Diagenetic and thermal history of the Jurassic-Tertiary succession of the Zagros Mountains in the Dezful Embayment (SW Iran): constraints from fluid inclusions |
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| Authors: | A Ceriani R Calabrò A Di Giulio R Buonaguro |
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| Institution: | 1.Dipartimento di Scienze della Terra,Università di Pavia,Pavia,Italy;2.Edison S.p.A.,Milan,Italy |
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| Abstract: | To constraint the diagenetic and thermal history in the Mesozoic-Tertiary succession of the Zagros Fold-Belt, a study was
performed on fluid inclusions trapped in intergranular, vug, and fracture-filling cements in Jurassic to Miocene outcrop samples
collected along the Anneh and Fahliyan Valleys of Khuzestan Province, southwest Iran. Petrographic observations showed at
least two systems of fractures that postdate intergranular cementation. Two different types of oil-filled fluid inclusions
occur in the intergranular cements and in the first fracture network, but they are absent in the second fracture network.
Microthermometry of fluid inclusions was used to determine the temperature and salinity of fluids responsible for mineral
precipitation. Within intergranular cements and calcite fillings the oldest fractures, precipitation occurred from high saline
fluids in a temperature range of 60–120°C, depending on the stratigraphic depth. The strong correlation between fluid inclusions
temperature and stratigraphic depth suggests that the intergranular cementation and the first fracture-filling event occurred
prior to structural deformation. Furthermore, this correlation indicates a relatively constant paleogeothermal gradient at
the time of cement precipitation of about 28°C/Km. On the contrary, fluid inclusions trapped in cements within the second
fracture network lack oil and contain freshwater trapped at low temperatures that do not correlate to the stratigraphic position.
This suggests second fracturing event occurred after oil migration and during or after deformation of the Zagros Fold-Belt,
when the samples were in a near-surface position. |
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