Massive hydrothermal dolomites in the southwestern Cantabrian Zone (Spain) and their relation to the Late Variscan evolution

Hydrothermal Dolomites in the Early Albian (Cretaceous) Platform Carbonates (NW Spain): Nature and Origin of Dolomites and Dolomitising Fluids

“…The fact that the dolomite bodies are associated to faults indicates a tectonic control on the dolomite distribution ( Fig. 5, 6; GarciaMondéjar, 1996;Lopéz-Horgue et al, 2005Gasparrini et al, 2006;Shah et al, 2010;Swennen et al, in press). Various dolomite phases are believed to have formed due to the circulation of Mg-rich dolomitising fluids along faults/fractures, hence invoking multiple pulses of these fluids (Swennen et al, in press).…”

“…Besides a few cases of stratiform hydrothermal dolomites, these usually occur as fabric destructive, stratadiscordant cutting across host limestone and concentrated along major faults (Wilson et al, 1990;Nader et al, 2004;Gasparrini et al, 2006;Lopéz-Horgue et al, 2010;Shah et al, 2010;Swennen et al, in press). Some of the known oil (Ghawar, Saudi Arabia; Cantrell et al, 2004) and gas (North field, Arabian Gulf; Sudrie et al, 2006) carbonate reservoirs consist of porous dolomites, which are probably partly hydrothermal in origin.…”

Geochemical Characteristics and Paleoenvironmental Signi cance of the Ordovician Paleokarst Reservoir in the Maigaiti Slope of Tarim Basin

“…The δ 18 O values of calcite and bedrock fill in the Markit slope karst cave had negative characteristics such that the span of δ 13 C values was significant. This result is related to the Ordovician surface uplift, the overall open environment, meteoric water eluviation (Land, 1980;Rosen et al, 1989;Gasparrini et al, 2006) of widespread δ 12 C, and all δ 16 O of atmospheric CO3 2-sources (Veizer et al, 1999;Azmy et al, 2009). The relationship diagram of δ 13 C-δ 18 O (Figure 6) indicates that the filling materials in the Markit slope Ordovician carbonatite fracture cave can be divided into four classes indicating differences in formation's environment (Table 5).…”

“…Owing to the influence of fresh atmospheric water (Gasparrini et al, 2006), the δ 13 C values were apparently smaller than the bedrock carbon isotope values, which were formed in the open environment.…”

Thermal history of the Sabero Coalfield (Southern Cantabrian Zone, NW Spain) as revealed by apatite fission track analyses from tonstein horizons: implications for timing of coalification

“…As a consequence, the effects of this episode are irregularly distributed within the basins (Brime et al 2001;Aller et al 2005). Fluid inclusion results confirm that there was fracture-controlled fluid flow along thrusts and/or strike-slip faults (Gasparrini et al 2003(Gasparrini et al , 2006Ayllon et al 2003). The porosity and degree of compaction of the Stephanian sediments also likely to have played an important role in the coalification process, since relatively uncompacted and uncemented sediments would have facilitated fluid circulation (Duddy et al 1994).…”