Oblique Arc-continent Collision Research Articles

A forearc pull-apart basin under oblique arc-continent collision: Insights from the North Luzon Trough

The North Luzon Trough, on the East Asian continental margin, is under transpression due to the oblique convergence between the Eurasian and Philippine Sea plates. Based on a seismic profile across the Manila subduction system and other geological data, we propose a strike-slip pull-apart basin model to account for the formation of the North Luzon Forearc Basin. The subduction system experienced four tectonic evolutionary stages: (1) initial subduction (~22–20 Ma): the Eurasian Plate began to subduct beneath the Philippine Sea Plate, and the incipient Manila Trench-North Luzon Volcanic Arc system started to form; (2) upper crustal deformation (~20–15 Ma): the overriding Philippine Sea Plate was strongly deformed by continuous subduction, and thrust faults, volcanic activity, and possibly strike-slip faulting weakened the forearc areas; (3) initiation of strike-slip faults (~15–6 Ma): continuous rotation of the Philippine Sea Plate initiated strike-slip faults in the weak zones of the forearc areas; (4) pull-apart basin formation (~6–0 Ma): the pull-apart basin formed in the forearc due to sinistral movement of two sets of strike-slip faults. We propose an indentation-escape process involving coupling between the sinistral strike-slip faults in the Taiwan-Luzon area and dextral strike-slip faults in the East Asia continental margin, for the evolution of the eastern South China Sea Basin margin.

From oblique arc-continent collision to orthogonal plate subduction in the southeastern central Asia Orogenic Belt during Paleozoic: Evidence from superimposed folds at the northern margin of the north China Craton

• Two stages of folds are identified on the northern margin of the North China Craton. • The D 1 folds were crossly superimposed by the D 2 folds and both formed in Paleozoic. • A dynamic transition occurred in middle Paleozoic in the northernNorth China Craton. Accretionary kinematic history of the Central Asia Orogenic Belt (CAOB) remains unclear in previous geological studies. Based on detailed structural analysis of newly identified folds on the northern margin of the North China Craton (NCC), we propose a tectonic model suggesting that Paleozoic accretion of the orogenic belt includes two phases of deformation. The first phase of deformation is oblique collision of the Bainaimiao Arc and the NCC, which was followed by orthogonal subduction of the Paleo-Asian Ocean in the second phase of deformation. The change of plate kinematics is supported by two generations of folding, namely D 1 (D B ) and D 2 (D A ). Both D 1 (D B ) and D 2 (D A ) folds developed in the Bayan Obo Group (BOG), a Meso- and Neoproterozoic rift sequence deposited on the passive continental margin of the NCC. D 1 (D B ) folds were superimposed by the east-west trending D 2 (D A ) folds. The D 1 (D B ) folds developed as a result of oblique collision of the Bainaimiao arc and the NCC. The D 2 (D A ) folds developed in response to the southward orthogonal subduction of the Paleo-Asian Ocean Plate. They formed between latest Silurian and Early Permian, coeval with the two accretion events at the northern edge of the NCC. Our study suggests that multiphase deformation of sedimentary layers on the subducting plates provide important constraints for kinematic evolution of plate tectonics.

Arc-continent collision of the Coastal Range in Taiwan: Geochronological constraints from U-Pb ages of zircons

Abstract The oblique arc-continent collision between the Luzon arc and the southeastern margin of the Eurasian continent caused the uplift of Taiwan. The Coastal Range in eastern Taiwan is the northern section of the Luzon arc in the collision zone and thus records important information about the arc-continent collision. In this paper, we determine and analyze the U-Pb ages of magmatic zircons from the volcanic arc and clastic zircons from the fore-arc basin in the Coastal Range. For the volcanic arc in the Coastal Range, the eruption ages range from 16.8–5 Ma. Given that the initial subduction of the South China Sea oceanic crust (17 Ma) occurred before the Luzon arc formed, we conclude that the volcanic activity of the Coastal Range began at 16.8 ± 1.3 Ma; it was most active from 14 to 8 Ma and continued until approximately 5 Ma. The U-Pb chronology also indicates that the initial stage of arc-continent collision of the Coastal Range started at approximately 5 Ma, when the northern section of the Luzon arc moved away from the magmatic chamber because of the kinematics of the Philippine Sea Plate.

Sedimentation in remnant ocean basin off SW Taiwan with implication for closing northeastern South China Sea

Taiwan is one of the most cited examples of modern mountain building in an oblique arc–continent collision. However, the recognition and significance of the Taiwan remnant ocean basin in the final stages of the collision of Luzon with the Chinese margin have long been ignored. This paper emphasizes the Taiwan remnant ocean basin as the main sink for sediments from the uplifted Taiwan suture zone and as a record of clues to the suturing history of the Taiwan collision zone. A part of the palaeo South China Sea has been closed by oblique collision of the Luzon Arc with the Chinese margin in the Taiwan region since about 4 Ma. As collision continued southward along the Taiwan–Luzon convergent zone the remaining South China Sea off SW Taiwan became the Taiwan remnant ocean basin. Beginning about 1.6 Ma much sediment from the longitudinal drainage of the Taiwan orogen was fed into this remaining basin and trapped in the intra-slope basins of the Kaoping slope, with some sediment bypassing via the Kaoping Canyon to the lower reach of the Penghu Canyon. This basin is characteristic of an axial canyon–deep-sea channel–oceanic trench system without significant sediment accumulation in submarine fans. Excess sediments from the Penghu Canyon mainly spill over out of the closing basin to the South China Sea and Manila Trench via the deep-sea Penghu Channel. The Taiwan–Luzon convergent zone continues along the NE South China Sea where the Taiwan remnant ocean basin exists. The implication of the convergence is that the Taiwan remnant ocean basin will keep shrinking in the next few million years southward to the northern end of the Manila Trench at around 20°N, where collision is replaced by subduction. The remnant ocean basin would be closed and deformed, and sediments would be accreted to uplifted collisional terranes north of the Manila Trench.

Depleted deep South China Sea δ13C paleoceanographic events in response to tectonic evolution in Taiwan–Luzon Strait since Middle Miocene

The most distinctive feature of the deep South China Sea (SCS) paleoceanography is the occurrence of long-term depleted deep-sea benthic foraminiferal δ13C values. They are lower than the global and the Pacific composite records in the last 16Ma, especially at 13.2, 10.5, 6.5, 3.0 and 1.2–0.4Ma. This distinct deep SCS paleoceanograhic history coincides with the subduction–collision history in the Taiwan region where waters of the West Pacific (WP) and the SCS exchange. The depleted deep-sea benthic foraminiferal δ13C events indicate that the SCS deep basin became progressively a stagnant environment in the last 16Ma due to either closure of the connection with the WP bottom water or temporary reduction of the WP deep water flowing into the deep SCS. Both the Taiwan accretionary prism and the Luzon arc became the main tectono-morphological barriers for the WP bottom water flowing into the SCS deep basin when eastward subduction of the SCS oceanic lithosphere beneath the Philippine Sea Plate started from the Middle Miocene (18–16Ma). This began a long-term trend of depleted SCS deep-sea benthic δ13C values in the last 16Ma. The oblique arc–continent collision since ~6.5Ma uplifted the Taiwan accretionary prism rapidly above sea level and further isolated the SCS from the open Pacific. The collision simultaneously causes backthrusting deformations in the North Luzon Trough forearc basin and sequentially closes interarc water gates between volcanic islands from north to south. The Loho and the Taitung interarc water gates in the advanced collision zone were closed at ~3.0Ma and ~1.2Ma, coinciding with the very low SCS deep-sea benthic δ13C events at 3.0 and 1.2–0.4Ma, respectively. The Taitung Canyon between the Lutao and Lanyu volcanic islands in the incipient collision zone is semi-closed presently. These closure events also lead to the result that the WP deep water intrudes westward into the SCS principally through the Bashi Channel between the Lanyu and Batan volcanic islands in the subduction zone.

Generation of calc-alkaline andesite of the Tatun volcanic group (Taiwan) within an extensional environment by crystal fractionation

The Pliocene–Pleistocene northern Taiwan volcanic zone (NTVZ) is located within a trench-arc–back-arc basin and oblique arc–continent collision zone. Consequently the origin and tectonic setting of the andesitic rocks within the NTVZ and their relation to other circum-Pacific volcanic island-arc systems is uncertain. Rocks collected from the Tatun volcanic group (TTVG) include basaltic to andesitic rocks. The basalt is compositionally similar to within-plate continental tholeiites whereas the basaltic andesite and andesite are calc-alkaline; however, all rocks show a distinct depletion of Nb-Ta in their normalized incompatible element diagrams. The Sr-Nd isotope compositions of the TTVG rocks are very similar and have a relatively restricted range (i.e. ISr = 0.70417–0.70488; εNd(T) = +2.2 to +3.1), suggesting that they are derived directly or indirectly from the same mantle source. The basalts are likely derived by mixing between melts from the asthenosphere and a subduction-modified subcontinental lithospheric mantle (SCLM) source, whereas the basaltic andesites may be derived by partial melting of pyroxenitic lenses within the SCLM and mixing with asthenospheric melts. MELTS modelling using a starting composition equal to the most primitive basaltic andesite, shallow-pressure (i.e. ≤1 kbar), oxidizing conditions (i.e. FMQ +1), and near water saturation will produce compositions similar to the andesites observed in this study. Petrological modelling and the Sr-Nd isotope results indicate that the volcanic rocks from TTVG, including the spatially and temporally associated Kuanyinshan volcanic rocks, are derived from the same mantle source and that the andesites are the product of fractional crystallization of a parental magma similar in composition to the basaltic andesites. Furthermore, our results indicate that, in some cases, calc-alkaline andesites may be generated by crystal fractionation of mafic magmas derived in an extensional back-arc setting rather than a subduction zone setting.

Structural analysis of a newly emerged accretionary prism along the Jinlun-Taimali coast, southeastern Taiwan: From subduction to arc-continent collision

In southern Taiwan the initial collision of the Luzon volcanic arc with the passive continental margin of China results in the emergence of an accretionary prism of, predominantly, turbidites in composition, thus providing an appropriate place to study the temporal and spatial variation of deformation during the transition of subduction to arc-continent collision. Field surveys have recently been carried out in slightly metamorphosed rocks along the well-exposed Jinlun-Taimali coast in southeastern Taiwan. Three folding phases are identified in the area. The first phase is characterized by gently dipping but widely distributed phyllitic cleavage (S1). The second phase is represented by sparsely distributed crenulation cleavage (S2) that folded the phyllitic cleavage. The third phase is characterized by E–W trending antiforms (F3) that involved both types of pre-existing cleavages. Restoration of such an antiform in the north using a method proposed in this paper reveals that phyllitic cleavage in the overturned beds dips gently towards the southeast or east-southeast before the antiform, in relation to the first-phase thrusting or folding under regional ESE-WNW compression. From the first to third phase, the maximum horizontal compression underwent an about 90° anticlockwise rotation from ESE-WNW to E–W or NE–SW to N–S, and the deformation depth seems to decrease drastically, in terms of the decreasing proportion of pervasive deformation. All these variations are attributed to the oblique arc-continent collision that exhumed the whole accretionary prism and induced a local stress perturbation in southeastern Taiwan.

Stream-power incision model in non-steady-state mountain ranges: An empirical approach

Stream-power incision model has always been applied to detecting the steady-state situation of ranges. Oblique arc-continent collision occurring during the period of Penglai Orogeny caused the Taiwan mountain belt to develop landscape of three evolution stages, namely stages of pre-steady-state (growing ranges in southern Taiwan), steady-state (ranges in central Taiwan) and post-steady-state (decaying ranges in northern Taiwan). In the analysis on streams of the Taiwan mountain belt made by exploring the relationship between the slope of bedrock channel (S) and the catchment area (A), the topographic features of the ranges at these three stages are acquired. The S-A plot of the steady-state ranges is in a linear form, revealing that the riverbed height of bedrock channel does not change over time (dz/dt = 0). The slope and intercept of the straight line S-A are related to evolution time of steady-state topography and tectonic uplift rate respectively. The S-A plots of the southern and northern ranges of Taiwan mountain belt appear to be in convex and concave forms respectively, implying that the riverbed height of bedrock channel at the two ranges rises (dz/dt > 0) and falls (dz/dt < 0) over time respectively. Their tangent intercept can still reflect the tectonic uplift rate. This study develops an empirical stream-power erosion model of pre-steady-state and post-steady-state topography.

Temporal and spatial records of active arc-continent collision in Taiwan: A synthesis

Well-documented stratigraphy and clearly defined geodynamics in Taiwan, where some of the best records on arc-continent collision have been preserved, offer a unique example for the study of collision belts worldwide. The oblique arc-continent collision in Taiwan caused a simultaneous and sequential migration of four tectonic processes. Beginning from 16 to 15 Ma, subduction of the South China Sea oceanic crust beneath the Philippine Sea plate resulted in volcanism in the Coastal Range and formation of an accretionary prism in the Central Range. Beginning in the latest Miocene–earliest Pliocene, the subduction was followed by initial arc-continent collision, as supported by the following: unroofing and erosion of the deformed accretionary prism, and deposition of sediments thus derived in the adjacent accretionary forearc (5 Ma) and slope basins (4 Ma); waning of volcanism (north, 6–5 Ma; south, 3.3 Ma); buildup of fringing reefs on the gradually quiescent volcanoes (north, 5.2 Ma; south, 2.9 Ma); arc subsidence by strike-slip faulting and the development of pull-apart intra-arc basins (north, 5.2–3.5 Ma; south, 2.9–1.8 Ma); thrusting of forearc sequences to generate a collision complex starting from 3 Ma; and clockwise rotation of the arc-forearc sequences (north, 2.1–1.7 Ma; south, 1.4 Ma). The collision propagated southward and reached southern Taiwan by 5 Ma, as evidenced by the successive deformation of the associated accretionary wedge en route. Afterward, the advanced arc-continent collision stage appeared in the earliest Pleistocene, as marked by the westward thrusting and accretion of the Luzon arc-forearc against the accretionary wedge (north, 1.5 Ma; south, 1.1 Ma) and exhumation of the underthrust Eurasian continent rocks (north, 2.0–1.0 Ma; south, 1.0–0.5 Ma). The final stage of the tectonic process, arc collapse-subduction, began by 1 Ma off the northern Coastal Range. The geologic records compiled and presented in this study strongly support the scenario of a continuous southward migration of tectonic processes and a change in sediment source and structural style. Most importantly, the model has a broad potential for reconstructing and predicting the evolution of arc-continent collision through space and time.

Tectonic evolution of accretionary prism in the arc-continent collision terrane of Taiwan

The thick sedimentary and meta-sedimentary rocks west of the Eocene-Paleozoic metamorphic basement of Taiwan represent an accretionary prism developed between the Eurasian continent and the Philippine Sea plate. The accretionary prism consists of a subduction wedge in the east and a collision prism in the west. The deep-marine subduction wedge developed during the eastward subduction of the South China Sea oceanic crust since the Early Miocene. In the Central Range, a regional unconformity with mylonite structure occurred between the Miocene deep-marine slates-turbidites and the Paleozoic-Eocene metamorphic basement. The unconformity marks the tectonostratigraphic break between the overlying subduction wedge and the underlying underthrust Eurasian continent. The subduction wedge extends from the western Central Range southwards through the Hengchun Peninsula to the offshore Hengchun Ridge. Subduction of the South China Sea oceanic crust further led to the oblique arc-continent collision starting about 6.5 Ma in northern Taiwan. During the collision, the shallow-marine passive margin and foreland sequences were progressively incorporated to the collision prism by a series of west-vergent thrusts in the Hsüehshan Range and the Western Foothills. The Kaoping Slope west of the subduction wedge of the Hengchun Ridge represents the modern collision prism in the active arc-continent collision zone. The collision prism is juxtaposed against the subduction wedge to the east along the Lishan-Laonung-Hengchun fault, which extends offshore to the 30-km-wide fault zone between the Kaoping Slope and the Hengchun Ridge. Before the onset of the arc-continent collision, the Lishan-Laonung-Hengchun fault developed along the northern part of the proto-Manila trench and acted as the thrust front located to the west of the subduction wedge. At present, the thrust front has migrated southwestward to the west of the collision prism. The arc-continent collision propagated southwards and yielded the time-transgressive deformations from north to south to result a south tapering configuration of Taiwan. This paper is the first to recognize the consistent occurrence of the subduction wedge and collision prism onshore and offshore Taiwan. This allows reconstruction of the tectonic evolution of the accretionary prism during the subduction and collision tectonics of Taiwan.

Strike-slip faults offshore southern Taiwan: implications for the oblique arc-continent collision processes

Taiwan is the site of present-day oblique arc-continent collision between the Luzon arc of the Philippine Sea plate and the Chinese continental margin. The major structural pattern revealed from marine geophysical studies in the area offshore southern Taiwan is that of a doubly-vergent orogenic belt, bounded by significant zones of thrusting on the west and east of the submarine accretionary wedge. Due to the oblique collision process, strike-slip faults could play an important role in this convergent domain. Topographic lineaments revealed from new digital bathymetry data and seismic reflection profiles confirm the existence of three sets of strike-slip faults in the collision-subduction zone offshore southern Taiwan: the N-S-trending left-lateral strike-slip faults within the Luzon volcanic arc, the NE-SW-trending right-lateral strike-slip faults across the accretionary wedge, and the NNE-SSW-trending left-lateral strike-slip faults lie in the frontal portion of the accretionary wedge. These strike-slip faults overprint pre-existing folds and thrusts and may convert into oblique thrusts or thrusts as the forearc blocks accrete to the mountain belt. A bookshelf rotation model is used to explain the observed geometrical relationships of these strike-slip fault systems. Based on this model, the counter-clockwise rotation of the forearc blocks in the area offshore southern Taiwan could have caused extrusion of the accretionary wedge material into the forearc basin. The originally continuous forearc basin is thus deformed into several closed and separate proto-collisional basins such as the Southern Longitudinal Trough and Taitung Trough. A tectonic evolution model which emphasizes on the development of various structures at different stages of the oblique arc-continent collision for the Taiwan mountain belt is proposed.

Marine geology in the arc-continent collision zone off southeastern Taiwan: Implications for late neogene evolution of the coastal range

Marine geology in the region between Taiwan and Luzon is characterized by a convergent tectonics in the south and an oblique arc-continent collision in the north. In the collision zone six geologic provinces are recognized. They are the Manila Trench, the accretionary prism of the Hengchun Ridge, the sutural basin of the Southern Longitudinal Trough, the subduction mélange of the Huatung Ridge, the forearc basins of the Taitung and the North Luzon Troughs, and the volcanic arc of the North Luzon Ridge. The oceanic crust of the South China Sea is subducting eastward beneath the Philippine Sea plate along the Manila Trench south of 20°N. Further to the north, the Trench has changed progressively its axis toward the west from the subduction mélanges off southeastern Taiwan at 3 Ma to the Hengchun peninsula of southern Taiwan at 2-1 Ma, and then to the present-day location off southwestern Taiwan. Because of the continuing collision and the westward shifting of the Manila Trench, sediments deposited in the region are passively incorporated into the accretionary prism and deformed to the Hengchun Ridge. After the collision the Southern Longitudinal Trough, consisting of a 2 km thick of orogenic sediments, represents a sutural basin superposed on the plate boundary between the accretionary prism of the Hengchun Ridge (Asian continent) and the subduction mélange of the Huatung Ridge (Philippine Sea plate). The Huatung Ridge is a bathymetric high connected to the southern Coastal Range and is characteristic of low, negative free-air gravity and magnetic anomalies. The Ridge contains deeply weathered sedimentary blocks with abraded deep-water late Pliocene foraminifera and identical clay mineral compositions as those in the onshore Lichi Mélange. This implies that at least a portion of the Huatung Ridge is composed of mélange materials and represents a former subduction zone extending from the Lichi Mélange of the southern Coastal Range. The North Luzon Trough and the Taitung Trough are the constructed foreac basins with 2 km of orogenic sediments unconformably overlying the volcanic islands and the subduction melange. The Taitung Trough is southward connected to the North Luzon Trough through a bathymetric passage, which was formed by narrowing the North Luzon Trough as a consequence of clockwise rotation of the Lutao volcanic island during the late Pleistocene. A detailed study of the four Neogene tectonostratigraphic units in the Coastal Range shows that the overall history of the formation of the Range can be related to the present-day geologic provinces and the on-going collision processes in the region off southeastern Taiwan. The Range had evolved from a southward accretion of the Shuilien-Loho remnant forearc basin and the Chimei volcanic pair at 2 Ma, followed by the Chengkung-Taiyuan remnant forearc basin and the Chengkuangao volcanic island pair at 1 Ma, and the Taitung Trough and the Lutao volcanic island pair presently in process. By analogy, the northern part of the North Luzon Trough and the Lanhsu volcanic island will be accreted to the Coastal Range in the next million years. The paired forearc basin-volcanic island accretion model proposed in this study may thus have implications for mountain ranges that evolved from similar tectonics of oblique arc-continent collision.