Super-deep, TSR-controlled Phanerozoic MVT type Zn-Pb deposits hosted by Zechstein-2 gas reservoir carbonate (Ca2), Lower Saxony Basin, Germany

REY and Trace Element Chemistry of Fluorite from Post-Variscan Hydrothermal Veins in Paleozoic Units of the North German Basin

“…Changing tectonic settings, from extensional to divergent movements and the stepwise and long-term subsidence followed by a later inversion of the basin enabled fluid migration along structurally controlled pathways and led to the formation of several hydrothermal vein systems in the NGB [2,[11][12][13][14][15]. The possible fluid sources (e.g., meteoric or magmatic water) and the heat source for the enhanced geothermal gradients are also discussed by these authors.…”

“…Basinal brines that migrated through igneous units (i.e., thick successions of Rotliegend volcanics in the ABB and FCB) may also have acquired the necessary fluorine contents to achieve hydrothermal saturation and deposition along structurally controlled veins within the NGB. In the LSB zones of hydrothermal sulphide mineralization, specifically sphalerite and galena, have been documented in Zechstein carbonates by several authors i.e., [2,[82][83][84]. Although researchers have argued about the possible sources of the mineralizing fluids and the style of mineralization (from magmatic to MVT) [82,[85][86][87][88][89][90][91][92], recent studies have presented convincing evidence that structurally and thermochemical sulphate reduction (TSR)-controlled hydrothermal basinal brines led to the Pb-Zn mineralization and the associated fluorite-barite mineralization [2]-a model that can be equally applied to the hydrothermal fluorite mineralization in the ABB, although a different lithology (i.e., thick volcanic layers) translates into distinct variations compared to the LSB [14,93].…”

“…Fourteen major elements and oxides (CaO, F, SiO 2 For error correction, internal rock standards of fluorspar, stream sediments, kinzingite and phosphate rock were used for the first determination. For the second determination, the internal rock standards OREAS 134b Zn-Pb-Ag, Gold-Enargite, Greenstone Ore, Canmet SU-1b and Canmet CPB-2 were used.…”

“…Lüders et al [12], for example, provide evidence from fluid inclusion investigations that indicated high water-rock interactions with Permian volcanic and sedimentary rocks in the ABB. However, a primary volcanogenic fluid source can be discarded for both the ABB and LSB [2,12,18,93]. The flat REY CN signature [95,96] and the overall low concentrations are strong indicators that basinal brines derived from marine water represent the mineralizing fluid in the LSB.…”

“…Although the structure, stratigraphy and evolution of the NGB and its sub-basins are well-studied due to extensive exploration and production drilling programs, hydrothermal mineralization, including fluorite-barite and base metal sulphide mineralization in different parts of the basin, have not been studied in detail until recently [1][2][3]. Here, we present macro-and micro-scale petrographic observations (optical microscopy, back-scattered secondary electron (BSE) and cathodoluminescence (CL) imaging) in combination with geochemical data (laser ablation inductively coupled mass spectrometry (LA-ICP-MS), bulk rock X-ray fluorescence (XRF)), including REE and minor and trace element contents, for hydrothermal fluorite from four distinct areas within the NGB-specifically, the Altmark-Brandenburg Basin (ABB) as part of the North East German Basin (NEGB), the Lower Saxony Basin (LSB) in the western part of the NGB, the Flechtingen High (Flechtingen Calvörde Block, FCB) and the Harz Mountains south of the ABB.…”