000			02901nab a2200289 4500
005			20260520003058.0
008			260224s2012 xxu ing
041			_aInglés
245	0	0	_aThe Ranero Hydrothermal Dolomites (Albian, Karrantza Valley, Northwest Spain) _bImplications on Conceptual Dolomite Models
260			_a _b _cene./feb. 2012
270			_a19/04/2013 ; 18/04/2013
300			_a20 p. ; 9-29
520			_aTranscripción del resumen del autor: Field characteristics, petrographic and geochemical signatures, as well as some petrophysical aspects of fault-related dolomite bodies in the Ranero area (Karrantza Valley, NW Spain) are presented in this paper. These dolomite bodies are hosted by Albian slope to platform carbonates, which were deposited in the Basque-Cantabrian Basin. Replacive and void-filling dolomite phases – postdating palaeo- and hypogene karstification – are interpreted to have originated from hydrothermal fluid pulses, and are spatially related with faults and fractures. Hydrothermal calcite cements pre- and postdate dolomitization. Mineralogical and geochemical investigations (XRD, ICP-MS/OES, XRF, stable and Sr isotopes) helped in distinguishing various dolomite and calcite phases. Dolomite phases can be grouped into ferroan (early) and non-ferroan (late). Dolomites are generally stoichiometric and exhibit a broad range of depleted d18O values (–18.7 to –10.5‰ V-PDB), which advocate for multiphase dolomitization and/or recrystallization at relatively high temperatures (150-200°C). The observation that bed-parallel stylolites pre- and post-date dolomites suggests that dolomitization occurred during the Late Albian regional tectonic activity and related fluid expulsions. Based on carbonate chemistry, authigenic silicate chemistry and replacement relationships, two contrasting types of dolomitizing fluids are inferred. Both arguably may have initiated as sulphatedominated brines and/or basin compactional fluids, but they seemingly undergo sulphate reduction in contact with host rocks of contrasting compositions (Fe-rich silicate vs Fe-poor carbonate) thus evolving either to acidic and ferroan (limestone replacive) or to neutral, Fe-poor and sulfidic (Fe-dolomite replacive). Fluid drives are not well constrained by our data, but both fluid types are focused along major faults that cross cut the platform edge and are associated with diapir tectonics.
581			_a1
773	0		_tOil and Gas Science and Technology _g67
942			_cARTICULO
100	1		_aNader, F.H. _933385
100	1		_aLópez-Horgue, M.A. _953041
100	1		_aShah, M.M. _953042
100	1		_aDewit, J. _953043
100	1		_aGarcia, D. _945586
100	1		_aSwennen, R. _936689
100	1		_aIriarte, E. _953044
100	1		_aMuchez, P. _953045
100	1		_aCaline, B. _953046
999			_c187616 _d187616