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I. Kenis Ph. Muchez G. Verhaert A. Boyce M. Sintubin 《Contributions to Mineralogy and Petrology》2005,150(1):102-118
Fluid inclusions in quartz veins of the High-Ardenne slate belt have preserved remnants of prograde and retrograde metamorphic
fluids. These fluids were examined by petrography, microthermometry and Raman analysis to define the chemical and spatial
evolution of the fluids that circulated through the metamorphic area of the High-Ardenne slate belt. The earliest fluid type
was a mixed aqueous/gaseous fluid (H2O–NaCl–CO2–(CH4–N2)) occurring in growth zones and as isolated fluid inclusions in both the epizonal and anchizonal part of the metamorphic
area. In the central part of the metamorphic area (epizone), in addition to this mixed aqueous/gaseous fluid, primary and
isolated fluid inclusions are also filled with a purely gaseous fluid (CO2–N2–CH4). During the Variscan orogeny, the chemical composition of gaseous fluids circulating through the Lower Devonian rocks in
the epizonal part of the slate belt, evolved from an earlier CO2–CH4–N2 composition to a later composition enriched in N2. Finally, a late, Variscan aqueous fluid system with a H2O–NaCl composition migrated through the Lower Devonian rocks. This latest type of fluid can be observed in and outside the
epizonal metamorphic part of the High-Ardenne slate belt. The chemical composition of the fluids throughout the metamorphic
area, shows a direct correlation with the metamorphic grade of the host rock. In general, the proportion of non-polar species
(i.e. CO2, CH4, N2) with respect to water and the proportion of non-polar species other than CO2 increase with increasing metamorphic grade within the slate belt. In addition to this spatial evolution of the fluids, the
temporal evolution of the gaseous fluids is indicative for a gradual maturation due to metamorphism in the central part of
the basin. In addition to the maturity of the metamorphic fluids, the salinity of the aqueous fluids also shows a link with
the metamorphic grade of the host-rock. For the earliest and latest fluid inclusions in the anchizonal part of the High-Ardenne
slate belt the salinity varies respectively between 0 and 3.5 eq.wt% NaCl and between 0 and 2.7 eq.wt% NaCl, while in the
epizonal part the salinity varies between 0.6 and 17 eq.wt% NaCl and between 3 and 10.6 eq.wt% for the earliest and latest
aqueous fluid inclusions, respectively. Although high salinity fluids are often attributed to the original sedimentary setting,
the increasing salinity of the fluids that circulated through the Lower Devonian rocks in the High-Ardenne slate belt can
be directly attributed to regional metamorphism. More specifically the salinity of the primary fluid inclusions is related
to hydrolysis reactions of Cl-bearing minerals during prograde metamorphism, while the salinity of the secondary fluid inclusions
is rather related to hydration reactions during retrograde metamorphism. The temporal and spatial distribution of the fluids
in the High-Ardenne slate belt are indicative for a closed fluid flow system present in the Lower Devonian rocks during burial
and Variscan deformation, where fluids were in thermal and chemical equilibrium with the host rock. Such a closed fluid flow
system is confirmed by stable isotope study of the veins and their adjacent host rock for which uniform δ180 values of both the veins and their host rock demonstrate a rock-buffered fluid flow system. 相似文献
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Quantitative X-ray texture analysis was used to identify the fiber elongation direction of microfibrous quartz varieties
in materials that contain narrow bands of closely spaced, radially divergent spherulitic fiber bundles. The statistical approach
of X-ray texture analysis makes it possible to determine the fiber axis direction even when the maximum divergence angle of
fibers within spherulitic fiber bundles diverge ±20° from a common growth direction. Representative samples of chalcedony
<11&2macr;0>, quartzine [0001], and pseudochalcedony were selected for additional study with transmis-sion electron microscopy. All
varieties of microfibrous quartz were found to contain high concentrations of polysynthetic Brazil twins and domains characterized
by a modulated microstructure. Trace element profiles of aluminum and iron concentration were measured by electron microprobe
analysis for an agate sample that contains alternating bands of chalcedony <11&2macr;0> and quartzine fibers. The elemental concentration profiles were measured in a direction parallel to the growth direction
of microfibrous quartz. Although fibers within the chalcedony bands initially displayed cooperative helical twisting, the
fibers became untwisted during the later stages of growth within any one band. The trace element profiles revealed that higher
concentrations of aluminum are associated with quartzine and non-twisted <11&2macr;0> fibers, rather than twisted chalcedony <11&2macr;0> fibers. Except for the presence of iron-rich inclusions between quartzine and chalcedony bands, trace concentrations of
iron were below the detection limit for the different varieties of microfibrous quartz analyzed.
Received: 6 January 1997 / Accepted: 4 September 1997 相似文献
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Sintubin Manuel Nefly Mohammed Rijpens Jan Van Zegbroek Bart 《Geologie en Mijnbouw》1997,76(3):187-195
At its eastern termination, the High Atlas Fault in the Western High Atlas in Morocco, consists of a splay of three faults. In the interjacent fault blocks, Neo- and Paleoproterozoic basement, forming the northernmost extremity of the NW-African Craton, is cropping out. The Precambrian basement witnesses a long history of brittle deformation starting at the end of the Pan-African Orogeny. A subsequent episode of normal faulting can be related to the development of a Hercynian basin along the northern passive margin of the cratonic promontory. With regard to the main tectonic activity in the Western High Atlas, basically two models exist: one emphasising block tectonics reflecting Mesozoic rifting followed by Alpine uplift and inversion, the other emphasising Late Paleozoic dextral wrench tectonics. The analysis of the fault activity along the splay faults reveals a predominantly Alpine history, consisting of the Triassic development of the Atlas Rift along the axial zone of the orogen, followed by uplift and inversion. The Late Jurassic to Cenozoic fault activity took place in a sinistral transpressive regime and was partitioned over the three splay faults. Dextral strike-slip fault activity could not be demonstrated in the fault blocks nor along the splay faults. Therefore the faults were probably not involved in Late Paleozoic dextral wrench tectonics. 相似文献
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Manuel Sintubin Timothy Nick Debacker Hervé Van Baelen 《Comptes Rendus Geoscience》2009,341(2-3):156-173
The Lower Palaeozoic rocks exposed in the Brabant-Ardenne region (Belgium, France) recorded the Early Palaeozoic history on the southern margin of the perigondwanan microcontinent of Avalonia, north of the Rheic suture. These rocks crop out in the Brabant basement and in the Ardenne basement inliers within the Variscan Ardenne allochthon. The two main unconformities are classically associated with distinct orogenic episodes, the Late Ordovician “Ardennian” event and the Early Devonian “Brabantian” event. A review of the current state-of-knowledge with respect to the reconstruction of Early Palaeozoic geodynamics in the Brabant-Ardenne region is presented. It is demonstrated that an unconformity does not necessarily represent an orogenic event, and that the hiatus related to an unconformity does not necessarily coincide with tectonic activity, especially when tectonism is diachronous in nature. The former applies to the Ardennian unconformity, while the latter applies to the Brabantian unconformity. Finally, the well-constrained Brabantian orogeny, as well as the Ardenne-Eifel basin development, is tentatively framed within the Early Palaeozoic geodynamic context of the northern margin of the Rheic realm. By doing so, it is shown that the Brabant-Ardenne region links, both in space and time, the Rheic and Rhenohercynian ocean. 相似文献
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K. Piessens Muchez S. Dewaele A. Boyce W. De Vos M. Sintubin T. N. Debacker E. A. J. Burke W. Viaene 《Tectonophysics》2002,348(1-3)
In the Lower Palaeozoic rocks of the Brabant Massif (Belgium), a recently discovered polysulphide mineralisation is related to a low-angle reverse shear zone. This shear zone has been attributed to the main early Devonian deformation event. Data from boreholes and outcrops allow a detailed investigation of the alteration pattern and palaeofluid flow along this shear zone. Macroscopic observations of the mineralogy and quantitative changes in the phyllosilicate mineralogy indicate that this shear zone is characterised by an envelope of intense sericitisation and silicification. In addition, chloritisation is associated with this alteration. The alteration zone may reach a thickness of 250 m. Ore mineralisation occurred synkinematically and is spatially related to the shear zone. The mineralisation consists of pyrite, marcasite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, galena, stibnite and smaller amounts of tetrahedrite and other sulphosalts. It is concentrated in quartz–sulphide veins or occurs diffusely in the host rock. The mineralising fluids have a low-salinity H2O–CO2–CH4–NaCl–(KCl) composition and a minimum temperature of 250–320 °C. The δ18O values of quartz vary between +12.3‰ and +14.5‰ SMOW, and δD compositions of the fluid inclusions in the quartz crystals range from −65‰ to −35‰ V-SMOW. The δD and the calculated δ18O values of the mineralising fluids fall in the range typical for metamorphic fluids and partly overlap with that for primary magmatic fluids. The δ34S values, between +4.7‰ and +10.6‰ CDT, fall outside the interval typical for I-type magmas. Important migration of likely metamorphic fluids, causing a widespread alteration and a polysulphide mineralisation along a low-angle shear zone, has, thus, been identified for the first time in the Caledonian Anglo-Brabant fold belt. 相似文献
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Dominique Similox-Tohon Manuel Sintubin Philippe Muchez Griet Verhaert Kris Vanneste Max Fernandez Sara Vandycke Hannelore Vanhaverbeke Marc Waelkens 《Tectonophysics》2006,420(3-4):371-387
The archaeological site of Sagalassos (SW Turkey) is located in a region characterized by the absence of any significant recent seismic activity, contrary to adjacent regions. However, the assessment of earthquake-related damage at the site suggests that the earthquakes that have been demonstrated to have struck this Pisidian city in ca. AD 500 and in the middle or second half of the 7th century AD are characterized by an MSK intensity of at least VIII and occurred on a fault very close to the city. Different investigation techniques (archaeoseismology, remote sensing and geomorphology, surface geology and structural data, 2D resistivity imaging and palaeoseismological trenching) have been applied at the archaeological site and its direct surroundings in search for the causative fault of these earthquakes. This multidisciplinary approach shows that each of the different approaches independently provides only partial, non-conclusive information with respect to the fault identification. Integration is imperative to give a conclusive answer in the search for the causative fault. This study has, indeed, revealed the existence of a to date unknown active normal fault system passing underneath ancient Sagalassos, i.e. the Sagalassos fault. A historical coseismic surface rupture event on this fault could be identified. This event possibly corresponds to the devastating Sagalassos earthquakes of ca. AD 500 and the middle or second half of the 7th century AD. Finally, this study demonstrates that in the particular geodynamic setting of SW Turkey archaeological sites with extensive earthquake-related damage form an important tool in any attempt to asses the seismic hazard. 相似文献
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The presence of convergent cleavage fans in folded Silurian pelitic deposits along the southern extremity of the Brabant Massif has commonly been considered as an indication for a polyphase deformation history. Recent field work on the classic section at Ronquières shows, however, that all the structural elements can be explained by a single progressive deformation, taking place at gradually higher structural levels. This deformation is considered to have occurred at the time of the Acadian orogeny. The section under study contains a fold train of five gentle to open first-order folds, unconformably overlain by gently S-dipping Givetian rocks. Although the Silurian turbidite deposits are predominantly pelitic, the folds are characterized by convergent cleavage fans. The trend of the cleavage fan axes remains constant in the various folds throughout the section. In contrast, the trend of the folds hinge lines gradually changes along the section from a clockwise relation with the cleavage fan axis in the northern part (anticlockwise cleavage transection) towards an anticlockwise relation in the southern part (clockwise cleavage transection). Individual fault/fault intersections have a constant trend throughout the section, parallel to the cleavage fan axes and the mean fold hinge line. Small kink bands and small transverse joints reflect the same structural trend. The coaxial disposition of the structural elements seems at first sight incompatible with the presence of both clockwise and anticlockwise cleavage-transected folds. This disposition may, however, be explained by an en-echelon periclinal nature of the fold train, possibly formed in a slightly constrictional deformation environment. 相似文献
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