms of intracrystalline and intercrystalline deformation." Canadian Journal of Earth Sciences 44, no. 11 (November 1, 2007): 1587–602. http://dx.doi.org/10.1139/e07-055.

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The Apennine Pollino–Ciagola limestone unit in northern Calabria is characterized by subgreenschist, heterogeneous ductile strain localized along narrow deformation zones at several stratigraphic levels. Paleogene conglomerates and Jurassic calcareous breccias and ooidal packstones have been analyzed with the aim of characterizing the deformation of limestone as a function of the strain recorded by sedimentary markers. Reference sections parallel to principal finite strain planes were prepared at each locality for the study of specific parameters. Image analysis of polished sections by scanning electron microscopy (SEM) was used to obtain the finite strain of calcite grains by Rf/ϕ, harmonic mean and normalized Fry methods. For the range of grain sizes analyzed (1–10 µm), the ellipticity of calcite grains varies as a function of grain size according to a power-law relationship, from which the size of isometric grains is empirically predicted. The finite strain (ellipticity) determined from single calcite grains shows consistently lower values than the corresponding rock strain. For a fixed grain size, grain ellipticity initially increases with rock strain; however for larger strain, scattered ellipticity values are recorded, probably because of dynamic recrystallization. Comparison of bulk strain with grain strain suggests that intercrystalline deformation involving grain boundary sliding contributes 50%–80% of the total strain, for grain sizes in the range of 2–10 µm, increasing to 90% or more for smaller grain sizes. Microstructures (optical, SEM, transmission electron microscopy) are consistent with dominant grain boundary sliding accommodated by dislocation processes. The weakly deformed samples (Rs <4) exhibit straight and subsidiary curved mechanical twins in large grains (d >10 µm), with well-developed glide dislocation substructures in both coarse and micrite grains. In the moderately to highly deformed samples (Rs >4), large grains show curved, thick, and patchy twins, with the development of undulose extinction and subgrains. Subwalls are formed from dislocation networks and relate to subgrain rotation recrystallization in the coarsest grains. Both large and small grains exhibit complex dislocation substructures comprising dislocation networks indicative of concurrent intercrystalline and intracrystalline deformation, whereby grain boundary sliding is accommodated by dislocation processes. Integration of tectonic constraints, field observations, finite strain data, microstructures, and experimental data is consistent with natural deformation at 250 °C, 15–50 MPa, and bulk shear strain rates on the order of 10–13 s–1 to 10–12 s–1.

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25

González-Casado, J. M., P. Gumiel, J. L. Giner-Robles, R. Campos, and A. Moreno. "Calcite e-twins as markers of recent tectonics: insights from Quaternary karstic deposits from SE Spain." Journal of Structural Geology 28, no. 6 (June 2006): 1084–92. http://dx.doi.org/10.1016/j.jsg.2006.03.019.

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26

Burgin, Hugo B., Khalid Amrouch, Philippe Robion, and David Kulikowski. "An integrated approach to determining 4D stress development at Castle Cove." APPEA Journal 59, no. 1 (2019): 410. http://dx.doi.org/10.1071/aj18173.

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Models for basin evolution and natural fracture development often contain many uncertainties. Multiscale approaches to structural analysis assist in reducing these by providing checkpoints for structural evolution to better constrain the development of paleostress phases through time. In this study, we integrate the analysis of calcite twins, magnetic fabrics, stylolites and natural fractures at Castle Cove in the eastern Otway Basin, producing a five-phase model for stress evolution consisting of: phase 1 ~NW–SE Mid-Cretaceous strike-slip or compression; phases 2 and 3 Late Cretaceous extension, coinciding with the development of ~NW–SE and ~NE–SW striking extensional fracture sets; phase 4 ~NE–SW strike-slip and compression, representing an enigmatic period of stress evolution with respect to the current understanding of the Otway Basin; and phase 5, present day ~NW–SE strike-slip stress. The results contribute to a 4D structural history construction for the eastern Otway Basin and suggest that the evolution of the region may require reassessing in order to determine the timing and nature of the detected ~NE–SW oriented compressional event. This study also demonstrates how the use of a calcite stress inversion technique can assist in providing mechanical checkpoints for the evolution of complex natural fracture networks, which can easily be expanded within the sub-surface.

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27

Tourneret, C., and P. Laurent. "Paleo-stress orientations from calcite twins in the North Pyrenean foreland, determined by the Etchecopar inverse method." Tectonophysics 180, no. 2-4 (August 1990): 287–302. http://dx.doi.org/10.1016/0040-1951(90)90314-x.

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28

Holbek, Simon C., Madison Frank, James M. Scott, Steven A. F. Smith, Petrus J. le Roux, Tod E. Waight, Robert Van Hale, Malcolm R. Reid, and Claudine H. Stirling. "Structural Controls on Shallow Cenozoic Fluid Flow in the Otago Schist, New Zealand." Geofluids 2020 (August 25, 2020): 1–25. http://dx.doi.org/10.1155/2020/9647197.

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The Otago Schist in the South Island of New Zealand represents an exhumed Mesozoic accretionary prism. Two coastal areas (Akatore Creek and Bruce Rocks) south of Dunedin preserve structural and geochemical evidence for the development of postmetamorphic hydrothermal systems that involved widespread fluid-rock reaction at shallow crustal depths. The Jurassic to Triassic pumpellyite-actinolite (Akatore Creek) to upper greenschist facies (Bruce Rocks) metamorphic fabrics were crosscut by sets of regionally extensive Cretaceous exhumation joints. Many of the joints were subsequently reactivated to form networks of small-displacement (<metres) strike-slip faults containing cemented fault breccias and veins composed of hydrothermal calcite, siderite, and ankerite. Paleostress analysis performed on infrequent fault slickenlines indicates an overall strike-slip paleostress regime and a paleo-σ1 orientation (azimuth 094°) similar to the contemporary σ1 orientation in Otago and Canterbury (azimuth c. 110°-120°). High δ18O values in vein calcite (δ18OVPDB=21 to 28‰), together with the predominance of Type I calcite twins, suggest that vein formation occurred at low temperatures (<200°C) in the shallow crust and was associated with strongly channelized fluid flow along the joint and fault networks. Mass-balance calculations performed on samples from carbonate alteration zones show that significant mobilisation of elements occurred during fluid flow and fluid-rock reaction. Whole-rock and in situ carbonate 87Sr/86Sr data indicate varying degrees of interaction between the hydrothermal fluids and the host rock schists. Fluids were likely derived from the breakdown of metamorphic Ca-rich mineral phases with low 87Rb in the host schists (e.g., epidote or calcite), as well as more radiogenic components such as mica. Overall, the field and geochemical data suggest that shallow fluid flow in the field areas was channelized along foliation surfaces, exhumation joints, and networks of brittle faults, and that these structures controlled the distribution of fluid-rock reactions and hydrothermal veins. The brittle fault networks and associated hydrothermal systems are interpreted to have formed after the onset of Early Miocene compression in the South Island and may represent the manifestation of fracturing and fluid flow associated with reverse reactivation of regional-scale faults such as the nearby Akatore Fault.

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29

Lacombe, O., J. Angelier, and P. Laurent. "Determining paleostress orientations from faults and calcite twins: a case study near the Sainte-Victoire Range (southern France)." Tectonophysics 201, no. 1-2 (January 1992): 141–56. http://dx.doi.org/10.1016/0040-1951(92)90180-e.

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30

Burkhard, Martin. "Calcite twins, their geometry, appearance and significance as stress-strain markers and indicators of tectonic regime: a review." Journal of Structural Geology 15, no. 3-5 (March 1993): 351–68. http://dx.doi.org/10.1016/0191-8141(93)90132-t.

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31

Lacombe, Olivier. "Paleostress magnitudes associated with development of mountain belts: Insights from tectonic analyses of calcite twins in the Taiwan Foothills." Tectonics 20, no. 6 (December 2001): 834–49. http://dx.doi.org/10.1029/2001tc900019.

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Arboit, Francesco, Khalid Amrouch, Alan S. Collins, Rosalind King, and Christopher Morley. "Determination of the tectonic evolution from fractures, faults, and calcite twins on the southwestern margin of the Indochina Block." Tectonics 34, no. 8 (August 2015): 1576–99. http://dx.doi.org/10.1002/2015tc003876.

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Zhang, Yi, Jing-Ran Zhu, and Xiao-Yan Yu. "A Comparative Study of the Gemological Characteristics and Inclusions in Spinels from Myanmar and Tajikistan." Crystals 12, no. 5 (April 27, 2022): 617. http://dx.doi.org/10.3390/cryst12050617.

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Currently, most of the popular spinels in the jewellery market come from Myanmar and Tajikistan. It is well known that provenance is one of the main factors affecting the value of a gemstone, and the geographic origin of a gemstone can be determined by examining its gemological and inclusion characteristics. This study systematically characterized the conventional gemology of spinels from Myanmar and Tajikistan and compared the inclusions in the spinels from these two countries by means of gemological microscopy and Raman spectroscopy. The results showed that most red and pink Myanmarese spinels were octahedral or contact twins, while Tajikistani spinels are slabbed or octahedral distorted crystals. Columnar zircon is frequently found in Tajikistani spinels but rare in Myanmarese spinels, appearing as tiny accessory inclusions. There are three types of carbonate inclusions (magnesite, dolomite, and calcite) in Myanmarese spinels, but Tajikistani spinels have only one (magnesite). In addition, spinels of different origins include special inclusions. Myanmarese spinels contain pyrite inclusions; Tajikistani spinels contain rutile and talc inclusions.

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Lacombe, O., J. Angelier, Ph Laurent, F. Bergerat, and Ch Tourneret. "Joint analyses of calcite twins and fault slips as a key for deciphering polyphase tectonics: Burgundy as a case study." Tectonophysics 182, no. 3-4 (October 1990): 279–300. http://dx.doi.org/10.1016/0040-1951(90)90168-8.

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35

Paulsen, Timothy S., Christie M. Demosthenous, Paul M. Myrow, Nigel C. Hughes, and S. K. Parcha. "Paleostrain stratigraphic analysis of calcite twins across the Cambrian–Ordovician unconformity in the Tethyan Himalaya, Spiti and Zanskar valley regions, India." Journal of Asian Earth Sciences 31, no. 1 (August 2007): 44–54. http://dx.doi.org/10.1016/j.jseaes.2007.04.001.

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Lacombe, Olivier. "Comparison of paleostress magnitudes from calcite twins with contemporary stress magnitudes and frictional sliding criteria in the continental crust: Mechanical implications." Journal of Structural Geology 29, no. 1 (January 2007): 86–99. http://dx.doi.org/10.1016/j.jsg.2006.08.009.

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37

Gągała, Łukasz. "Reliability of selected procedures of stress inversion and data separation for inhomogeneous populations of calcite twins and striated faults: insights from numerical experiments." International Journal of Earth Sciences 98, no. 2 (November 24, 2007): 461–79. http://dx.doi.org/10.1007/s00531-007-0262-3.

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Constantin, Joël, Philippe Laurent, Pierre Vergély, and Justo Cabrera. "Paleo-deviatoric stress magnitudes from calcite twins and related structural permeability evolution in minor faults: Example from the toarcian shale of the French Causses Basin, Aveyron, France." Tectonophysics 429, no. 1-2 (January 2007): 79–97. http://dx.doi.org/10.1016/j.tecto.2006.09.014.

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39

Lykova, Inna, Dmitry Varlamov, Nikita Chukanov, Igor Pekov, Dmitry Belakovskiy, Oleg Ivanov, Natalia Zubkova, and Sergey Britvin. "Chromium Members of the Pumpellyite Group: Shuiskite-(Cr), Ca2CrCr2[SiO4][Si2O6(OH)](OH)2O, a New Mineral, and Shuiskite-(Mg), a New Species Name for Shuiskite." Minerals 10, no. 5 (April 26, 2020): 390. http://dx.doi.org/10.3390/min10050390.

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A new pumpellyite-group mineral shuiskite-(Cr), ideally Ca2CrCr2[SiO4][Si2O6(OH)](OH)2O, was found at the Rudnaya mine, Glavnoe Saranovskoe deposit, Middle Urals, Russia. It occurs on the walls of 0.5 to 1 cm thick fractures in chromitite, filled with calcite, Cr-bearing clinochlore, and uvarovite. Shuiskite-(Cr) forms long prismatic to acicular crystals up to 0.1 × 0.5 × 7 mm elongated along [010] and slightly flattened on [100]. The crystals are commonly combined into radial, sheaf-like aggregates. Most observed crystals are simple twins with a (001) composition plane. Shuiskite-(Cr) is greenish-black under daylight or purplish-black under incandescent light. It is optically biaxial (–), α = 1.757(5), β = 1.788(6), γ = 1.794(6), 2V (meas.) = 45(10)°, 2V (calc.) = 46° (589 nm). The Dcalc is 3.432 g/cm3. The IR spectrum is reported. The chemical composition (wt.%) is CaO 21.33, MgO 3.17, Al2O3 5.41, Cr2O3 28.50, TiO2 0.18, SiO2 33.86, H2O 5.82, total 98.27. The empirical formula calculated based on the sum of eight metal cations and Si atoms per formula unit is Ca2.02Mg0.42Cr3+1.99Al0.56Ti0.01Si3.00O10.57(OH)3.43. The simplified formula is Ca2(Cr,Mg)(Cr,Al)2[SiO4][Si2O6(OH,O)](OH,O)(OH)2. Shuiskite-(Cr) is monoclinic, C2/m, a = 19.2436(6), b = 5.9999(2), c = 8.8316(3) Å, β = 97.833(3)°, V = 1010.17(6) Å3, and Z = 4. The crystal structure, solved from single-crystal X-ray diffraction data (R = 0.0469), is based on a pair of chains of edge-sharing Cr-centred octahedra running along the b axis, linked together via the [SiO4] and [Si2O6(OH)] groups and Ca-centred polyhedra. The mineral species shuiskite, ideally Ca2MgCr2[SiO4][Si2O6(OH)](OH)3, was renamed to shuiskite-(Mg) by the decision of the IMA CNMNC. The shuiskite solid solution series with the general formula Ca2XCr2[SiO4][Si2O6(OH,O)](OH)2(OH,O), which includes shuiskite-(Mg) and shuiskite-(Cr) with X = Mg and Cr3+, respectively, appeared in the pumpellyite group.

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Pokroy, B., M. Kapon, F. Marin, N. Adir, and E. Zolotoyabko. "Protein-induced, previously unidentified twin form of calcite." Proceedings of the National Academy of Sciences 104, no. 18 (April 25, 2007): 7337–41. http://dx.doi.org/10.1073/pnas.0608584104.

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Using single-crystal x-ray diffraction, we found a formerly unknown twin form in calcite crystals grown from solution to which a mollusc shell-derived 17-kDa protein, Caspartin, was added. This intracrystalline protein was extracted from the calcitic prisms of the Pinna nobilis shells. The observed twin form is characterized by the twinning plane of the (108)-type, which is in addition to the known four twin laws of calcite identified during 150 years of investigations. The established twin forms in calcite have twinning planes of the (001)-, (012)-, (104)-, and (018)-types. Our discovery provides additional evidence on the crucial role of biological macromolecules in biomineralization.

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Ferrill, David A., Alan P. Morris, Mark A. Evans, Martin Burkhard, Richard H. Groshong, and Charles M. Onasch. "Calcite twin morphology: a low-temperature deformation geothermometer." Journal of Structural Geology 26, no. 8 (August 2004): 1521–29. http://dx.doi.org/10.1016/j.jsg.2003.11.028.

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42

Yamaji, Atsushi. "How tightly does calcite e-twin constrain stress?" Journal of Structural Geology 72 (March 2015): 83–95. http://dx.doi.org/10.1016/j.jsg.2015.01.008.

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Groshong, Richard H. "Origin and Application of the Twinned Calcite Strain Gauge." Geosciences 11, no. 7 (July 16, 2021): 296. http://dx.doi.org/10.3390/geosciences11070296.

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This paper is a personal account of the origin and development of the twinned-calcite strain gauge, its experimental verification, and its relationship to stress analysis. The method allows the calculation of the three-dimensional deviatoric strain tensor based on five or more twin sets. A minimum of about 25 twin sets should provide a reasonably accurate result for the magnitude and orientation of the strain tensor. The opposite-signed strain axis orientation is the most accurately located. Where one strain axis is appreciably different from the other two, that axis is generally within about 10° of the correct value. Experiments confirm a magnitude accuracy of 1% strain over the range of 1–12% axial shortening and that samples with more than 40% negative expected values imply multiple or rotational deformations. If two deformations are at a high angle to one another, the strain calculated from the positive and negative expected values separately provides a good estimate of both deformations. Most stress analysis techniques do not provide useful magnitudes, although most provide a good estimate of the principal strain axis directions. Stress analysis based on the number of twin sets per grain provides a better than order-of-magnitude approximation to the differential stress magnitude in a constant strain rate experiment.

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44

Wall, F., M. J. Le Bas, and R. K. Srivastava. "Calcite and carbocernaite exsolution and cotectic textures in a Sr,REE-rich carbonatite dyke from Rajasthan, India." Mineralogical Magazine 57, no. 388 (September 1993): 495–513. http://dx.doi.org/10.1180/minmag.1993.057.388.11.

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AbstractA carbonatite dyke from the Sarnu-Dandali alkaline complex, Rajasthan, India, contains a remarkable suite of rare earth, strontium-rich minerals with spectacular primary textures.Sr, Mn-rich calcite in the outer 5 mm of the dyke contains exsolved lamellae of carbocernaite, (Ca,Na)(Sr,Ce,Ba)(CO3)2, orientated parallel to its twin and cleavage planes. The amount of exsolved carbocernaite increases away from the dyke margin as the Sr content of the calcite increases to a maximum 13 wt.%. Sr levels as high as this in calcite have previously been recorded only in experimental work. The carbocernaite exsolution suggests that Sr-rich calcium carbonate can be a host for major amounts of REE in carbonatite magma.Separated by a sharp internal boundary, is a complex possibly cotectic intergrowth of carbocernaite and Sr-rich calcite with late Ca-rich strontianite (19 wt.% CaO). Other minerals in the dyke include baryte, pyrrhotite, alabandite, sphalerite and occasional bastnäsite-(La) and thorite. Bands of late britholite-(Ce) traverse the dyke.The host rock for the dyke is fenitized melanephelinite which is itself traversed by narrow, <1 mm, carbonatite veins beleived to predate the carbonatite dyke. Allanite, britholite-(Ce) and rare monazite-(Ce), developed at the boundary between the carbonatite dyke and the fenite, may have been produced by a reaction between the dyke and the wall rock, or may be related to the later britholite mineralisation.The textures and mineral compositions indicate primary crystallisation. They are unique amongst rare earth-rich carbonatites which are usually late-stage phenomena with signs of secondary alteration.Comparison with experimental data available for the calcite-strontianite system suggests conditions of 500°C and 2 kbar for coexisting Sr-rich calcite and Ca-rich strontianite. A smaller scale intergrowth of calcite containing only 2.9 wt.% SrO and coexisting Ca-strontianite may correspond to a further unmixing at 350°C and 2 kbar. Since no experimental data are available for a calcite-carbocernaitestrontianite system, mineral chemistries and the interpreted sequence of crystallisation have been used to construct a hypothetical phase diagram.

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Yamaji, Atsushi. "Generalized Hough transform for the stress inversion of calcite twin data." Journal of Structural Geology 80 (November 2015): 2–15. http://dx.doi.org/10.1016/j.jsg.2015.08.001.

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46

Richards, R. Peter. "The Four Twin Laws of Calcite and How To Recognize Them." Rocks & Minerals 74, no. 5 (January 1999): 308–17. http://dx.doi.org/10.1080/00357529909602559.

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47

Walkden, Gordon M., J. Roddy Irwin, and Anthony E. Fallick. "Carbonate spherules and botryoids as lake floor cements in the East Kirkton Limestone of West Lothian, Scotland." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 84, no. 3-4 (1993): 213–21. http://dx.doi.org/10.1017/s0263593300006039.

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ABSTRACTThe East Kirkton Limestone is typically a carbonate/organic laminite characterised at many levels by abundant radial-fibrous calcite (RFC) spherules and by less common larger stromatolite-like accretions of laminated botryoidal RFC. The spherules are mostly c. 1 mm in diameter and have cyanophyte and chlorophyte inclusions. Some spherules enclose parallel bundles of complete cyanophyte fibres and probably grew within a living cyanophyte mat. The botryoidal accretions were commonly seeded upon wood and other exposed organic remains such as bone, and they completely enclose twigs and branches where these were held above the sediment surface. Botryoidal accretions commonly contain the remains of a benthos of cyanophytes, chlorophytes and ostracods.Both types of calcite have carbon and oxygen stable isotope values similar to those of known fresh-water precipitates. Their stable isotope and trace element geochemistries are consistent with precipitation on the floor of a tropical fresh-water lake within a volcanic setting, but removed from the influence of any hot-spring activity. Spherules and botroids are mineralogically closely similar and, whilst precipitation may have been biogenically mediated, they are regarded as passive lake floor cements.The carbonate laminae are dominated by rhombohedral calcite. Many of these laminae may have originated as calcite suspensoids which settled to the lake floor during relatively brief precipitation events, blanketing the normally richly organic substrate, smothering the cyanophyte mats, and leading to the preservation of individual organic laminae. Crystals later became enlarged and intergrown within the sediment, but this occurred early and prior to significant compaction, because detail of fragile and degradable organic constituents is commonly preserved. The likely source of the carbonate is through leaching of the local basic volcanic terrain. The precipitation of two types of calcite implies regular fluctuations in the chemistry of the lake waters, or in the factors controlling precipitation, which may have been a biogenic and/or seasonal effect.

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ROBERTS, DAVID, and KLAAS BOUKE ZWAAN. "Marble dykes emanating from marble layers in an amphibolite-facies, multiply-deformed carbonate succession, Troms, northern Norway." Geological Magazine 144, no. 5 (August 13, 2007): 883–88. http://dx.doi.org/10.1017/s0016756807003810.

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In one of the higher nappes of the Caledonides of Troms, northern Norway, rare thin dykes of calcite marble lie subparallel to the axial surfaces of folds in multilayered marble beds. The dykes emanate from pure calcite marble layers mostly in or close to the hinge zones of these flat-lying, tight to sub-isoclinal, F3 folds. In many cases, they appear to penetrate along the axial surfaces of these same folds, and there is an up to 10° angular disparity between dyke orientation and axial surfaces. The dykes are considered to have originated, and been expelled, from parent calcite marble layers either at or shortly after the peak of amphibolite-facies metamorphism between the D2 and D3 deformation phases of the Scandian orogeny. The dykes display a dyke-parallel, dark grey to white, colour banding, the origin of which is uncertain at present. In thin-section, an equigranular texture is dominated by 2–3 mm, equant, unstrained, calcite grains with straight boundaries and low-T twin lamellae, denoting a late-stage recrystallization. A weak, oblique, calcite grain-shape orientation fabric curves into a dyke-parallel alignment along the finer-grained margins, reflecting the simple-shear deformation imposed on the host rock. Regarding the initiation of these marble dykes, it seems likely that a combination of P–T conditions and possibly partial melting processes was conducive to generating extreme ductility/superplasticity, at least locally, and that this led to the sudden expulsion of a partially molten carbonate aggregate which had momentarily attained a critical pressure and intruded preferentially along available, transient fractures prior to the imposition of the D3 simple-shear regime.

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Laurent, Philippe. "Shear-sense determination on striated faults from e twin lamellae in calcite." Journal of Structural Geology 9, no. 5-6 (1987): 591–95. http://dx.doi.org/10.1016/0191-8141(87)90144-1.

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50

Burgin, Hugo B., Khalid Amrouch, Mojtaba Rajabi, David Kulikowski, and Simon P. Holford. "Determining paleo-structural environments through natural fracture and calcite twin analyses: a case study in the Otway Basin, Australia." APPEA Journal 58, no. 1 (2018): 238. http://dx.doi.org/10.1071/aj17099.

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The structural history of the Otway Basin has been widely studied; however, previous works have focussed on large kilometre scale, basin and seismic structures, or have over-simplified natural fracture analysis with an excessive focus on fracture strike direction and a disregard for 3D geometry, a crucial characteristic when considering states of stress responsible for natural fracture formation. In this paper, we combine techniques of natural fracture analysis and calcite twin stress inversion to investigate the meso (outcrop and borehole) and micro (crystal) scale evidence for structural environments that have contributed to basin evolution. Our results indicate that basin evolution during the post-Albian may be markedly more complex than the previously thought stages of late Cretaceous inversion, renewed rifting and long-lived mid-Eocene to recent compression, with evidence for up to six structural environments detected across the basin, including; NE–SW and NW–SE extension, NW–SE compression, a previously undetected regime of NE–SW compression, and two regimes of strike-slip activity. By constraining structural environments on the meso- and micro-scale we can deliver higher levels of detail into structural evolution, which in turn, provides better-quality insights into multiple petroleum system elements, including secondary migration pathways and trap formation. Our research also shows that the Otway Basin presents a suitable environment for additional micro-scale structural investigations through calcite twin analyses.

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