Alkaline basaltic volcanism of the Sea of Japan and the Philippine Sea: Similar and distinct geochemical and genetic features

The results of study of the deep sources of volcanic rocks from the Sea of Japan and the Philippine Sea with continental and oceanic basements, respectively, are presented. This problem is considered with the example of alkaline volcanic rocks of the Middle Miocene to Pliocene complex of the Sea of Japan and the Eocene–Oligocene Urdaneta Plateau of the Philippine Sea. The rocks have a similar geochemistry typical of OIBs, which indicates their deep (plume) origin. The presence of the Oligocene calc-alkaline volcanic rocks, which were formed prior to the marginal sea volcanism in the Sea of Japan, however, is the main difference in volcanism of the Sea of Japan from that of the Urdaneta Plateau, and this is explained by the different basements of these seas.     

Pliocene–Holocene Alkali-Basaltoid Volcanism of the Tsushima Basin of the Sea of Japan: New Geochemical and Geodynamic Data

Oceanology - Abstract—The paper contains original data on the rock-forming and rare element compositions in the Pliocene–Holocene alkaline basaltoids of the Tsushima Basin Sea of Japan,...     

The role of volcanism in the development of the Japan,Okhotsk, and Philippine marginal seas

Newly obtained petrological and geochemical data on Late Mesozoic-Cenozoic volcanic complexes in the Japan, Okhotsk, and Philippine marginal seas of the Pacific Ocean made it possible to specify the types and characteristics of various stages of volcanism in the seas, trace the evolutionary history of the volcanic processes, and identify the geodynamic environments in which the deep-sea basins were formed, as well as to distinguish inherent features in the evolution of marginal seas in the continent-ocean transition zone in the Central Asian sector of the Pacific Ocean. These features imply that the processes that formed this zone in the region were similar. Significant differences revealed between the zones in the region were predetermined, first of all, by the different types of the Earth’s crust that was involved in the major tectonic-magmatic processes and participated in the generation of the magmatic melts.     

Miocene-pleistocene volcanism of deep-water basins of the Sea of Japan and Sea of Okhotsk

This paper reports the results of petrographic and geochemical studies of the Miocene-Pleistocene volcanic rocks that accompanied the formation of the deep-water basins of the Sea of Japan and Sea of Okhotsk. The geochemical types of these rocks, their geodynamic settings, and their derivation from different magmatic sources were determined. The marginal-sea basaltoids of the Sea of Japan are derivatives of fluid-enriched mantle (EMI), while the volcanics of the Kurile basin were generated from mantle enriched in continental crust (EMII). In spite of the different conditions of their genesis, they share some common geochemical features, in particular, their calc-alkaline signatures. These traces of the influence of sialic crust on magma generation confirm the development of the basins of both these seas on continental basement.     

Petrology of andesites from the Yamato central rise,Sea of Japan

The composition of andesites from the Yamato central submarine rise and adjacent structures (Sea of Japan) points to the presence of a Late Cretaceous shortened and Oligocene-Miocene extended calc-alkaline series. With the general similarity of mineral assemblages of andesites, they are distinct in composition of minerals, which testifies to different formation conditions. The andesites of the extended type are the products of crystallization differentiation, whereas those of the shortened type are characterized by nonequilibrium composition of minerals, which reflects the heterogeneous primary melt, the composition of which discretely varied (probably repeatedly) during crystallization.     

Geochemistry of the submarine Vityaz Ridge at the pacific slope of the Kurile island arc

This paper reports the results of geological studies at the submarine Vityaz Ridge carried out during cruises 37 and 41 on the R/V “Akademik Lavrent’ev” in 2005 and 2006. The studied area is located at the near-island trench of the slope in the central part of the Kurile island arc. Morphologically, it consists of two parts: inner volcanic arc represented by the Great Kurile Range and outer arc corresponding to the submarine Vityaz Ridge. Diverse rocks that compose the basement and sedimentary cover of the ridge were recovered by dredging. Based on K-Ar dating and geochemistry, the volcanics were divided into Paleocene, Eocene, late Oligocene, and Pliocene-Pleistocene complexes. Each of the distinguished complexes reflects the tectonomagmatic stage in the ridge evolution. The geochemical and isotope data on the volcanics indicate the contribution of ancient crustal material in magma source and, correspondingly, the formation of this structure on the continental basement. Two-stage model ages, T_DM2, vary in a wide range from zero values in the mafic rocks to 0.77 Ga in felsic varieties, pointing to the presence of Precambrian protolith in the source of the felsic rocks of the Vityaz Ridge. The Pliocene-Pleistocene volcanics are classed with the tholeiitic, calc-alkaline, and subalkaline series, which differ in alkali contents and REE fractionation. The values of (La/Sm)_N and (La/Yb)_N ratios vary from 0.74 and 0,84 in the tholeiitic varieties to 1.19 and 1.44 in the calcalkaline and 2.32 and 3.73 in the subalkaline rocks. All three varieties occur within the same volcanic edifices and were formed during differentiation of magmatic melt that were channeled along fault zones from the mantle source slightly enriched in crustal component     

Volcanism as an indicator of a depth mechanism for the formation of the Seas of Japan and Okhotsk

The results of the geochemical studies of the Late Oligocene-Pleistocene volcanic rocks that accompanied the formation of the deep-water basins of the Seas of Japan and Okhotsk are presented. These rocks have an initially mantle origin that is a derivative of a single source—spinel perodotites. They formed as a result of the partial melting of secondary plumes located in the head part of the major mantle plume. This plume rose very closely to the surface in the area of the Japanese (Central) basin, where the marginal-sea basaltoids with chemical properties of HIMU (OIB) sources were established. The continental lithosphere (the upper mantle and the crust) was involved in the magma formation in the area of the Kuril basin and the Vityaz Ridge at the earliest rifting stage in the Late Oligocene-Early Miocene and at the final stage in the Pliocene-Pleistocene.     

Geology and volcanism of the underwater Vityaz Ridge (Pacific slope of the Kuril Island Arc)

This paper presents the results of geological studies carried out during the two marine expeditions of the R/V Akademik M.A. Lavrent’ev (cruises 37 and 41) in 2005 and 2006 at the underwater Vityaz Ridge. Dredging has yielded various rocks from the basement and sedimentary cover of the ridge within the limits of three polygons. On the basis of the radioisotope age determinations, petrochemical, and paleontological data, all the rocks have been subdivided into the following complexes: the volcanic ones include the Paleocene, Eocene, Late Oligocene, Middle Miocene, and Pliocene-Pleistocene; the volcanogenic-sedimentary ones include the Late Cretaceous-Early Paleocene, Paleogene undifferentiated, Oligocene-Early Miocene, and Pliocene-Pleistocene. The determination of the age and chemical composition of the rocks has enabled us to specify the formation conditions of the extracted complexes and to trace the geological evolution of the Vityaz Ridge. The presence of young Pliocene-Pleistocene volcanites allows one to come to a conclusion about the modern tectono-magmatic activity of the central part of the Pacific slope of the Kuril Islands.     

Large‐scale regional delineation of riparian vegetation in the arid and semi‐arid Pilbara region,WA

Multiscene Landsat 5 TM imagery, Principal Component Analysis, and the Normalized Difference Vegetation Index were used to produce the first region‐scale map of riparian vegetation for the Pilbara (230,000 km²), Western Australia. Riparian vegetation is an environmentally important habitat in the arid and desert climate of the Pilbara. These habitats are supported by infrequent flow events and in some locations by groundwater discharge. Our analysis suggests that riparian vegetation covers less than 4% of the Pilbara region, whereas almost 10.5% of this area is composed of groundwater dependent vegetation (GDV). GDV is often associated with open water (river pools), providing refugia for a variety of species. GDV has an extremely high ecological value and are often important Indigenous sites. This paper demonstrates how Landsat data calibrated to Top of Atmosphere reflectance can be used to delineate riparian vegetation across 16 Landsat scenes and two Universal Transverse Mercator spatial zones. The proposed method is able to delineate riparian vegetation and GDV, without the need for Bidirectional Reflectance Distribution Function correction. Results were validated using ground truth data from local and regional scale vegetation surveys.     

Delineation of riparian vegetation from Landsat multi‐temporal imagery using PCA

A deficiency in crucial digital data, such as vegetation cover, in remote regions is a challenging issue for water management and planning, especially for areas undergoing rapid development, such as mining in the Pilbara, Western Australia. This is particularly relevant to riparian vegetation, which provides important ecological services and, as such, requires regional protection. The objective of this research was to develop an approach to riparian vegetation mapping at a regional scale using remotely sensed data. The proposed method was based on principal component analysis applied to multi‐temporal Normalized Difference Vegetation Index datasets derived from Landsat TM 5 imagery. To delimit the spatial extent of riparian vegetation, a thresholding method was required and various thresholding algorithms were tested. The accuracy of results was estimated for various Normalized Difference Vegetation Index multi‐temporal datasets using available ground‐truth data. The combination of a 14‐dry‐date dataset and Kittler's thresholding method provided the most accurate delineation of riparian vegetation.