Internal fault planes

Internally complex, ferroan dolomite-cemented fractures are a prominent feature within a fluvial sand body at Ballycastle, on the margins of the Rathlin basin in northeast Ireland. The cemented fractures display a tight modal orientation that is coincident with the dominant local normal faulting trend, and are interpreted to have formed in the same tectonic regime. However, there is no clear trend in the spatial distribution or width of the fractures with respect to a fault plane situated at one end of the outcrop. 

Twin planes are most frequently internal boundaries across which the crystal matrix is reflected (Section 3.11). Some twin planes do not change the composition of the crystal while at others atoms are lost and a composition change can result. If faults that alter the composition are introduced in considerable numbers, the crystal will take on the aspect of a modular material and show a variable composition. 

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... 

Jeon S., Kim X, Seo Y. 2004. Effect of a fault and weak plane on the stability of a tunnel in rock—a scaled model test and numerical analysis. International Journal of Rock Mechanics Mining Sciences. 41(3) l-6. 

Crystalline solids contain different types of stractural defects. If the imperfection is limited to one stractural or lattice site and its immediate vicinity, the imperfection is termed a point defect. Vacancies and interstitial atoms are point defects. An impurity atom present in a crystal and that either occupies a lattice site or an interstitial site is also termed a point defect. But in addition to the point defects the stractural defects also comprise line and plane defects. The line defects are dislocations which are characterised by displacements in the stractirre in certain directions. The plane defects comprise stacking faults, grain boundaries, internal and external surfaces. 

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