3D Modelling of a Hydrothermal System in a Densely Populated Urban Area – the Alfama Springs Case-Study (Lisbon, Portugal)

Abstract In the XIX th century, the Alfama thermal and non-thermal springs were qualified as “mineral water” by the governmental authorities. But after a few years of legal usage in balneotherapy, all of them knew a constant and progressive definitive decay, and the last balneotherapic facility was abandoned and sealed more than 40 years ago. Despite their significant influence in Lisbon life along the History, their exact location is now only approximate. Nowadays, they are all buried below the city buildings, squares and streets. Since some of the Alfama springs reached temperatures up to 34 °C, groundwater from these springs can be used in a new modern spa or in district heating facilities in the heart of the city of Lisbon, if adequately recovered. But priorly, to carry out this task, a global understanding of the conceptual hydrogeological model is needed. However, the springs are located in a densely urbanized and touristic area, where geological outcrops are no longer visible and old springs’ location is unknown; therefore, a review of geological and hydrogeological data and geotechnical reports was carried out to plan further research works. Adding to this exhaustive bibliographic review and data integration, new seismic reflection data were acquired, and brought some new insights on the groundwater circulation system. All these data interpretations contributed significantly to achieve a better knowledge on the main and secondary faults that control the occurrence of Alfama springs and framed them into the complex regional tectonic framework. The entire set of historical hydrogeological data, geotechnical information, and newly acquired data lead to a reasonably accurate and data supported 3D geological and hydrogeological conceptual model of the deep groundwater flow circuit. This paper describes the research work that led to the conception of the local and complex 3D hydrogeological model of the Alfama springs system. With this 3D model, the best location for a dipped well can now be envisaged, keeping in mind the narrow local urban constraints, possible future users, and stakeholders.

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Mantle-derived helium released through the Japan trench bend-faults

Scientific Reports ◽

10.1038/s41598-021-91523-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jin-Oh Park ◽

Naoto Takahata ◽

Ehsan Jamali Hondori ◽

Asuka Yamaguchi ◽

Takanori Kagoshima ◽

...

Keyword(s):

Upper Mantle ◽

Large Scale ◽

Japan Trench ◽

Helium Isotope ◽

Normal Faults ◽

Circulation System ◽

Deep Penetration ◽

Oceanic Plate ◽

Seismic Reflection Data ◽

Reflection Data

AbstractPlate bending-related normal faults (i.e. bend-faults) develop at the outer trench-slope of the oceanic plate incoming into the subduction zone. Numerous geophysical studies and numerical simulations suggest that bend-faults play a key role by providing pathways for seawater to flow into the oceanic crust and the upper mantle, thereby promoting hydration of the oceanic plate. However, deep penetration of seawater along bend-faults remains controversial because fluids that have percolated down into the mantle are difficult to detect. This report presents anomalously high helium isotope (3He/4He) ratios in sediment pore water and seismic reflection data which suggest fluid infiltration into the upper mantle and subsequent outflow through bend-faults across the outer slope of the Japan trench. The 3He/4He and 4He/20Ne ratios at sites near-trench bend-faults, which are close to the isotopic ratios of bottom seawater, are almost constant with depth, supporting local seawater inflow. Our findings provide the first reported evidence for a potentially large-scale active hydrothermal circulation system through bend-faults across the Moho (crust-mantle boundary) in and out of the oceanic lithospheric mantle.

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Impact of Tectonic, Glacial and Contour Current Processes on the Late Cenozoic Sedimentary Development of the Southeast Greenland Margin

Geosciences ◽

10.3390/geosciences9040157 ◽

2019 ◽

Vol 9 (4) ◽

pp. 157 ◽

Cited By ~ 1

Author(s):

Katrien Heirman ◽

Tove Nielsen ◽

Antoon Kuijpers

Keyword(s):

Ocean Circulation ◽

Seismic Reflection Data ◽

Accommodation Space ◽

Reflection Data ◽

Irminger Sea ◽

Denmark Strait ◽

Regional Tectonic ◽

Glacial Periods ◽

Greenland Margin ◽

Entire Margin

To understand the geomorphological contrast between the northern and southern parts of the Southeast Greenland margin with its marked differences in sedimentary regime, bathymetric and seismic reflection, data have been compiled and analysed. While previous studies focused on selected parts of this margin, the present study provides an intergraded overview of the entire margin from Cap Farewell to Denmark Strait. The prominent north–south contrast shows a wide northern shelf and a narrow southern shelf. The origin of this width disparity can be traced back to the initial formation stage of the Irminger Sea due to regional differences in uplift versus oceanic subsidence. This regional tectonic discrepancy also created a difference in sediment accommodation space that, in combination with a weak ocean circulation regime, favoured formation of Oligocene–Miocene turbidite fan complexes along the lower southern slope. These fan complexes became the core of sediment drift ridges that strike perpendicular to the slope. Strong bottom currents, which gradually increase in strength towards the south, were mainly prevalent during warmer climate stages. During glacial periods, downslope transport of glacigenic sediments and hyperpycnal meltwater flow further shaped the large drift ridges and formed several relatively narrow, V-shaped turbidite channels extending towards the deep Irminger Sea basin. These V-shaped channels are still active today when cascading dense winter water from the shelf flows downwards along the shelf to the Irminger Sea basin.

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The Sask Craton and Hearne Province margin: seismic reflection studies in the western Trans-Hudson Orogen

Canadian Journal of Earth Sciences ◽

10.1139/e05-026 ◽

2005 ◽

Vol 42 (4) ◽

pp. 403-419 ◽

Cited By ~ 38

Author(s):

Z Hajnal ◽

J Lewry ◽

D White ◽

K Ashton ◽

R Clowes ◽

...

Keyword(s):

Seismic Reflection ◽

Three Dimensional ◽

Three Dimensional Model ◽

Seismic Reflection Data ◽

Reflection Data ◽

Regional Tectonic ◽

Detachment Zone ◽

Tectonic Development ◽

Seismic Images ◽

Basal Detachment

A three-dimensional model of the regional crustal architecture of the western Trans-Hudson Orogen, based on the interpretation of 590 km of deep-sounding seismic reflection data and a comparable length of existing seismic reflection information, is presented. The seismic images identify the regional geometry of the basal detachment zone (Pelican thrust) that separates juvenile allochthonous terranes from the underlying Archean microcontinent (Sask craton). The Sask Craton is inferred to have a minimum spatial extent of over 100 000 km2 with an associated crustal root that extends for 200 km along strike. During terminal collision, complete convergence of the RaeHearne and Superior continental blocks was precluded by the presence of the Sask Craton, resulting in the preservation of anomalous amounts of oceanic and associated sedimentary juvenile material. Along regional tectonic strike, consistency of crustal structure across the RaeHearne margin Reindeer zone boundary is established. Several phases of tectonic development, including multistage subduction and continentcontinent collision, are inferred for the western margin of the orogen. A bright, shallow (23.5 s two-way traveltime) band of reflectivity (Wollaston Lake reflector) imaged over ~150 000 km2 area is inferred to be a large post-orogenic mafic intrusion. A highly reflective, well-defined and structurally disturbed Moho discontinuity is mapped throughout the western Trans-Hudson Orogen. The present-day crustal architecture of the western Trans-Hudson Orogen is described in terms of the tectonic evolution within the region.

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Oblique reactivation of lithosphere-scale lineaments controls rift physiography – The upper crustal expression of the Sorgenfrei-Tornquist Zone, offshore southern Norway

10.5194/se-2017-97 ◽

2017 ◽

Cited By ~ 1

Author(s):

Thomas B. Phillips ◽

Christopher A.-L. Jackson ◽

Rebecca E. Bell ◽

Oliver B. Duffy

Keyword(s):

Strike Slip ◽

Structural Development ◽

Stress Regime ◽

Seismic Reflection Data ◽

Existing Structures ◽

Reflection Data ◽

Tectonic Events ◽

Kinematic Evolution ◽

Regional Tectonic ◽

Southern Norway

Abstract. Pre-existing structures within sub-crustal lithosphere may localise stresses during subsequent tectonic events, resulting in complex fault systems at upper crustal levels. As these sub-crustal structures are difficult to resolve at great depths, the evolution of kinematically and perhaps geometrically linked upper-crustal fault populations can offer insights into their deformation history, including when and how they reactivate and accommodate stresses during later tectonic events. In this study, we use borehole-constrained 2D and 3D seismic reflection data to investigate the structural development of the Farsund Basin, offshore southern Norway; this E-trending basin represents the upper crustal expression of the Sorgenfrei-Tornquist Zone, a major lithosphere-scale lineament extending >1000 km across Central Europe. The southern margin of the Farsund Basin is characterised by N-S and E-W-striking fault populations, the latter extending down through the Moho and potentially linking with the Sorgenfrei-Tornquist Zone as imaged within sub-crustal lithosphere. Due to this geometric linkage, we can analyse the upper crustal fault populations to infer the kinematics of the Sorgenfrei-Tornquist Zone. We use throw-length (T-x) analysis and fault displacement backstripping techniques to determine the geometric and kinematic evolution of upper-crustal fault populations during the multiphase evolution of the Farsund Basin. We document a period of sinistral strike-slip activity along E-W-striking faults during the Early Jurassic, representing a hitherto undocumented phase of activity along the Sorgenfrei-Tornquist Zone. These E-W-striking upper-crustal faults are later obliquely reactivated under a dextral stress regime during the Early Cretaceous, with new faults also propagating away from pre-existing ones, representing a switch to a phase of dextral transtension along the Sorgenfrei-Tornquist Zone. We show that the Sorgenfrei-Tornquist Zone represents a long-lived lithosphere-scale lineament that is periodically reactivated throughout its protracted geological history. The upper crustal component of the lineament is reactivated in a range of tectonic styles, including both sinistral and dextral strike-slip motions, with the geometry and kinematics of these faults often inconsistent with what may otherwise be inferred from regional tectonics alone. Understanding these different styles of reactivation not only allows us to better understand the influence of sub-crustal lithospheric structure on rifting, but also offers insights into the prevailing stress field during regional tectonic events.

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