Thermochronology and REE analyses as new tools to track thermal anomaly and fluid flow along a crustal scale fault (Têt fault, French Pyrenees)

2020 ◽  
Author(s):  
Gaétan Milesi ◽  
Monié Patrick ◽  
Philippe Münch ◽  
Roger Soliva ◽  
Sylvain Mayolle ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Hot Springs ◽  
Hot Spring ◽  
Numerical Models ◽  
Hanging Wall ◽  
Damage Zone ◽  
Thermal Anomaly ◽  
Geothermal Gradient ◽  
Fault Damage Zone ◽  
Hydrothermal Flow

<p>The Têt fault is a crustal scale major fault in the eastern Pyrenees that displays about 30 hot springs along its surface trace with temperatures between 29°C and 73°C. The regional process of fluid circulation at depth has previously been highlighted by thermal numerical modelling supported by hydrochemical analyses and tectonic study. Numerical modelling suggests the presence of a strong subsurface anomaly of temperature along-fault (locally > 90°C/km), governed by topography-driven meteoric fluid upflow through the fault damage zone (advection). On the basis of this modelling, we focused our thermochronological study on 30 samples collected close and between two hot spring clusters in both the hanging wall and the footwall of the Têt fault, where the most important thermal anomaly is recorded by models. We analysed apatite using (U-Th)/He (AHe) dating combined with REE analyses on the same dated grains.</p><p>Along the fault, AHe ages are in a range of 26 to 8 Ma in the footwall and 43 and 18 Ma in the hanging wall, and only few apatite grains have been impacted by hydrothermalism near the St-Thomas hot spring cluster. By contrast, particularly young AHe ages below 6 Ma, correlated to REE depletion, are found around the Thuès-les-bains hot spring cluster. These very young ages are therefore interpreted as thermal resetting due to an important hydrothermal activity. A thermal anomaly can be mapped and appears restricted to 1 km around this cluster of hot springs, i.e. more restricted than the size of the anomaly predicted by numerical models. These results reveal that AHe dating and REE analyses can be used to highlight neo- or paleo-hydrothermal anomaly recorded by rocks along faults.</p><p>This study brings new elements to discuss the onset of the hydrothermal circulations and consequences on AHe and REE mobilisation, and suggest a strong heterogeneity of the hydrothermal flow pattern into the fault damage zone. Moreover, this study suggests that crustal scale faults adjacent to reliefs can localise narrow high hydrothermal flow and important geothermal gradient.  Besides these results, this study provides new constraints for geothermal exploration around crustal faults, as well as a discussion on the use of thermochronometers into fault damage zones. </p>

scholarly journals Tracking geothermal anomalies along a crustal fault using (U-Th)/He apatite thermochronology and REE analyses, the example of the Têt fault (Pyrenees, France)

2020 ◽  
Author(s):  
Gaétan Milesi ◽  
Patrick Monié ◽  
Philippe Münch ◽  
Roger Soliva ◽  
Audrey Taillefer ◽  
...  
Keyword(s):  
Hot Springs ◽  
Hot Spring ◽  
Hanging Wall ◽  
Regional Scale ◽  
Damage Zone ◽  
Hydrothermal Activity ◽  
Thermal Anomalies ◽  
Eastern Pyrenees ◽  
Major Fault ◽  
Surface Manifestation

Abstract. The Têt fault is a crustal scale major fault in the eastern Pyrenees along which 29 hot springs emerge mainly within the footwall damage zone of the fault. In this study, (U-Th)/He apatite (AHe) thermochronology is used in combination with REE analyses to investigate the imprint of hydrothermal activity nearby two main hot spring clusters and in between in an attempt to better define the geometry and intensity of the recent thermal anomalies along the fault and to compare them with previous results from numerical modelling. This study displays 99 new AHe ages and 63 REE analyses on samples collected in the hanging wall (18 to 43 Ma) and footwall (8 to 26 Ma) of the Têt fault. In the footwall, the results reveal AHe age resetting and apatite REE depletion due to hydrothermal circulation along the Têt fault damage zone, nearby the actual hot springs (Thuès-les-Bains and St-Thomas) but also in areas lacking actual geothermal surface manifestation. These age resetting and element depletions are more pronounced around Thuès-les-Bains hot spring cluster and are spatially restricted to a limited volume of the damage zone. Outside this damage zone, the modelling of thermochronological data in the footwall suggests the succession of two main phases of exhumation, between 30 and 24 Ma and a second one around 10 Ma. In the hanging wall, few evidences of hydrothermal imprint on AHe ages and REE signatures have been found and thermal modelling records a single exhumation phase at 35–30 Ma. Low-temperature thermochronology combined with REE analyses allows to identify the spatial distribution of a recent geothermal perturbation related to hydrothermal flow along a master fault zone in the eastern Pyrenees, opens new perspectives for the exploration of geothermal fields and provides at the regional scale new constraints on the tectonic uplift of the footwall and hanging wall massifs.

scholarly journals Episodic fluid flow in an active fault

Geology ◽  
2019 ◽  
Vol 47 (10) ◽  
pp. 938-942 ◽  
Author(s):  
Sarah Louis ◽  
Elco Luijendijk ◽  
István Dunkl ◽  
Mark Person
Keyword(s):  
Fluid Flow ◽  
Numerical Models ◽  
Damage Zone ◽  
Normal Fault ◽  
Geothermal Gradient ◽  
Hydrothermal Activity ◽  
The Past ◽  
Discharge Rates ◽  
Fault Damage Zone ◽  
Wide Zone

Abstract We present a reconstruction of episodic fluid flow over the past ∼250 k.y. along the Malpais normal fault, which hosts the Beowawe hydrothermal system (Nevada, USA), using a novel combination of the apatite (U-Th)/He (AHe) thermochronometer and a model of the thermal effects of fluid flow. Samples show partial resetting of the AHe thermochronometer in a 40-m-wide zone around the fault. Numerical models using current fluid temperatures and discharge rates indicate that fluid flow events lasting 2 k.y. or more lead to fully reset samples. Episodic fluid pulses lasting 1 k.y. result in partially reset samples, with 30–40 individual fluid pulses required to match the data. Episodic fluid flow is also supported by an overturned geothermal gradient in a borehole that crosses the fault, and by breaks in stable isotope trends in hydrothermal sinter deposits that coincide with two independently dated earthquakes in the past 20 k.y. This suggests a system where fluid flow is triggered by repeated seismic activity, and that seals itself over ∼1 k.y. due to the formation of clays and silicates in the fault damage zone. Hydrothermal activity is younger than the 6–10 Ma age of the fault, which means that deep (∼5 km) fluid flow was initiated only after a large part of the 230 m of fault offset had taken place.

scholarly journals Tracking geothermal anomalies along a crustal fault using (U − Th)∕He apatite thermochronology and rare-earth element (REE) analyses: the example of the Têt fault (Pyrenees, France)

Solid Earth ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 1747-1771 ◽  
Author(s):  
Gaétan Milesi ◽  
Patrick Monié ◽  
Philippe Münch ◽  
Roger Soliva ◽  
Audrey Taillefer ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Hot Springs ◽  
Hot Spring ◽  
Thermal Evolution ◽  
Hanging Wall ◽  
Damage Zone ◽  
Hydrothermal Activity ◽  
Eastern Pyrenees

Abstract. The Têt fault is a major crustal-scale fault in the eastern Pyrenees (France) along which 29 hot springs emerge, mainly within the footwall damage zone of the fault. In this study, (U-Th)/He apatite (AHe) thermochronology is used in combination with rare-earth element (REE) analyses in order to investigate the imprint of hydrothermal activity around two main hot spring clusters (Thuès-les-Bains and St Thomas) and between them. The main goal is to better define the geometry and intensity of the recent thermal anomalies along the fault and to compare them with previous results from numerical modelling. This study displays 99 new AHe ages and 63 REE analyses on single apatite grains from samples collected in the hanging wall (18 to 43 Ma) and footwall (8 to 26 Ma) of the Têt fault. In the footwall, the results reveal AHe age resetting and apatite REE depletion due to hydrothermal circulation along the Têt fault damage zone, near the two hot spring clusters, and also in areas lacking present-day geothermal surface manifestation. These age resettings and element depletions are more pronounced around the Thuès-les-Bains hot spring cluster and are spatially restricted to a limited volume of the damage zone. Outside this damage zone, new modelling of thermochronological data specifies the thermal evolution of the massifs. The footwall model suggests the succession of two main phases of cooling: between 30 and 24 Ma and a second one around 10 Ma. In the hanging wall, little evidence of hydrothermal imprint on AHe ages and REE signatures has been found, and thermal modelling records a single cooling phase at 35–30 Ma. Low-temperature thermochronology combined with REE analyses allows us to identify the spatial extent of a recent geothermal perturbation related to hydrothermal flow along a master fault zone in the eastern Pyrenees, opens new perspectives to constrain the geometry and intensity of geothermal fields, and provides new regional constraints on the cooling history of the footwall and hanging-wall massifs.

scholarly journals QUANTITATIVE ANALYSIS OF DEFORMATION ALONG THE FAULT DAMAGE ZONE OF THE KLIMATIA THRUST (NW GREECE, IONIAN ZONE)

2001 ◽  
Vol 34 (4) ◽  
pp. 1643
Author(s):  
A. Kostakioti ◽  
P. Xypolias ◽  
S. Kokkalas ◽  
T. Doutsos
Keyword(s):  
Hanging Wall ◽  
Damage Zone ◽  
Deformation Pattern ◽  
Fracture System ◽  
Fracture Density ◽  
Fracture Orientation ◽  
Transport Direction ◽  
Structural Fracture ◽  
Fault Damage Zone ◽  
Northwestern Greece

In this study, we present structural, fracture orientation and fracture density (FD) data in order toquantify the deformation pattern of a damage zone that form around the slip plane of a large scalethrust fault which is located on the Ionian zone (External Hellenides) in northwestern Greece. Structuralanalysis showed at least two major deformation stages as indicated by the presence of refolding,backthrusting and break-back faulting. The fracture orientation analysis revealed three mainfracture systems, a dominant conjugate fracture system which is perpendicular to the transport direction(NW-to NNW trending sets), a conjugate fracture system trending parallel to the transport direction(ENE-trending conjugate sets) and a third diagonal conjugate fracture system (WNW andNNE trending sets). Resulting fracture density-distance diagrams display a decrease of total fracturedensity away from the studied fault, which is largely heterogeneous and irregular on both footwalland hanging wall. The conjugate fracture system trending perpendicular to the transport directionhas the dominant contribution to the accumulation of total fracture density. Based on theseresults we suggest that the observed heterogeneous and irregular distribution of fracture densityfashioned during the second deformation stage and is attributed to the formation of backthrusts andbreak-back thrust faults.

scholarly journals Geochemical Characterization of Nyamyumba Hot Spring, Northwest Rwanda

2021 ◽  
Author(s):  
Francois Hategekimana ◽  
Theophile Mugerwa ◽  
Cedrick Nsengiyumva ◽  
Digne Rwabuhungu ◽  
Juliet Confiance Kabatesi
Keyword(s):  
Hot Springs ◽  
Hot Spring ◽  
Geothermal Gradient ◽  
Hot Water ◽  
World Health ◽  
Rift System ◽  
Volcanic Complex ◽  
East African Rift System ◽  
Recreational Waters ◽  
Lake Kivu

Abstract Hot spring is a hot water that is naturally occurring on the surface from the underground and typically heated by subterranean volcanic activity and local underground geothermal gradient. There are four main hot springs in Rwanda such as: Kalisimbi, Bugarama, Kinigi and Nyamyumba former name Gisenyi hot springs. This research focused on the geochemical analysis of Nyamyumba hot springs located near the fresh water of Lake Kivu. Nyamyumba hot springs are located in the western branch of the East African Rift System and they are located near Virunga volcanic complex, explaining the rising and heating of water. The concentrations of Sulfate, Iron, Ammonia, Alkalinity, Silica, Phosphate, Salinity, Alkalinity, and Conductivity using standard procedures were measured. The results showed that hot spring water has higher concentrations of chemicals compared to Lake Kivu water and the geochemistry of these hot springs maybe associated with rock dissolution by hot water. The measured parameters were compared with World Health Organization (WHO) standards for recreational waters and it has been identified that Nyamyumba hot spring are safe to use in therapeutic activities (Swimming).

scholarly journals Study of geothermometers and chemical composition of hot springs in Zavkhan province

2019 ◽  
pp. 61-67
Author(s):  
Bolormaa Ch ◽  
Oyuntsetseg D ◽  
Bolormaa O
Keyword(s):  
Hot Springs ◽  
Hot Spring ◽  
Geothermal Gradient ◽  
Spring Water ◽  
Geothermal Water ◽  
Reservoir Temperature ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Temperature Ranges ◽  
Total Dissolved Solid

In this study, we collected hot spring water sample from Otgontenger, Tsetsuukh, Zart, Ulaan Khaalga and Khojuul in Zavkhan province. The purpose of this study is to determine the temperature of geothermal water and its depth which based on the hydrochemical component. Hot spring water analyses showed that temperature ranges between 33.4 to 45.5°C, pH ranges 8.40 to 9.56, and the total dissolved solid amount was 170 to 473 mg/L. From the result of hydrochemical analyses, hot spring samples were included in SO4-Na and HCO3-Na type. In comparison to other hot spring samples, Tsetsuukh hot spring has shown negative oxidation reduction potential, -0.8 mV and dissolved hydrogen, 0.22 mg/L. Therefore, it has a higher ability for medical treatment than other hot spring water due to its reduction state. The reservoir temperature of these hot springs is calculated by several geothermometer methods, and temperatures ranged between 102оC to 149оC. According to this result, it assumed that geothermal water with low temperature which has the ability to use for room heating and producing energy by the binary system. Thus, we determined that reservoir depth is 1.3 to 3.7 km using annual average surface and reservoir temperature, and regional geothermal gradient. Завхан аймгийн халуун рашаануудын химийн найрлага, геотермометрийн судалгаа Хураангуй: Бид энэхүү судалгааны ажлаар Завхан аймгийн нутагт орших Отгонтэнгэр, Зарт, Цэцүүх, Улаан хаалга, Хожуулын халуун рашаануудын гидрохимийн найрлагыг нарийвчлан тогтоосоны үндсэн дээр тухайн рашаануудын газрын гүний халуун усны температур болон гүнийг тогтоох зорилго тавин ажиллаа. Завхан аймгийн рашаанууд нь халуун 33.4-45.5°C температуртай, шүлтлэг орчинтой (pH 8.4-9.56), 170-473 мг/л хүртэл эрдэсжилттэй, HCO3-Na болон SO4-Na-ийн төрлийн халуун рашааны ангилалд хамаарагдаж байна. Эдгээр рашаануудаас Цэцүүхийн халуун рашааны исэлдэн ангижрах потенциал нь -0.8 мВ, ууссан устөрөгчийн агуулга 0.22 мг/л илэрсэн нь судалгаанд хамрагдсан бусад рашаануудтай харьцуулахад ангижрах төлөвт оршиж байгаа бөгөөд илүү эмчилгээний идэвхтэй болохыг харуулж байна. Судалгаанд хамрагдсан халуун рашаануудын гүний температурыг химийн найрлагаас нь хамааруулан хэд хэдэн геотермометрийг ашиглан тооцоход дунджаар 102-149oС байсан ба энэ нь бага температуртай усны ангилалд хамаарагдаж байгаа учир тухайн халуун усны нөөцийг өрөө тасалгаа халаах болон бинари системийг ашиглан цахилгаан гаргаж авах боломжтой байна. Мөн Завхан аймгийн халуун рашаануудын газрын гүний халуун усны нөөц нь газрын гадаргаас доош 1.3-3.7 км-ийн гүнд байрладаг болохыг орд дээрх температур, газрын гүний халуун усны температур болон бүс нутгийн геотермал градиентад үндэслэн тооцоолон тодорхойллоо. Түлхүүр үг: Гидрохими, халуун рашаан, геотермометр, гүний температур.

scholarly journals Signature of transition to supershear rupture speed in the coseismic off-fault damage zone

2021 ◽  
Vol 477 (2255) ◽  
Author(s):  
Jorge Jara ◽  
Lucile Bruhat ◽  
Marion Y. Thomas ◽  
Solène L. Antoine ◽  
Kurama Okubo ◽  
...  
Keyword(s):  
High Resolution ◽  
Fracture Mechanics ◽  
Shear Wave Velocity ◽  
Observational Studies ◽  
Numerical Models ◽  
Damage Zone ◽  
Precise Location ◽  
Earthquake Ruptures ◽  
Fault Damage Zone ◽  
Rupture Speed

Most earthquake ruptures propagate at speeds below the shear wave velocity within the crust, but in some rare cases, ruptures reach supershear speeds. The physics underlying the transition of natural subshear earthquakes to supershear ones is currently not fully understood. Most observational studies of supershear earthquakes have focused on determining which fault segments sustain fully grown supershear ruptures. Experimentally cross-validated numerical models have identified some of the key ingredients required to trigger a transition to supershear speed. However, the conditions for such a transition in nature are still unclear, including the precise location of this transition. In this work, we provide theoretical and numerical insights to identify the precise location of such a transition in nature. We use fracture mechanics arguments with multiple numerical models to identify the signature of supershear transition in coseismic off-fault damage. We then cross-validate this signature with high-resolution observations of fault zone width and early aftershock distributions. We confirm that the location of the transition from subshear to supershear speed is characterized by a decrease in the width of the coseismic off-fault damage zone. We thus help refine the precise location of such a transition for natural supershear earthquakes.

scholarly journals Petrophysical, geochemical, and hydrological evidence for extensive fracture-mediated fluid and heat transport in the Alpine Fault's hanging-wall damage zone

2021 ◽  
Author(s):  
John Townend ◽  
Rupert Sutherland ◽  
VG Toy ◽  
ML Doan ◽  
B Célérier ◽  
...  
Keyword(s):  
Numerical Models ◽  
Hanging Wall ◽  
Damage Zone ◽  
Active Faults ◽  
Outer Zone ◽  
Earthquake Rupture ◽  
Fault Rock ◽  
Spatial And Temporal Scales ◽  
Alpine Fault ◽  
Earthquake Rupture Processes

© 2017. American Geophysical Union. All Rights Reserved. Fault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hanging-wall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDP-2). We present observational evidence for extensive fracturing and high hanging-wall hydraulic conductivity (∼10−9 to 10−7 m/s, corresponding to permeability of ∼10−16 to 10−14 m2) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDP-2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hanging-wall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and off-fault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation.

scholarly journals Fault-Related Controls on Upward Hydrothermal Flow: An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France)

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Audrey Taillefer ◽  
Roger Soliva ◽  
Laurent Guillou-Frottier ◽  
Elisabeth Le Goff ◽  
Guillaume Martin ◽  
...  
Keyword(s):  
Hot Springs ◽  
Geothermal Gradient ◽  
High Elevation ◽  
Fault Zones ◽  
Hydrothermal Systems ◽  
Crystalline Rocks ◽  
Fault System ◽  
Hydrogeological Model ◽  
Eastern Pyrenees ◽  
Hydrothermal Flow

The way faults control upward fluid flow in nonmagmatic hydrothermal systems in extensional context is still unclear. In the Eastern Pyrénées, an alignment of twenty-nine hot springs (29°C to 73°C), along the normal Têt fault, offers the opportunity to study this process. Using an integrated multiscale geological approach including mapping, remote sensing, and macro- and microscopic analyses of fault zones, we show that emergence is always located in crystalline rocks at gneiss-metasediments contacts, mostly in the Têt fault footwall. The hot springs distribution is related to high topographic reliefs, which are associated with fault throw and segmentation. In more detail, emergence localizes either (1) in brittle fault damage zones at the intersection between the Têt fault and subsidiary faults or (2) in ductile faults where dissolution cavities are observed along foliations, allowing juxtaposition of metasediments. Using these observations and 2D simple numerical simulation, we propose a hydrogeological model of upward hydrothermal flow. Meteoric fluids, infiltrated at high elevation in the fault footwall relief, get warmer at depth because of the geothermal gradient. Topography-related hydraulic gradient and buoyancy forces cause hot fluid rise along permeability anisotropies associated with lithological juxtapositions, fracture, and fault zone compositions.

scholarly journals Petrophysical, geochemical, and hydrological evidence for extensive fracture-mediated fluid and heat transport in the Alpine Fault's hanging-wall damage zone

2021 ◽  
Author(s):  
John Townend ◽  
Rupert Sutherland ◽  
VG Toy ◽  
ML Doan ◽  
B Célérier ◽  
...  
Keyword(s):  
Numerical Models ◽  
Hanging Wall ◽  
Damage Zone ◽  
Active Faults ◽  
Outer Zone ◽  
Earthquake Rupture ◽  
Fault Rock ◽  
Spatial And Temporal Scales ◽  
Alpine Fault ◽  
Earthquake Rupture Processes

© 2017. American Geophysical Union. All Rights Reserved. Fault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hanging-wall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDP-2). We present observational evidence for extensive fracturing and high hanging-wall hydraulic conductivity (∼10−9 to 10−7 m/s, corresponding to permeability of ∼10−16 to 10−14 m2) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDP-2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hanging-wall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and off-fault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation.

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