Paleogene carbonates, United Arab Emirates

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Nov 12, 2015 - g Soran University, Faculty of Science, Department of Petroleum ... of marine Paleogene carbonates in eastern United Arab Emirates, which are ...
Marine and Petroleum Geology 74 (2016) 1e21

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Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo

Research paper

Saddle dolomite and calcite cements as records of fluid flow during basin evolution: Paleogene carbonates, United Arab Emirates M. Sirat a, I.S. Al-Aasm b, *, S. Morad c, A. Aldahan d, O. Al-Jallad e, A. Ceriani c, D. Morad f, H. Mansurbeg g, A. Al-Suwaidi c a

ADCO, P.O. Box 270, Abu Dhabi, United Arab Emirates Department of Earth and Environmental Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada c Department of Petroleum Geosciences, The Petroleum Institute, P.O. Box 2533, Abu Dhabi, United Arab Emirates d Department of Geology, United Arab Emirates University, Al Ain, United Arab Emirates e Ingrain Company, Abu Dhabi, United Arab Emirates f Department of Earth Sciences, University of Oslo, Oslo, Norway g Soran University, Faculty of Science, Department of Petroleum Geosciences, Iraq b

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Article history: Received 28 April 2015 Received in revised form 5 November 2015 Accepted 7 November 2015 Available online 12 November 2015

Field observations indicate that tectonic compression, anticline formation and concomitant uplift events of marine Paleogene carbonates in eastern United Arab Emirates, which are related to the Zagros Orogeny, have induced brecciation, karstification, and carbonate cementation in vugs and along faults and fractures. Structural analysis, stable isotopes and fluid inclusion microthermometry are used to constrain the origin and geochemical evolution of the fluids. Fluid flow was related to two tectonic deformation phases. Initially, the flux of moderately 87Sr-rich basinal NaCleMgCl2eH2O brines along reactivated deep-seated strike-slip faults have resulted in the precipitation of saddle dolomite in fractures and vugs and in dolomitization of host Eocene limestones (d18OV-PDB !15.8‰ to !6.2‰; homogenization temperatures of 80e115 " C and salinity of 18e25 wt.% eq. NaCl). Subsequently, compression and uplift of the anticline was associated with incursion of meteoric waters and mixing with the basinal brines, which resulted in the precipitation of blocky calcite cement (d18OV-PDB !22‰ to !12‰; homogenization temperatures of 60e90 " C and salinity of 4.5e9 wt.% eq. NaCl). Saddle dolomite and surrounding blocky calcite have precipitated along the pre- and syn-folding EeW fracture system and its conjugate fracture sets. The stable isotopes coupled with fluid-inclusion micro-thermometry (homogenization temperatures of #50 " C and salinity of