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1 Dipartimento di Scienze della Terra, Universitae di Pavia, Pavia, Italy, 27100; andrea.ceriani{at}unipv.it
2 Dipartimento di Scienze della Terra, Universitae di Pavia, Pavia, Italy, 27100; digiulio{at}unipv.it
3 University of Kansas, Department of Geology, 1475 Jayhawk Boulevard, Room 120, Lawrence, Kansas, 66045-7613; gold{at}ku.edu
4 Departamento de Petrologia y Geoquimica, Facultad de Ciencias Geologicas, Universidad Complutense, Madrid, 28040, Spain; crossi{at}geo.ucm.es
Andrea Ceriani is a postdoctoral student at the University of Pavia (Italy). He received his M.S. degree (1995) and Ph.D. (2001) from the University of Pavia. His current research includes diagenesis of carbonates and siliciclastics, with particular attention to fluid-inclusions studies, and provenance of modern sands and ancient arenites.Andrea Di Giulio is associate professor at the University of Pavia (Italy). He received his B.Sc. degree in geological science in 1985 and then began his research, focusing mostly on the sedimentology and petrology of clastic sequences. His current interests include diagenesis of reservoir rocks, modeling of foredeep basins, and models to relate source land geology, climate, and relief to the composition of so-called daughter sediments.
Robert H. Goldstein is the Haas Distinguished Professor at the University of Kansas. He received his B.S. degree from Juniata College, Huntingdon, Pennsylvania, and his M.S. degree and Ph.D. from the University of Wisconsin. His current research includes development of the fluid-inclusion tool for diagenetic research, integration of diagenesis with sequence stratigraphy and tectonic setting, and evaluation of controls on the sequence stratigraphic character of carbonate rocks.
Carlos Rossi is an associate professor in the Department of Petrology and Geochemistry at Complutense University (Madrid). He received a Ph.D. in geology from Complutense University in 1993. His main research interests are sequence stratigraphy and diagenesis of carbonates, Quaternary karst, and diagenesis of sandstone petroleum reservoirs, especially from north Africa.
Fluid inclusions in quartz and dolomite cements were used to determine temperature, timing, origin, and function of fluids in the diagenetic evolution of the Lower Cretaceous Upper Sarir Sandstone (Sirt basin, Libya). Transmitted light, backscattered electron, and scanning electron microscope (SEM) cathodoluminescence analyses were carried out to determine the paragenesis.
In quartz overgrowths, fluid inclusions along the grain-overgrowth boundary yield homogenization temperatures from 130 to 141°C and salinities between seawater and freshwater. Aqueous fluid inclusions in later quartz overgrowths have homogenization temperatures from 114 to 129°C and salinities between 18 and 21 wt. % NaCl equivalent. Fluid inclusions in dolomite have variable homogenization temperatures (120-141°C) and high salinities (20-22 wt. % NaCl equivalent).
This trend in homogenization temperatures of fluid inclusions is interpreted as the result of quartz cement precipitation in the presence of hot, low-salinity, connate fluids connected with an increased heat flow related to regional rifting. Later quartz overgrowths precipitated during regional cooling concurrent with the end of the rifting and after invasion of saline fluids, possibly brought in from adjacent areas or refluxed downward during or after times of evaporite deposition.
This diagenetic history linked to a decreasing heat flow could be common in other aborted-rift basins, which are important targets for oil exploration.
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