Dolomite deformation

Figure 9.26. Stacking faults on (0001) induced by (0001) slip in dolomite deformed at 420°C. (From Barber et al. 1981.)...

Conclusively, the material is characterized by an N-linked aromate, which, together with additional aliphatic and aromatic structures, and probably under participation of sulfur and phosphorus, composes complex molecules. In the exterior sheath of the microspheres, dolomite is indicated by the lines at 1100, 725 and 300 cm-1. A weak line at 1445 cm-1 might belong either to dolomite or to a C—H deformation (Pflug et al., 1979)117) (Fig. 34). There is scarcely any doubt that the detected organic substances represent decomposed and fossilized remains of cell material. 

Calcite and dolomite form large parts of the sedimentary continental crust. Consequently, their mechanical properties have been studied in some detail, and Wenk et al. (1983) have reviewed the rheology and associated microstructural development. Deformation takes place by both twinning and dislocation glide. 

Microstructures in deformed dolomite. The deformation characteristics of dolomite are markedly different from those of calcite and have been studied in detail by Barber, Heard, and Wenk (1981). Not only are the twin laws different, but twinning in dolomite occurs only at temperatures above about 250°C. The lower dislocation densities observed in twinned dolomite and at twin intersections is perhaps due to the greater ease of stress relaxation at the higher temperatures required for twinning. 

Defect microstructures in deformed and recovered dolomite. Tectono-physics, 39, 193-213. 

Barber, D. J., Freeman, L. A., Smith, D. J. (1983). Analysis of high-voltage, high-resolution images of lattice defects in experimentally-deformed dolomite. Phys. Chem. Minerals, 9, 102-8. 

Barber, D. J., Heard, H. C., Wenk, H.-R. (1981). Deformation of dolomite single crystals from 20-800° C. Phys. Chem. Minerals, 7, 271-86. 

D.J. Barber and HR. Wenk, Deformation twinning in calcite, dolomite, and other rhombohedral carbonates. Phys. Chem. Minerals 5, pp. 141-165 (1979). 

Available drill cores from the 0-35 well show very low thin-section porosity (<5%). Advanced mechanical compaction, including shale-clast deformation, together with ferroan dolomite cement and quartz overgrowths, has occluded most of the porosity. 

Internally complex, ferroan dolomite-cemented fractures at Ballycastle are closely associated with regional normal faulting and are genetically linked with cataclastic textures typical of brittle deformation in porous sandstones. Cemented fractures described in this paper are distinguished from the principal slip planes ( faults ) on the basis of minimal displacement (centimetre scale at most), and the definition encompasses the tectonodiagenetic products of initial cataclasis, cementation of the... 

Fig. 14.11. Sketch of a road-cut exposing a deformed layer of diopside in dolomite. The diopside has zones of tremolite and calcite at its contact. Quartz occurs interstitially. Five minerals, five components. No problem ...

Cement, lime, limestone filler and filler from other rocks, such as a mixture of diabase and dolomite, as well as sulfur filler, were used in the past (Fiber and Pichler 1993). A substantial effect on the permanent deformation behaviour was seen only with the use of sulfur (Denning and Carswell 1981b Fromm and Kennepohl 1979). 

It shows that the modulus of elasticity and the peak compressive strength have positive correlation with dolomite, calcite, feldspar,but negative correlation with chlorite, illite and quartz. In marl strata, mechanical strength of rock is variant because of different minerals content. This standpoint could be confirmed by the structure of rock mass in Badong town. There are many of crushed beds in marly rock, which is developed on the interface of hard and soft rock because of different deformations. 

Fig. 3. Dislocations in carbonates (a) Dark-field TEM image showing dislocations and stacking faults on the <2 i i 0) planes generated by basal slip in a dolomite single crystal deformed at 420°C [52]. (b) Dislocations associated with crossing mechanical twins in calcite (TEM, bright field) [161].

The characteristics of dislocation configurations seen by TEM in dolomite are markedly different from those for calcite. In comparison, active shp systems for dolomite are more easily identified in deformed and unrecovered samples because dislocations tend to keep to their shp planes and frequently are geometrical in shape. Shp bands are common in experimentally deformed specimens. Because dolomite is an ordered mineral with a superlattice of both cations and anions (CO3 groups), perfect dislocations in the structure are, senso strictu, superdislocations. 

Fig. 6. TEM images of microstructures in experimentally deformed dolomite single crystals [52] (a) At low-temperature dislocations are concentrated in slip bands, (b) At higher temperature climb and dislocation interactions produce dislocation loops.

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