The Qinling–Dabie–Sulu orogen is the most prominent Phanerozoic orogenic belt in China. The discovery of ultra-high pressure (UHP) minerals in zircon inclusions suggests that the crust was subducted ...to deeper than 120km into the mantle and then exhumed to shallow crustal. Recently, low temperature thermochronology has been applied to constrain the final exhumation of Dabie Shan, while there are few studies describing the Cenozoic exhumation history of the Sulu belt. Here we report some (U–Th)/He ages for various lithologies from Sulu Orogenic belt and its northern part-Jiaobei terrane. The single grain He ages range between 18 and 154Ma, and most of the samples having large intra-sample age scattering. Several reasons such as invisible U/Th-rich inclusions, grain size effect, slow cooling rate, and zonation of parent nuclide or radiation damage effect may account for this dispersion. For all samples, the pattern of the single grain age data exhibits a peak at ~45Ma which is consistent with the borehole fission-track age pattern in adjacent Hefei Basin. Both (U–Th)/He and fission track ages of the Sulu area suggest an enhanced exhumation/cooling in Early-Middle Eocene in the southern part of Tan-Lu fault zone. This enhanced cooling event coincides with rapid subsidence of North China Basin and rapid uplift of its surrounding reliefs, which indicates basin-mountain coupling. This Eocene event is widespread in central China and could be far-field consequence of India–Asia collision. The convergence rate between Pacific Plate and Eurasia decreased substantially during early Tertiary and reached a minimum in Eocene (~30–40mm/yr) while at the same time the collision between India and Asia was completed. Therefore, the Cenozoic exhumation history of the Sulu Orogenic Belt was a combined result of far-field effect of India–Asia collision and declined subduction rate of the Pacific Plate under Eurasia.
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•We provided first batch of regional-scale He ages in Shandong Peninsula.•Most of the samples have large intra-sample age dispersion for different grains.•An Eocene enhanced cooling event was recognized in this region.•India–Asia collision might have a far-field effect on the Early Eocene cooling occurred in the study area.
A new data set combining thermobarometry, geo‐thermochronology, chronostratigraphic, and structural analyses highlights the tectono‐thermal evolution of the St. Martin granodiorite from its ...emplacement to its surface exposure. The described vertical motions in this part of the upper plate of the Lesser Antilles subduction zone since 30 Myrs are linked to the migration of the Lesser Antilles volcanic arc toward the plate interior. Results suggest that the St. Martin granodioritic pluton emplaced at 4–5 km depth and underwent a four‐step history: (a) 30–27 Ma, emplacement along N20–40° transtensive structures oblique to the trench followed by, (b) 27–24 Ma, rapid post‐emplacement cooling and exhumation (∼0.6 mm/yr) controlled by perpendicular to the trench N45° trending structures, (c) 24–9 Ma, slow subsidence (0.01 mm/yr) and development of carbonate platforms associated to tectonic quiescence, westward migration of the arc, and subsequent cooling of the crust, (d) 9 Ma to present‐day, exhumation (∼0.25 mm/yr) and uplift of Neogene carbonate platforms mainly along N45° faults that likely accommodate the progressive trench curvature since 30 Ma. Pecube forward modeling using this scenario reproduces both the observed present‐day geometry and thermochronometric ages. A similar sequence of events is observed in the Virgin Islands. Along with our new data, this suggests a southward migration of the deformation associated with the opening of the Anegada Trough.
Key Points
The tectono‐thermal history of the St. Martin Oligocene granodiorite is reconstructed
Exhumation occurred during two periods: between 27 and 24 Ma and since 9 Ma, along N45° trending normal faults
Regionally, exhumation rates suggest a southward migration of the deformation associated with the opening of the Anegada Trough
Crustal deformation is characterized by brittle and ductile faults that accommodate at different scales the strain imposed by plate tectonics. The aim of this contribution is to show with the help of ...different examples how the in situ \(\mbox {}^{40}\)Ar/\(\mbox {}^{39}\)Ar dating of synkinematic neocrystallized minerals in ductile shear zones and the step-heating \(\mbox {}^{40}\)Ar/\(\mbox {}^{39}\)Ar dating of synkinematic authigenic clays in fault gouges can bring information on the timing of fault activity. However, due to their complex evolution, interpretation of the argon signature in fault zones requires consideration of several effects among which re- or neocrystallization, inheritance and fluid interaction processes are dominant.
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.
Crustal deformation is characterized by brittle and ductile faults that accommodate at different scales the strain imposed by plate tectonics. The aim of this contribution is to show with the help of ...different examples how the in situ 40 Ar/ 39 Ar dating of synkinematic neocrystallized minerals in ductile shear zones and the step-heating 40 Ar/ 39 Ar dating of synkinematic authigenic clays in fault gouges can bring information on the timing of fault activity. However, due to their complex evolution, interpretation of the argon signature in fault zones requires consideration of several effects among which re-or neocrystallization, inheritance and fluid interaction processes are dominant.
Crustal deformation is characterized by brittle and ductile faults that accommodate at different scales the strain imposed by plate tectonics. The aim of this contribution is to show with the help of ...different examples how the in situ $\mbox {}^{40}$Ar/$\mbox {}^{39}$Ar dating of synkinematic neocrystallized minerals in ductile shear zones and the step-heating $\mbox {}^{40}$Ar/$\mbox {}^{39}$Ar dating of synkinematic authigenic clays in fault gouges can bring information on the timing of fault activity. However, due to their complex evolution, interpretation of the argon signature in fault zones requires consideration of several effects among which re- or neocrystallization, inheritance and fluid interaction processes are dominant.
(U‐Th)/He ages on apatite obtained in the vicinity of the Têt fault hydrothermal system show a large variability. In the inner damage zone adjacent to the fault core, where fluid flows are ...concentrated, AHe ages display a large scatter (3–41 Ma) and apatite ageing. Samples from the outer damage zone show young ages with less dispersion (0.9–21.1 Ma) and apatite rejuvenation. Outside the damage zone, ages are consistent with the regional exhumation history between 20 and 12 Ma. The important age dispersion found in the damage zone is interpreted as the result of 4He mobility during fluid infiltration. Our results show that thermochronological data close to a fault should be interpreted with caution, but may offer a new tool for geothermal exploration.
The timing of transition between the contractional and extensional regimes along the Pyrenean range remains debated. Compared to its central and western parts, the eastern part of the chain was ...significantly affected by extensional tectonics mostly related to the opening of the Gulf of Lion. The Têt normal fault is the best example of this tectonic activity, with topographic reliefs above 2,000 m in its footwall. In this study, we synthetized previous thermochronological data and performed new (U‐Th)/He and fission track dating in the Eastern Pyrenean massifs. Output apparent exhumation rate and thermal modeling in the hanging wall of the Têt fault highlight a rapid exhumation (0.48 km/Ma) and cooling (∼30°C/Ma) phase between 38 and 35 Ma, followed by slower exhumation/cooling afterward. In the footwall, cooling subsequently propagated westward along the fault during Priabonian (35–32 Ma), upper Oligocene and lower Miocene (26–19 Ma), and Serravallian‐Tortonian times (12–9 Ma). These data and modeling outcomes suggest that the exhumation of the Têt fault hanging wall related to southward thrusting ended at 35 Ma, and was followed by different extensional stages, with a propagation of the deformation toward the West during the upper Miocene. We propose that the onset of extension in the Eastern Pyrenees occurred during the late Priabonian period, contemporaneously with the large‐scale rifting episode recorded in Western Europe. After this event, the Têt fault activity and the westward propagation of the deformation appear mainly controlled by the opening of the Gulf of Lion.
Plain Language Summary
The Pyrenees result from the North‐South convergence of the Eurasian and Iberian plates. The eastern part of the range experienced strong extensional tectonics mostly related to the opening of the Gulf of Lion, which timing and influence on the modern topographic relief remain unclear. To better characterize the transition timing between contractional and extensional regimes and the tectonic evolution in the Eastern Pyrenees, we used low‐temperature thermochronology and thermal modeling to reconstruct the exhumation/cooling histories of the different massifs along the Têt fault. Our data and modeling outcomes show a switch between contractional and extensional tectonics during the Priabonian (ca. 35 Ma), followed by different extensional stages recorded in the Têt fault footwall, coeval with a global westward propagation of the deformation along the fault until ca. 9 Ma.
Key Points
Tectonic evolution along a major normal fault recorded by low‐temperature thermochronology
Priabonian (35–32 Ma) switch between contractional and extensional regime in the Eastern Pyrenees
Cenozoic westward propagation of the deformation along the Têt fault
Located on the margin of the west Alboran basin, the Gibraltar Arc (Betic-Rif mountain belt) displays post-Pliocene vertical movements evidenced by uplifted marine sedimentary basins and marine ...terraces. Quantification of vertical movements is an important clue to understand the origin of present-day relief generation in the Betic-Rif mountain chain together with the causes of the Messinian Salinity Crisis. In this paper, we present the results of a pluridisciplinary study combining an analysis of low temperature thermochronology and Pliocene basins evolution to constrain the exhumation history and surface uplift of internals units of the Rif belt (Northern Morocco). The mean (U-Th)/He apatite ages obtained from 11 samples are comprised between 14.1 and 17.8Ma and display a wide dispersion, which could be explained by a great variability of apatite chemistries in the analyzed samples. No correlations between altitude and age have been found along altitudinal profile suggesting a rapid exhumation during this period. Thermal modeling using our (U-Th)/He apatite ages and geochronological data previously obtained in the same area (40Ar/39Ar and K/Ar data on biotite, zircon and apatite fission track) allow us to propose a cooling history. The rocks suffered a rapid cooling at 60–100°C/Ma between 22.5 and 19Ma, then cooled to temperatures around 40°C between 19 and 18Ma. They were re-heated at around 110°C between 18 and 15Ma then rapidly cooled and exhumed to reach the surface temperature at around 13Ma. The re-heating could be related to a renewal in thrusting and burying of the inner zones. Between 15 and 13Ma the cooling resumed at a rate of 50°C/Ma indicating an exhumation rate of 0.8mm/y considering an average 40°C/km geothermal gradient. This exhumation may be linked to the extension in the Alboran Sea. Otherwise biostratigraphic and sedimentological analysis of Pliocene basins of the internal Rif provided informations on the more recent events and vertical movements. Pliocene deposits of the Rifian coast represent the passive infilling of palaeo-rias between 5.33 and 3.8Ma. The whole coastal area was uplifted at slow average rates (0.01–0.03mm/y) in relation with a northeastward tilting of 0.2–0.3° since the Lower-Pliocene. A late Pliocene to present extensional tectonics associated to uplift has been identified all along the coastal ranges of the Internal Zone of the Rif chain. This extension was coeval with the major late Pliocene to Pleistocene extensional episode of the Alboran Sea and appears to be still active nowadays. No significant late Messinian uplift was evidenced, thus calling into question the geodynamic models relating the closure of the marine gateways and the MSC to slab roll back.
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