Timing of fault gouge formation and fluid-rock interaction during tectonic inversion of the Penninic Frontal Thrust (SW Alps)

2021 ◽  
Author(s):  
Antonin Bilau ◽  
Yann Rolland ◽  
Stéphane Schwartz ◽  
Nicolas Godeau ◽  
Abel Guihou ◽  
...  
Keyword(s):  
Isotope Analysis ◽  
Isotopic Signature ◽  
Fault Gouge ◽  
Fault System ◽  
Rock Interaction ◽  
Brittle Ductile Transition ◽  
Formation And Evolution ◽  
Clumped Isotope ◽  
Fault Displacement ◽  
Tectonic Boundary

<p>In the last decade, important improvements in dating methods have been made and make it possible to go into the details of fault gouge formation and evolution. Common minerals like calcite and hematite can now bring detailed information on timing of fault development and fluid-rock interaction. We applied those novel techniques to a tectonically well constrains alpine context, though still lacking key chronological constrains. The targeted fault zone is the Penninic Frontal Thrust (PFT) of SW Alps, which is a major tectonic boundary that juxtaposed the metamorphic internal Alps over the unmetamorphosed external Alps, primarily as a thrust during the Oligocene (Simon-Labric et al., 2009). The PFT was later reactivated as an extensional detachment in the Mio-Pliocene, though the age of this reactivation remained unconstrained. Sue and Tricart (2003) showed that ongoing extensional seismic activity along the PFT, corresponding to the High-Durance Fault System (HDFS), is characterized at the surface, by an extensional fault network. In this context, the HDFS corresponds to extensional reactivation of the PFT as a consequence of Pelvoux external crystalline massif exhumation.</p><p>In this study, we coupled field tectonic, in-situ calcite U-Pb and hematite (U-Th-Sm)/He dating to stable and clumped isotope analysis to infer the HDFS activation age and to investigate the related fluid circulations. Isotopic signature (δ<sup>13</sup>C and δ<sup>18</sup>O) of compressional veins, en-echelon extensional veins and cataclasite fault gouge have been determined (Bilau et al., 2020).</p><p>This study allows pinpointing the evolution of deformation and fluid-rock interaction in the PFT footwall during its progressive extensional exhumation. The older U-Pb ages obtained on the cement of the gouge fault range between 5 to 3.5 Ma and taking into consideration uplift rate, comparison to currently seismicity depth and calcite brittle/ductile transition temperature, calcite crystallization may have occurred between 5 to 2 km. The hematite crystallization appears at shallower levels in the latest stages of the fault displacement at 3-1 km depth. A transition in the nature of fluids, controlling the redox state, can be highlighted here. This transition occurs between the calcite and hematite forming events at 2-3 km depth, which is probably related to a significant influx of meteoric fluids into the drainage of the fault system.</p>

scholarly journals The δ13C, δ18O and Δ47 records in biogenic, pedogenic and geogenic carbonate types from paleosol-loess sequence and their paleoenvironmental meaning

2021 ◽  
pp. 1-17
Author(s):  
Kazem Zamanian ◽  
Alex R. Lechler ◽  
Andrew J. Schauer ◽  
Yakov Kuzyakov ◽  
Katharine W. Huntington
Keyword(s):  
Land Snail ◽  
Isotopic Signature ◽  
Sediment Layer ◽  
Isotopic Signatures ◽  
Pedogenic Carbonates ◽  
Rhine Valley ◽  
Clumped Isotope ◽  
Time Specific ◽  
Sediment Layers ◽  
Paleoenvironmental Reconstructions

Abstract Paleoenvironmental reconstructions are commonly based on isotopic signatures of a variety of carbonate types, including rhizoliths and land-snail shells, present in paleosol-loess sequences. However, various carbonate types are formed through distinct biotic and abiotic processes over various periods, and therefore may record diverging environmental information in the same sedimentological layer. Here, we investigate the effects of carbonate type on δ13C, δ18O, and clumped isotope-derived paleotemperature [T(Δ47)] from the Quaternary Nussloch paleosol-loess sequence (Rhine Valley, SW Germany). δ13C, δ18O, and T(Δ47) values of co-occurring rhizoliths (-8.2‰ to -5.8‰, -6.1‰ to -5.9‰, 12–32°C, respectively), loess dolls (-7.0‰, -5.6‰, 23°C), land-snail shells (-8.1‰ to -3.2‰, -4.0‰ to -2.2‰, 12–38°C), earthworm biospheroliths (-11‰, -4.7‰, 8°C), and “bulk” carbonates (-1.9‰ to -0.5‰, -5.6‰ to -5.3‰, 78–120°C) from three sediment layers depend systematically on the carbonate type, admixture from geogenic carbonate, and the duration of formation periods. Based on these findings, we provide a comprehensive summary for the application of the three isotopic proxies of δ13C, δ18O, and Δ47 in biogenic and pedogenic carbonates present in the same sediment layer to reconstruct paleoenvironments (e.g., local vegetation, evaporative conditions, and temperature). We conclude that bulk carbonates in Nussloch loess should be excluded from paleoenvironmental reconstructions. Instead, pedogenic and biogenic carbonates should be used to provide context for interpreting the isotopic signature for detailed site- and time-specific paleoenvironmental information.

scholarly journals Variable thermoregulation of Late Cretaceous dinosaurs inferred by clumped isotope analysis of fossilized eggshell carbonates

Heliyon ◽  
2020 ◽  
Vol 6 (10) ◽  
pp. e05265
Author(s):  
Amzad H. Laskar ◽  
Dhananjay Mohabey ◽  
Sourendra K. Bhattacharya ◽  
Mao-Chang Liang
Keyword(s):  
Late Cretaceous ◽  
Isotope Analysis ◽  
Clumped Isotope

scholarly journals An Optimized Snowmelt Lysimeter System for Monitoring Melt Rates and Collecting Samples for Stable Water Isotope Analysis

2019 ◽  
Vol 67 (1) ◽  
pp. 20-31 ◽  
Author(s):  
Andrea Rücker ◽  
Massimiliano Zappa ◽  
Stefan Boss ◽  
Jana von Freyberg
Keyword(s):  
Isotopic Composition ◽  
Isotope Analysis ◽  
Ground Level ◽  
Isotopic Signature ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Environmental Tracers ◽  
Hydrograph Separation ◽  
Stable Water Isotopes ◽  
Restricted Volume

Abstract The contribution of snow meltwater to catchment streamflow can be quantified through hydrograph separation analyses for which stable water isotopes (18O, 2H) are used as environmental tracers. For this, the spatial and temporal variability of the isotopic composition of meltwater needs to be captured by the sampling method. This study compares an optimized snowmelt lysimeter system and an unheated precipitation collector with focus on their ability to capture snowmelt rates and the isotopic composition of snowmelt. The snowmelt lysimeter system consists of three individual unenclosed lysimeters at ground level with a surface of 0.14 m2 each. The unheated precipitation collector consists of a 30 cm-long, extended funnel with its orifice at 2.3 m above ground. Daily snowmelt samples were collected with both systems during two snowfall-snowmelt periods in 2016. The snowmelt lysimeter system provided more accurate measurements of natural melt rates and allowed for capturing the small-scale variability of snowmelt process at the plot scale, such as lateral meltwater flow from the surrounding snowpack. Because of the restricted volume of the extended funnel, daily melt rates from the unheated precipitation collector were up to 43% smaller compared to the snowmelt lysimeter system. Overall, both snowmelt collection methods captured the general temporal evolution of the isotopic signature in snowmelt.

Clumped Isotope Paleothermometry: Principles, Applications, and Challenges

2012 ◽  
Vol 18 ◽  
pp. 101-114 ◽  
Author(s):  
Hagit P. Affek
Keyword(s):  
Isotope Composition ◽  
Isotope Analysis ◽  
Atomic Scale ◽  
Clumped Isotopes ◽  
Temperature Dependent ◽  
Deep Time ◽  
Diagenetic Alteration ◽  
Carbonate Formation ◽  
Rare Isotopes ◽  
Clumped Isotope

Clumped isotopes geochemistry measures the thermodynamic preference of two heavy, rare, isotopes to bind with each other. This preference is temperature dependent, and is more pronounced at low temperatures. Carbonate clumped isotope values are independent of the carbonate δ13C and δ18O, making them independent of the carbon or oxygen composition of the solution from which the carbonate precipitated. At equilibrium, it is therefore a direct proxy for the temperature in which the carbonate mineral formed. In most cases, carbonate clumped isotopes record the temperature of carbonate formation, irrespective of the mineral form (calcite, aragonite, or bioapatite) or the organism making it. The carbonate formation temperatures obtained from carbonate clumped isotope analysis can be used in conjunction with the δ18O of the same carbonate, to constrain the oxygen isotope composition of the water from which the carbonate has precipitated. There are, however, cases of deviation from thermodynamic equilibrium, where both clumped and oxygen isotopes are offset from the expected values. Such carbonates must be characterized and calibrated separately. For deep-time applications, special care must be paid to the preservation of the original signal, in particular with respect to diagenetic alteration associated with atomic scale diffusion that may be undetectable by common tests for diagenesis.

Investigating the diet of the omnivorous mirid Dicyphus hesperus using stable isotopes

2009 ◽  
Vol 99 (4) ◽  
pp. 347-358 ◽  
Author(s):  
J.A. Bennett ◽  
D.R. Gillespie ◽  
S.L. VanLaerhoven
Keyword(s):  
Nitrogen Isotopes ◽  
Trophic Position ◽  
Isotope Analysis ◽  
Isotopic Signature ◽  
Encarsia Formosa ◽  
Verbascum Thapsus ◽  
Diet Variability ◽  
Feeding Trials ◽  
Plant Sources ◽  
Over Time

AbstractOmnivory involves numerous feeding relationships and a complex web of interactions. When using omnivores in biocontrol, these interactions need to be understood to maximize feeding on the target species and minimize non-target interactions. Dicyphus hesperus is used along with Encarsia formosa for biocontrol of whiteflies in greenhouse tomato crops. Dicyphus hesperus is a generalist omnivore which feeds on all components of the system. To quantify these interactions, stable isotope analysis was used to identify trophic position with nitrogen isotopes (δ15N) and plant sources with carbon isotopes (δ13C). Feeding trials were used to establish baseline isotopic data for D. hesperus and their diet, including Verbascum thapsus, an alternative plant food. Cage trials were used to monitor population abundances and the isotopic signature of D. hesperus. In feeding trials, D. hesperus were enriched relative to their food, suggesting an elevated trophic position. However, large amounts of isotopic variation were found within all diet components, with only V. thapsus exhibiting a distinct signature. In cage trials, the average δ15N and δ13C of the omnivore declined over time, coinciding with declines in total available prey, though it may be confounded by changes in temperature. The range of δ13C, but not the range of δ15N, also declined over time. This suggests a change in the plant source within the diet, but also some unquantified variability within the population. We suggest that diet variability exists within D. hesperus populations, declining as prey become less abundant.

Impact of basin architecture on diagenesis and dolomitization in a fault-bounded carbonate platform: outcrop analogue of a pre-salt carbonate reservoir, Red Sea rift, NW Saudi Arabia

2019 ◽  
Vol 26 (3) ◽  
pp. 448-461 ◽  
Author(s):  
Khalid Al-Ramadan ◽  
Ardiansyah Koeshidayatullah ◽  
Dave Cantrell ◽  
Peter K. Swart
Keyword(s):  
Red Sea ◽  
Elevated Temperatures ◽  
Carbonate Platform ◽  
Isotope Analysis ◽  
Carbonate Reservoir ◽  
Carbonate Platforms ◽  
Hydrocarbon Reservoir ◽  
Red Sea Rift ◽  
Platform Margin ◽  
Clumped Isotope

The early Miocene Wadi Waqb carbonate in the Midyan Peninsula, NE Red Sea is of great interest not only because of its importance as an archive of one of the few pre-salt synrift carbonate platforms in the world, but also as a major hydrocarbon reservoir. Despite this importance, little is known about the diagenesis and heterogeneity of this succession. This study uses petrographical, elemental chemistry, stable isotope (δ13C and δ18O) and clumped isotope (Δ47) analyses to decipher the controlling processes behind the formation of various diagenetic products, especially dolomite, from two locations (Wadi Waqb and Ad-Dubaybah) that have experienced different diagenetic histories. Petrographically, the dolomites in both locations are similar, and characterized by euhedral to subhedral crystals (50–200 µm) and fabric-preserving dolomite textures. Clumped isotope analysis suggests that slightly elevated temperatures were recorded in the Ad-Dubaybah location (up to 49°C), whereas the Wadi Waqb location shows a sea-surface temperature of c. 30°C. These temperature differences, coupled with distinct δ18OVPDB values, can be used to infer the chemistry of the fluids involved in the dolomitization processes, with fluids at the Wadi Waqb location displaying much higher δ18OSMOW values (up to +4‰) compared to those at the Ad Dubaybah location (up to −3‰). Two different dolomitization models are proposed for the two sites: a seepage reflux, evaporative seawater mechanism at the Wadi Waqb location; and a fault-controlled, modified seawater mechanism at the Ad-Dubaybah location. At Ad-Dubaybah, seawater was modified through interaction with the immature basal sandstone aquifer, the Al-Wajh Formation. The spatial distribution of the dolostone bodies formed at these two locations also supports the models proposed here: with the Wadi Waqb location exhibiting massive dolostone bodies, while the dolostone bodies in the Ad-Dubaybah location are mostly clustered along the slope and platform margin. Porosity is highest in the slope sediments due to the interplay between higher precursor porosity, the grain size of the original limestone and dolomitization. Ultimately, this study provides insights into the prediction of carbonate diagenesis in an active tectonic basin and the resultant porosity distribution of a pre-salt carbonate reservoir system.

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

Sedimentology ◽  
2020 ◽  
Author(s):  
Mattia Tagliavento ◽  
Cédric M. John ◽  
Kresten Anderskouv ◽  
Lars Stemmerik
Keyword(s):  
Isotope Analysis ◽  
Clumped Isotope

scholarly journals Hidden Archaean and Palaeoproterozoic crust in NW Ireland? Evidence from zircon Hf isotopic data from granitoid intrusions

2009 ◽  
Vol 146 (6) ◽  
pp. 903-916 ◽  
Author(s):  
M. J. FLOWERDEW ◽  
D. M. CHEW ◽  
J. S. DALY ◽  
I. L. MILLAR
Keyword(s):  
Source Region ◽  
Isotope Analysis ◽  
Isotopic Signature ◽  
Detrital Zircons ◽  
Metasedimentary Rocks ◽  
Deep Crust ◽  
Gneiss Complex ◽  
Granitoid Rocks ◽  
Granitoid Intrusions

AbstractThe presence of major crystalline basement provinces at depth in NW Ireland is inferred from in situ Hf isotope analysis of zircons from granitoid rocks that cut structurally overlying metasedimentary rocks. Granitoids in two of these units, the Slishwood Division and the Tyrone Central Inlier, contain complex zircons with core and rim structures. In both cases, cores have average ϵHf values that differ from the average ϵHf values of the rims at 470 Ma (the time of granitoid intrusion). The Hf data and similarity in U–Pb age between the inherited cores and detrital zircons from the host metasedimentary rocks suggests local contamination during intrusion rather than transport of the grains from the source region at depth. Rims from the Slishwood Division intrusions have average ϵHf470 values of −7.7, consistent with a derivation from juvenile Palaeoproterozoic crust, such as the Annagh Gneiss Complex or Rhinns Complex of NW Ireland, implying that the deep crust underlying the Slishwood Division is made of similar material. Rims from the Tyrone Central Inlier have extremely negative ϵHf470 values of approximately −39. This isotopic signature requires an Archaean source, suggesting rocks similar to the Lewisian Complex of Scotland, or sediment derived wholly from it, occurs at depth in NW Ireland.

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