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Aim: To assess the long-term incidence and predictive factors for recurrence after laparoscopic ventral hernia repair using a bridging technique.Methods: The study group consisted of 213 consecutive patients operated by laparoscopy for primary ventral (n = 158) or incisional hernia (n = 55) between 2001 and 2014. Patients had a repair without fascia closure by intra-peritoneal onlay placement of a Parietex® composite mesh centred on the defect with an overlap of at least 3 cm. Clinical outcome was assessed by a combination of office consultation, patient's electronic medical file review and telephone interview.Results: There were 144 men and 69 women with a mean age of 55 ± 12 years and a BMI of 32 ± 6. With a mean follow-up of 69 ± 44 months, a recurrent hernia was noted in 16 patients (7.5%). Univariate analysis showed a statistically significant higher recurrence rate in the following conditions: incisional hernia (15%), BMI ≥ 35 (21%), defect width >4 cm (27%), defect area >20 cm2 (27%), mesh overlap <5 cm (32%) and ratio of mesh area to defect area (M/D ratio) ≤12 (48%). Multivariate logistic analysis revealed that M/D ratio was the only independent predictive factor for recurrence (coefficient -0.79, OR 0.46, p < 0.002). With a M/D ratio ≤8, between 9 and 12, between 13 and 16, and ≥17, the recurrence rate was, respectively, 70, 35, 9 and 0% (p < 0.001).Conclusions: In laparoscopic repair of ventral hernia using a bridging technique, an overlap of at least 5 cm is not all that is required to prevent hernia recurrence. The M/D ratio is the most important predictive factor for recurrence. A ratio of 13 appears as the threshold under which that technique cannot be recommended and 16 as the threshold over which the risk of recurrence is virtually nil. If a satisfactory M/D ratio cannot be achieved, other surgical repair should be proposed to the patient. [ABSTRACT FROM AUTHOR]

The vein-type tungsten deposit at Nyakabingo in the central Tungsten belt of Rwanda is located in the eastern flank of the complex Bumbogo anticlinal structure. The host rock is composed of alternating sequences of sandstones, quartzites, and black pyritiferous metapelitic rocks. Two types of W-mineralized quartz veins have been observed: bedding-parallel and quartz veins that are at high angle to the bedding, which are termed crosscutting veins. Both vein types have been interpreted to have been formed in a late stage of a compressional deformation event. Both vein types are associated with small alteration zones, comprising silicification, tourmalinization, and muscovitization. Dating of muscovite crystals at the border of the veins resulted in a maximum age of 992.4 ± 1.5 Ma. This age is within error similar to the ages obtained for the specialized G4 granites (i.e., 986 ± 10 Ma). The W-bearing minerals formed during two different phases. The first phase is characterized by scheelite and massive wolframite, while the second phase is formed by ferberite pseudomorphs after scheelite. These minerals occur late in the evolution of the massive quartz veins, sometimes even in fractures that crosscut the veins. The ore minerals precipitated from a HO-CO-CH-N-NaCl-(KCl) fluid with low to moderate salinity (0.6-13.8 eq. wt% NaCl), and minimal trapping temperatures between 247 and 344 °C. The quartz veins have been crosscut by sulfide-rich veins. Based on the similar setting, mineralogy, stable isotope, and fluid composition, it is considered that both types of W-mineralized quartz veins formed during the same mineralizing event. Given the overlap in age between the G4 granites and the mineralized quartz veins, and the typical association of the W deposits in Rwanda, but also worldwide, with granite intrusions, W originated from the geochemically specialized G4 granites. Intense water-rock interaction and mixing with metamorphic fluids largely overprinted the original magmatic-hydrothermal signature. [ABSTRACT FROM AUTHOR]

In the Lower Palaeozoic Anglo–Brabant fold belt in Belgium, a detailed study of the geochemistry of different generations of pyrite has been carried out by electron microprobe analysis. The occurrence of pyrite is related to different episodes in the evolution of this fold belt. Pyrite occurs either as a pre- or as a syn-deformation phase in the metamorphosed sedimentary and igneous rocks. Pre-cleavage pyrite in greenschist metamorphosed sedimentary rocks has a relative higher Ni-content. As illustrated in the Kupferschiefer, this could be due to the release of Ni from organic matter during diagenesis. Pre-cleavage pyrite in the igneous rocks has higher Cu, Pb, Cd and Zn contents, which could be caused by the incorporation of these elements in the sulphide phase during the final stage of the crystallisation of the magma. Syn-deformation pyrite along cleavage planes and in quartz/carbonate veins is characterised by higher As, Sb, Se and Au contents, typical for hydrothermal mineralisation in a greenschist facies fold belt. [ABSTRACT FROM AUTHOR]

Mineralised vein systems have been investigated at nine localities at the southern margin of the Anglo-Brabant fold belt in Belgium. During the late Silurian to early Middle Devonian Caledonian orogeny, shear zones formed, inferred to be associated with granitoid basement blocks in the subsurface. The circulation of a metamorphic fluid, possibly originating in the Cambrian core of the fold belt, along these shear zones resulted in the formation of mesozonal orogenic mineralisation at the southern margin of the Anglo-Brabant fold belt. The fluid had a composition dominated by H2O–CO2–X–NaCl–KCl. The shear zones form part of a greater fault zone, the Nieuwpoort–Asquempont fault zone, which is characterised by normal faulting that started before the Givetian and by the reactivation of the shear zones. Two fluid generations are associated with this normal faulting. First, a low salinity H2O–NaCl(–KCl) fluid migrated through the Palaeozoic rocks after the Silurian. Based on the isotopic composition, this fluid could be a late-metamorphic Caledonian fluid or a younger fluid that originated from the Rhenohercynian basin and interacted with Lower Devonian rocks along its migration path. Second, a high salinity H2O–NaCl–CaCl2 fluid was identified in the fault systems. Similar fluids have been found in southern and eastern Belgium, where they produced Mississippi Valley-type Zn–Pb deposits. These fluids are interpreted as evaporative brines that infiltrated the Lower Palaeozoic basement, from where they were expelled during extensional tectonism in the Mesozoic. [ABSTRACT FROM AUTHOR]

Reports on the identification of a Lower Palaeozoic mesothermal gold mineralization formed during the Caledonian orogeny in Wales, Scotland and Ireland. Application of [sup 40]Ar/[sup 39]Ar technique in the dating of mineralizing events; Brittle-ductile origin of the shear zone in the Marcq area.

The origin of giant, sedimentary rock-hosted copper-cobalt (Cu-Co) provinces remains contentious, in part due to the lack of precise and reliable ages for mineralisation. As such, no consensus has been reached on the genetic model for ore formation, and the relationships between tectonism, palaeo-fluid circulation and mineralisation. Here, we link the timing of Cu-Co mineralisation in the Central African Copperbelt to compressional tectonics during the Lufilian Orogeny by using new ca. 609-473 Ma ages given by rhenium-osmium (Re-Os) isotope data for individual Cu-Co sulphides (carrolite and bornite) from the Cu-Co Kamoto deposit. The initial Os isotope composition of carrolite is compatible with the leaching of Os and Cu(-Co) from Mesoproterozoic Cu sulphide deposits hosted in fertile basement. In contrast, the ca. 473 Ma Cu-Au mineralisation stage, which is coeval with late- to post-compressional deformation, may be a distal expression of fluid flow and heat transfer caused by magmatic intrusions in the core of the collisional orogen. The Re-Os ages support a model for mineralisation driven by evaporite dissolution and percolation of large volumes of dense brines in the Katangan Basin during the Lufilian Orogeny. [ABSTRACT FROM AUTHOR]