Boron and boron isotopes as tracers for diagenetic reactions and depth of mobilization, using muds and authigenic carbonates from eastern Mediterranean mud volcanoes

Abstract

Authigenic carbonates and muds from six mud volcanoes in the eastern Mediterranean Sea were recovered during the French/Dutch MEDINAUT cruise utilizing the submersible Nautile in November 1998. The mud volcanoes are active seafloor vents in two areas at the plate boundary between the converging African and Eurasian Plates: the Mediterranean Ridge accretionary prism near Crete (Greece) and the Anaximander Mountains south of Turkey. B contents and 6HB signatures were measured with the aim of identifying the diagenetic processes and source depths of the material in the collision zone. B concentrations of the carbonate precipitates cover a range of 8-45 ppm and vary isotopically from +15.6 to +22.9%0 (corresponding to a parent solution of 34.9-42.2%0 at pH 7). Both the B-enrichment and a 6 laB valve slightly lower than seawater suggest the mud domes originate from a moderately deep fluid source, with local admixture of seawater. B contents and 6HB of the mud show distinct differences between the areas: the Mediterranean Ridge mud domes have lower B contents and higher 8 ~B (average 3.9%0) compared to Anaximander Mountains mud volcanoes (611B average -0.6%0). These B results attest the release of structurallybound B from clay mineral lattices, probably due to stronger deformation near Turkey. These mudstones, which had previously been affected by deep-seated thrusting beneath the Antalya Complex, may have been liquefied and remobilized in their present setting. By contrast, the mud on the Mediterranean Ridge represents offscraped clay-rich strata that was incorporated into the large accretionary wedge.

Boron isotope geochemistry ofNa‐bicarbonate,Na‐chloride, andCa‐chloride waters from theNorthernApennineForedeep basin: other pieces of the sedimentary basin puzzle

“…According to Vengosh et al (2000), other porewaters were affected by boron adsorption on minerals, particularly for the samples clustered above the line representing the evaporation of their seawater component (Fig. In fact, both the B concentration (105 mg l À1 ) and d 11 B (+18.9&) of the overpressured SAL sample resemble those estimated for the fluid issuing (Vengosh et al 1998a(Vengosh et al , 2000 and mud volcanoes (Kopf & Deyhle 2002;Deyhle et al 2003), respectively (key). In contrast, the porewaters shifted down the evaporation line and grouped near the line joining the SAL and SM samples with seawater might represent diagenetic boron from clay minerals following stressdriven or temperature-induced effects, as described by Deyhle et al (2003).…”

“…In contrast, the porewaters shifted down the evaporation line and grouped near the line joining the SAL and SM samples with seawater might represent diagenetic boron from clay minerals following stressdriven or temperature-induced effects, as described by Deyhle et al (2003). In fact, both the B concentration (105 mg l À1 ) and d 11 B (+18.9&) of the overpressured SAL sample resemble those estimated for the fluid issuing (Vengosh et al 1998a(Vengosh et al , 2000 and mud volcanoes (Kopf & Deyhle 2002;Deyhle et al 2003), respectively (key). Note that the symbol dimension and logarithmic scale of the 1/B abscissa cancel the gap between weight and volume basis concentrations (see Table S1).…”

“…4, the line connecting the SM and SAL samples with seawater and the seawater evaporation line delimit a triangular area within which some of the Mediterranean porewaters fall. In contrast, the porewaters shifted down the evaporation line and grouped near the line joining the SAL and SM samples with seawater might represent diagenetic boron from clay minerals following stressdriven or temperature-induced effects, as described by Deyhle et al (2003). 4).…”

Unraveling Sources and Climate Conditions Prevailing during the Deposition of Neoproterozoic Evaporites Using Coupled Chemistry and Boron Isotope Compositions (δ11B): The Example of the Salt Range, Punjab, Pakistan

“…A third group of samples (Mainly formed by the KS and NPW sections) plots outside of these trends (Figure 5B) and seems to symbolize diagenetic B emitted from clay minerals following stress-driven or temperature-induced effects, as illustrated by Boschetti et al [49] and Deyhle et al [53]. Indeed, their B concentration (KS = 106 ppm, NPW = 75 ppm) and their δ 11 B (KS = 17.44‰, NPW = 19.18‰) are similar to those reported in Salvarola (Italy) for overstressed fluids by Boschetti et al [49], as well as to fluids rising from a mud volcano reported by You et al [54] in the vicinity of a decollement zone (i.e.…”

Evidence of late-Holocene mud-volcanic eruptions in the Modena foothills (northern Italy)

“…Serra, 1986). Boron isotopes have been considered potential tracers of geologically recent marine effects (Barth, 1993;Deyhle et al, 2003). Boron isotope values of the considered geofluids are within the range of brines (e.g.…”