Fluid channeling along thrust zones: the Lagonegro case history, southern Apennines, Italy

Abstract

A regional study on late burial syntectonic dolomites and syntectonic calcite and quartz veins occurring in the hemipelagic Triassic-Jurassic succession of the Lagonegro Basin (southern Apennines) was carried out by integrating fieldwork with structural, fluid inclusion, and geochemical investigations on both surface and subsurface samples. The main goal was to characterize the parent fluids – partly dolomitizing – channelled along a major, out of sequence thrust zone. Calcite veins from the deeper tectonic mélange zone that occurs at the base of the allochthonous wedge – as evidenced by numerous oil wells – were investigated as well. The results point out that the fluids at peak burial conditions, achieved during the first deformation stage, were characterized by temperatures of 120-140 °C and salinities averaging 2 wt % NaCl eq, whereas those channelled along the late (out of sequence) thrust zone and responsible for partial dolomitization of the succession had slightly lower temperatures (Th=95±10 °C) and salinities in the range of slightly modified to normal marine seawater (mean at 3.7 wt % NaCl eq). Similar low salinities are encountered in late dolomites from other Fold and Thrust Belts of the Italian peninsula. The most probable source for the fluids channelled along the investigated out of sequence thrust zone is represented by Miocene marine pore-waters expelled from the tectonic mélange zone. A role on fluid salinities appears to be played by the different lithologies of the Fold and Thrust Belts décollement surface

Reflux dolomitization of the Upper Permian Changxing Formation and the Lower Triassic Feixianguan Formation, NE Sichuan Basin, China

“…; Whitaker & Xiao ; Gabellone et al . ). Compaction‐driven flow would presumably have pushed older brines through overlying younger strata and so left its isotopic (especially 87 Sr/ 86 Sr) imprint.…”

“…If intermediate to deep subsurface dolomitization was important in the study area, a mechanism would have been required to force large quantities of water through the precursor carbonate sediment. The principal mechanisms proposed for moving Mg-bearing waters through subsurface carbonates include (i) compaction-driven flow; (ii) topography-driven flow; and (iii) thermal convection (Machel 2004;Whitaker et al 2004;Whitaker & Xiao 2010;Gabellone et al 2013). Compaction-driven flow would presumably have pushed older brines through overlying younger strata and so left its isotopic (especially 87 Sr/ 86 Sr) imprint.…”

A decoupled kinematic model for active normal faults: Insights from the 1980, MS = 6.9 Irpinia earthquake, southern Italy

“…WNW-ESE-trending segments follow the pattern of older (i.e., Pliocene age; Caiazzo et al, 1992) structures, which also include E-W-trending faults (Amato et al, 1992). This points to the reactivation, in the current extensional tectonic regime, of preexisting discontinuities that developed during the multistage structural evolution of the southern Apennines (e.g., Cello and Mazzoli, 1998;Caiazzo et al, 2006;Spina et al, 2008Spina et al, , 2009Spina et al, , 2011Iannace et al, 2012;Vitale et al, 2012;Gabellone et al, 2013).…”

Origin of dolomites in the Cambrian (upper 3rd‐Furongian) formation, south‐eastern Sichuan Basin, China

“…The driving mechanism of the migrating evaporated brine was the density contrast between the strongly evaporated brines on the platform and the normal seawater of the nearby ocean (Gabellone et al . ; Jiang et al . ).…”

“…The movement of this evaporated brine resulted in progressive dolomitization. The driving mechanism of the migrating evaporated brine was the density contrast between the strongly evaporated brines on the platform and the normal seawater of the nearby ocean (Gabellone et al 2013;Jiang et al 2013). Salinity of the dolomitizing fluids decreased during reflux, and the d 18 O values of the oolitic dolomite were therefore lower than those of the dolomicrite (Adams & Rhodes 1960;Saller & Henderson 1998;Warren 2000;Rameil 2008;Garcia-Fresca et al 2012).…”