scholarly journals Maluku Sea Plate Faulting Regime Analysis: A Preliminary Study

2021 ◽  
Vol 873 (1) ◽  
pp. 012100
Author(s):  
Jonathan Adii ◽  
Dian Kusumawati ◽  
Cevian Falevi ◽  
David P Sahara
Keyword(s):  
Middle Miocene ◽  
Tectonic Setting ◽  
Ternary Diagram ◽  
Philippine Sea Plate ◽  
Accretionary Complex ◽  
Eurasian Plate ◽  
Seismicity Distribution ◽  
Preliminary Study ◽  
Diagram Analysis ◽  
Subducting Slab

Abstract Present day Molucca or Maluku sea plate in the eastern of Indonesia possesses a complex tectonic setting. This complex tectonic setting has been formed due to the collision of an actively moving Eurasian plate and Philippine sea plate toward the Maluku sea plate. At the west, Maluku sea plate is subducting beneath Sangihe arc, which began in the early Miocene. While at the east, Maluku sea plate is subducting under Halmahera arc, since in the middle Miocene. These subduction processes take place up to the present. Therefore, it has formed Maluku sea plate into an inverted U-shape slab under a thickening accretionary complex. Seismicity distribution has clearly shown the U-shape slab. Earthquake events take place on the subducting slab, and interestingly on the above accretionary complex as well. Maluku sea plate might pose hazards to surrounding islands: northern Sulawesi, Halmahera island, Sangihe island and Talaud island. The possible hazard, for instance, a thrusting earthquake which may generate tsunami to the nearby islands. Hence, understanding its tectonic and seismicity signature, especially at the shallow part, are indeed important in the Maluku sea region. Faulting regime could be analyzed using focal mechanism ternary diagram analysis, by categorizing the focal mechanisms’ strike, dip and rake values. Thus, in this study we aim to analyze faulting regime and hazard potential in the complex. Maluku setting using ternary diagram analysis.

Frequency-dependent attenuation of shear waves in the crust of the southern Kanto area, Japan

1994 ◽  
Vol 84 (5) ◽  
pp. 1387-1396
Author(s):  
Shigeo Kinoshita
Keyword(s):  
Shear Waves ◽  
Strong Motion ◽  
Body Waves ◽  
Philippine Sea Plate ◽  
Eurasian Plate ◽  
Philippine Sea ◽  
Motion Data ◽  
Basement Rocks ◽  
Acceleration Data ◽  
Attenuation Characteristics

Abstract The attenuation characteristics of shear waves in the crust of the southern Kanto area, central Japan, were estimated using strong-motion data, including acceleration data recorded in the pre-Tertiary basement rocks by means of downhole observation. The quality factor Qs(f) was determined for a range of discrete frequencies from 0.5 to 16 Hz from the analysis of data from 13 local earthquakes with focal depths of less than about 50 km that occurred in the Philippine Sea plate and in the boundary zone between the lower part of the Eurasian plate and the upper part of the Philippine Sea plate. The estimated 1/Qs(f) shows a peaked structure in this frequency range on the assumption that the geometrical spreading exponent is -1 (body waves). The estimated peak 1/Qs(f) is of the order of 10-2 at 0.8 Hz.

Comparative studies on two phases of Archaean TTG magmas from different blocks of the North China Craton: petrogenesis and constraints on crustal evolution

2020 ◽  
pp. 1-16
Author(s):  
Houxiang Shan ◽  
Mingguo Zhai ◽  
RN Mitchell ◽  
Fu Liu ◽  
Jinghui Guo
Keyword(s):  
North China Craton ◽  
Lower Crust ◽  
North China ◽  
Tectonic Setting ◽  
Source Material ◽  
Crustal Growth ◽  
Garnet Amphibolite ◽  
The North ◽  
Western Block ◽  
Subducting Slab

Abstract Whole-rock major and trace elements and Hf isotopes of magmatic zircons of tonalite–trondhjemite–granodiorite (TTG) rocks with different ages (2.9, 2.7 and 2.5 Ga) from the three blocks (the Eastern Block, Western Block and Trans-North China Orogen) of the North China Craton were compiled to investigate their respective petrogenesis, tectonic setting and implications for crustal growth and evolution. Geochemical features of the 2.5 Ga TTGs of the Eastern Block require melting of predominant rutile-bearing eclogite and subordinate garnet-amphibolite at higher pressure, while the source material of the 2.7 Ga TTGs is garnet-amphibolite or granulite at lower pressure. The 2.5 Ga TTGs have high Mg#, Cr and Ni, negative Nb–Ta anomalies and a juvenile basaltic crustal source, indicating derivation from the melting of a subducting slab. In contrast, features of the 2.7 Ga TTGs suggest generation from melting of thickened lower crust. The 2.5 and 2.7 Ga TTGs in the Trans-North China Orogen were formed at garnet-amphibolite to eclogite facies, and the source material of the 2.5 Ga TTGs in the Western Block is most likely garnet-amphibolite or eclogite. The 2.5 Ga TTGs in the Trans-North China Orogen and Western Block were generated by the melting of a subducting slab, whereas the 2.7 Ga TTGs in the Trans-North China Orogen derived from melting of thickened lower crust. The Hf isotopic data suggest both the 2.5 and 2.7 Ga TTG magmas were involved with contemporary crustal growth and reworking. The two-stage model age (TDM2) histograms show major crustal growth between 2.9 and 2.7 Ga for the whole North China Craton.

scholarly journals Melt equilibration depths as sensors of lithospheric thickness during Eurasia-Arabia collision and the uplift of the Anatolian Plateau

Geology ◽  
2019 ◽  
Vol 47 (10) ◽  
pp. 943-947 ◽  
Author(s):  
M.R. Reid ◽  
J.R. Delph ◽  
M.A. Cosca ◽  
W.K. Schleiffarth ◽  
G. Gençalioğlu Kuşcu
Keyword(s):  
Late Miocene ◽  
Large Scale ◽  
Middle Miocene ◽  
Volcanic Rocks ◽  
Suture Zone ◽  
Arabian Plate ◽  
Seismic Structure ◽  
Eurasian Plate ◽  
Lithospheric Thickness ◽  
Anatolian Plateau

Abstract A co-investigation of mantle melting conditions and seismic structure revealed an evolutionary record of mantle dynamics accompanying the transition from subduction to collision along the Africa-Eurasia margin and the >1 km uplift of the Anatolian Plateau. New 40Ar/39Ar dates of volcanic rocks from the Eastern Taurides (southeast Turkey) considerably expand the known spatial extent of Miocene-aged mafic volcanism following a magmatic lull over much of Anatolia that ended at ca. 20 Ma. Mantle equilibration depths for these chemically diverse basalts are interpreted to indicate that early to middle Miocene lithospheric thickness in the region varied from ∼50 km or less near the Bitlis suture zone to ∼80 km near the Inner Tauride suture zone. This southward-tapering lithospheric base could be a vestige of the former interface between the subducted (and now detached) portion of the Arabian plate and the overriding Eurasian plate, and/or a reflection of mantle weakening associated with greater mantle hydration trenchward prior to collision. Asthenospheric upwelling driven by slab tearing and foundering along this former interface, possibly accompanied by convective removal of the lithosphere, could have led to renewed volcanic activity after 20 Ma. Melt equilibration depths for late Miocene and Pliocene basalts together with seismic imaging of the present lithosphere indicate that relatively invariant lithospheric thicknesses of 60–70 km have persisted since the middle Miocene. Thus, no evidence is found for large-scale (tens of kilometers) Miocene delamination of the lower lithosphere from the overriding plate, which has been proposed elsewhere to account for late Miocene and younger uplift of Anatolia.

K-richterite–olivine–phlogopite–diopside–sanidine lamproites from the Afyon volcanic province, Turkey

2008 ◽  
Vol 145 (4) ◽  
pp. 570-585 ◽  
Author(s):  
CÜNEYT AKAL
Keyword(s):  
Middle Miocene ◽  
Primitive Mantle ◽  
Western Anatolia ◽  
Eurasian Plate ◽  
African Plate ◽  
Near Surface ◽  
Volcanic Province ◽  
Ree Patterns ◽  
Opaque Minerals ◽  
Metasomatized Mantle

AbstractMiddle Miocene volcanic activity in the Afyon volcanic province (eastern part of Western Anatolia) is characterized by multistage potassic and ultrapotassic alkaline volcanic successions. The volcanism is generally related to the northward subduction of the African plate beneath the Eurasian Plate. In Afyon, the Middle Miocene volcanic products consist of melilite leucitite, tephriphonolite, trachyte, basaltic–trachyandesite, phonolite, phonotephrite, tephriphonolite and lamproite rocks. Near-surface emplacement and relatively quiescent subaerial eruptions of lamproitic magma produced different emplacement forms such as dome/plug-shaped bodies and lava flows, showing variation in volume and texture. The mineralogical constituents of the lamproites are sanidine, olivine (77 < Mg no. < 81), phlogopite (74 < Mg no. < 78), K-richterite, clinopyroxene (74 < Mg no. < 78), with accessory apatite, calcite and opaque minerals. Afyon lamproites resemble Mediterranean-type Si-rich lamproites. Their compositional range is 50–52 wt% SiO2, 4–8 wt% MgO, and they display a typical lamproitic affinity. Chondrite-normalized REE patterns exhibit enrichment in LREE relative to HREE ((La/Yb)CN=15.3–17.0). They show extreme enrichment in LILE relative to primitive mantle values and troughs of Nb and Ti. The lamproites give a range of high initial87Sr/86Sr ratios and low143Nd/144Nd ratios. The geochemical and isotopic characteristics suggest that lamproitic magma is derived from highly metasomatized mantle. The enrichment history may include metasomatic events related to subduction, as in other active orogenic areas of the Mediterranean.

scholarly journals Petrographic Characteristics and Geochemistry of Volcanic Rocks in the Kyaukmyet Prospect, Monywa District, Central Myanmar

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Toe Naing Oo ◽  
Agung Harijoko ◽  
Lucas Donny Setijadji
Keyword(s):  
Middle Miocene ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Volcanic Field ◽  
Research Area ◽  
Eu Anomaly ◽  
Volcanic Suite ◽  
Copper Gold ◽  
Arc Setting ◽  
Insight Into

The Kyaukmyet prospect lies approximately 5 km ENE of the highsulfidation Kyisintaung copper-gold deposit, Monywa district, central Myanmar. Geologically, the research area is remarked by magmatic extrusion that occurred during the Late Oligocene to Middle Miocene of Magyigon Formation which led to the outcrops of volcanic rocks. Study detailed on petrographical and geochemical of the Kyaukmyet volcanic rocks has not been performed before the present work. The principal aim of this paper is to document the petrographical and geochemical characteristics of volcanic suite rocks exposed in the Kyaukmyet prospect. The results of this data have provided insight into the origin of the rocks and petrogenetic processes during evolution. Petrographically, all the studied volcanic rocks in the research area show that trachytic and porphyritic textures with phenocrysts of quartz, plagioclase, and K-feldspar which are embedded in a fine to medium grained groundmass. The accessory minerals of this rock consist of biotite, chlorite and opaque mineral.Geochemically, these volcanic rocks having calc-alkaline nature and classified as volcanic field (rhyolite) as well as volcanic arc setting. Based on the chondrite normalized spider diagram, LREE has enriched to HREE in this area which indicated negative Eu anomaly and subduction tectonic setting.

U–Pb ages of Miocene near-trench granitic rocks of the Southwest Japan arc: implications for magmatism related to hot subduction

2019 ◽  
Vol 158 (1) ◽  
pp. 47-71 ◽  
Author(s):  
Hironao Shinjoe ◽  
Yuji Orihashi ◽  
Ryo Anma
Keyword(s):  
Middle Miocene ◽  
Japan Sea ◽  
Wide Distribution ◽  
Granitic Rocks ◽  
Philippine Sea Plate ◽  
Kii Peninsula ◽  
The Japan Sea ◽  
Igneous Activity ◽  
Mariana Arc ◽  
Back Arc

AbstractWe present a new dataset of zircon U–Pb ages that document igneous activity in the SW Japan arc during middle Miocene time and discuss its relationship with the opening of the Japan Sea, Philippine Sea plate migration, and subduction of the young hot lithosphere of the Shikoku Basin. Precursory magmatism, characterized by dike and stock intrusions, started c. 15.6 Ma in both Kyushu and the Kii Peninsula. Most plutonism occurred between 15.5 and 13.5 Ma in an area 600 km long and 150 km wide. No along-arc trend was recognized in the U–Pb ages of igneous activity near the trench. Our data indicate that all near-trench middle Miocene igneous activity occurred immediately after the opening of the Japan Sea ceased, i.e. after 16 Ma, implying that melt extraction and the emplacement of granites in the near-trench region had some influence on the back-arc opening. Our data also imply that the trench–trench–trench-type triple junction between the Japan arc and the Izu–Bonin–Mariana arc must have reached the east side of the Kii Peninsula by 15.6 Ma. The wide distribution of contemporaneous magmatic activity along the arc requires a trench-parallel heat source, such as the subduction of a trench-parallel ridge or a young and highly segmented ridge–fracture zone system in addition to the hot wedge mantle condition related to the opening of Japan Sea.

scholarly journals Large-scale slope failure and active erosion occurring in the southwest Ryukyu fore-arc area

2001 ◽  
Vol 1 (4) ◽  
pp. 203-211 ◽  
Author(s):  
T. Matsumoto ◽  
M. Kimura ◽  
M. Nakamura ◽  
T. Ono
Keyword(s):  
Large Scale ◽  
Slope Failure ◽  
Gravitational Instability ◽  
Plate Boundary ◽  
Philippine Sea Plate ◽  
Eurasian Plate ◽  
Philippine Sea ◽  
Topographic Features ◽  
Ishigaki Island ◽  
Tensional Stress

Abstract. The southwestern Ryukyu area east of Taiwan Island is an arcuate boundary between Philippine Sea Plate and Eurasian Plate. The topographic features in the area are characterised by (1) a large-scale amphitheatre off Ishigaki Island, just on the estimated epicentre of the tsunamigenic earthquake in 1771, (2) lots of deep sea canyons located north of the amphitheatre, (3) 15–20 km wide fore-arc basin, (4) 15–20 km wide flat plane in the axial area of the trench, (5) E-W trending half grabens located on the fore-arc area, etc., which were revealed by several recent topographic survey expeditions. The diving survey by SHINKAI6500 in the fore-arc area on a spur located 120 km south of Ishigaki Island was carried out in 1992. The site is characterised dominantly by rough topography consisting of a series of steep slopes and escarpments. A part of the surface is eroded due to the weight of the sediment itself and consequently the basement layer is exposed. The site was covered with suspended particles during the diving, due to the present surface sliding and erosion. The same site was resurveyed in 1997 by ROV KAIKO, which confirmed the continuous slope failure taking place in the site. Another example that was observed by KAIKO expedition in 1997 is a largescale mud block on the southward dipping slope 80 km south of Ishigaki Island. This is apparently derived from the shallower part of the steep slope on the southern edge of the fan deposit south of Ishigaki Island. The topographic features suggest N-S or NE-SW tensional stress over the whole study area. In this sense, the relative motion between the two plates in this area is oblique to the plate boundary. So, the seaward migration of the plate boundary may occur due to the gravitational instability at the boundary of the two different lithospheric structures. This is evidenced by a lack of accretionary sediment on the fore-arc and the mechanism of a recent earthquake which occurred on 3 May 1998 in the Philippine Sea Plate 250 km SSE of Ishigaki Island.

Structural evolution and significance of a mélange in a collision belt: the Lichi Mélange and the Taiwan arc–continent collision

2001 ◽  
Vol 138 (6) ◽  
pp. 633-651 ◽  
Author(s):  
C. P. CHANG ◽  
J. ANGELIER ◽  
C. Y. HUANG ◽  
C. S. LIU
Keyword(s):  
Plate Boundary ◽  
Structural Evolution ◽  
Philippine Sea Plate ◽  
Eurasian Plate ◽  
Seismic Profiles ◽  
Forearc Basin ◽  
Weak Zone ◽  
Manila Trench ◽  
Mountain Belts ◽  
Coastal Range

The analysis of ‘mélanges’ of various types (sedimentary, diapiric, tectonic and polygenetic) is generally difficult and depends on a variety of criteria. However, understanding the nature and origin of mélanges is crucial to deciphering the evolution of some mountain belts. The Lichi Mélange of the Taiwan Coastal Range is juxtaposed against remnant forearc basin sequences by thrust faults and is composed of exotic ophiolite and sedimentary blocks, with sizes ranging from metres to kilometres, and coherent turbidite beds, all embedded in a sheared scaly argillaceous matrix. The Lichi Mélange has been interpreted either as a subduction complex, or as an olistostrome. By separating four main deformation levels based on the degree of disruption within the Lichi Mélange and adjacent sedimentary rocks, we have made new detailed geological maps and structural profiles in two key areas of the Lichi Mélange. We paid particular attention to the original stratigraphic relationships between the mélange and the adjacent flysch formation. Our field results compared with submarine seismic profiles suggest that the present-day structure of the Lichi Mélange results mainly from the shearing of lower forearc basin sequences, rather than from a subduction complex or a mere olistostrome. In Late Miocene time, because lithospheric subduction turned into arc–continent collision in the southern Taiwan area, the site of the proto-Manila trench changed from an active plate boundary into a deformation zone with several thrusts. A new plate suture zone between the Eurasian plate (eastern Central Range) and the Philippine Sea plate (Coastal Range) was therefore formed along the Longitudinal Valley. The Longitudinal Valley originated as a submarine arc–prism boundary, an innate weak zone within the overriding plate, and has become a prominent tectonic feature of the arc–continent collision. This inference is supported by observations on the Lichi Mélange in the Coastal Range and the Huatung Ridge off southeastern Taiwan.

K–Ar geochronology of a middle Miocene submarine volcano-plutonic complex in southwest Japan

2004 ◽  
Vol 141 (1) ◽  
pp. 1-13 ◽  
Author(s):  
T. IMAOKA ◽  
T. ITAYA
Keyword(s):  
Basaltic Andesite ◽  
Large Scale ◽  
Middle Miocene ◽  
Tectonic Setting ◽  
Japan Sea ◽  
Contact Metamorphism ◽  
Southwest Japan ◽  
Tectonic Event ◽  
Plutonic Complex ◽  
In The Beginning

A volcano-plutonic complex in the Susa area, southwest Japan, consists of the Yamashima andesites, the Koyama gabbros and syn-plutonic porphyrite dykes derived from a common basaltic andesite magma. The complex is closely associated with middle Miocene turbidite deposits. The Yamashima andesites are composed mainly of basaltic andesite feeder dykes, massive submarine lavas with hyaloclastites, and their reworked deposits. The lavas and deposits immediately overlie turbidite deposits, indicating submarine volcanic activity. The Koyama gabbros formed hornfels by contact metamorphism of the surrounding turbidites and andesites. Highly purified clinopyroxene and plagioclase mineral separates from the Yamashima andesites were dated by a K–Ar method using an ultra-low blank K analysis procedure. Ages obtained from duplicate analyses are 16.5±1.5, 15.2±1.4, 15.8±1.7, and 16.5±2.0 Ma for clinopyroxene, and 14.2±0.8, 15.2±0.9, and 15.6±0.9 Ma for plagioclase. The clinopyroxene and plagioclase data define a mineral isochron age of 14.7±0.9 (1σ) Ma with an initial 40Ar/36Ar ratio of 297.3±2.4 (1σ), suggesting that clinopyroxene has no excess argon and can be reliably dated by K–Ar. Most of the groundmass ages are considerably younger (12.1–14.6) than the isochron age, perhaps due to argon loss during alteration. The gabbros give ages of 14.2±0.3 and 14.1±0.3 Ma for biotite, and 13.7±0.3 and 13.7±0.7 Ma for green hornblende. The porphyrite dyke yields an age of 12.5±0.3 Ma for the groundmass, and the pelitic hornfels gives a biotite age of 14.8±0.3 Ma. Our new K–Ar ages, together with previous studies, show that a series of geological events took place in the Susa area between 16 and 13 Ma. Conglomerates and sandstones were deposited in the beginning of marine transgression. Subsequent abrupt deepening led to deposition of a thick black shale unit, turbidite deposits and large-scale submarine channel-fill deposits. Coeval igneous activity formed the volcano-plutonic complex. The magmato-tectonic event was synchronous with the opening of the Japan Sea and the associated clockwise rotation of the southwest Japan arc sliver, recording a unique tectonic setting.

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