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71.
Hossein Azizi Fatemeh Nouri Robert J. Stern Marie Azizi Federico Lucci Yoshihiro Asahara 《International Geology Review》2020,62(13-14):1635-1657
ABSTRACT We address the growing controversy about the tectonic setting in which Jurassic magmatism of Iran occurred: arc or continental rift. In the Ghorveh area of the northern Sanandaj Sirjan zone (SaSZ), the Ghalayan metabasites are interlayered with marble and schist and locally cut by acidic dikes. Zircon U-Pb dating of the metabasitic rocks shows that these crystallized at ca. 145–144 Ma ago in the Late Jurassic (Tithonian). This complex was metamorphosed in the lower greenschist facies, however, some protolithic structures such as pillow lava and primary minerals are preserved. The metabasites are tholeiites with low SiO2 (45.6–50.5 wt.%), moderate Al2O3 (11.3–17.0 wt.%), and high TiO2 (0.7–2.9 wt.%) and Fe2O3 (9.4–14.1 wt.%). The Ghalayan metabasites are enriched in Light rare earth elements (LREEs) without significant Nb, Ta, Pb, Sr and Ba anomalies, similar to modern continental intra-plate tholeiitic basalts such as Afar and East African rifts. The Ghalaylan metabasites show wide ranges for 87Sr/86Sr(i) (0.7039–0.7077) and positive εNd(t) values (+0.1 to +4.6). These isotopic compositions are similar to those expected for slightly depleted subcontinental lithospheric mantle sources. Independently built discrimination diagrams indicate an intra-continental rifting regime for the source of Jurassic metabasites in the northern SaSZ. Geochemical and tectonic evidence suggests that rifting or a mantle plume was responsible for volcanic activity in the Upper Jurassic SaSZ. Considering the variation of ages of basaltic volcanism along the SaSZ, we suggest that Ghalayan basaltic magmatism reflected a submarine volcano that formed as part of the late stage continental rift, similar to Afar in the East African Rift system. Our results indicate that an extensional tectonic regime dominated SaSZ tectonics in the Middle to Late Jurassic. 相似文献
72.
Fatemeh Sarjoughian Somayeh Javadi Hossein Azizi Wenli Ling Yoshihiro Asahara David Lentz 《International Geology Review》2020,62(13-14):1769-1795
ABSTRACT Soheyle-Pakuh granitoid rocks, with a variety of quartz diorite, quartz monzodiorite, granodiorite, tonalite, and granite, have been emplaced into the Tertiary volcanic rocks in the Urumieh-Dokhtar magmatic arc in central Iran. Zircon U–Pb dating yields an age of 39.63 ± 0.93 Ma for the crystallization of this body. Whole-rock compositions show that SiO2 changes from 52.31 to 65.78 wt.% and Al2O3 varies from 15.54 to 18.24 wt.%, as well as high concentrations of large-ion lithophile elements (LILE, e.g. Cs, Rb, Ba, and K) and quite low contents of high field strength elements (HFSE, e.g. Nb, Ti, P), as expected in I-type arc granitoids formed in an active continental margin setting. Initial ratios of 87Sr/86Sr and 143Nd/144Nd exhibit ranges 0.7043–0.7047 and 0.51284 to 0.51287, respectively, with positive εNd(t) from +4.9 to +5.5 with a young TDM1 age (483–674 Ma); this tracer isotopic data suggesting that the SPG originated from juvenile basaltic crust derived from depleted mantle (~90%) with variable contributions from undepleted mantle and approximately 10% old lower crust, despite diverse processes (e.g. magma mixing and fractional crystallization) during their evolution and emplacement into a local extensional setting within the continental margin arc. The isotopic data are similar to those of other Phanerozoic granitoids of the Central Asian Orogenic Belt and corroborate melting of predominantly mantle-derived juvenile crustal protoliths and indicating extensive addition of new continental crust, during Cambrian-Neoproterozoic time, in the suprasubduction zone beneath the central Urumieh-Dokhtar magmatic arc. Generation of these types of granitoids favours a model whereby rollback and (or) break-off of a subducted slab with subsequent lithospheric extension triggered by mantle upwelling, heat advection, and underplating resulting in melting of the central UDMA mantle-derived juvenile lower continental crust in the Late Eocene. 相似文献
73.
74.
Yoshinobu Aramaki Takushi Yokoyama Yoshihiro Okaue Akira Imai Koichiro Watanabe 《Resource Geology》2005,55(3):281-284
Abstract. Silica scales containing large amounts of smectite were recently found in the pipelines for geothermal water at a geothermal power plant. To elucidate the mechanism of smectite formation, seven silica scale samples were characterized by powder X-ray diffraction, chemical analysis and 27 A1 MAS NMR. Smectite was present in samples with MgO levels above 10 wt% and Al2 O3 levels below 10 wt%. In 27 A1 MAS NMR spectra, peaks assigned to both tetrahedrally and octahedrally coordinated aluminum (Al(4) and Al(6)) were observed for Mg-rich samples, whereas a peak due to Al(4) alone appeared in Mg-poor samples. From these observation and comparison between 27 A1 MAS NMR spectra for synthesized precipitates of Al2 O3 -SiO2 containing MgO and not containing MgO, it is concluded that magnesium plays an important role in the stabilization of Al(6), and results in the formation of smectite 相似文献
75.
We investigate the initial rupture process of microearthquakes to reveal relationships between nucleation region sizes and eventual earthquake sizes. In order to obtain high quality waveform data, we installed a trigger recording system with a sampling frequency of 10 kHz at the base of a deep borehole at the Nojima Fault, Japan. We analyze waveform data of 31 events around the borehole, with seismic moment ranging from 4.2 × 109 Nm to 7.1 × 1011 Nm. We use both a circular crack model with an accelerating rupture velocity (SK model) [Sato, T., Kanamori, H., 1999. Beginning of earthquakes modeled with the Griffith's fracture criterion, Bull. Seism. Soc. Am., 89, 80-93.], which generates a slow initial phase of velocity pulse, and a circular crack model with a constant rupture velocity (SH model) [Sato, T, Hirasawa, T., 1973. Body wave spectra from propagating shear cracks, J. Phys. Earth, 21, 415-431.], which generates a ramp-like velocity pulse. Source parameters of these two models are estimated by waveform inversion of the first half cycle of the observed velocity pulse applying both a grid search and a non-linear least squares method. 14 of 31 events are never reproduced by the SH model with a constant Q operator. But SK model with a constant Q operator provides a size of the pre-existing crack, corresponding to the size of the nucleation regions, and a size of the eventual crack. We recognize that (i) the eventual seismic moment is approximately scaled as the cube of the size of pre-existing cracks, (ii) the eventual seismic moment is scaled as the cube of the size of eventual cracks, and (iii) the size of eventual cracks is roughly proportional to the size of pre-existing cracks. We, thus, conclude that the size of eventual earthquakes is controlled by the size of the nucleation regions. 相似文献
76.
Nitrate pollution of groundwater in the Yellow River delta,China 总被引:8,自引:0,他引:8
Jianyao Chen Makoto Taniguchi Guanqun Liu Kunihide Miyaoka Shin-ichi Onodera Tomochika Tokunaga Yoshihiro Fukushima 《Hydrogeology Journal》2007,15(8):1605-1614
Nitrate pollution of groundwater in the Yellow River delta, China is an important issue related not only to nitrate dispersion and health concerns but also to mass transport and interactions of groundwater, sea, and river waters in the coastal area. The spatial distribution of nitrate, nitrate sources, and nitrogen transformation processes were investigated by field surveys and geochemical methods. Nitrate occurred mainly in shallow layers and had a spatial distribution coinciding with geomorphology and land/water use. Irrigation water from the Yellow River and anthropogenic waste are two main nitrogen sources of nitrate in the delta, and both denitrification and mixing processes could take place according to characteristics identified by ionic and isotopic data. 相似文献
77.
78.
Imad Kadhim Abdulzahra Ayten Hadi Yoshihiro Asahara Hossein Azizi Koshi Yamamoto 《Chemie der Erde / Geochemistry》2018,78(2):215-227
The Shalair area, which is located in northeastern Iraq, is considered to be part of the northern Sanandaj-Sirjan Zone (SaSZ) and contains several granitoid bodies. One of these bodies, the Mishao porphyritic-granite (MG), was crystallized at 111.6?±?2.4 Ma, based on its zircon U-Pb age. Its geochemical characteristics suggest that the MG rocks are calc-alkaline, peraluminous, I-type granites with microgranular mafic enclaves. They are enriched in SiO2, Na2O, Al2O3 and Zr and depleted in MgO, Fe2O3, Nb and Ti; in contrast, the enclave sample records lower SiO2 content and higher contents of MgO and Fe2O3. These rocks show an enrichment of LREE relative to HREE, and pronounced negative Eu anomalies implying feldspar fractionation. The isotopic and geochemical characteristics of the MG samples suggest that these rocks are evolved through fractional crystallization. In the La/Nb-Nb diagram and Sm/Nd ratios, the MG rocks and the enclave samples exhibit strong evidence for crustal contamination. The MG rocks record high initial 87Sr/86Sr (0.70625–0.70740) and low 143Nd/144Nd(i) (0.51235–0.51274) ratios. These Sr-Nd isotopic data, combined with the presence of high Th/U and Rb/Sr ratios and significant depletions of Nb, Ta and Ti, show a relation of these bodies to an active continental margin regime. Based on the age and geochemical data of the MG, this study presents new information about the occurrence of Middle Cretaceous magmatic activities, which are related to the active continental margins in the SaSZ that run parallel to the Zagros Fold-Thrust Belt. 相似文献
79.
Coal fly ash (CFA) and paper waste (PW) related environmental problems and its recycling techniques have been a major challenge to society. Therefore, it is of crucial importance to develop new recycling methods for CFA and PW. This work proposes a potential new way of developing synthetic aggregates (SA) using CFA, PW, starch waste and ammonium sulfate (AS) as a granular nitrogen fertilizer medium, and their utilization as a soil amendment to improve crop production in the low productive acidic red soil of Okinawa, Japan. Three types of SA with three different nitrogen (N) percentages were produced and used to amend acidic red soil in a pot experiment for the cultivation of Komatsuna, which is also called as Japanese mustard spinach (Brassica rapa var. pervidis). SA had a low bulk density (0.58–0.62 g/cm3), high water holding capacity (0.60–0.64 kg/kg), high saturated hydraulic conductivity (2.34·10–2 cm/s), high mean weight diameter (MWD) (4.32–4.48 mm), alkaline pH (8.58–8.61), high electrical conductivity (EC) (82.18–84.35 mS/m) and high carbon (C) content (68.71–70.07 g/kg) in comparison with the acidic red soil. The trace element concentrations of the developed SA were below the maximum pollutant concentration of individual metals for land application of sewage sludge given by the US Environmental Protection Agency. Scanning electron microscopic (SEM) studies showed the higher structural surface area of SA, where round shaped CFA particles were embedded into the fibrous PW matrix. Incorporation of SA into the acidic red soil not only enhanced soil fertility but also improved the physical and chemical properties of the soil compared to soil without SA addition. SA addition to the acidic red soil significantly increased the growth and yield parameters of Komatsuna compared to soil without SA addition. 相似文献
80.
我们对日本西南部南海俯冲板块界面过渡带发生的超低频地震进行报道。由矩震级为3.1~3.5的超低频地震引起的地震波显示其卓越长周期约为20s。超低频地震活动伴随深源低频颤动和慢滑事件同时发生,并随之移动。慢地震一直被认为会增加向上倾斜的大型逆冲地震断裂带上的应力,而这3种现象的同时发生提高了人们对慢地震的探测和特性鉴定水平。 相似文献