Origin of the megabreccias in the Katanga Copperbelt (D.R.Congo)

© 2018 Elsevier Ltd The megabreccias in the Katanga part of the Neoproterozoic Central African Copperbelt contain up to several km-long blocks and fragments of the Mines Subgroup which host most of the stratiform Cu-Co deposits. New observations, particularly on cores from boreholes drilled at Luiswishi indicate three types of fracturing: 1) brittle post-folding in the Mines Subgroup; 2) hydraulic; and 3) ductile in soft incompetent siltstones of the R.A.T. and Dipeta subgroups. These fracturing phases dislocated the Roan succession into blocks and fragments and, in particular, clearly showed that there is an evolution from an in situ hydraulic fracturing, to a heterometric brecciation implying some movement and abrasion of the fragments. The process points to significant compression, and was accompanied by fluid expulsion and precipitation of dolomite after decompression. Fluid inclusion microthermometry in dolomite grains shows that the fluids were of high salinity and high temperature, suggesting dissolution of evaporites most likely contained in the Roan sedimentary pile. These saline fluids allowed the fluidization of the breccias, facilitating the displacement of the nappes, pinching out (extrusion-like) megabreccias along thrust-faults, and resulting in intrusion of breccias between the blocks or into large fractures. Breccias between the blocks are clearly identified as friction breccias. They contain a fine material, as part of the matrix, resulting from abrasion of the fragments during transportation. Abrasion and attrition explain the rounding of the fragments. A late cementation phase from less saline and lower temperature fluids suggests the addition of meteoric water in the system, and the mixing with the ambient fluids. The minimum burial depth of the meteoric water incursion is estimated at 2.8 km. Such under-saturated fluids may have contributed to the dissolution of residual evaporites and of the evaporitic material from the Kiubo rocks at the base of the nappes, and led to further brecciation, possibly explaining the multi-phase features of the breccia. The megabreccias occur at the base of the thrusts sheets and are marked by thrust-fault zones. Results of the study support a process of formation of the megabreccias related to a fold-and-trust event, and invalidate a syn-orogenic sedimentary origin as an olistostrome formed by subaqueous conglomeratic debris flows and clastic syn-orogenic sediments. They also contradict a pure salt tectonic hypothesis that propose the extrusions and enlargements of allochthonous evaporites-gigabreccia before the Lufilian deformation. However, the model is compatible with a “fluid behaviour” of pressured saline fluids trapped in folds and/or thrust sheets, and resulting from evaporites dissolution at variable depth.status: publishe

Guidelines for the Li–Fraumeni and heritable TP53 -related cancer syndromes

Abstract: Fifty years after the recognition of the Li–Fraumeni syndrome (LFS), our perception of cancers related to germline alterations of TP53 has drastically changed: (i) germline TP53 alterations are often identified among children with cancers, in particular soft-tissue sarcomas, adrenocortical carcinomas, central nervous system tumours, or among adult females with early breast cancers, without familial history. This justifies the expansion of the LFS concept to a wider cancer predisposition syndrome designated heritable TP53-related cancer (hTP53rc) syndrome; (ii) the interpretation of germline TP53 variants remains challenging and should integrate epidemiological, phenotypical, bioinformatics prediction, and functional data; (iii) the penetrance of germline disease-causing TP53 variants is variable, depending both on the type of variant (dominant-negative variants being associated with a higher cancer risk) and on modifying factors; (iv) whole-body MRI (WBMRI) allows early detection of tumours in variant carriers and (v) in cancer patients with germline disease-causing TP53 variants, radiotherapy, and conventional genotoxic chemotherapy contribute to the development of subsequent primary tumours. It is critical to perform TP53 testing before the initiation of treatment in order to avoid in carriers, if possible, radiotherapy and genotoxic chemotherapies. In children, the recommendations are to perform clinical examination and abdominal ultrasound every 6 months, annual WBMRI and brain MRI from the first year of life, if the TP53 variant is known to be associated with childhood cancers. In adults, the surveillance should include every year clinical examination, WBMRI, breast MRI in females from 20 until 65 years and brain MRI until 50 years

Cancer Surveillance Guideline for individuals with PTEN hamartoma tumour syndrome

Abstract: PTEN hamartoma tumour syndrome is a diverse multi-system disorder predisposing to the development of hamartomatous growths, increasing risk of breast, thyroid, renal cancer, and possibly increasing risk of endometrial cancer, colorectal cancer and melanoma. There is no international consensus on cancer surveillance in PHTS and all current guidelines are based on expert opinion. A comprehensive literature review was undertaken and guidelines were developed by clinicians with expertise from clinical genetics, gynaecology, endocrinology, dermatology, radiology, gastroenterology and general surgery, together with affected individuals and their representatives. Recommendations were put forward for surveillance for breast, thyroid and renal cancers. Limited recommendations were developed for other sites including endometrial, colon and skin. The proposed cancer surveillance recommendations for PHTS require a coordinated multidisciplinary approach and significant patient commitment. The evidence base for cancer surveillance in this guideline are limited, emphasising the need for prospective evaluation of the effectiveness of surveillance in the PHTS population

Appendice. La serpentinite de B. 265

De Putter Thierry. Appendice. La serpentinite de B. 265. In: Les cahiers de Mariemont, volume 27, 1996. pp. 24-25

Etude sédimentologique de la Grande brèche viséenne ("V3a") du Bassin de Namur-Dinant

Doctorat en SciencesVol.1 :texte ;Vol.2 :Annexes (TH-000141)info:eu-repo/semantics/nonPublishe

Multidisciplinary study of prestige ornamental stones or 'marbles' in the Roman city of Alba Fucens (Abruzzo, Italy)

info:eu-repo/semantics/publishe

The Mindouli (Republic of the Congo) mining district revisited (1). geological context and preliminary results on the formation of complex, multiphase, Cu-Pb-Zn deposits

The Niari Syncline (Republic of the Congo) hosts complex Cu-Pb-Zn deposits, associated with ENE-WSW-trending sets of regional faults (Maurin et al. 1990). Abandoned mines at Mindouli, Ntola, M’Passa Mines, Mfouati, Boko-Songho have been investigated, with a double objective: (1) get an improved understanding of the formation of these deposits; (2) get an improved understanding of the use of copper and lead exploited from these mines in pre-colonial metallurgy (Nikis and De Putter, this volume).The studied Cu-Pb-Zn deposits are hosted along or near the N60°E faulted contact between the Neoproterozoic stromatolitic limestone of the “Schisto-Calcaire” and the younger Neoproterozoic pink sandstone of the Mpioka Group, both in the West-Congolian Supergroup. At some post-depositional and pre-mineralization stage, the stromatolitic limestone has undergone extensive karstic dissolution, and later dolomitization/silicification.A hydrothermal origin has been proposed for these deposits (Buffet et al. 1987), which is substantiated by the presence of massive Fe-Cu-Pb-Zn sulphides (chalcopyrite, sphalerite, galena) and sulphide-cemented breccia at depth in most deposits. Further work is ongoing to characterize/date the post-Mpioka hydrothermal phase of these (MVT-like?) deposits, possibly allowing connections with major geodynamic events in the study area. In later phases, the deposits experienced supergene overprints that varied according to their specific settings. At Mindouli, the porous and permeable faulted contact between the karstic limestone and the Mpioka sandstone favoured the formation of a rich paragenesis of Cu-Pb-Zn secondary minerals, dominated by silicates (dioptase, plancheite, hemimorphite) and carbonates (malachite, azurite) in the upper part of the deposits. At Mfouati, the karstic cavities in the limestone are filled with a highly porous iron-rich alterite that hosts a paragenesis dominated by Pb-Zn minerals (hemimorphite, smithsonite, wulfenite), with accessory Cu minerals (dioptase, chrysocolla, malachite). At Boko-Songho, the deposits are capped by a thick iron-rich alterite and the paragenesis is dominated by void-filling malachite (crusts, botryoids: De Putter et al. 2010). Supergene overprints on the studied deposits need to be dated and further connected with major regional paleosurfaces (De Putter et al. 2015).Fluid circulation patterns through these deposits – both hydrothermal and meteoric – have resulted in a vertical elemental distribution: Pb deeper than Cu deeper than Zn. As in the Katanga Copperbelt (D.R. Congo), a “late” (Cenozoic?) meteoric phase has remobilized copper and allowed the formation of void-filling malachite in the subsurface. This mineral is present/abundant in most deposits and has been exploited to fuel pre-colonial metallurgy, at the vicinity of the mines (Nikis and De Putter 2016).info:eu-repo/semantics/nonPublishe