000			03023nab a2200241 4500
005			20260520003059.0
008			260224s2012 xxu ing
041			_aInglés
245	0	0	_aHydrothermal Dolomites in the Early Albian (Cretaceous) Platform Carbonates (NW Spain) _bNature and Origin of Dolomites and Dolomitising Fluids
260			_a _b _cene./feb. 2012
270			_a19/04/2013 ; 19/04/2013
300			_a25 p. ; 97-122
520			_aTranscripción del resumen del autor: This study documents the temporal and lateral variation in petrographic and geochemical signatures of fault-related dolomite bodies in the Ranero and El-Moro areas (Karrantza valley, Cantabrian mountains; NW Spain). These dolomite bodies are hosted in Albian carbonates, which were deposited in the Basque-Cantabrian Basin as a result of an intense rift-related subsidence with associated faulting along various orientations. Fluid circulations generated replacive and cement dolomites, paragenetically followed by various calcite cements. Petrography, mineralogical and geochemical investigations (XRD, ICP, XRF, stable and Sr isotopes) helped in distinguishing hydrothermal stages. Two major dolomite facies were observed according to their Fe-content. Early dolomites are ferroan and replace limestone more significantly than the later, non ferroan dolomites. Dolomites are generally stoichiometric (49.76 to 51.59 M% CaCO3) and exhibit a broad range of depleted d18O values (–18.7 to –10.5‰ V-PDB), which may indicate multiphase dolomitisation and/or different degrees of recrystallisation. Decreasing d18O values correlate with decreasing Fe content in dolomites. In the Ranero area, dolomites show less slightly depleted d13C values (–0.15 to +2.13‰ V-PDB) relative to the host limestone d13C signature, while these values are substantially more depleted in El-Moro area (down to –2.18‰ V-PDB). Hydrothermal calcites predating dolomitisation show less depleted d18O values (–14.15 to –12.1‰ V-PDB) than postdolomitisation calcite (–18.1‰ V-PDB). Sr isotope data suggest that the fluids interacted with siliciclastic lithologies (sandstone, shale). The dolomite fabric is variably altered through dedolomitisation and cataclastic deformation. Dolomitisation occurred in at least two main episodes. A first episode of pervasive ferroan dolomitisation probably resulted from compactional dewatering of basinal fluids from the nearby Basque trough and hydrodynamic fluid flow along the faults/fractures in the Albian carbonate platform. Subsequently, a second episode of very hot and localised dolomitisation may be related to igneous activity and convective flow.
581			_a1
773	0		_tOil and Gas Science and Technology _g67
942			_cARTICULO
100	1		_aShah, M.M. _953042
100	1		_aNader, F.H. _933385
100	1		_aGarcia, D. _945586
100	1		_aSwennen, R. _936689
100	1		_aEllam, R. _953053
999			_c187619 _d187619