Response of clastic sediments to episodic hydrothermal fluid flows in intramontane troughs: a case study from Black Forest, Germany

Schlegel, Andreas; Brockamp, Olaf; Clauer, Norbert

doi:10.1127/0935-1221/2007/0019-1768

Cited by 10 publications

(7 citation statements)

References 39 publications

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“…; Schlegel et al . ) in the crystalline basement of the central Schwarzwald are very likely related to the influx of such NaCl‐rich fluids. Plagioclase dissolution and conversion to albite enriched the originally Ca‐poor bittern brine in Ca and in base metals.…”

Section: Discussionmentioning

confidence: 99%

Long‐term chemical evolution and modification of continental basement brines – a field study from the Schwarzwald, SW Germany

2016

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Highly saline, deep‐seated basement brines are of major importance for ore‐forming processes, but their genesis is controversial. Based on studies of fluid inclusions from hydrothermal veins of various ages, we reconstruct the temporal evolution of continental basement fluids from the Variscan Schwarzwald (Germany). During the Carboniferous (vein type i), quartz–tourmaline veins precipitated from low‐salinity (<4.5wt% NaCl + CaCl2), high‐temperature (≤390°C) H2O‐NaCl‐(CO2‐CH4) fluids with Cl/Br mass ratios = 50–146. In the Permian (vein type ii), cooling of H2O‐NaCl‐(KCl‐CaCl2) metamorphic fluids (T ≤ 310°C, 2–4.5wt% NaCl + CaCl2, Cl/Br mass ratios = 90) leads to the precipitation of quartz‐Sb‐Au veins. Around the Triassic–Jurassic boundary (vein type iii), quartz–haematite veins formed from two distinct fluids: a low‐salinity fluid (similar to (ii)) and a high‐salinity fluid (T = 100–320°C, >20wt% NaCl + CaCl2, Cl/Br mass ratios = 60–110). Both fluids types were present during vein formation but did not mix with each other (because of hydrogeological reasons). Jurassic–Cretaceous veins (vein type iv) record fluid mixing between an older bittern brine (Cl/Br mass ratios ~80) and a younger halite dissolution brine (Cl/Br mass ratios >1000) of similar salinity, resulting in a mixed H2O‐NaCl‐CaCl2 brine (50–140°C, 23–26wt% NaCl + CaCl2, Cl/Br mass ratios = 80–520). During post‐Cretaceous times (vein type v), the opening of the Upper Rhine Graben and the concomitant juxtaposition of various aquifers, which enabled mixing of high‐ and low‐salinity fluids and resulted in vein formation (multicomponent fluid H2O‐NaCl‐CaCl2‐(SO4‐HCO3), 70–190°C, 5–25wt% NaCl‐CaCl2 and Cl/Br mass ratios = 2–140). The first occurrence of highly saline brines is recorded in veins that formed shortly after deposition of halite in the Muschelkalk Ocean above the basement, suggesting an external source of the brine's salinity. Hence, today's brines in the European basement probably developed from inherited evaporitic bittern brines. These were afterwards extensively modified by fluid–rock interaction on their migration paths through the crystalline basement and later by mixing with younger meteoric fluids and halite dissolution brines.

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Section: Discussionmentioning

confidence: 99%

Long‐term chemical evolution and modification of continental basement brines – a field study from the Schwarzwald, SW Germany

2016

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“…Illitization is largely controlled by the K content of the host-rock pore waters, and was probably favored by rather low pHs in the sandstones (Lanson et al, 2002). It is often reported as resulting from either progressive K-fixation in a smectite-to-illite trend (e.g., Inoue et al, 1987), or as a direct mineral precipitation associated with concomitant alteration/dissolution of detrital K-bearing feldspar and micas (e.g., Schlegel et al, 2007;Brockamp et al, 2011). Systematic decrease of K-Ar dates with decreasing micrometric size fractions of clay-rich material has been often reported (e.g., Zwingmann et al, 1999;Cathelineau et al, 2004;Sant'Anna et al, 2006), the older ages of the coarser size fractions being generally considered as reflecting contribution of detrital minerals that accumulated more radiogenic argon.…”

Section: Significance Of the Illite K-ar Agesmentioning

confidence: 99%

“…Authigenic illite is known to reduce dramatically rock porosity, together with quartz and calcite, especially when consisting of filamentous particles (Macchi, 1987;Worden and Morad, 2003). Such illite either results from progressive conversion of illite-smectite mixed layers (labeled I-S hereafter; Inoue et al, 1987;Velde and Renac, 1996) monitored by K supply from either dissolution of K-bearing micas or feldspars during burial diagenesis, or interaction with longdistance migrating fluids of varied origins (Small et al, 1992;Lanson et al, 1996;Schlegel et al, 2007;Cathelineau et al, 2012). In the latter case, the reaction pathway leading to concomitant alteration of detrital grains and crystallization of authigenic minerals, and identification of the physical-chemical characteristics of the parent-fluid interactions are challenging to constrain (Lanson et al, 2002;Clauer and Lerman, 2012).…”

Section: Introductionmentioning

confidence: 99%

Reconstructing fluid-flow events in Lower-Triassic sandstones of the eastern Paris Basin by elemental tracing and isotopic dating of nanometric illite crystals

Blaise

Clauer

Cathelineau

et al. 2016

Geochimica et Cosmochimica Acta

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International audienceLower- to Middle-Triassic sandstones from eastern Paris Basin were buried to a maximum depth of 2500 m at a paleo-temperature of about 100 °C. They contain extensive amounts of authigenic platy and filamentous illite particles similar to those reported in reservoirs generally buried at 3000 to 5000 m and subjected to temperatures of 120 to 150 °C. To evaluate this unexpected occurrence, such sandstones were collected from drill cores between 1825 and 2000 m depth, and nanometric-sized sub-fractions were separated. The illite crystals were identified by XRD, observed by SEM and TEM, analyzed for their major, trace, rare-earth elements and oxygen isotope compositions, and dated by K-Ar and Rb-Sr.Illite particles display varied growth features in the rock pore space and on authigenic quartz and adularia that they postdate. TEM-EDS crystal-chemical in situ data show that the illite lath/fiber and platelet morphologies correspond at least to two populations with varied interlayer charges: between 0.7 and 0.9 in the former and between 0.8 and 1.0 in the latter, the Fe/Fe+Mg ratio being higher in the platelets. Except for the deeper conglomerate, the PAAS-normalized REE patterns of the illite crystals are bell-shaped, enriched in middle REEs. Ca-carbonates and Ca-phosphates were detected together with illite in the separates. These soluble components yield 87Sr/86Sr ratios that are not strictly in chemical equilibrium with the illite crystals, suggesting successive fluids flows with different chemical compositions. The K-Ar data of finer <0.05 μm illite separates confirm two crystallization events at 179.4 ± 4.5 and 149.4 ± 2.5 Ma during the Early and Late Jurassic. The slightly coarser fractions contain also earlier crystallized or detrital K-bearing minerals characterized by lower δ18O values. The δ18O of the finest authigenic illite separates tends to decrease slightly with depth, from 18.2 (± 0.2) to 16.3 (± 0.2) ‰, suggesting different but contemporaneous crystallization conditions deeper in the section.The illite platelets and filaments crystallized in changing physical-chemical crystallization conditions induced by fluids flows through the host-rock pore system. These flow events were probably driven by repetitive rifting episodes of the North Atlantic Ocean, although located several hundreds kilometers away from eastern Paris Basin, and/or by fracturing events in the nearby basement of the Vosges Massif. Complex relationships between geodynamical events, thermal anomalies, and advective fluids confirm that remote tectonic activities can impact quiescent basins, even if located far from tectono-thermal activities, by discrete and long-distance fluid flows

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“…In the northern Black Forest, a Late Jurassic hydrothermal alteration of Permian-Carboniferous sandstones was identified in the Baden-Baden and Offenburg-Teinach troughs with temperatures of 240À290ºC and 150À210ºC, respectively (Zuther & Brockamp, 1988;Brockamp et al, 2003). Further south, Schlegel et al (2007) found late Jurassic (~145 Ma), early Cretaceous (~130 Ma) and Palaeocene (~60 Ma) illite K-Ar ages from Permian and Triassic sandstones were attributed to the circulation of hot (150À250ºC) and low-saline (<10 wt.% NaCl eq ) fluids.…”

Section: Summary Of Illite K-ar Ages From Available Local and Regionamentioning

confidence: 99%

Thermal history of Triassic sandstones from the Vosges Mountains-Rhine Graben rifting area, NE France, based on K-Ar illite dating

Clauer¹,

Liewig²,

Ledésert³

et al. 2008

Clay miner.

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The thermal history of the Buntsandstein (Lower Triassic) sedimentary rocks that crop out in the Vosges Mountains, or are deeply buried in the Rhine Graben, was evaluated on the basis of a combined mineralogical, morphological, oxygen isotope and K-Ar-dating study of illite separates from five locations over a limited 120 km2 area. The results indicate a complex pre-rift evolution characterized by the following features: (1) in the northern Vosges, no record of diagenetic illite formation could be detected; (2) in the nearby Saverne rifting fracture-field, tectonic activity favoured the formation of faults in the crystalline basement ~210 Ma ago. This induced fluid migrations into the porous sandstone cover with illite precipitation occurring either repetitively over a period of ~25 Ma or as two separate events, the latter at ~185 Ma, affecting rocks to the east in the deeper part of the post-Eocene Upper Rhine Graben system; this latter stage of tectonic activity and fluid migration continued until 160 Ma, unless overprinted by another tectonic pulse at that time; (3) afterwards, the main tectonic activity moved to the Soultz-sous-Forêts area where two episodes could be identified at ~95 and 70 Ma by dating mineral crystallization; the latter illite age was also detected in more deeply buried Buntsandstein lithologies of the rift basin, west of Strasbourg, reflecting diverse crystallization under different physical and/or chemical conditions; (4) further illitization which at present is poorly constrained may have restarted ~55 My ago in the same deep part of the rift graben.The youngest detected illitization age is clearly older than the main Miocene rifting episode of the Rhine Graben, suggesting that no illite crystallization occurred in the Buntsandstein sandstones during this tectonic event. This is explained by the fact that these rocks, as well as most of the underlying crystalline basement, were already sealed by fluid migration and mineralization during late Mesozoic rifting, and were therefore almost impermeable to the circulation of Tertiary fluids. The overall evolution of the region between the Vosges Mountains and the central Rhine Graben appears to be more complex than that of equivalent rock lithologies elsewhere in Western Europe. Several episodes identified here have been detected in other regions, but no single location exists which was affected by all events.

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Response of clastic sediments to episodic hydrothermal fluid flows in intramontane troughs: a case study from Black Forest, Germany

Cited by 10 publications

References 39 publications

Long‐term chemical evolution and modification of continental basement brines – a field study from the Schwarzwald, SW Germany

Long‐term chemical evolution and modification of continental basement brines – a field study from the Schwarzwald, SW Germany

Reconstructing fluid-flow events in Lower-Triassic sandstones of the eastern Paris Basin by elemental tracing and isotopic dating of nanometric illite crystals

Thermal history of Triassic sandstones from the Vosges Mountains-Rhine Graben rifting area, NE France, based on K-Ar illite dating

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