Provenance of Cretaceous clastics in the Subhercynian Basin: constraints to exhumation of the Harz Mountains and timing of inversion tectonics in Central Europe

The Harz Mountains and the adjacent Subhercynian Cretaceous Basin figure as the most prominent surface representative for Late Cretaceous inversion structures in Central Europe. Facies, depositional architecture and provenance of the basin fill reflect mechanisms and timing of the exhumation of the Harz. From Hauterivian to Early Santonian there is no evidence for detrital input from the nearby Harz area. Sediments are mature quartzarenites derived from Paleozoic basement rocks and/or recycled Permian to Mesozoic sedimentary rocks. This situation changed drastically in Middle to Late Santonian when freshly exhumed and eroded Mesozoic sedimentary cover rocks of the Harz were delivered into the basin. Feldspar and lithoclasts reflect erosion of Triassic and, in places, Jurassic to Turonian strata. Apatite and garnet in heavy mineral spectra are derived from largely unweathered Lower Triassic Buntsandstein as indicated by apatite and garnet chemistry. In Early Campanian, Paleozoic lithoclasts indicate erosion cutting down into the basement of the Harz. Simultaneous strong decrease of feldspar, garnet and apatite suggest an almost complete removal of the 2–3 km thick Mesozoic cover of the Harz within only 2–4 Myr. This translates into an exhumation rate of approximately 1 mm/a consistent with apatite fission track data from granitoid rocks of the Harz Mountains.     

Deep structure and evolution of the Harz Mountains: results of three-dimensional gravity and finite-element modeling

A new Bouguer anomaly map is presented for the region of the entire Harz Mountains based on more than 60,000 gravity values. The various gravity anomalies are discussed and interpretation is carried out by high-resolution 3-D gravity modeling. One of the main subjects of interest in the investigation is the northern boundary fault zone of the Harz Mountains, separating the Mesozoic sediments in the north from the Palaeozoic rocks of the Harz in the south. Dip and vertical displacement are determined for this fault zone; mean values are 3400 m and 70°, respectively. Gravity modeling shows that the Brocken and the Ramberg Granites are distinctly different. The Brocken Granite is shallow, whereas the Ramberg Granite has a maximum depth of 8.5 km and a N---S dimension of 37 km. The prominent Benneckenstein Gravity High is explained by two different models, one based on a granodioritic intrusion (2900 kg/m³) with a center-depth of 14 km and the other based on phyllites (2740 kg/m³) on a depth of 3–4 km.

Studies on the geodynamic evolution of the Harz Mountains are carried out using the finite-element method. On the basis of a 3-D model, vertical displacements that can be related to horizontal forces are computed. For the period of the Variscan Orogeny an uplift of 600 m in the Harz area is calculated, for Late Cretaceous and Tertiary 400 m are determined. The total amount of 1000 m is about 1/2 of the vertical displacement of the northern boundary fault zone of the Harz Mountains shown by the gravity modeling. These results do not contradict geological ideas.     

Fault damage zone origin of the Teufelsmauer, Subhercynian Cretaceous Basin, Germany

Recognition of fractures as porosity-reducing deformation bands pervading all sandstone segments of the Teufelsmauer, Subhercynian Creatceous Basin, Germany, motivates a study relating the observed macroscopic and microscopic deformation to the damage zone of the nearby Harz border fault. Deformation bands, confirmed and documented by several porosity-reducing micro-mechanisms, such as cataclasis, particulate flow, pressure solution and a heavy quartz cementation, were mapped and analyzed in terms of the kinematics and deformation intensities expressed by them. Deformation band kinematics are uniform throughout the entire basin and consistent with the large-scale tectonic structures of the area. A strain intensity study highlights two narrow but long zones of deformation bands, sub-parallel to the Harz border fault. Deformation band kinematics, strain intensity, as well as micro-mechanisms are all consistent with a continuous but internally diverse deformation band damage zone of the entire Teufelsmauer structure along the Harz border fault, bringing new insights into the tectonic evolution and the origin of the heavy quartz cementation of the sandstones in the Subhercynian Cretaceous Basin.     

Mobility of heavy metals as a function of pH of samples from an overbank sediment profile contaminated by mining activities

Parts of the flood plains north of the Harz Mountains are contaminated with heavy metals, such as Pb, Cu, Zn and Cd derived from mining, which has been carried out in the Harz Mts. since the Middle Ages. It is important to know the mobility of the heavy metals in these overbank sediments in order to estimate the danger to the environment arising from this source. This paper deals with the effect of pH on heavy-metal mobility, using a constant-pH method. The investigations were carried out on an overbank sediment profile near Salzgitter Bad, north of the Harz Mts. The mobility of the heavy metals in the overbank sediment profile is described as a function of pH and depth. Besides the mobile heavy-metal fraction at a certain pH, the buffering capacity of the sediment at this pH must be taken into consideration. The different layers of the overbank sediment profile show distinct differences in buffering capacity and a natural pH harrier could be identified in the upper part of the profile. Therefore, to avoid increasing heavy-metal mobility the natural layering of the overbank sediment profile should not be disturbed. Two different kinds of desorption experiments at constant pH are also discussed, as well as the conversion of the heavy-metal species in the ore minerals into the species in the sediment.     

Bismuth selenides from St. Andreasberg,Germany: an oxidised five-element style of mineralisation and its relation to post-Variscan vein-type deposits of central Europe

International Journal of Earth Sciences - Carbonate veinlets at Roter Bär, a former underground mine in the polymetallic St. Andreasberg vein district of the Harz Mountains, Germany, host...     

Petrographie des Praezechsteins der Bohrung „Dransfeld l”

Core samples from the “Praezechstein” formation of the bore “Dransfeld 1” were investigated by optical, X-ray, and chemical methods. The rock formation consists of graywackes interbedded with Slates. The graywackes contain mineral.components and rock fragments which are also common in the graywackes of Harz and “Rheinisches Schiefergebirge”, so that a common source of derivation may be concluded, namely the “Mitteldeutsche Schwelle”. The distinctive features of the Dransfeld-graywackes however as compared to those of Harz and “Rheinisches Schiefergebirge” are:

1. 1.
   A higher content of rock fragments specially of volcanic origin.     
   
   

Hydrogeochemical characteristics of mine water in the Harz Mountains,Germany

Water samples (springs, creeks, mine adits) from different former mining districts of the Harz Mountains and the nearby Kupferschiefer (copper shale) basin of Sangerhausen were analysed for major ions and trace metals. Due to more intensive water rock interactions including the ore minerals, the mine water concentrations of main components and trace metals are generally higher compared to non mining affected surface waters of the mountain range. Furthermore, the content of major ions in mine water is enriched by mixing processes with saline waters from Permian layers in the Kupferschiefer district and at the deeper levels of the mines in the Upper Harz Mountains. The waters of the different mining districts can be distinguished by trace metal occurrences and concentrations derived from the different ore bodies. Water from the Kupferschiefer mines shows the highest Na, Cl, Cu, Mo and U concentrations, whereas a combination of elevated As and Se concentrations is typical for most of the samples from the mines around St. Andreasberg. However, there are exceptions, and some water samples of all the investigated mining districts do not follow these general trends. Despite the influence of mining activities and ore mineralisation, hydrochemical effects due to rain water dilution can be seen in most of the waters. According to the elevation of the mountain range, higher precipitation rates decrease the ion concentrations in the waters of springs, creeks and mine adits.     

Isotope composition of Medieval lead glasses reflecting early silver production in Central Europe

The lead isotope composition of 32 lead glasses excavated from strata of the twelfth to early fifteenth century in six countries of NW Europe made the predominance of the Harz Mountains in this period of the Medieval European lead and silver production highly probable. Post-Variscan vein type galena, Devonian syngenetic hydrothermal ore (Rammelsberg) and blended ore from both deposits in the Harz were used. Our evaluation of 200 mining sites in Germany, Britain and Ireland also demonstrated that minor lead sources for lead glass were located in Bavaria/Bohemia and England. Lead ores from the Rhenohercynian orogenic belt in Germany are derived from rock sources close to the upper continental crust composition in ²³⁸U/²⁰⁴Pb of about 10 and Th/U of about 4. The ores in Central England originated from rocks with ²³⁸U/²⁰⁴Pb of about 11. Received: 24 September 1996 / Accepted: 17 January 1997     

Petrology of the Weissliegendes sandstones in the Harz and Werra-Fulda areas,Germany

The Weissliegendes and adjacent related Permian sediments from the Harz and Werra-Fulda areas are petrologically described. The Weissliegendes sandstones are classified as moderately sorted, multicycle subgraywackes and orthoquartzites. Petrographic data indicate that the Weissliegendes and Zechsteinkonglomerate were derived in large part from the underlying Rotliegendes. Textural and stratification data show that the Weissliegendes sandstones were deposited in a shallow marine depositional environment and that the aeolian dune origin for the sandstones should be rejected. Rotliegendes sands and gravels were reworked by the transgressive Zechstein Sea, producing the sands of the Weissliegendes and the lag gravels of the Zechsteinkonglomerate. These two closely related units are time equivalent facies which represent the initial stage of the Zechstein Series.     

Neocalamites rugosus Sze和Equisetites asperrimus Franke是同物异名

研究表明,斯行健(1956)建立的我国晚三叠世植物化石新种Neocalamites rugosus Sze和德国哈茨山脉考依波期的Equisetites asperrimus Franke是同物异名。Franke提定的种名有优先权,但属名鉴定有误。斯行健鉴定的属名正确,但其种名却是Franke名称的晚出异名。根据国际植物命名法规,两者应合并为一种,特定名为Neocalamites asperrimus(Franke),comb.nov.     

Untersuchungen über die Petrographie kulmischer Kieselschiefer

Zusammenfassung Profile von kulmischen Kieselschiefern des hessischen Hinterlandes wurden optisch, röntgenographisch, chemisch, spektralanalytisch und differential-thermoanalytisch untersucht. Die nicht-lyditischen Bestandteile wurden besonders berlicksichtigt.Als Vergleichsmaterial dienten kulmische Kieselschiefer aus dem Harz, sowie tertiäre (Monterey), silurische und algonkische Kieselschiefer. Es wurde festgestellt, daß in der Kulmstufe II–III (dunkle und bunte Lydite) im hessischen Hinterland und im Harz zahlreiche, gering mächtige Tuffhorizonte auftreten; ihre Häufigkeit nimmt nach obenhin zu. Die bunten Lydite führen tuffitische Bänke, deren Grundmasse ursprünglich kalkig war. Die bisher nur aus dem Harz bekannten, kieseligen Tuffe des Kulms (Typ Lerbacher Adinole) Bind auch im hessischen Hinterland verbreitet.Met Röntgen- und DTA-Aufnahmen wurde zu zeigen versucht, daß die Kieselsäure seit der Entstehung des Sediments folgende Phasenumwandlungen erfahren hat:Opal Cristobalit mikrokristalliner Quarz (Chalzedon, Quarzin), und daß in paläozoischen Kieselsedimenten noch amorphe oder stark fehlgeordnete Kieselsäure vorhanden sein kann.Die Entstehung der kulmischen Kieselschiefer wird diskutiert.     

Early Cretaceous mineralizing activity in the St. Andreasberg ore district (Southwest Harz,Federal Republic of Germany)

In the St. Andreasberg ore district, southwest Harz, at some time between the main and subsequent stages of mineralization sensu Wilke (1952), potassium feldspar (adularia) was formed hydrothermally. Based on isotopic dating (Rb/Sr, ⁴⁰Ar/³⁹Ar), the formation of this mineral is ascribed to the Early Cretaceous. Thus, part of the St. Andreasberg mineralization is proved to have been formed in the Late Mesozoic. The mineralization process forming feldspar does not coincide with magmatic phases of the area.     

Reply to Hüneke’s (2005) comment

Hüneke (Int J Earth Sci 2005) gives a new interpretation of the tectonic setting of five ⁴⁰K/⁴⁰Ar analyses published by Huckriede et al. (Int J Earth Sci 93: 414–431, 2004). In this context, Hüneke discusses the significance and provenance of Late Proterozoic ⁴⁰K/⁴⁰Ar-cooling ages of detrital muscovites from pre-flysch sediments of the Blankenburg and Harzgerode Zones (Harz Mountains). Hüneke’s reinterpretation is based on a wrong concept concerning the extend of the Blankenburg Zone. This wrong concept originates from the incorrect distinction between the greywackes of the Tanne Zone and the greywackes of the Gießen-Harz Nappe. These greywackes can be easily distinguished by petrographic methods. Hüneke additionally defends the assumption that large areas of the eastern Harz Mountains consist of Viséan olistostromes. There is no need for an extended discussion of this topic because Hüneke presents no arguments.     

德国拉梅尔斯贝格铜-锌-铅-钡矿床研究进展

拉梅尔斯贝格矿床是中欧华力西期最重要的SHMS(以沉积岩为容矿围岩的块状硫化物)类矿床之一,位于莱茵海西期地体的上哈茨地块。该矿床形成于泥盆纪,矿体赋存于艾菲尔阶的威森巴赫页岩中,经华力西造山运动发生了强烈的变形。主要有新矿体、老矿体和富含重晶石的灰色矿体,主要硫化物矿物为黄铁矿、闪锌矿、方铅矿和黄铜矿。硫同位素数据显示,拉梅尔斯贝格矿床有2个硫源,一个是热液成因;一个是生物成因,来自细菌还原的海水中的硫酸盐。铅同位素说明,它的铅主要来自均匀的地壳。与其他SHMS类矿床相比,拉梅尔斯贝格矿床明显富铜。     

Overbank sediment profiles—evidence of early mining and smelting activities in the Harz mountains,Germany

Two overbank sediment cores to a depth of 5.6 m and 2.3 m respectively from the Uferbach catchment on the western foothills of the Harz mountains, Lower Saxony, Germany, revealed two anomalies of Pb, Zn, and Cu at 30–130 cm and at 204 cm, a PbZn-anomaly at 280 cm and a Pb-anomaly at 410 cm—evidence of four phases of mining and smelting activities in the catchment. The geochemical (major, minor, and trace elements) and mineralogical investigations (microscopy and microprobe analysis of matrix and slag particles) allowed for a broad interpretation of the element behavior (e.g., landuse) and the source region of the processed ore (hydrothermal deposits of the Upper Harz). A simple calculation model, based on¹⁴C-data, helped to estimate the time frame for the anomalies. The most likely interpretation requires an increase of the sedimentation rates over time (from 1 to 4 mm a⁻¹) and suggests medieval (1140–1345 A.D.), karolingian (82–890 AD), roman-germanic (425–500 A.D.) and early historic (825–625 B.C.) phases of smelting activities.     

Geophysical investigation of a sinkhole in the northern Harz foreland (North Germany)

The creek Jerstedter Bach is part of the Ringelheimer Mulde along the northern rim of the Harz Mountains in Northern Germany, a trough structure comprising steeply dipping limestones. The limestones are well karstified and drain parts of the region efficiently via sub-surface flow. As the entire region is intensively used by agriculture, contamination of the fast-flowing karst aquifer is a potential problem. During 2006, a small sinkhole (Windmühlenweg) developed alongside the Jerstedter Bach close to the city of Goslar. The sinkhole enlarged rapidly, with a small cave within the gravel cover diverting part of the creek to the subsurface karst catchment. Geophysical methods (gravimetry, geoelectrics) were used around the sinkhole to determine its extent and possible evolution. A negative Bouguer anomaly was found over the sinkhole, indicating more voids further downstream. The geoelectric survey helped to identify the old meandering course of the small river, which was straightened during the cultural land reform in the twentieth century.     

Petrographie und Mineralfazies einer konglomeratischen Tanner Grauwacke aus dem Unterharz

A very coarse grained graywacke from Strassberg in the Lower Harz Mountains (Germany) consists of rock-fragments, feldspars, quartz, chlorites, micas, accessories and ores. Low grade metamorphic mineral reactions are indicated by the formation of 2M-muscovite +chlorite+sphene+albite in the matrix of the graywacke, by prehnite+chlorite+ sphene+calcite+sericite+albite (±quartz) in volcanic rock-fragments, and by prehnite +calcite+quartz along fine fissures. The newly formed minerals in the coarse grained graywacke belong to the laumontite-prehnite-quartz-facies of the burial metmorphism. However, the formation of the low grade minerals is caused by thermal metamorphism in outer contact zones of the Ramberg granite intrusion in the Strassberg area.     

Detrital glaucophane in graywackes of the Rhenohercynian Harz mountains and the geodynamic implications

Detrital blue amphibole was found for the first time in two samples of the Famennian section of the South Harz-Selke Graywacke and the Tanne Graywacke (Middle Visean) of the Harz Mountains. Microprobe analyses reveal that the blue amphiboles represent glaucophane with Fe³⁺/(Fe³⁺+Al^VI)=0.22 molar ratio. The minimum pressure required for the formation of glaucophane of this composition is estimated to be approximately 8 kbar. The source area of the detrital glaucophane is assumed to be located between the Northern Phyllite Zone and the Mid-German Crystalline Rise, in areas which have been downfaulted (?subducted) during the Variscan orogeny. The age of blueschist-facies metamorphism in the source area must be of pre-Upper Devonian age. This metamorphic event is significantly older than the Lower Carboniferous high-pressure/low-temperature metamorphism documented in parts of the northern Phyllite zone. Hence, the convergent tectonics connected with blueschist-facies metamorphism is not restricted to the Lower Carboniferous, but can be traced back at least to the early Upper Devonian. These data are in accordance with a southerly directed underplating (?subduction) at the northern margin of the Saxothuringian zone active during at least from early Upper Devonian to Lower Carboniferous.     

A Sr isotope study on fluorite and siderite from post-orogenic mineral veins in the eastern Harz Mountains,Germany

Rb–Sr isotope data for siderite and fluorite from sediment-hosted epithermal mineral veins in the eastern Harz Mountains (Germany) are presented. Several fluorite and siderite-bearing paragenetic stages have been proposed for these veins, with the most important mineralization being related to a quartz–sulfide and a subsequent calcite–fluorite–quartz stage, which occurred at 226±1 and 209±2 Ma, respectively. Our Rb–Sr data do not permit the identification of distinct generations of siderite and fluorite, but rather reveal straight internal mixing relations, reflecting mixing of fluids or differential fluid–rock interaction processes. This indicates merely two significant phases of mineral deposition related to the quartz–sulfide and calcite–fluorite–quartz stages. It is shown that the Paleozoic sedimentary host rocks of the veins are the most likely source for the siderite Sr, whereas fluorite displays a two-component mixture between sedimentary Sr and radiogenic Sr derived from locally occurring Permian metavolcanic rocks. Editorial handling: B. Lehmann