Fluid-rock interaction control on fault reactivation: A review of the Montmell-Vallès Fault System, central Catalan Coastal Ranges (NE Iberia)

Structural inheritance is a key factor controlling the tectonic evolution of the central Catalan Coastal Ranges. Up to two periods of tectonic inversion (one positive during the Paleogene and the other negative during the Neogene) affected a previously well-developed Mesozoic extensional basin system and characterized the Cenozoic evolution of the area. In this scenario, tectonic fault inversion is often observed along the Montmell-Vallès Fault System. Fault reactivation shows differences along strike from NE to SW and appears decoupled from surface to depth due to its kinked-planar geometry and the change of fault dip from >60° to 30° in depth. The ability of the Mesozoic faults to be reactivated appears also influenced by changes in the mechanical properties of the inherited fault zone. Whereas the deeper and less dipping panels of the major faults are reactivated in the entire zone (contractional during the Paleogene and extensional during the late Oligocene-Neogene), the upper and highly dipping parts of the faults only show local reactivations. The observations indicate that fault dip, the indirect role of hosting lithologies (granites and siliciclastic metasediments versus carbonate rocks) on fault rocks, the indirect role of mineral precipitation and cementation product of fluid circulation, and the direct role of the mechanical properties of the resulting fault rocks (gouge versus cemented breccias) significantly control the fault reactivation. Upper crust low angle fault segments are easily reactivated during contractional deformation but not during the extensional one. Conversely, the segments with a high-angle dip are more easily reactivated during the extensional deformation but not during the contractional one. In the study area, this resulted in the formation of footwall short-cuts developed during the Paleogene compression and extensional short-cuts occurred during the Neogene extension. On the other hand, reactivation is effective in areas where granites and siliciclastic metasediments characterize the host-rock, and non-cohesive fault gouge forms the pre-existent fault core. Instead, fault reactivation appears restricted or even prevented where the host-rock includes thick carbonate successions, and the pre-existent damage zone is formed by highly cemented and cohesive breccias

Detrital zircon U[sbnd]Pb dating and geochemistry of the Paleogene-Neogene sediments in the Qaidam Basin (China): Implications for provenance and tectonics

Provenance analyses provide valuable insights into both the complex interaction between orogenic belts and surrounding sedimentary basins and the role of plate collision in the basin-mountain coupling process. This paper investigates the provenance of the Cenozoic sediments filling the Qaidam Basin (Qinghai Tibetan Plateau, China) by combining petrology, major elements, trace elements, rare earth elements (REEs), and Zircon U[sbnd]Pb dating analysis to provide new insight about the collision of the Indian and Asian plates. The petrographic analysis indicates that the studied sediments are poorly sorted and made of angular to subrounded clasts, suggesting deposition relatively near to the source area. The Chemical Index of Alteration (CIA) of the samples in the study area, which ranges from 68.88 to 74.08, indicates that the study area experienced moderate weathering from the early Eocene to the early Miocene. In addition, Zr/Sc versus Th/Sc shows that most samples did not experience recycling. KO/NaO, SiO, Th, Sc, Zr, La and Co contents indicate that the Cenozoic sediments filling the Qaidam Basin derived mainly from an active continental margin and a continental island arc setting. U[sbnd]Pb dating of detrital zircons denotes that the studied sediments were derived from rocks with five major sets of ages (200–350 Ma, 350–500 Ma, 500–1000 Ma, 1000–1500 Ma, and >1500 Ma), with the two first sets being more common. Based on the regional geology, therefore, these ages indicate that the main provenance source was shifted southwards from the Mesozoic crystalline basement (south Qilian Mountains) in the early-middle Eocene, to the Saishiteng Mountains in the middle-late Eocene, and to Lvliang and Qilian Mountains during the late Eocene-early Miocene. Zircon dating also indicates that the main source area was displaced eastward through time. Finally, it is concluded that the tectonic deformation progressed from west to east in the northern margin of the Qaidam Basin, reflecting a far-field response to the onset of the India-Asia collision.Founding was provided by the National Natural Science Foundation of China (grant No. 41872145) and the China scholarship council (grant No. 202104910423). This research was also carried out within the framework of the DGICYT Spanish projects DGICYT PID2021-122467NB-C22 and PGC2018-093903-B-C2

Paleoenvironmental and diagenetic evolution of the Aptian Pre-Salt succession in Namibe Basin (Onshore Angola)

The Aptian Pre-Salt sedimentary succession cropping out in Cangulo palaeovalley onshore Namibe Basin (Angola) was studied by a combination of field and analytical techniques to constrain the sedimentary and diagenetic evolution of the uppermost sag sequence of the South Atlantic passive margin. Field observations allows definition of four transgressive-regressive cycles characterised by fluvial to tidal-influenced mixed clastic-carbonate and carbonate-dominated deposits, that locally show evidence of evaporite dissolution; highlighting that evaporite deposition started earlier than deposition of the regional South Atlantic Loeme-Bambata evaporite formations. Two separate pre-salt carbonate units have been differentiated within the Cangulo Fm; i) a lower transitional to marginal marine, and ii) a younger upper non-marine freshwater travertine system, that is documented for the first time in the west African margin. Transgressive-regressive cycles control the early diagenesis of the tidal carbonates that include dolomitization due to mixing fluids during transgressions, and karstification due to evaporite dissolution by meteoric water circulation during regressive events. Clastic supply appears to have been completely shut down during carbonate deposition, suggesting major climatic change associated with carbonate deposition. During the lowstand between the two carbonate units, fluid flow through Cangulo palaeovalley was re-established resulting in extensive karstification and formation of a large-scale erosional unconformity that is interpreted to be time equivalent to an intra Chela-Cuvo Fm. event. The top of the studied succession corresponds to the transgressive deposits of the Bambata evaporites that are not preserved in the Cangulo palaeovalley due to its erosion but are regionally developed. The results of this study can be directly linked to along strike age equivalent Pre-Salt successions cropping out in the Namibe, Benguela and Kwanza basins, and directly offshore Angola and Brazil using well and seismic data. These new data shed important new light and constraints on the depositional and diagenetic evolution of the complex Pre-Salt reservoir systems of the South Atlantic, and the depositional and bathymetric setting at the time of onset of the main south Atlantic evaporite deposition.The geology of Cangulo palaeovalley was characterised through a combination of remote sensing mapping (RSM), fieldwork and laboratory analysis. Remote sensing mapping was performed using Equinor-Digitizer2, software, using very high resolution orthorectified satellite imagery, and a digital elevation model (DEM) with a resolution of 1.0 m. RSM and field mapping were supported by the interpretation of stratal relationships directly onto field photopanoramas.We thank Israel Cruz Orosa and Emilio Casciello for fruitful discussion during the development of the present study. Thanks to Equinor Angola and Rafael's camp staff for logistical support during field work, and all involved in the Equinor-Sonangol onshore field work collaboration program in the Namibe, Benguela and Kwanza basins between 2010 and 2014. Thank you to TGS for permission to use line drawing of seismic in Fig. 2. We thank associate editor Laura Tomassetti, Pierre-Alexandre Teboul and an anonymous reviewer who helped improve the quality of the manuscript. Carbon and oxygen isotopic analyses, and electron microprobe analyses were carried out at the Centre Científics i Tecnològics of the Universitat de Barcelona. XRD analyses were carried out in the laboratories of the Geoscience Barcelona (Geo3BCN–CSIC). This research is a contribution of the Group of Dynamics of the Lithosphere (GDL), Geosciences Barcelona (Geo3Bcn), Consejo Superior de Investigaciones Científicas (CSIC), Spain. The project work was sponsored by Equinor (Norway), ALORBE Project (PIE–CSIC–202030E310), FEIBOB project (PGC2018-093903-B-C22) and ORRI Spanish project (PID2021-122467NB-C22). This research is within the framework of the Grups Consolidats de Recerca “Modelització Geodinàmica de la Litosfera” (2017SGR-847) and “Geologia Sedimentària” (SGR-Cat 2021 349)

U-Pb dating and geochemical dataset of fracture-filling calcite veins from the Boixols-Sant Corneli anticline (Southern Pyrenees)

U-Pb dating and geochemical analyzes ( 818 O, 813 C, A47 , 87 Sr/ 86 Sr and elemental composition) have been applied to fracture-filling calcite veins and host carbonates from the Boixols-Sant Corneli anticline, which developed along the front of the Boixols thrust sheet in the Southern Pyrenees. This robust dataset is used to determine: (i) the absolute timing of fracturing and mineralization from fluid flow; (ii) the age and duration of fold evolution; and (iii) the variations and implications of fluid behavior across the anticline, as has been described in the article "Spatio-temporal variation of fluid flow behavior along a fold: The Boixols-Sant Corneli anticline (Southern Pyrenees) from U-Pb dating and struc-tural, petrographic, and geochemical constraints - Marine and Petroleum Geology (2022) (Munoz-Lopez et al., 2022). In this new contribution, we present the raw data that have been analyzed and discussed in the related research article and, also, the whole elemental and REE composition of cal-cite veins and host carbonates that has not been published yet. These data may be used to unravel the age and origin of veins, to understand their sequential evolution in orogenic belts and to compare our results with those obtained in sim-ilar settings worldwide.This is a contribution to the DGICYT Spanish projects PGC2018-093903-B-C22 and PID2021-122467NB-C22 (Ministerio de Ciencia, Innovación y Universidades/Agencia Estatal de Investigación /10.13039/501100011033/ Fondo Europeo de Desarrollo Regional, Unión Europea), the Grup Consolidat de Recerca “Geologia Sedimentària” (2017-SGR-824) and the Grup Consolidat de Recerca “Modelització Geodinàmica de la Litosfera” (2017SGR-847). This work was also partially funded by ALORBE project (PIE–CSIC–202030E310). This is FIERCE contribution No. 107. We thank all comments provided by an anonymous reviewer, which helped improve the quality of the manuscript. Carbon and oxygen isotopic analyzes were carried out at the Centre Científics i Tecnològics of the Universitat de Barcelona. Strontium analyses were performed at the CAI de Geocronología y Geoquímica Isotópica of the Universidad Complutense de Madrid. The elemental composition was analyzed at the geochemistry facility lab-GEOTOP of Geosciences Barcelona (GEO3BCN–CSIC). U–Pb analyzes were performed at the Frankfurt Isotope and Element Research Center (FIERCE) from the Goethe-University Frankfurt (Germany)

Paleoenvironmental and diagenetic evolution of the Aptian Pre-Salt succession in Namibe Basin (Onshore Angola)

The Aptian Pre-Salt sedimentary succession cropping out in Cangulo palaeovalley onshore Namibe Basin (Angola) was studied by a combination of field and analytical techniques to constrain the sedimentary and diagenetic evolution of the uppermost sag sequence of the South Atlantic passive margin. Field observations allows definition of four transgressive-regressive cycles characterised by fluvial to tidal-influenced mixed clastic-carbonate and carbonate-dominated deposits, that locally show evidence of evaporite dissolution; highlighting that evaporite deposition started earlier than deposition of the regional South Atlantic Loeme-Bambata evaporite formations. Two separate pre-salt carbonate units have been differentiated within the Cangulo Fm; i) a lower transitional to marginal marine, and ii) a younger upper non-marine freshwater travertine system, that is documented for the first time in the west African margin. Transgressive-regressive cycles control the early diagenesis of the tidal carbonates that include dolomitization due to mixing fluids during transgressions, and karstification due to evaporite dissolution by meteoric water circulation during regressive events. Clastic supply appears to have been completely shut down during carbonate deposition, suggesting major climatic change associated with carbonate deposition. During the lowstand between the two carbonate units, fluid flow through Cangulo palaeovalley was re-established resulting in extensive karstification and formation of a large-scale erosional unconformity that is interpreted to be time equivalent to an intra Chela-Cuvo Fm. event. The top of the studied succession corresponds to the transgressive deposits of the Bambata evaporites that are not preserved in the Cangulo palaeovalley due to its erosion but are regionally developed. The results of this study can be directly linked to along strike age equivalent Pre-Salt successions cropping out in the Namibe, Benguela and Kwanza basins, and directly offshore Angola and Brazil using well and seismic data. These new data shed important new light and constraints on the depositional and diagenetic evolution of the complex Pre-Salt reservoir systems of the South Atlantic, and the depositional and bathymetric setting at the time of onset of the main south Atlantic evaporite deposition.publishedVersio

Diagenesis of Platform Carbonates Flanking the Tazoult Salt Wall (High Atlas, Morocco).

The Central High Atlas of Morocco is a double verging major diapiric province encompassing SW-NE trending salt-related ridges and Lower to Middle Jurassic deposits over synclines (minibasins) in between them. Typically, Pliensbachian and Bajocian platform carbonates flanking diapirs exhibit partial dolomitization in the vicinity of the diapir wall. The interpretation of the diagenetic products and diagenetic evolution of these dolomitized carbonates may be complex due to different fracture patterns, brecciation, fluid pathways, heterogeneities, localized uplift associated with diapiric activity, among others. The present work focuses on the dolomitization affecting Late Aalenian-Bajocian platform carbonates flanking the Tazoult salt wall, localized in the center of the Central High Atlas. Analytical work includes standard microscopy, cathodoluminescence and ¿¿13C¿¿¿18O isotopic analyses. A paragenetic sequence is discussed to reconstruct the diagenetic evolution of the flanking platform carbonates. The results highlight the major influence of diapirism and igneous intrusions on the fluid circulation. Moreover, the present work complements a previous work related to the Liassic successions flanking the Tazoult salt wall

Diapiric growth within an Early Jurassic rift basin: The Tazoult salt wall (central High Atlas, Morocco)

The central High Atlas (Morocco) constitutes a diapiric province that hosts a complex array of elongated diapirs and minibasins that formed during the Lower Jurassic rift of the Atlas Basin. This paper aims to study the structure and growth evolution of the Tazoult diapiric wall, located in the central High Atlas, by means of structural and sedimentological fieldwork integrated with remote sensing mapping. The Tazoult salt wall is a 20km long×3km wide NE-SW trending ridge that exposes Upper Triassic red beds and basalts along its core. The succession flanking the salt wall ranges from Hettangian to Bajocian ages displaying spectacular sedimentary wedges in the SE and NW flanks. The Hettangian-early Sinemurian carbonates mainly crop out as blocks embedded in the core rocks. The ~1km thick Pliensbachian platform carbonates display large subvertical flap structures along the flanks of the Tazoult salt wall with unconformities bounding tapered composite halokinetic sequences. In contrast, the ~2.5km thick late Pliensbachian-Aalenian mixed deposits form tabular composite halokinetic sequences displaying small-scale hook halokinetic sequences. Passive diapirism resulted in the lateral extrusion of the evaporite-bearing rocks to form an allochthonous salt sheet toward the adjacent SE Amezraï minibasin. The Bajocian platform carbonates partially fossilized the Tazoult salt wall and thus constitute a key horizon to constrain the timing of diapir growth and discriminate diapirism from Alpine shortening. The Pliensbachian carbonate platform evolved as a long flap structure during the early growth of the Tazoult salt wall, well before the onset of the Alpine shortening. © 2016. American Geophysical Union. All Rights Reserved.Additional funding was provided by the Spanish Ministry of Education and Science (MEC) through the projects Intramural Especial (CSIC 201330E030) and 201530E082), Atiza (CGL2009-1355), Tecla (CGL2011-26670), and the postdoctoral research contract to E.S. (CSIC-FSE 2007-2013 JAE-Doc), as well as by the Generalitat de Catalunya (2014GSR251).Peer reviewe

Origin of the coloured karst fills in the neogene extensional system of ne iberia (Spain)

Karst fills from the onshore Penedès Basin and offshore València Trough display red, pink, orange and ochre colours. Their Mössbauer spectra indicate that Fe contained in goethite is the dominant species in reddish-pink fills, whereas Fe contained in dolomite and clays is more dominant in the orange and ochre ones. The lower δ C values and higher Sr/ Sr ratios of the karst fills with respect to their host carbonates can reflect the input of soil-derived CO and an external radiogenic source into the karst system. This geochemical composition, together with the non-carbonate fraction of the fills, consists of authigenic and transported illite, illite-smectite interlayers, as well as kaolinite, chlorite, pyrite, quartz, ilmenite, magnetite, apatite and feldspar, account for a mixed residual-detrital origin of fills. This polygenic origin agrees with that of the terra rossa sediments described worldwide. The different colours of karst fills are attributed to fluctuations in the water table, which control the Eh/pH conditions in the karst system. Thus, reddish colours reflect low water table levels and oxidising episodes, and orange and ochre ones reflect high water table levels and more reducing episodes. The greenish colours of fills could be related to fluctuations in the Fe /Fe ratio

U-Pb dating and geochemical dataset of fracture-filling calcite veins from the Bóixols-Sant Corneli anticline (Southern Pyrenees)

U-Pb dating and geochemical analyzes (δ18O, δ13C, Δ47, 87Sr/86Sr and elemental composition) have been applied to fracture-filling calcite veins and host carbonates from the Bóixols-Sant Corneli anticline, which developed along the front of the Bóixols thrust sheet in the Southern Pyrenees. This robust dataset is used to determine: (i) the absolute timing of fracturing and mineralization from fluid flow; (ii) the age and duration of fold evolution; and (iii) the variations and implications of fluid behavior across the anticline, as has been described in the article “Spatio-temporal variation of fluid flow behavior along a fold: The Bóixols-Sant Corneli anticline (Southern Pyrenees) from U–Pb dating and structural, petrographic, and geochemical constraints – Marine and Petroleum Geology (2022) (Muñoz-López et al., 2022). In this new contribution, we present the raw data that have been analyzed and discussed in the related research article and, also, the whole elemental and REE composition of calcite veins and host carbonates that has not been published yet. These data may be used to unravel the age and origin of veins, to understand their sequential evolution in orogenic belts and to compare our results with those obtained in similar settings worldwide.</p

Origin of the coloured karst fills in the neogene extensional system of ne iberia (Spain)

Karst fills from the onshore Penedès Basin and offshore València Trough display red, pink, orange and ochre colours. Their Mössbauer spectra indicate that Fe3+ contained in goethite is the dominant species in reddish-pink fills, whereas Fe2+ contained in dolomite and clays is more dominant in the orange and ochre ones. The lower δ 13C values and higher 87Sr/86Sr ratios of the karst fills with respect to their host carbonates can reflect the input of soil-derived CO2 and an external radiogenic source into the karst system. This geochemical composition, together with the non-carbonate fraction of the fills, consists of authigenic and transported illite, illite-smectite interlayers, as well as kaolinite, chlorite, pyrite, quartz, ilmenite, magnetite, apatite and feldspar, account for a mixed residual-detrital origin of fills. This polygenic origin agrees with that of the terra rossa sediments described worldwide. The different colours of karst fills are attributed to fluctuations in the water table, which control the Eh/pH conditions in the karst system. Thus, reddish colours reflect low water table levels and oxidising episodes, and orange and ochre ones reflect high water table levels and more reducing episodes. The greenish colours of fills could be related to fluctuations in the Fe3+/Fe2+ ratio