The GIS (Geographic Information System) Central Europe, in support of the Alpine-Balkan-Carpathian-Dinarides (ABCD) GEODE Project, is composed of spatially referenced geographical, geological, geophysical, geochemical and mineral deposit thematic layers, and their respective attribute data. It has been created to establish insights in the region’s mineral potential and its past and future mining activities, and to determine parameter combinations that control the spatial-temporal distribution of the ore deposits. To contribute to the sustainability of the mining industry, environmental data are also integrated in the information system, allowing a regional scale risk assessment for old and new mining projects. The data analysis and synthesis, required to arrive at the different thematic layers, already highlight parameters that may be tentatively linked to ore deposit formation and localization. The assessment and compilation of heat flow data show a large anomalous area of high heat flow, located within the Pannonian basin, adjacent to the east Carpathians with anomalously low heat flow values. Such high contrasts in the thermal regime in the crust may play a role in the ore genesis. The compilation of multisource gravity information has returned enhanced gravity maps, Bouguer and isostatic anomalies, gravity gradients and gravity discontinuities. Linked in with the earthquake epicenter distribution, these layers contribute to a better understanding of the crustal structure, regionally with the topo-isostatic anomaly map and more locally with the vertical gradient anomaly map. The present-day structure of the crust, completed by the structure of the lithosphere, e.g. with the 3-D seismic tomography visualization, allows to verify the region’s geodynamic evolution. The 3-D visualization (and the correlation with the heat flow thematic layer) reconfirms the preferred positioning of Neogene (Au) deposits above shallow low velocity bodies. The visualization also suggests that (subducted) lithosphere underlying these low velocity bodies obstructs the emplacement of the deposits (e.g. Aegean arc and mainland Greece), unless this subducted lithosphere has been positioned at/around the 660 km discontinuity (Rhodope and Apuseni regions). Geodynamically this observation can be explained by the insufficient influx of asthenospheric heat in the narrow mantle wedges above shallow subducted lithosphere. In relation to the geodynamic setting certain ore deposit types mark the tectono-magmatic evolution of the Tethys and the Carpatho-Balkan arc. Oceanic type mineralizations (chromite, Cu massive sulphides) formed during the oceanic rifting from Jurassic to Upper Cretaceous, and hydrothermal-porphyry types (base- and precious-metal mineralizations) formed during two major stages, during the Cretaceous to Paleogene, and subsequently during the Neogene. Linked in with information on materials processing (waste production and management, toxicity information), land use, infrastructure in/around mining districts, and other socio-economic information help the GIS to evolve towards a modern tool for the sustainable management of mineral resources in southeastern Europe.
A structural classification of podiform chromite orebodies from southern New Caledonia results in a division of deposits into three major types: discordant, subconcordant, and concordant, with penetrative structures (foliation and lineation) in the enclosing peridotite. Discordant deposits are very irregular in shape and clearly crosscut banding and foliation. Subconcordant deposits are generally tabular in shape and lie within 10 degrees to 25 degrees in strike and/or dip to the foliation. Concordant deposits are also tabular and lie parallel to foliation in peridotite; pyroxene lineation in host peridotite always indicates the elongation direction of these deposits. Within subconcordant and discordant deposits, chromite lineations are often oblique to those in the surrounding rocks; they follow local variations in the orebody shape and indicate possible deposit extensions at depth. The classification of chromite bodies corresponds to three stages of increasing deformation, as evidenced by chromite ore textures. Discordant deposits which are the least deformed are characterized by primary textures such as the nodular one, the foam texture, the chromite net, and the occluded silicate texture. Within subconcordant and mainly concordant deposits, massive, disseminated, and antinodular ores show evidence of strong deformation. The lack of geochemical distinctions between the different deposit types supports such an hypothesis.These chromite deposits in ophiolitic harzburgites are thought to have been formed beneath an oceanic spreading ridge. If the discordant pods are considered as representative of the original situation, it is proposed that the chromite has crystallized and has been dynamically concentrated along steep conduits traversing the enclosing harzburgite and feeding a magma chamber. Next the chromite-enriched pipes are caught up by plastic deformation in the mantle and tectonically reoriented toward the foliation.The chromite deposits in the Massif du Sud are located within a domain about 1.5 km thick in the harzburgites and dunite zones. This domain is limited upward by the first cumulates and gabbros and downward by the transition to a different plastic flow regime in the harzburgites.Finally, some guides to chromite prospecting and exploration are cited, applicable at different geologic scales and based on lithologic and structural criteria.
The 2,430 Ma Burakovsky layered complex, located in Karelia, Russia, is one of the largest layered Fennoscandian intrusions. It consists, from the base to the top, of a thick ultramafic part dominated by dunite and peridotite overlain by a layered mafic part that consists of alternating layers of pyroxenite, wehrlite and gabbro (Transitional Banded Zone, TBZ), and a thick sequence of gabbroic rocks [Gabbronorite Zone (GNZ), Pigeonite Gabbronorite Zone (PGNZ), Magnetite Gabbronorite–Diorite zone (MGDZ), which predominates. The Main Chromite Horizon, located at the interface between the ultramafic part and the layered series, hosts laurite and Os–Ir alloy grains observed as tiny inclusions in chromite crystals. The Transitional Banded Zone and Gabbronorite Zone are characterized by disseminated sulfide blebs hosted by clinopyroxene and plagioclase. The blebs consist of a chalcopyrite – pyrrhotite – pentlandite assemblage locally associated with PGM found as discrete grains in sulfides, in clinopyroxene, but more commonly around the margin of sulfide grains. Platinum-group minerals consist of dominant Pd and Pt arsenides and sulfarsenides and Pt–(Pd–Bi) tellurides (sperrylite, platarsite, palladoarsenide, kotulskite, moncheite) with minor amounts of native Pt. The expression of the mineralization is consistent with the late crystallization of an immiscible semimetal-rich liquid that forms discrete PGM grains around sulfide blebs and in veinlets injected in the adjacent silicates. The PGM were also observed in association with secondary phases, dominated by epidote replacing primary base-metal sulfides. This feature, commonly described in other layered intrusions, is here mainly observed around the platinum-group minerals – base-metal sulfides association hosted by plagioclase. The existence of compositional heterogeneities in primary plagioclase likely acts as a target for the development of alteration.
The Au–Ag epithermal mineralization of the Shila Cordillera is dated at about 10.7 Ma (K/Ar on adularia). The vein system is characterized by the association of a major ≈east–west vein and N120–135°E secondary fractures. The strike-slip faults controlling the veins indicate an initial NE–SW to ENE–WSW shortening direction, which is compatible with that generally accepted for this period. These structures were reopened during a second phase and channelized mineralizing fluids, the circulation of which may have began at the end of stage 1. Les minéralisations épithermales à Au–Ag de la Cordillera Shila sont datées à environ 10,7 Ma (K/Ar sur adulaire). Le système de veines est caractérisé par l'association entre une veine principale sensiblement est–ouest et des fractures satellites N120 à N135°E. Les décrochements contrôlant les veines indiquent une direction de raccourcissement initiale NE–SW à ENE–WSW, compatible avec celle généralement admise pour cette période. Dans un deuxième stade, ces structures sont ré-ouvertes pour servir de réceptacle aux fluides minéralisateurs, dont la circulation débute probablement dès la fin du stade 1.
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