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Titolo:
DEDOLOMITES ASSOCIATED WITH KARSTIFICATION - AN EXAMPLE OF EARLY DEDOLOMITIZATION IN LACUSTRINE SEQUENCES FROM THE TERTIARY MADRID BASIN, CENTRAL SPAIN
Autore:
CANAVERAS JC; SANCHEZMORAL S; CALVO JP; HOYOS M; ORDONEZ S;
Indirizzi:
CSIC,MUSEO NACL CIENCIAS NAT,DEPT GEOL,JOSE GUTIERREZ ABASCAL 2 E-28006 MADRID SPAIN UNIV COMPLUTENSE MADRID,FAC CIENCIAS GEOL,DEPT PETROL & GEOQUIM E-28040 MADRID SPAIN
Titolo Testata:
Carbonates and evaporites
fascicolo: 1, volume: 11, anno: 1996,
pagine: 85 - 103
SICI:
0891-2556(1996)11:1<85:DAWK-A>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOUTH-CENTRAL TEXAS; CARBONATE-AQUIFER; CALCITE; DIAGENESIS; EVOLUTION; ORIGIN; DOLOMITIZATION; MISSISSIPPIAN; MINERALOGY; SPELEOTHEM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
91
Recensione:
Indirizzi per estratti:
Citazione:
J.C. Canaveras et al., "DEDOLOMITES ASSOCIATED WITH KARSTIFICATION - AN EXAMPLE OF EARLY DEDOLOMITIZATION IN LACUSTRINE SEQUENCES FROM THE TERTIARY MADRID BASIN, CENTRAL SPAIN", Carbonates and evaporites, 11(1), 1996, pp. 85-103

Abstract

A variety of calcite fabrics formed by dedolomitization of middle to upper Miocene continental sediments of the Madrid basin, central SpainThe dedolomites are associated with other carbonates that show abundant diagenetic features. The diagenetic carbonates (Diagenetic Carbonate Zone, DCZ) overlies and grades laterally into lacustrine dolomite (Lower Dolomite Unit, LDU) and evaporites (Evaporitic Unit, EU), and in turn is capped by a paleokarst surface. The main dedolomite fabrics include sutured calcites and radial-fibrous calcites, the latter consisting of pseudospherulite mosaics and fibrous crusts. Other subordinate dedolomite fabrics consist of micro to mesocrystalline mosaics of rhombic, occasionally zoned calcites as well as reworked pseudospherulite crystals. These fabrics are interpreted to have been formed from extensive calcitization of dolostones and associated evaporite facies, the process being triggered and fostered by input of meteoric waters throughout a karstic system. The origin of the radial-fibrous calcites is discussed more specifically in view of their similarities to other calcite fabrics (e.g. Microcodium) often described in meteoric diagenetic environments. Geochemical evidence indicates that dedolomitization occurred in the shallow subsurface (< 40 m depth) and was achieved by oxidizing meteoric-derived ground waters. The diagenetic system behaved as an open system for nearly all trace elements analyzed; but in the shallower zone (vadose zone) the system is partially close respect to strontium. Vertical trends of the stable isotopes also support the proposed paleokarst model characterized by an irregular shallow water tableand a narrow vadose zone. The results obtained from the geochemical simulation support that dedolomitization could develop by two combined hydrographical patterns: authigenic recharge through limestones and allogenic recharge. The dissolution/precipitation rates calculated for the main minerals involved in the process are consistent with petrographic- and geochemical evidence.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/09/20 alle ore 17:02:20