reinhard wolff | University of Münster (original) (raw)

Papers by reinhard wolff

Journal of the Geological Society

Active graben systems in south Tibet and the Himalaya are the surface expression of ongoing E-W e... more Active graben systems in south Tibet and the Himalaya are the surface expression of ongoing E-W extension, however, the cause and spatio-temporal evolution of normal faulting remain debated. Here, we reconstruct the exhumation history driven by normal faulting at the southern Tangra Yumco graben using new thermochronological data. The Miocene cooling history of the footwall of the main graben-bounding fault is constrained by zircon (U-Th)/He ages (16.7±1.0 to 13.3±0.6 Ma), apatite fission track ages (15.9±2.1 to 13.0±2.1 Ma), and apatite (U-Th)/He ages (7.9±0.4 to 5.3±0.3 Ma). Thermo-kinematic modelling of the data indicates that normal faulting began 19.0±1.1 Ma ago at a rate of ∼0.2 km/Myr and accelerated to ∼0.4 km/Myr at ∼5 Ma. In the northern Tangra Yumco rift, re-modelling of published data shows that faulting started ∼5 Ma later at 13.9±0.8 Ma. The age difference and the distance of 130 km between the two sites indicates that rifting and normal faulting propagated northward a...

EGU General Assembly Conference Abstracts, Mar 23, 2020

&lt;p&gt;Rapid rock exhumation in mountain belts is often associated with crustal... more &lt;p&gt;Rapid rock exhumation in mountain belts is often associated with crustal-scale normal faulting during late-orogenic extension. The process of normal faulting advects hot footwall rocks towards the Earth's surface, which shifts isotherms upwards and increases the geothermal gradient. When faulting stops, this process is reversed and isotherms move downwards during thermal relaxation. Owing to these temporal changes of the geothermal gradient, it is not straightforward to derive the history of faulting from mineral cooling ages (Braun, 2016). Here, we combine thermochronological data with thermokinematic modeling to illustrate the importance of syntectonic heat advection and posttectonic thermal relaxation for a crustal-scale normal fault in the European Alps. The N&amp;#8211;S trending Brenner fault defines the western margin of the Tauern Window and caused the exhumation of medium-grade metamorphic rocks during Miocene orogen-parallel extension of the Alps (Rosenberg &amp; Garcia, 2011; F&amp;#252;genschuh et al., 2012). We analyzed samples from a 2-km-thick crustal section, including a 1000-m-long drillcore. Zircon and apatite (U-Th)/He ages along this transect increase with elevation from ~8 to ~10&amp;#160;Ma and from ~7 to ~9&amp;#160;Ma, respectively, but differ by only ~1&amp;#160;Myr in individual samples. Thermokinematic modeling of the ages indicates that the Brenner fault became active 19&amp;#177;2 Ma ago and caused 35&amp;#177;10&amp;#160;km of crustal extension, which is consistent with independent geological constraints. The model results further suggest that the fault slipped at a total rate of 4.2&amp;#177;0.9&amp;#160;km/Myr and became inactive 8.8&amp;#177;0.4&amp;#160;Ma ago. Our findings demonstrate that both syntectonic heat advection and posttectonic thermal relaxation are responsible for the cooling pattern observed in the footwall of the Brenner normal fault.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Braun, J., 2016, Strong imprint of past orogenic events on the thermochronological record: Tectonophysics, v. 683, p. 325&amp;#8211;332.&lt;/p&gt;&lt;p&gt;F&amp;#252;genschuh, B., Mancktelow, N., Schmid, S., 2012, Comment on Rosenberg and Garcia: Estimating displacement along the Brenner Fault and orogen-parallel extension in the Eastern Alps: Int. J. Earth Sci., v. 101, p. 1451&amp;#8211;1455.&lt;/p&gt;&lt;p&gt;Rosenberg, C.L., Garcia, S., 2011, Estimating displacement along the Brenner Fault and orogen-parallel extension in the Eastern Alps: Int. J. Earth Sci., v. 100, p. 1129&amp;#8211;1145.&lt;/p&gt;&lt;p&gt;Wolff, R., Hetzel, R., Dunkl, I., Anczkiewicz, A.A., Pomella, H. 2020, Fast cooling of normal-fault footwalls: rapid fault slip or thermal relaxation? Geology, v. 48, doi:10.1130/G46940.1.&lt;/p&gt;

This bundled data collection contains three different data sets that were used in the study on th... more This bundled data collection contains three different data sets that were used in the study on the Danghe Nan Shan thrust fault, NE Tibet. The first data set comprises a series of topographic profiles, which were used to quantify the amount of vertical uplift along an asymmetric fold in the hanging wall of the Danghe Nan Shan thrust fault (shown in Figure 4 of Xu et al.). The second data set includes the analytical details of the 10Be exposure ages obtained for the fluvial terraces in the hanging wall of the thrust fault (shown in Table 1 of Xu et al.). The third data contains GPS data that we compiled from two published papers (Gan et al., 2007; Wang & Shen, 2020). The respective GPS vectors are shown in Figure 1 of Xu et al.

The GPS data compiled from Gan et al. (2007) and Wang & Shen (2020) illustrate the ongoing crusta... more The GPS data compiled from Gan et al. (2007) and Wang & Shen (2020) illustrate the ongoing crustal shortening by thrust faulting along the active mountain ranges in northern Tibet (shown in Figure 4 of Xu et al.).

The topographic profiles extend across a fault related fold in the hanging wall of the Danghe Nan... more The topographic profiles extend across a fault related fold in the hanging wall of the Danghe Nan Shan frontal thrust. The vertical distance between the fold hinge and the reference level represents the amount of uplift (shown in Figure 4 of Xu et al.).

Geochimica et Cosmochimica Acta, 2016

Precise analysis of the diffusion characteristics of helium in fluorite is crucial for establishi... more Precise analysis of the diffusion characteristics of helium in fluorite is crucial for establishing the new fluorite (U-Th-Sm)/ He thermochronometer (FHe), which potentially provides a powerful tool for dating ore deposits unsuitable for the application of conventional geochronometers. Incremental helium outgassing experiments performed on fluorites derived from a spectrum of geological environments suggest a thermally activated volume diffusion mechanism. The diffusion behaviour is highly variable and the parameters range between log D 0 /a 2 = 0.30 ± 0.27-7.27 ± 0.46 s À1 and E a = 96 ± 3.5-182 ± 3.8 kJ/mol. Despite the fact that the CaF 2 content of natural fluorites in most cases exceeds 99 weight percent, the closure temperature (T c) of the fluorite (U-Th-Sm)/He thermochronometer as calculated from these diffusion parameters varies between 46 ± 14°C and 169 ± 9°C, considering a 125 lm fragment size. Here we establish that minor substitutions of calcium by rare earth elements and yttrium (REE + Y) and related charge compensation by sodium, fluorine, oxygen and/or vacancies in the fluorite crystal lattice have a significant impact on the diffusivity of helium in the mineral. With increasing REE + Y concentrations F vacancies are reduced and key diffusion pathways are narrowed. Consequently, a higher closure temperature is to be expected. An empirical case study confirms this variability: two fluorite samples from the same deposit (Horni Krupka, Czech Republic) with ca. 170°C and ca. 43°C T c yield highly different (U-Th-Sm)/He ages of 290 ± 10 Ma and 79 ± 10 Ma, respectively. Accordingly, the fluorite sample with the high T c could have quantitatively retained helium since the formation of the fluorite-bearing ores in the Permian, despite subsequent Mesozoic burial and associated regional hydrothermal heating. In contrast, the fluorite with the low T c yields a Late Cretaceous age close to the apatite fission track (AFT) and apatite (U-Th)/He ages (AHe) from the same locality. Remarkably, thermal modelling of FHe yields comparable results to the well-established modelling based on AFT and AHe.

Economic Geology, 2015

The Erzgebirge region of Germany records two major episodes of hydrothermal activity, which inclu... more The Erzgebirge region of Germany records two major episodes of hydrothermal activity, which includes a Late Carboniferous to Early Permian event associated with significant Sn-W mineralization that is related to late Variscan granite magmatism, and a Mesozoic episode of polymetallic vein mineralization. In contrast to the first event, the age of the younger hydrothermal activity is poorly constrained. For the latter, various geochronological methods yielded a wide age range from Permian to early Tertiary. Here we apply fluorite (U-Th-Sm)/He thermochronology (FHe) on both types of mineralization with a twofold goal: (1) to investigate the sensitivity and applicability of the new FHe method (Evans et al., 2005), and (2) to constrain the thermal history of ore deposits in the Erzgebirge region. Two hundred and thirty-three aliquots from seven mineralization localities have been dated. Fluorite from six deposits yielded Cretaceous FHe ages between 112 to 79 Ma, which are independent of their paragenesis. In contrast, fluorite from the Sadisdorf Sn-W deposit yielded an age of 234 Ma. The younger ages are interpreted as cooling ages indicating the time of the last thermal overprint, including possible hydrothermal activity, in the Erzgebirge. The oldest, Triassic FHe ages at Sadisdorf indicate that the Mesozoic thermal overprint only partially reset the (U-Th-Sm)/He system of the late Variscan mineralization. Thermal modeling based on FHe ages and He diffusion parameters in fluorite results in thermal histories comparable to the results from the well-established apatite-based thermal modeling. This study emphasizes the applicability of fluorite (U-Th-Sm)/He thermochronology, which is especially suited for ore deposits where apatite is lacking. Regional Geology and Post-Variscan Tectonic Evolution The Erzgebirge forms an antiform structure exposing high-to medium-grade metamorphic gneisses in the core surrounded by a sequence of low-grade metamorphic units, mainly composed of micaschists and phyllites. This metamorphic assemblage formed by crustal stacking during the Carboniferous (e.g., Werner and Lippolt, 2000) and was later intruded by late-to post-Variscan granitoids and locally covered by rhyolites (Kossmat, 1925; Romer et al., 2007; see Fig. 1b). The Erzgebirge is bordered in the east by the Lausitz thrust to the Cadomian basement of the Lausitz block (Linnemann and Romer, 2002). This fault is sealed by Cretaceous deposits that formed at the margin of the synsedimentary uplifting block in the east. The initially flexural margin was later transformed into a thrust (Linnemann and Romer, 2010). The Eger fault delimits the Erzgebirge toward the south (e.g., Kroner et al., 2007; Fig. 1b). The post-Variscan

Tectonics, 2021

The ongoing convergence between India and Asia causes widespread deformation of the Tibetan Plate... more The ongoing convergence between India and Asia causes widespread deformation of the Tibetan Plateau (e.g., Styron et al., 2010; Tapponnier and Molnar, 1977; Taylor et al., 2003). In the northern part of the plateau (i.e., north of the Kunlun strike-slip fault), deformation is mainly partitioned into thrust and strikeslip faulting (e.g., Meyer et al., 1998; Zheng et al., 2013a). In contrast to the more easily accessible plateau margins (i.e., the Altyn Tagh fault and the Qilian Shan), where various studies have determined fault slip rates (e.g.,

International Journal of Earth Sciences

The Brenner normal fault bounds the Tauern Window to the west and accommodated a significant port... more The Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The model...

Geology

Rapid rock exhumation in mountain belts is commonly associated with crustal-scale normal faulting... more Rapid rock exhumation in mountain belts is commonly associated with crustal-scale normal faulting during late-orogenic extension. The process of normal faulting advects hot footwall rocks toward Earth’s surface, which shifts isotherms upwards and increases the geothermal gradient. When faulting stops, this process is reversed and isotherms move downwards during thermal relaxation. Owing to these temporal changes of the geothermal gradient, it is not straightforward to derive the history of faulting from mineral cooling ages. Here, we combine thermochronological data with thermokinematic modeling to illustrate the importance of syntectonic heat advection and posttectonic thermal relaxation for a crustal-scale normal fault in the European Alps. The north-south–trending Brenner fault defines the western margin of the Tauern window (Austria) and caused the exhumation of medium-grade metamorphic rocks during Miocene orogen-parallel extension of the Alps. We analyzed samples from a 2-km-t...

Earth Surface Processes and Landforms

Tectonophysics, 2012

ABSTRACT The Ivrea-Verbano Zone of the western Southern Alps (NW Italy) exposes a well-preserved ... more ABSTRACT The Ivrea-Verbano Zone of the western Southern Alps (NW Italy) exposes a well-preserved tilted section across the lower continental crust, making it a key region for studying deep crustal and exhumation processes. This paper refines the cooling and exhumation history of the Ivrea-Verbano Zone using K/Ar dating of mica and illite-rich fault gouges as well as zircon fission track and (U-Th)/He thermochronology. The adjacent Strona-Ceneri Zone, Sesia-Lanzo Zone and Lower Penninic nappes are included in the study to derive a broader picture of the low-temperature history of the area.In the Strona profile of the Ivrea-Verbano unit the biotite K/Ar, zircon fission track and (U-Th)/He geochronometers show well preserved, but unusually wide partial retention zones. The youngest ages, representing the formerly deepest position, are situated along the Insubric Line.The main foliation of the Ivrea-Verbano Zone is vertical. The exhumation of the Ivrea-Verbano Zone, which section has a horizontal position on the surface now – took place in three steps. During Jurassic time the Ivrea-Verbano Zone was exhumed to a shallow to mid-crustal position by continental-scale extension. In this displacement the Pogallo Line probably played a dominant role. The studied section occupied an oblique position with a calculated angle of ca. 15 to 23° in the Jurassic. Later the Ivrea-Verbano Zone experienced a minor cooling event in the Late Eocene (~ 38 Ma zircon fission track ages) that was probably related to thrusting and erosion. The final exhumation towards the surface took place in the mid-Miocene as documented by the ca. 14 Ma zircon (U-Th)/He ages and a 12.8 Ma K/Ar fault gouge age. The magnitude and the high rate of final exhumation suggest orogen-parallel extension as a driving force, which is widespread in the Alps in the Lower to Middle Miocene and is most probably connected to orogenic collapse.