Dolomite-cemented fractures trends

Triassic (re)activation of NNW-SSE-trending faults at Waterfoot (east Antrim) was accompanied by injection of sandstone neptunian dykes but without associated dolomite-cemented fractures (Kerr, 1987). In contrast, no neptunian dykes are seen at Ballycastle. 

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. 

Stable isotope analysis of intergranular, vein-fill and poikilotopic dolomite cements produced very similar results (Fig. 12). Overall, dolomite 5 0 values fall between -3.8 and -0.9%o pdb and 5 C values between -4.2 and -9.5%o pdb. The bulk of the data display a crude positive covariance, albeit with several outlying points. However, no consistent trends were detected across individual cemented fractures. Three samples of ferroan dolomite pseudomorphing gastropods in the overlying... 

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