scholarly journals Pliocene adakite-like accent of andesites and dacites from the Orlov volcanic field (Sakhalin Island)

2021 ◽  
Vol 5 (3) ◽  
pp. 255-274
Author(s):  
S.V. Rasskazov ◽  
◽  
A.V. Rybin ◽  
A.V. Degterev ◽  
I.S. Chuvashova ◽  
...  
Keyword(s):  
Middle Miocene ◽  
Japan Sea ◽  
Volcanic Field ◽  
Sakhalin Island ◽  
Aleutian Island ◽  
Back Side ◽  
Geological Environment ◽  
Structural Reorganization ◽  
The One ◽  
Thin Crust

Adakite-like geochemical signature (high Sr/Y ratio at a low Y concentration) is recognized in andesites and dacites, associated with intraplate basalts in the Orlov volcanic field of Sakhalin Island. These rocks denote the final (Pliocene) accent of intraplate volcanism in the Lesogorsk zone, which began in the Middle Miocene in an area of its junction with the Chekhov zone of the preceded (Oligocene-Early Miocene) suprasubduction one. The adakite-like accent was related to the Sakhalin folding phase that accompanied the general structural reorganization in the back-side region in the Japan arc system. Such a geological environment differed from the one of classical adakites generation resulted from melting of a young slab in the Aleutian island arc. It is supposed, that the Sakhalin adakite-like magmas were produced in deep-seated sources of the crust-mantle transition displayed in the Sakhalin-Hokkaido-Japan Sea zone of hot transtension due to drastic change of tectonic deformations from the thin crust of the South Tatar Basin to the thicker one of its northeastern extremity.

scholarly journals Seasonal variation of phycoerythrin chromophores of Synechococcus spp. in the East Sea/Japan Sea

2019 ◽  
Vol 1 (1) ◽  
pp. 6
Author(s):  
Defri Yona ◽  
Mi Ok Park
Keyword(s):  
Seasonal Variation ◽  
Environmental Factors ◽  
High Salinity ◽  
Japan Sea ◽  
Water Clarity ◽  
High Light Intensity ◽  
East Sea ◽  
Seasonal Patterns ◽  
Distributional Pattern ◽  
The One

The very small size of Synechococcus spp. as one important contributor of ocean primary productivity can be identified using its phycoerythrin pigment chromophores, phycourobilin (PUB) and phycoerythrobilin (PEB). Seasonal variation of the excitation (EX) ratio of PUB and PEB in the surface water of East Sea/Japan Sea was observed. This study aimed to describe the effects of environmental factors during different season to the excitation ratio of PUB and PEB contained Synechococcus spp.  Summer and winter showed slightly similar distributional pattern with PUBEX:PEBEX ratio > 1, while PUBEX:PEBEX ratio < 1 could be found in autumn and spring. The results of this study showed seasonal patterns of phycoerythrin pigment from Synechococcus were highly related with variability of environmental factors. High light intensity during summer and high salinity during winter were the reasons of high PUB:PEB ratio of Synechococcus spp. Moreover, high PUB type of Synechococcus spp. was also dominated the offshore study areas as the result of higher water clarity compared to the one in the coastal areas.

scholarly journals Chemo-Stratigraphy, Petrology and U-Pb Geochronology of Karakılıçlı Volcanic Field in NW Anatolia: Implications for Hellenic Subduction System

2020 ◽  
Author(s):  
Ali İskenderoğlu ◽  
NAMIK AYSAL
Keyword(s):  
Middle Miocene ◽  
Magma Mixing ◽  
Volcanic Field ◽  
Western Anatolia ◽  
Exact Nature ◽  
Magma Chambers ◽  
Precision Data ◽  
High Precision Data ◽  
Subduction System ◽  
Roll Back

Western Anatolia comprises a vast amount of various volcanic successions spanning from Eocene to Upper Miocene periods. These units mainly display southward younging in broad sense and display large amounts of chemical variation that spanned from basalt to rhyolite. The southward younging of magmatism and chemical variations have been largely attributed to the retreat and roll-back of the Hellenic slab and the western escape of the Anatolian microplate. However, there is still a lack of high precision data to pinpoint the exact nature of the magmatism and lithospheric tectonics. In this contribution we investigated a poorly known region along the Western Anatolia along Manisa district called Karakılı&ccedil;lı volcanic field. We investigated two different volcanic sections (Kalpakkaya and &Ccedil;amlık hill) that display the best volcano-sedimentary features in terms of geochronology and geochemistry. Samples acquired from the bottom, middle and upper portions of these sections display Early-Middle Miocene ages of 17.64&plusmn;0.20, 17.22&plusmn;0.15, 16.16&plusmn;0.17 and 16.36&plusmn;0.13, 15.79&plusmn;0.71 and 13.61&plusmn;0.20 Ma respectively. The results indicate that the volcanism in the region generated by the melting of the mantle and/or lithospheric mantle by slab retreat and roll-back of the Hellenic slab and evolved in the shallow magma chambers/mushes by fractional crystallization, magma mixing and crustal assimilation.

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.

The evolution of the Eagle Peak volcano — a distinctive phase of middle miocene volcanism in the western Mogollon-Datil volcanic field, New Mexico

1995 ◽  
Vol 69 (3-4) ◽  
pp. 159-186 ◽  
Author(s):  
Dana J. Bove ◽  
James C. Ratté ◽  
William C. McIntosh ◽  
Lawrence W. Snee ◽  
Kiyoto Futa
Keyword(s):  
New Mexico ◽  
Middle Miocene ◽  
Volcanic Field

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.

scholarly journals Badenian (middle Miocene) continental paleoenvironment in the Novohrad–Nógrád Basin (Central Paratethys): a volcano-sedimentary record from the Páris-patak Valley in Hungary

2021 ◽  
Vol 151 (2) ◽  
pp. 159
Author(s):  
Emese M. Bordy ◽  
Orsolya Sztanó
Keyword(s):  
Grain Size ◽  
Middle Miocene ◽  
River System ◽  
High Energy ◽  
Volcanic Field ◽  
Bedload Transport ◽  
Coarse Grained ◽  
Facies Association ◽  
Cross Bedding ◽  
Facies Associations

Two levels of volcaniclastics, comprising conglomerates, sandstones and mudstones, are interbedded with upper middle Miocene (upper Badenian) andesite pyroclastics near the Hungarian-Slovakian border in the distal region of the Central Slovakian Neogene Volcanic Field. Based on the field sedimentological investigations, the facies of the volcaniclastics (e.g., lateral and vertical grain size changes, sedimentary structures, textures, clast composition), their geometry and field relationships are documented herein with the aim of reconstructing the depositional environment. The silica-cemented volcaniclastics are mostly andesite clasts with only ~ 5% being granitoid, quarzitic, and tuff clasts as well as charred fossil wood fragments. The coarse-grained facies association includes crudely stratified, tabular or lenticular, clast-supported pebble-cobble conglomerates with erosive basal surfaces, b-axis imbrication, alternating with sets of cross-bedding. The fine-grained facies association comprises cross-bedded pebbly to medium-grained sandstone and lenses of tuffaceous clayey siltstone with rare horizontal lamination and water-escape structures. Rip-up mudstone clasts, with diametre up to 1 m, are present in both facies associations, revealing the co-existence of abandoned silty palaeo-channel plugs. Facies associations are arranged in several 0.5-4-m-thick, fining-upwards successions that likely formed in shallow channels as downstream- to laterally accreting longitudinal bars, extensive gravel sheets and bars that migrated in peak flow during floods. Palaeocurrent indicators (i.e., clast imbrication, direction of planar cross-bedding, orientation of petrified wood logs) show bedload transport by traction currents, initially towards ~S, and later towards ~W. Intermittently debris flows also occurred. Cross-bedded sandstones formed as in-channel transverse bars during medium/low discharge. Variation of grain size shows frequent discharge fluctuations during permanently wet conditions in the late Badenian. The 4-5-m-deep, low-sinuosity channels were part of a high-energy, gravel-bed braided-river system on the south-eastern foothills of the Lysec palaeo-volcano. Here, pyroclastics were reworked and redeposited as volcaniclastics during inter-eruption, high-discharge episodes.

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