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

Abstract

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 (- 11.37 ‰ δ18O VPDB). 03) 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. NaC1), high temperatures (Th 110-155 °C) and similar negative values of oxygen isotopes (- 11.27 ‰ δ18 O VPDB). (D) Calcite replacing (dedolomite) saddle and rhombic dolomite (- 8.61 to - 6.76 ‰ δ18 O VPDB and -4.38 to + 0.07 ‰ δ13C VPDB). (E) Calcite cement filling vertical fractures. They have the highest Th (160-260 °C), negative values of oxygen isotopes (- 9.97 to -13.44 ‰ δ18 O VPDB). (F) Calcite cement filling bed-parallel stylolites ( - 8.81‰ δ18 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.