The low-temperature thermal history of northern Switzerland as revealed by fission track analysis and inverse thermal modelling

Abstract

Low-temperature thermal history of N-Switzerland 255 ABSTRACT New zircon and apatite fission track (FT) data from four boreholes, which penetrate the Mesozoic and pre-Mesozoic sediments and crystalline basement of northern Switzerland, are presented. Inverse thermal modelling of the measured apatite FT parameters unravels the low-temperature (below ~120 °C) thermal history of the crystalline basement of northern Switzerland. Zircon FT central and single-grain ages cluster around 250 Ma, thus maximum palaeotemperatures did not exceed ~330 °C after late-Variscan consolidation of the crystalline basement. Apatite FT central ages vary between 25 and 87 Ma. Confined mean track lengths range between 9.3 µm and 11.6 µm, suggesting substantial track annealing within all apatite samples. Modelled time-temperature paths offer a clear picture about the low-temperature thermal history of the crystalline basement of northern Switzerland: Cretaceous cooling is followed by an Eocene heating event and subsequent cooling to present-day temperatures. The Eocene heating episode is contemporaneous with the initial rifting stage of the nearby Upper Rhine Graben and the associated increasing volcanic activity. Crustal-scale faults of the Permo-Carboniferous Trough of northern Switzerland could have acted as major pathways for circulating hydrothermal fluids giving rise to the observed Middle to Late Eocene thermal event. ZUSAMMENFASSUNGNeue Zirkon-und Apatit-Spaltspurdaten werden aus vier Bohrungen, welche die mesozoische und pre-mesozoische Sedimentbedeckung, sowie das oberste kristalline Grundgebirge der Nordschweiz durchteufen, vorgelegt. Inverse thermische Modellierung der gemessenen Apatit-Spaltspurparameter erlaubt, die Niedrigtemperaturgeschichte (unter ~120 °C) des kristallinen Grundgebirges der Nordschweiz zu enträtseln. Die Zirkon-Spaltspuralter (Zentralalter) und die Einzelkornalter zeigen eine Häufung um 250 Ma. Daraus folgt, dass die maximalen Paläotemperaturen nach der spätvariszischen Konsolidierung des Kristallins ~330 °C nicht mehr überschritten haben. Apatit-Spaltspuralter (Zentralalter) variieren zwischen 25 und 87 Ma. Die mittleren Spaltspurlängen reichen von 9,3 µm bis 11,6 µm und weisen auf eine substantielle Ausheilung in den Apatiten hin. Die modellierten Zeit-Temperatur-Pfade bieten ein klares Bild der Niedrigtemperaturgeschichte des kristallinen Grundgebirges in der Nordschweiz: Einer kretazischen Abkühlung folgt ein eozänes Wärmee-reignis und anschliessend eine Abkühlung zur heutigen Temperaturverteilung. Der eozäne Wärmepuls ist zeitgleich mit der initialen Riftingphase des nahegelegenen Oberrheingrabens und der damit verbundenen erhöhten vulkanischen Aktivität. Zum Nordschweizer Permokarbontrog-System gehörige Stö-rungen im Krustenmassstab könnten als Fliesswege für zirkulierende Fluide gedient haben, die zum beobachteten mittel-bis späteozänen thermischen Ereignis führten.

Origin of high Zn contents in Jurassic limestone of the Jura mountain range and the Burgundy: evidence from Zn speciation and distribution

“…The cooling of the hydrothermal fluids that transport Zn either as Zn-Cl or Zn-H-S complexes was combined with a pH change towards more alkaline values due to interaction with the encasing carbonate rocks. Under the conditions experienced by the investigated limestone [maximal burial depth of 1,000 m and burial temperature of 70°C (Elie and Mazurek 2008;Mazurek et al 2006;Timar-Geng et al 2006)], these changes probably resulted in sphalerite precipitation (Daskalakis and Helz 1993;Tagirov et al 2007). Recent direct Rb-Sr dating of sphalerite crystals from the Auenstein section (JMR, Late Bajocian/Early Bathonian) yielded an age of 162 ± 4 Ma, corresponding to Late Callovian/Early Oxfordian, which confirms that formation of sphalerite probably occurred after sediment deposition (Efimenko et al 2009).…”

“…The low burial temperature (max. 70°C) experienced by these Jurassic limestone (Elie and Mazurek 2008;Mazurek et al 2006;Timar-Geng et al 2006) would also preclude the formation of hematite from goethite. In support, evidence for secondary sulfide oxidation caused by the infiltration of oxygenated surface waters and post-dating Zn mineralizations in the Muschelkalk of the Black forest has been inferred from sulfur isotope ratios (Hofmann and von Gehlen 1993).…”

“…Bajocian to Bathonian sediments consist of oolitic carbonate (Hauptrogenstein formation, Celtic realm, domain west of the today's Aare river, Gonzalez and Wetzel 1996, and references therein), whereas sediments of the Oxfordian are characterized by bioclastic carbonates intercalated with episodic siliciclastic sediments (Hug 2003, and references therein). These Jurassic sediments experienced two burial phases during the Cretaceous and the Miocene, with maximum burial depth of about 1,000 m below sea level and burial temperature reaching a maximum of 70°C during the Late Cretaceous (Elie and Mazurek 2008;Mazurek et al 2006;Timar-Geng et al 2006). Also, two phases of uplift with meteoric water inputs during Early Cretaceous (Barremian and Aptian/Albian, respectively) affected the Jurassic limestone of the Burgundy platform (Brigaud et al 2009).…”

Sea‐water circulation on an oolite‐dominated carbonate system in an epeiric sea (Middle Jurassic, Switzerland)

“…If so, the pre‐existing basement structures had a high potential to become reactivated (Brockkamp et al ., ). In fact, re‐activation during the Jurassic is evidenced by vein mineralization data and changes in lithofacies, as well as thickness changes across faults in the crystalline basement; in many instances, thickness anomalies exceed depositional water depth and, hence, imply synsedimentary differential tectonic movements (Wetzel et al ., ; Timar‐Geng et al ., ; Brockkamp et al ., ). However, the sediments were deformed mainly flexurally as vertical movements in the basement were dissipated by Triassic salt.…”

Quantifying Multiple Erosion Events in the Distal Sector of the Northern Alpine Foreland Basin (North-Eastern Switzerland), by Combining Basin Thermal Modelling with Vitrinite Reflectance and Apatite Fission Track Data

“…These data from the stratigraphic record enable one to (i) define the original Several studies have been done to estimate the magnitude of the erosion in the study area. Several methods have been used such as analysis of vitrinite reflectance data (%Ro) [3][4][5][6], stratigraphic and porosity extrapolation [7]; subsidence analysis [8], clay mineral transformation [9], seismic interval analysis [7], and apatite fission tracks [6,[10][11][12][13][14][15].…”