Dip-slip Kinematics Research Articles

40Ar–39Ar geochronology and palaeostress analysis using lamprophyre dikes and quartz veins in the Sizhuang gold deposit: new implications for Early Cretaceous stress regime in the Jiaodong Peninsula, North China Craton

AbstractLamprophyre dikes and quartz veins in the Sizhuang gold deposit are used to date and unravel the Early Cretaceous stress regime in the Jiaodong Peninsula, North China Craton. The lamprophyre dikes are grouped into two major sets, trending NNW–SSE and NNE–SSW, respectively, and a subsidiary one, trending WNW–ESE, whereas the quartz veins trend mainly NNE–SSW. The age of lamprophyre dikes’ intrusion was robustly calculated at c. 119 Ma by phlogopite 40Ar–39Ar dating. The fuzzy clustering technique defined four stress states, which were grouped into three stress regimes in Sizhuang. Furthermore, these stress regimes were interrelated with two regional far-field stress regimes, ST1 and ST2, defined by the available published fault-slip data near Sizhuang by applying the separation and stress inversion TR method (TRM). The palaeostress reconstruction indicates that extension and strike-slip tectonics (i.e. transtension) affect the emplacement of the lamprophyre dikes and quartz veins. More precisely, the dike emplacement occurred under unstable stress conditions related to the shift from E–W pure extension–transtension to WNW–ESE transtension, whereas the quartz veins formed under relatively stable WNW–ESE transtension with the variant and increasing fluid pressure ( ${P_{\rm{f}}})$ giving rise to the strike-slip against dip-slip kinematics along the faults. The change from the ST1 to ST2 stress regimes reflects the significant clockwise rotation in the palaeo-Pacific plate subduction direction and defines the switching time at c. 119 Ma as precisely obtained by the lamprophyre dating.

Late Miocene NE-SW strike-slip fault system of the Mexico basin, central Trans-Mexican Volcanic Belt: Origin, deformation, and reactivation

A NE-SW fault system, observed in the northeast portion of the eastern sector of the Trans-Mexican Volcanic Belt, has been active since the Pliocene-Holocene time with dip-slip kinematics. These NE-SW faults belong to the Tenochtitlan fault system that extends from the southwest coast of Mexico to the NE zone of the Mexico basin. The length of this fault system suggests a complex deformation history, which is unknown before the Pliocene. In addition, the kinematics of the NE-SW faults and the tectonic conditions are unknown before their current activity. In this study, we investigate the geometry and kinematics of the NE-SW faults in the Miocene rocks in the central part of the Mexico basin (Guadalupe Range) for to know the kinematics of these faults during the Late Miocene time. Our results suggest that the Miocene rocks record two deformation events, one event is related to crustal shortening which produced a strike-slip activity in the NE-SW faults during the Late Miocene. The second deformation event is associated with crustal extension and the activity of the NE-SW faults with dip-slip kinematics. This extensional event was active during the Pliocene-Holocene. The re-activation analysis and our observations in the Guadalupe Range suggests that the NE-SW normal faults in the Tizayuca-Chignahuapan region are the product of the re-activation of previous NE-SW strike-slip faults. The change in the kinematics of the NE-SW faults explains the complex geometry of the damage zone and the high amount of the geological fractures in the Miocene rocks of the Mexico Basin. The activity type of the NE-SW faults is probably related to the dynamic of the subduction process in the southwest of Mexico, associated with the change in the inclination (decrease) and the convergence velocity of the Cocos Plate.

Complex geometry and kinematics of subsidiary faults within a carbonate-hosted relay ramp

Minor fault geometry and kinematics within relay ramps is strongly related to the stress field perturbations that can be produced when two major fault segments overlap and interact. Here we integrate classical fieldwork and interpretation of a virtual outcrop to investigate the geometry and kinematics of subsidiary faults within a relay ramp along the Tre Monti normal fault in the Central Apennines. Although the Tre Monti fault strikes parallel to the regional extension (NE-SW) it shows predominant dip-slip kinematics, suggesting a NW-SE oriented extension acting at sub-regional scale (1–10 km). Conversely, the slickenlines collected on the front segment of the relay ramp highlight right-lateral kinematics. The subsidiary faults in the relay ramp show a complex geometry (variable attitudes) and slickenlines describe multiple kinematics (left-lateral, dip-slip, right-lateral), independently of their orientation. Our fault slip analysis indicates that a local stress field retrieved from the kinematic inversion of the slickenlines collected on the front segment, and likely promoted by the interaction between the overlapping fault segments that bound the relay zone, can explain most of the geometry and kinematics of the subsidiary faults. Further complexity is added by the temporal interaction with both the regional and sub-regional stress fields.

Transpression and the build-up of the Cordillera: the example of the Bucaramanga fault (Eastern Cordillera, Colombia)

Widespread wrench tectonics have been described along the northern Andes. The Bucaramanga fault, described as sinistral strike-slip, bounds the high Santander Massif. We combine structural and thermochronological data from the central-southern portion of the fault to investigate the vertical displacement. The structural survey data show old phases of activity preserved in the host rocks along the fault trace, with the superimposition of different generations of slickenlines, and both strike-slip and dip-slip kinematics indicators. New and previous thermochronological data show that differential exhumation of the fault walls has been ongoing for the last 50 Ma. The hanging wall, the Santander Massif, records, in the central portion, decreasing exhumation rates from the early Miocene to the mid- to late Miocene and, in the southern portion, constant rates from the Late Oligocene to the Pliocene. Combining such observations, the thermochronological offset resulting from the relative motion of the two fault walls is comparable with the observed drop in elevation across the fault, suggesting that the present topography of the Santander Massif is related to vertical movement along the Bucaramanga fault. We infer that the fault has a significant Neogene reverse component, consistent with the present day horizontal global positioning system vector data, long-term exhumation rates and the structural assemblage. Supplementary Material: The Supplementary Materials contain methodological information on the thermochronological procedures, a compilation of the previously published data used in this study and the structural geology dataset, https://doi.org/10.6084/m9.figshare.c.4620140

Complexity of the 2009 L'Aquila earthquake causative fault system (Abruzzi Apennines, Italy) and effects on the Middle Aterno Quaternary basin arrangement

An Mw 6.1, devastating earthquake, on April 6, 2009, struck the Middle Aterno Valley (Abruzzi Apennines, Italy) due to the activation of a poorly known normal fault system. Structural analysis of the fault population and investigation of the relationships with the Quaternary continental deposits through integrated field and laboratory techniques were conducted in order to reconstruct the long-term, tectono-sedimentary evolution of the basin and hypothesize the size of the fault segment.A polyphasic evolution of the Middle Aterno Valley is characterized by a conjugate, ∼E-W and ∼NS-striking fault system, during the early stage of basin development, and by a dip-slip, NW-striking fault system in a later phase.The old conjugate fault system controlled the generation of the largest sedimentary traps in the area and is responsible for the horst and graben structures within the basin. During the Early Pleistocene the E-W and NS system reactivated with dip-slip kinematics. This gave rise to intra-basin bedrock highs and a significant syn-tectonic deposition, causing variable thickness and hiatuses of the continental infill.Subsequently, since the end of the Early Pleistocene, with the inception of the NW-striking fault system, several NW-strands linked into longer splays and their activity migrated toward a leading segment affecting the Paganica-San Demetrio basin: the Paganica-San Demetrio fault alignment.The findings from this work constrain and are consistent with the subsurface basin geometry inferred from previous geophysical investigations. Notably, two major elements of the ∼E-W and ∼NS-striking faults likely act as transfer to the nearby stepping active fault systems or form the boundaries, as geometric complexities, that limit the Paganica-San Demetrio fault segment overall length to 19 ± 3 km. The resulting size of the leading fault segment is coherent with the extent of the 6 April 2009 L'Aquila earthquake causative fault.The positive match between the geologic long-term and coseismic images of the 2009 seismogenic fault highlights that the comprehensive reconstruction of the deformation history offers a unique contribution to the understanding faults seismic potential.

A transitional volume beneath the Sannio-Irpinia border region (southern Apennines): Different tectonic styles at different depths

In this paper we investigate the border between the Sannio and Irpinia seismogenic regions, a sector of the southern Apennine chain considered among the most active seismic areas of the Italian peninsula, to shed further light on its complex seismotectonic setting. We integrated recent seismicity with literature data. A detailed analysis of the seismicity that occurred in the 2013–2016 time interval was performed. The events were relocated, after manual re-picking, using different approaches. To retrieve information about the stress field active in the area, inversion of Fault Plane Solutions was also carried out. Hypocentral distribution of the relocated events (ML≤3.5), whose depth is included between 5 and 25km with the deepest ones located in the NW sector of the study area, shows a different pattern between the northern sector and the southern one. The computed Fault Plane Solutions can be grouped in three depth ranges: <12km, dominated by normal dip-slip kinematics; 12–18km, characterized by normal dip-slip and strike-slip kinematics; >18km, dominated by strike-slip kinematics. Stress field inversion across the whole area shows that we are dealing with an heterogeneous set of data, apparently governed by distinct stress fields. We built an upper crustal model profile through integration of geological data, well logs and seismic tomographic profiles. Our results suggest the co-existence of different tectonic styles at distinct crustal depths: the upper crust seems to be affected mostly by normal faulting, whereas strike-slip faulting prevails in the intermediate and lower crust. We infer about the existence of a transitional volume, located between 12 and 18km depth, between the Sannio and Irpinia regions, acting as a vertical transfer zone.

Activation of preexisting transverse structures in an evolving magmatic rift in East Africa

Inherited crustal weaknesses have long been recognized as important factors in strain localization and basin development in the East African Rift System (EARS). However, the timing and kinematics (e.g., sense of slip) of transverse (rift-oblique) faults that exploit these weaknesses are debated, and thus the roles of inherited weaknesses at different stages of rift basin evolution are often overlooked. The mechanics of transverse faulting were addressed through an analysis of the Kordjya fault of the Magadi basin (Kenya Rift). Fault kinematics were investigated from field and remote-sensing data collected on fault and joint systems. Our analysis indicates that the Kordjya fault consists of a complex system of predominantly NNE-striking, rift-parallel fault segments that collectively form a NNW-trending array of en echelon faults. The transverse Kordjya fault therefore reactivated existing rift-parallel faults in ∼1 Ma lavas as oblique-normal faults with a component of sinistral shear. In all, these fault motions accommodate dip-slip on an underlying transverse structure that exploits the Aswa basement shear zone. This study shows that transverse faults may be activated through a complex interplay among magma-assisted strain localization, preexisting structures, and local stress rotations. Rather than forming during rift initiation, transverse structures can develop after the establishment of pervasive rift-parallel fault systems, and may exhibit dip-slip kinematics when activated from local stress rotations. The Kordjya fault is shown here to form a kinematic linkage that transfers strain to a newly developing center of concentrated magmatism and normal faulting. It is concluded that recently activated transverse faults not only reveal the effects of inherited basement weaknesses on fault development, but also provide important clues regarding developing magmatic and tectonic systems as young continental rift basins evolve.

3D modelling of the Tremiti salt diapir in the Gargano offshore (Adriatic Sea, southern Italy): constraints in the Tremiti Structure development

The reinterpretation of public seismic profiles, the stratigraphic review of hydrocarbon exploration well logs in the Adriatic offshore of Gargano (Apulia, southern Italy), and the use of Surfer® (Golden Software, Inc.) and MoveTM (Midland Valley Ltd.) softwares, allowed us to obtain the Two Way Times (TWT) contour map and the 3D model of the upper Trias salt surface of the Tremiti diapir.The obtained 3D model of the Tremiti diapir shows two types of shape indicating at least as many modes of salt emplacement: single flap and piercing. Inherited faults were used by salt, which promoted the contemporaneous development of piercing and single flap in the same diapiric body.In addition, the sea floor deformations suggest that the diapirism, which mostly developed during Plio-Pleistocene time, is probably still active. Despite the NW-SE shortening due to the regional EW dextral shearing, that likely triggered halokinesis, the upward growth rate of the diapir was able to promote dip-slip kinematics, which locally hid the strike-slip one.

Slip re-orientation in oblique rifts

Oblique extension is expected to result in a combination of dip-slip and strike-slip displacement along faults with strike orthogonal and oblique to the extension direction, respectively. This general concept is in disagreement with observations from natural oblique rifts, where faults show dip-slip kinematics indicating pure extension irrespective of the fault strike with respect to the regional extension direction. Consequently, along oblique structures, slip is re-oriented, and oblique to the applied extension direction. Besides, at fault scale, slip is re-oriented along strike such that it is dip slip at the fault center and becomes highly oblique slip toward the fault tips. Here, we use analogue experiments to show that this discrepancy can be resolved when a preexisting weak zone (WZ) is present in the crust at the onset of oblique extension. The WZ is implemented within the lower crust and strikes oblique to the extension direction. Our experimental results show that an inherited WZ within the ductile crust favors the re-orientation of slip such that oblique extension results in pure dip-slip displacement on faults that strike oblique with respect to the extension direction. Furthermore, we show that slip is re-oriented along strike of major faults, such that the fault center shows dip-slip kinematics, whereas its tips display strike-slip kinematics. These findings call into question the use of paleostress reconstructions to constrain plate kinematics in oblique extensional tectonic settings.

Spatial distribution and structural analysis of vents in the Lunar Crater Volcanic Field (Nevada, USA)

Volcanoes within monogenetic volcanic fields often are arranged in alignments and clusters, which are related to effects of magma source geometry in the upper mantle, principal stress orientations, and crustal structures on their magma feeding systems. We use cluster analysis with dendrogram, vent morphometric analysis, and field structural data to explore the relationships between volcanoes and tectonic features in the Plio-Pleistocene part of the Lunar Crater Volcanic Field (LCVF; Pancake Range, Nevada, USA), which includes 96 monogenetic volcanic edifices totaling 119 vents. Structural analysis identified three main sets of faults with dip-slip kinematics (mostly normal with a few examples of thrust faults), striking N-S, E-W, and NE-SW. The NE-SW set comprises dip-slip faults with a dominant normal component of movement which are consistent with the modern state of stress based upon the World Stress Map database. Spatial distribution pattern analysis suggests a clustered distribution of vents in the LCVF, and GIS-based spatial density analysis shows that these clusters trend mostly NE-SW. Morphometric study of the monogenetic cones, which provides information on feeder dike orientation where dikes are not directly exposed, suggests dominant NNE-SSW to NE-SW orientations of near-surface inferred dikes. An amount of 27 out of 31 inferred feeder dikes within the LCVF is parallel to the present orientation of the greatest principal horizontal stress (σHmax) as suggested by World Stress Map data derived from hydrofracturing and earthquake focal mechanisms. In some cases, dike strike is parallel with that of pre-existing Quaternary dip-slip faults. We suggest that the spatial distribution of vents is related to domains of different scales of partial melting and compositional heterogeneity in the upper mantle source, which is substantiated by geochemical data. The relationship of feeder dikes with respect to shallow tectonic structures, although somewhat ambiguous at LCVF, is consistent with behavior that is intermediate between volcanic fields with high- and low-long-term magma fluxes.

Morphotectonic evolution of connected intermontane basins from the southern Apennines, Italy: the legacy of the pre-existing structurally controlled landscape

The opening kinematics of several Pliocene to Quaternary tectonically controlled continental basins scattered along the axis of the southern Italian Apennines and their morphological features and evolution have been compared to define the behaviour of this particular interconnected negative morphostructure. In particular, three different but morphologically connected intermontane basins have been here investigated from a morphotectonic point of view (from the north: Auletta, Vallo di Diano, and Sanza basins). They are filled by more or less thick marine and/or continental sequences of sediments, Pliocene to Quaternary in age. Such basins are shaped by erosional land surfaces and fluvial dissection. The ages of the morphological de-activation of the terraced surfaces have been roughly defined on the basis of their morpho-stratigraphic relationships with Pliocene and Quaternary deposits, and better constrained by radiometric dating. The NNW–SSE-trending fault of the Alburni Mts, bordering the Auletta basin, indicates former left-lateral transtensional kinematics and later dip-slip kinematics, whereas the N140–150°-striking master fault bounding the Vallo di Diano basin is a normal fault. The Sanza basin can be assimilated to a morphostructural trough coinciding with a long-term transfer zone of the chain, in which a severe change in stress field, uplift rate, climate conditions, and relief production occurred during Pleistocene times. Such a complicated morphostructural setting may be interpreted as a function of the original orientation of the structural depressions, only partially coeval. In this sense, the Vallo di Diano basin should represent the structural low generated by pure extension during the Pleistocene, but probably already living as a Pliocene seaway, whereas both the Auletta and Sanza basins stand for two lateral branches with oblique kinematics, inherited from a pre-existing (i.e. Pliocene in age) set.

Deformation and granite intrusion in the Sirohi area, SW Rajasthan—Constraints on Cryogenian to Pan-African crustal dynamics of NW India

This study provides further evidence for a Cryogenian (∼770–760Ma) deformation event in NW India, a region generally regarded tectonically stable during the Rodinia to Gondwana transition. This deformation is prominent in the Sirohi region (southwestern Rajasthan State), previously referred to as the ‘Sirohi Orogeny’, younger to and independent of the ∼1Ga to 820Ma Delhi Orogeny. Synkinematic intrusion of the Balda Granite during the NW-directed thrusting and folding of sediments of the Neoproterozoic Sirohi Group is constrained by combined field, microstructural and magnetic fabric analyses. Thrusting (D1) occurred under medium grade deformation conditions along mylonitic to ultramylonitic shear zones featuring quartz and feldspar recrystallization. Steepening of thrust planes and transition from dip-slip kinematics to oblique and dextral strike-slip in high strain areas indicate transpressive kinematics during the late-stage of D1 deformation. A second deformation event (D2) is documented in strain concentration along a conjugate set (N–S & E–W) of shear zones wherein dilation along the N–S trending structures provided space for voluminous synkinematic quartz mineralization. This linear structure, traceable for ∼10km and named ‘Balda-Paladi Shear Zone’, has overprinted the NE–SW trending magmatic fabrics in the Balda Granite by N–S oriented shearing. Brittle behavior of feldspar constrains this overprint as a low temperature deformation event that also represents the terminal Cryogenian imprint in the Sirohi sector. The findings of this study indicate that an early Cryogenian imprint, seen in three different tectonomagmatic zones, from E to W referred to as South Delhi high-grade metamorphic terrane, Sirohi anatectic terrane and Sirohi fold and thrust terrane, is coeval with the initial closure of the Mozambique Ocean as constrained for central and northern Madagascar. A continuation of early Cryogenian mobile belts extending from southern India, crossing Madagascar into NW India is proposed. Related structures could have served as pathways for heat convection and triggered local late Pan-African thermal resetting in NW India.

Geometry and kinematics of the Montelanico-Carpineto Backthrust (Lepini Mts., Latium) in the hangingwall of the early Messinian thrust front of the central Apennines: implications for the Apennine chain building

The paper updates knowledge on the Montelanico-Carpineto Backthrust, which is confined in the Lepini Mts. thrust sheet, at the hangingwall of the Neogene Latina Valley Thrust Front.The local stratigraphic setting consists of a pre-orogenic succession of Mesozoic carbonates from the Latium-Abruzzi platform Auct. The carbonates are paraconformably overlain by Miocene ramp limestones, which evolve upwards into planktonic marls. The Sub-Ligurian unit thrusted over this dominantly carbonate succession.In the Latina Valley, siliciclastic turbidites (Frosinone Formation Auct.), which evolved from the above-mentioned Miocene units, constitute the upper Tortonian foredeep deposits, now preserved in the footwall of the Lepini Mts. thrust sheet. In the Segni-Montelanico area, conglomerates, unconformably overlying the carbonatebedrock and coeval with the Frosinone Formation, are interpreted as late Tortonian thrust-top deposits (Gavignano and Gorga unit). The Lepini Mts. ridge has two series of distinctive tectonic features: the first is related to the Neogene shortening events due to the Apennine chain building; the other results from Plio-Quaternary extensional events associated with the collapse of the Tyrrhenian margin.The Montelanico-Carpineto Backthrust, as evidenced by the structural survey, is a compressive fault plane dipping 45°-50° towards NE with a SW-verging dip-slip kinematics. The fault has an offset of about 700 m, ramp geometries and a cut-off of about 20°. The Montelanico-Carpineto Backthrust and the Latina Valley Thrust Front define a pop-up structure. The presumable age of the Montelanico-Carpineto Backthrust is the early Messinian, because the lateTortonian Gavignano and Gorga unit is involved in its brittle shear zone. This implies that the formation of the Montelanico-Carpineto Backthrust and of the related pop-up structure is coeval with the early Messinian thrusting of the Lepini Mts. thrust sheet upon the geodynamic propagation of the central Apennine chain-foredeep-foreland system.

The fracture system and the melt emplacement beneath the Deception Island active volcano, South Shetland Islands, Antarctica

AbstractA new magnetotelluric (MT) survey, along with new topographic parametric sonar (TOPAS) profiles and geological field observations, were carried out on the Deception Island active volcano. 3-D resistivity models reveal an ENE–WSW elongated conductor located at a depth between two and ten kilometres beneath the south-eastern part of the island, which we interpret as a combination of partial melt and hot fluids. The emplacement of the melt in the upper crust occurs along the ENE–WSW oriented, SSE dipping regional normal fault zone, which facilitates melt intrusion at shallower levels with volcanic eruptions and associated seismicity. Most of the onshore and offshore volcanic rocks are deformed by high-angle normal and sub-vertical faults with dominant dip-slip kinematics, distributed in sets roughly parallel and orthogonal to the major ENE–WSW regional tectonic trends. Faults development is related to perturbations of the regional stress field associated with magma chamber overpressure and deflation in a regional setting dominated by NW–SE to NNW–SSE extension.

Constraining deformation stages in brittle–ductile shear zones from combined field mapping and 40Ar/ 39Ar dating: The structural evolution of the Grimsel Pass area (Aar Massif, Swiss Alps)

40Ar/ 39Ar dating of syn-kinematic white mica (phengite) and biotite is used to constrain the age of shear zones within the granodiorites of the Grimsel Pass area (Aar Massif, Central Alps). Three sets of steeply dipping shear zones have been mapped. Stage 1 shear zones are very broad (∼200 m wide) zones of biotite-bearing rocks, with a progressive increase in intensity of ductile deformation from rim to core, and have dip-slip kinematics. Subsequent Stage 2 shear zones are narrower, contain phengite-rich mylonites, and show a gradual change from dextral strike-slip to dip-slip kinematics across strike. Strain localisation during the formation of Stage 2 shear zones is interpreted to have been aided by reaction-weakening during extensive fluid–rock interaction. Brittle precursors of Stage 2 shear zones are marked by biotite-rich cataclasites preserved along the northern contact of the overprinting main Stage 2 shear zone. Biotite from a Stage 1 shear zone yields an age of 21.1 ± 0.2 Ma. Phengites in Stage 2 mylonites in the Grimsel Pass area have a very narrow age range (13.8–12.2 Ma), which is interpreted to bracket the duration of ductile deformation during Stage 2 deformation at mid-crustal levels. However, the biotite-rich cataclasites at the margin of a Stage 2 shear zone may have localised fluid flow up to ∼2 Ma prior to the onset of main Stage 2 ductile deformation. Stage 3 shear zones are brittle strike-slip faults containing cataclasites, breccias and clay fault gouges. Earlier studies have established that these late faults formed at <9 Ma and were active until at least 3 Ma.