Arc-parallel Strike-slip Research Articles

Arc-Parallel Strike-Slip Faulting in an Island Arc under Arc-Normal Subduction: The Case of Kamchatka

Arc-Parallel Strike-Slip Faulting in an Island Arc under Arc-Normal Subduction: The Case of Kamchatka

Right-lateral offset associated with the most recent earthquake on the Ikeda fault of the Median Tectonic Line, southwest Japan, revealed by ground-penetrating radar profiling

The Median Tectonic Line (MTL) is an arc-parallel strike-slip fault that accommodates much of the arc-parallel component of the oblique convergence of the Philippine Sea and Eurasian plates at the Nankai Trough. The MTL in Shikoku is one of the fastest-slipping faults in Japan, with a late Quaternary right-lateral slip rate of 5–10 mm/yr. To estimate the right-lateral slip amounts of the past faulting events on the MTL, we acquired 2D and pseudo-3D ground-penetrating radar (GPR) sections across the ENE-trending Ikeda fault of the MTL in eastern Shikoku. We conducted the GPR surveys at the Higashi-Miyoshi site, where two terrace riser offsets mark the active fault trace. The 2D lines were about 28–64 m long, and the pseudo-3D data were sized 20 m × 30 m with a 0.5-m inline spacing. We used 50 MHz GPR antennas and conducted wide-angle measurements to estimate the electromagnetic wave velocity. We identified three paleochannels on the final depth-converted GPR sections, and two of them are deflected by the fault. A paleochannel at 0.6–1.4 m depth is observed on all inline sections of the pseudo-3D GPR data. We built a 3D model of this paleochannel and estimated the right-lateral and vertical displacements of ~ 3.5 m and ~ 0.5 m, respectively. This paleochannel offset is probably caused by the most recent surface-rupturing earthquake on the Ikeda fault, which may be the 1596 Keicho-Fushimi earthquake. This study demonstrates the usefulness of the GPR surveys to identify geological features displaced laterally and vertically by the most recent surface-rupturing earthquake.

Assimilation, differentiation, and thickening during formation of arc crust in space and time: The Jurassic Bonanza arc, Vancouver Island, Canada

Research Article| March 01, 2016 Assimilation, differentiation, and thickening during formation of arc crust in space and time: The Jurassic Bonanza arc, Vancouver Island, Canada Rameses J. D’Souza; Rameses J. D’Souza † 1School of Earth and Ocean Science, University of Victoria, Victoria, British Colombia V8W 3P6, Canada †rdsouza@uvic.ca Search for other works by this author on: GSW Google Scholar Dante Canil; Dante Canil 1School of Earth and Ocean Science, University of Victoria, Victoria, British Colombia V8W 3P6, Canada Search for other works by this author on: GSW Google Scholar Robert A. Creaser Robert A. Creaser 2Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Search for other works by this author on: GSW Google Scholar GSA Bulletin (2016) 128 (3-4): 543–557. https://doi.org/10.1130/B31289.1 Article history received: 30 Jan 2015 rev-recd: 21 Aug 2015 accepted: 06 Oct 2015 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Rameses J. D’Souza, Dante Canil, Robert A. Creaser; Assimilation, differentiation, and thickening during formation of arc crust in space and time: The Jurassic Bonanza arc, Vancouver Island, Canada. GSA Bulletin 2016;; 128 (3-4): 543–557. doi: https://doi.org/10.1130/B31289.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Continental arcs and island arcs, eventually accreted to continental margins, are thought to have been the locus of continental growth since at least the Proterozoic Eon. The Jurassic Bonanza arc, part of the Wrangellia terrane on Vancouver Island, British Columbia, exposes the stratigraphy of an island arc emplaced between 203 and 164 Ma on a thick preexisting substrate of noncontinental origin. We measured the bulk major- and trace-element geochemistry, and Rb-Sr and Sm-Nd isotope compositions of 18 plutonic samples to establish if differentiation involved contamination of the Bonanza arc magmas by the pre-Jurassic basement rocks. The 87Sr/86Sr and 143Nd/144Nd isotope ratios of the plutonic rocks at 180 Ma vary from 0.70253 to 0.7066 and 0.512594 to 0.512717, respectively. Assimilation–fractional crystallization modeling using trace-element concentrations and Nd and Sr isotope ratios indicates that contamination by a Devonian island arc in the Wrangellia basement is less than 10%. Rare earth element modeling indicates that the observed geochemistry of Bonanza arc rocks represents two lineages, each defined by two stages of fractionation that implicate removal of garnet, varying in modal proportion up to 15%. Garnet-bearing cumulate rocks have not been reported from the Bonanza arc, but their inference is consistent with our crustal thickness estimates from geological mapping and geobarometry, indicating that the arc grew to at least 23 km total thickness. The inference of garnet-bearing cumulate rocks in the Bonanza arc is a previously unsuspected similarity with the coeval Talkeetna arc (Alaska), where garnet-bearing cumulate rocks have been described. Geochronological data from the Bonanza arc show a continuum in plutonic ages from 203 to 164 Ma, whereas the volcanic rocks show a bimodal age distribution over the same span of time with modes at 198 and 171 Ma. We argue that the bimodal volcanic age distribution is likely due to sampling or preservation bias. East-west separation of regions of young and old volcanism could be produced by rollback of a west-dipping slab, forearc erosion by an east-dipping slab, or juxtaposition of two arcs along arc-parallel strike-slip faults. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Protolith of ultramafic rocks in the Kluane Schist, Yukon, and implications for arc collisions in the northern Cordillera

Mafic and ultramafic rocks crop out as decimetre- to centimetre-sized bodies of talc–antigorite–olivine (±orthopyroxene) and chlorite–amphibole schists interleaved in the pelitic Kluane Schist of southwestern Yukon. The metamorphic assemblages in ultramafic rocks exposed at Doghead Point overprint two generations of cleavage and are consistent with metamorphism reaching >550 °C (talc + olivine) and >750 °C (olivine + enstatite) in the contact aureole of the Eocene Ruby Range batholith. The bulk rock major and trace element patterns in the ultramafic schists (>40 wt.% MgO, Mg/(Mg + Fe) > 0.90) are unlike residual mantle from partial melting (i.e., ophiolite, orogenic massif, abyssal ocean floor) but are similar to peridotite or pyroxenite cumulates from arc magmas. Identical trace element concentrations and patterns are observed in several late Triassic basalts, pyroxenites, and websterites occurring to the southeast in Stikinia (present coordinates). A highly discordant U–Pb zircon date for one antigorite–talc–olivine schist sample (200–210 Ma) is within the range of U–Pb zircon ages for the late Triassic Lewes River – Stuhini arc in northwestern Stikinia (200–208 Ma, 216–220 Ma). When combined with other published age information, the ultramafic rocks in the Kluane Schist are interpreted as fragments of deeper arc-related mafic and ultramafic intrusive rocks introduced to the Kluane forearc basin between 95 and 82 Ma by exhumation along shear zones in northwestern Stikinia, most likely the Wann River or Llewellyn Faults. The Kluane Schist represents a west-facing forearc basin bordered to the east by arc-parallel strike-slip fault(s) that served to exhume and imbricate large knockers into the accretionary prism.

Oblique convergence, arc-parallel extension, and the role of strike-slip faulting in the High Himalaya

Arc-parallel extension is an important component of the active deformation of the Himalaya. This extension is accommodated via arc-perpendicular normal faults linked to arc-parallel strike-slip faults. Analysis of ~130 global positioning system geodetic velocities indicates >3 cm yr –1 of arc-parallel extension of the Himalaya. Several models have sought to explain Himalayan arc-parallel extension and strike-slip faulting, including lateral extrusion of Tibet, oroclinal bending of the Himalaya, radial spreading of Tibet and the Himalaya, and variably oblique convergence between India and the Himalaya. Predictions of each model are tested against structural and geodetic observations. These tests indicate that the oblique convergence model best describes Himalayan extensional and strike-slip deformation.

Orogen-parallel, active left-slip faults in the Eastern Himalaya: Implications for the growth mechanism of the Himalayan Arc

One of the key issues about the evolution of the Himalayan orogen is how its map-view curvature has changed with time. Some researchers propose that the arc curvature has decreased due to arc-perpendicular rifting while others suggest that it has increased due to arc-parallel strike–slip faulting. To quantify this problem we conducted field mapping, geomorphologic analysis of active structures, and dating of Pliocene–Quaternary sedimentary units in southeastern Tibet. This study reveals the existence of a ∼ 100-km wide and > 500-km long, east-striking left-slip fault zone in the eastern Himalaya. The left-slip faults initiated prior to 3–4 Ma and have a total left-slip rate of 4–8 mm/yr across the fault zone. Although the left-slip rate in the eastern Himalaya is broadly comparable to the right-slip rate across the western Himalayan arc, the distributed and short-segmented geometry of left-slip faulting in the eastern Himalaya contrasts sharply to the discrete geometry of right-slip faulting in the western Himalaya. The different geometry may have resulted from an earlier initiation and a greater magnitude of fault motion on the right-slip faults, which implies that asymmetric eastward extrusion of western Tibet across the Himalayan arc was a dominant process in the earlier Himalayan history. This was replaced by oroclinal bending since 4 Ma, producing symmetric right-slip and left-slip faulting in the western and eastern Himalaya, respectively.

Subsidence and strike-slip tectonism of the upper continental slope off Manzanillo, Mexico

The direction of convergence between the Rivera and North American plates becomes progressively more oblique (in a counter-clockwise sense as measured relative to the trench-normal direction) northwestward along the Jalisco subduction zone. By analogy to other subduction zones, the forces resulting from this distribution of convergence directions are expected to produce a NW moving, fore-arc sliver and a NW–SE stretching of the fore-arc area. Also, a series of roughly arc parallel strike-slip faults may form in the fore-arc area, both onshore and offshore, as is observed in the Aleutian arc. In the Jalisco subduction zone, the Jalisco block has been proposed to represent such a fore-arc sliver. However, this proposal has encountered one major problem. Namely, right-lateral strike-slip faulting within the fore-arc sliver, and between the fore-arc sliver and the North American plate, should be observed. However, evidence for the expected right-lateral strike-slip faulting is sparse. Some evidence for right-lateral strike-slip faulting along the Jalisco block–North American plate boundary (the Tepic–Zacoalco rift system) has been reported, although some disagreement exists. Right-lateral strike-slip faulting has also been reported within the interior of the Jalisco block and in the southern Colima rift, which forms the SE boundary of the Jalisco block. Threefold, multi-channel seismic reflection data were collected in the offshore area of the Jalisco subduction zone off Manzanillo in April 2002 during the FAMEX campaign of the N/O L'Atalante. These data provide additional evidence for recent strike-slip motion within the fore-arc region of the Jalisco subduction zone. This faulting offsets right-laterally a prominent horst block within the southern Colima rift, from which we conclude that the sense of motion along the faulting is dextral. These data also provide additional evidence for recent subsidence within the area offshore of Manzanillo, as has been proposed.

Oblique Plate Convergence in the Indo-Burma (Myanmar) Subduction Region

— The Indo-Burma (Myanmar) subduction boundary is highly oblique to the direction of relative velocity of the Indian tectonic plate with respect to the Eurasian plate. The area includes features of active subduction zones such as a Wadati-Benioff zone of earthquakes, a magmatic arc, thrust and fold belts. It also has features of oblique subduction such as: an arc-parallel strike-slip fault (Sagaing Fault) that takes up a large fraction of the northward component of motion and a buttress (the Mishmi block) that resists the motion of the fore-arc sliver. In this paper, I have examined the seismicity, slip vectors and principal axes of the focal mechanisms of the earthquakes to look for features of active subduction zones and for evidence of slip partitioning as observed in other subduction zones. The data set consists of Harvard CMT solutions of 89 earthquakes (1977–1999 with 4.8≰M w ≰7.2 and depths between 3–140 km). Most of these events are shallow and intermediate depth events occurring within the Indian plate subducting eastward beneath the Indo-Burman ranges. Some shallow events within the fore-arc region have arc-parallel Paxes, reflecting buttressing of the fore-arc sliver at its leading edge. Some of the shallowest events have nearly E-W oriented P axes which might account for recent folding and thrusting. Examination of earthquake slip vectors in this region shows that the slip vector azimuths of earthquakes in the region between 20°–26°N are rotated towards the trench normal, which is an indication of partial partitioning of the oblique convergence. It is seen that all aspects of seismicity, including the paucity of shallow underthrusting earthquakes and the orientation of P axes, are consistent with oblique convergence. The conclusions of this paper are consistent with recent geological studies and interpretations such as the coexistence of eastward subduction, volcanic activity and transcurrent movement through mid-Miocene to Quaternary period.

Active right-lateral strike-slip fault zone along the southern margin of the Japan Sea

We describe an active right-lateral strike-slip fault zone along the southern margin of the Japan Sea, named the Southern Japan Sea Fault Zone (SJSFZ). Onshore segments of the fault zone are delineated on the basis of aerial photograph interpretations and field observations of tectonic geomorphic features, whereas the offshore parts are interpreted from single-/multichannel seismic data combined with borehole information. In an effort to evaluate late Quaternary activity along the fault zone, four active segments separated by uplifting structures are identified in this study. The east–northeast-trending SJSFZ constitutes paired arc-parallel strike-slip faults together with the Median Tectonic Line (MTL), both of which have been activated by oblique subduction of the Philippine Sea plate during the Quaternary. They act as the boundaries of three neotectonic stress domains around the eastern margin of the Eurasian plate: the near-trench Outer zone and NW–SE compressive Inner zone of southwest Japan arc, and the southern Japan Sea deformed under E–W compression from south to north.

Tectonics of the Jurassic‐Early Cretaceous magmatic arc of the north Chilean Coastal Cordillera (22°–26°S): A story of crustal deformation along a convergent plate boundary

The tectonic evolution of a continental magmatic arc that was active in the north Chilean Coastal Cordillera in Jurassic‐Early Cretaceous times is described in order to show the relationship between arc deformation and plate convergence. During stage I (circa 195–155 Ma) a variety of structures formed at deep to shallow crustal levels, indicating sinistral arc‐parallel strike‐slip movements. From deep crustal levels a sequence of structures is described, starting with the formation of a broad belt of plutonic rocks which were sheared under granulite to amphibolite facies conditions (Bolfin Complex). The high‐grade deformation was followed by the formation of two sets of conjugate greenschist facies shear zones showing strike‐slip and thrust kinematics with a NW–SE directed maximum horizontal shortening, i.e., parallel to the probable Late Jurassic vector of plate convergence. A kinematic pattern compatible to this plate convergence is displayed by nonmetamorphic folds, thrusts, and high‐angle normal faults which formed during the same time interval as the discrete shear zones. During stage II (160–150 Ma), strong arc‐normal extension is revealed by brittle low‐angle normal faults at shallow levels and some ductile normal faults and the intrusion of extended plutons at deeper levels. During stage III (155–147 Ma), two reversals in the stress regime took place indicated by two generations of dikes, an older one trending NE–SW and a younger one trending NW–SE. Sinistral strike‐slip movements also prevailed during stage IV (until ∼125 Ma) when the Atacama Fault Zone originated as a sinistral trench‐linked strike‐slip fault. The tectonic evolution of the magmatic arc is interpreted in terms of coupling and decoupling between the downgoing and overriding plates. The structures of stages I and IV suggest that stress transmission due to seismic coupling between the plates was probably responsible for these deformations. However, decoupling of the plates occurred possibly due to a decrease in convergence rate resulting in extension and the reversals of stages II and III.

Pseudostratigraphy and origin of the Early Proterozoic Payson ophiolite, central Arizona

The Payson ophiolite (ca. 1.73 Ga), exposed within the Early Proterozoic orogenic belt of central Arizona, is a shallow-dipping, pseudostratigraphic sequence of gabbro, sheeted dikes, and submarine volcanic rocks, partly disjointed by later intrusion and deformation. An older basement complex occurs as roof pendants in the gabbro and screens in the sheeted dike complex and was tilted and eroded prior to development of the ophiolite. Gabbro-dike mingling and mutual intrusion in the transition from gabbro to sheeted dikes indicates that the dikes are rooted in the gabbro. Analysis of detailed measured sections of well-exposed sheeted dikes (600 m) reveals 90%–100% dikes with lateral variations in the proportions of tonalitic or dacitic dikes and basement screens. The transition from sheeted dikes to submarine basalts is abrupt and marked by a stratigraphically continuous zone of intensely altered rocks. The sheeted dike complex, pseudostratigraphic structure, and synmagmatic hydrothermal alteration of the Payson ophiolite are diagnostic of a crustal section formed by sea-floor spreading. The Payson ophiolite intrudes, and is intruded by, arc granitoids and is overlain by arc-derived volcanic and sedimentary rocks. A model of an intra-arc basin formed along an arc parallel strike-slip fault is proposed to account for (1) screens of older arc crust, (2) inferred arc-parallel extension, and (3) juxtaposition of the ophiolite with a distinct arc terrane prior to regional convergent deformation and accretion of the arc to North America during the Yavapai orogeny (ca. 1.70 Ga).

The Precordilleran fault system of Chuquicamata, Northern Chile: evidence for reversals along arc-parallel strike-slip faults

The Chilean Precordillera, situated between the Longitudinal Valley and the Western Cordillera of Northern Chile, was the site of the Andean magmatic arc from the late Cretaceous to the Eocene-Oligocene boundary. Magmatism came to an end during the Incaic tectonic phase (38 Ma), which caused arc-normal shortening and the development of longitudinal dextral strike-slip faults (Precordilleran Fault System). This magmatic arc tectonism is also related to the formation of the Chuqicamata porphyry copper ore deposit as well as of other important deposits of this type in the Precordillera. Structural investigations in and around the Chuqicamata open-pit mine have shown that wrench tectonics determined the kinematics of the area. The NS-striking West Fissure, which separates a 35-Ma-old non-mineralised pluton to the west from a central late Paleozoic basement ridge containing the mineralization, became a sinistral fault along with other parallel faults in the area. The central part is separated from similar Paleozoic rocks to the east by the Messabi-Este fault and a narrow faulted and sheared syncline of Mesozoic-Cenozoic sediments. This fault bears structures indicating dextral movements, which probably are of an age that is similar to the mylonites (34.8 Ma) in the western pluton. The dextral movements preceded the sinistral shear. Thus, the fault system of Chuqicamata displays a reversal of arc-parallel shear movements. According to the orientation of quartz veins in the mineralized body, it is presumed that the sense of displacement of these strike-slip motions reversed, when mineralization started at about 32 Ma. During this time the stress field must have changed fundamentally. The Incaic Phase dextral transpression is supposed to have been induced by the oblique vector of plate motion. The following sinistral transtension corresponds to a time of reduced convergence rate and possibly reduced plate coupling. As, however, the vector of plate motion remained unchanged during that time, oblique subduction cannot be used as an argument for arc-parallel sinistral shear movements.

Variations in deformation fields during development of a large-volume magmatic arc, central Sierra Nevada, California

Mid- to Late Cretaceous plutons in the central Sierra Nevada magmatic arc show widely preserved magmatic foliation, whereas regionally developed solid-state foliation is absent. Relatively slow cooling of these plutons and expected strain rates (10^(−14)) suggest that the plutons were emplaced in a neutral or weakly extensional deformation regime. Domains of solid-state ductile shear of only slightly younger age than the plutons, on the other hand, indicate a contractional regime. Timing of pluton emplacement and movement on the shear zones have been constrained using Pb-U (zircon) and ^(40)Ar/^(39)Ar (hornblende and biotite) geochronology. Both plutons and ductile shear zones become younger toward the east. The four more westerly shear zones, which were active between ca. 100 and 90 Ma, show steeply plunging stretching lineations, whereas the most easterly and/or youngest zones, active between ca. 88 and 78 Ma, show mostly oblique and/or subhorizontal stretching lineations, indicating a change in kinematics at ca. 90 Ma. The above events define a complex deformation pattern in which strain regimes fluctuated in time and space between neutral or weak extensional and contractional. We propose a tectonic model in which thenospheric mantle corner flow produced eddy pairs in the mantle corner that transmitted a neutral or weak extensional regime to the overlying crust and facilitated the movement of granitic magma to mid- and upper levels, probably as dikes via fractures. Slab flattening caused the neutral or weak extensional regime to move eastward away from the trench. Increased coupling between upper and lower plates induced by the slab flattening promoted contractional strain in the cooling plutons, and domains of ductile shear formed in progressively younger plutons to the east. The above events were accompanied by an oblique convergence vector between North America and Farallon plates (Engebretson et al., 1985), which imposed a relatively small component of right-lateral shear onto the arc that increased with time. We estimate that at ca. 100 Ma the convergence vector made an angle (Φ_(obl)) ≈ 20° to the arc normal, and we suggest that around ca. 90 Ma Φ_(obl) passed through a critical value, conceivably (20° < Φ_(oblcrit) < 30°). At this juncture, the component of right-lateral shear became sufficiently large to induce significant arc-parallel strike-slip movement on the most easterly shear zones; these kinematics continued as the dominant scheme, possibly as late as ca. 78 Ma.

Ridge collision tectonics in terrane development

Some allochthonous terranes form along active continental margins when slivers of forearc crust (or more extensive crust) are displaced along arc-parallel strike-slip faults. Such faults can be generated or reactivated in response to either oblique subduction or ridge collision (collision between an oceanic spreading ridge and the leading edge of the forearc). The mechanical and thermal effects of ridge collision are important factors in the origin crustal development of some forearc sliver terranes. Some of the effects of ridge collision are well illustrated in the South American forearc near the Chile triple junction (46° S) where the Chile Rise is colliding today. Impingement of the Chile Rise, in conjuction with oblique subduction, has caused an elongate forearc sliver terrane to move northward away from an extensional zone at the collision site. The terrane is bounded on the east by the arc-parallel Liquiñe-Ofqui fault system (LOF) which coincides roughly with the forearc-arc boundary, and on the south by the Golfo de Penas extensional basin. Fault fabrics, recent seismicity, and paleomagnetic results indicate a component of right-lateral strike-slip movement on the LOF. Neotectonic geomorphology and pre- and post-seismic vertical strain data from the 1960 Concepcíon earthquake indicate a west-down dip-slip component of movement. Three-dimensional finite element models of ridge collision in this region substantiate these shear strains and development of an arc-parallel fault at about 150–200 km from the trench.Development of the forearc crust during Miocene and younger collision also involved intrusion of silicic magmas and emplacement of the Pliocene(?) Taitao ophiolite within about 15 km of the trench. The ophiolite and the silicic magmas constitute anomalous additions to the forearc crust, and record tectonic events leading to the origin of the allochthonous terrane carrying them. Similar ophiolite/silicic plutonic associations may help unravel the origin of other allochthonous terranes.

Terrane motion by strike-slip faulting of forearc slivers

Forearc slivers, bounded by a trench and an active strike-slip fault, occur in about 50% of modern subduction zones. Analysis of earthquake slip vectors indicates that modern sliver terranes typically migrate at rates of 1–2 cm/yr. Tertiary transport of some forearc slivers by 1000 km or more is therefore expected as a consequence of normal subduction. Active arc-parallel strike-slip faulting occurs whenever interplate coupling is strong and convergence is somewhat oblique; strike-slip rate increases with greater convergence obliquity.