Multiphase carbonate cementation related to fractures in the Upper Jurassic limestones, Maestrat Basin (Iberian Range, Spain)

In the western part of the Penyagolosa subbasin (Maestrat Basin, Spain), carbonate cementation occludes fractures and infills stylolites in Tithonian-Berriasian limestones. Field relationships, petrography, cathodoluminesence and geochemical analyses (microprobe, fluid inclusions, oxygen, carbon and strontium isotopes) of the carbonate cements show that the paragenetic sequence includes (A) calcite cements in echelon tension gashes (- 11.37parts per thousand delta(18)O VPDB). (B) Scarce isolated rhombic dolomite replacement cement. (C) Saddle dolomite replacement cement with fluid inclusions that are characterized by high salinity (21.5 to 23.5% wt.. eq. NaCl), high temperatures (Th 110-155 degreesC) and similar negative values of oxygen isotopes (- 11.27parts per thousand delta(18)O VPDB). (D) Calcite replacing (dedolomite) saddle and rhombic dolomite (- 8.61 to - 6.76parts per thousand delta(18)O VPDB and - 4.38 to + 0.07parts per thousand delta(13)C VPDB). (E) Calcite cement filling vertical fractures. They have the highest Th (160-260 degreesC), negative values of oxygen isotopes (- 9.97 to - 13.44parts per thousand delta(18)O VPDB). (F) Calcite cement filling bed-parallel stylolites (- 8.81parts per thousand delta(18)O VPDB). This paragenetic sequence reflects multiple phases of fracture-controlled carbonate cements. The first stage calcite is related to syn-sedimentary rifting of the Late Jurassic-Early Cretaceous and progressive burial depth. The later phases of dolomite and calcite in vertical veins are considered hydrothermal in origin and indicate a mix of saline waters, possibly derived from the underlying Triassic and Liassic evaporites, with deep circulating meteoric water with higher temperature than the surrounding rocks and related to the regional Alpine compression. (C) 2003 Elsevier Science B.V. All rights reserved.