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11.
Landry Soh Tamehe Chongtao Wei Sylvestre Ganno Carlos Alberto Rosiere Jean Paul Nzenti Chesther Gatse Ebotehouna Guanwen Lu 《地学前缘(英文版)》2021,12(2):549-572
The discovery of the Gouap banded iron formations(BIFs)-hosted iron mineralization in the northwestern of the Nyong Group(Ntem Complex)in southwestern Cameroon provides unique insights into the geology of this region.In this contribution,we firstly report detailed study of geochemistry,isotopic and geochronology of well preserved samples of the Gouap BIFs collected from diamond drillcores.The Gouap BIFs consist mainly of amphibole BIFs and amphibole-pyrite BIFs characterized by dominant Fe2O3+SiO2contents and variable contents of CaO,MgO and SO3,consistent with the presence of amphibole,chlorite,epidote and pyrite,formed during amphibolite facies metamorphism and overprinted hydrothermal event.The amphibole–pyrite BIFs are typically enriched in trace and rare earth elements(REE)compared to the amphibole BIFs,suggesting the influence of detrital materials as well as secondary hydrothermal alteration.The Post Archean Australian Shale(PAAS)-normalized REE–Y profiles of the Gouap BIFs display positive La,Eu anomalies,weak negative Ce anomalies,indicating a mixture of low-temperature hydrothermal fluids and relatively oxic conditions probably under relative shallow seawater.We present here the first isotopic data of BIFs within the Ntem Complex.Theδ30SiNBS28values of the quartz from the Gouap BIFs vary from-1.5‰to-0.3‰and from-0.8‰to-0.9‰for the amphibole BIFs and amphibole–pyrite BIFs,respectively.The quartz hasδ18OV-SMOW values of 6.8‰–9.5‰(amphibole BIFs)and 9.2‰–10.6‰(amphibole–pyrite BIFs).The magnetite from the Gouap BIFs showsδ18O values ranging from-3.5‰to-1.8‰and from-3‰to-1.7‰for the amphibole BIFs and amphibole–pyrite BIFs,respectively.Moreover,the pyrite grains in the amphibole–pyrite BIFs displayδ34S values of 1.1‰–1.8‰.All isotopic data of the Gouap BIFs confirm that they might have precipitated from low-temperature hydrothermal fluids with detrital input distant from the volcanic activity.According to their geochemical and isotopic characteristics,we propose that the Gouap BIFs belong to the Superior type.In situ U–Pb zircon dating of BIFs was conducted to assess the BIF depositional age based on strong evidence of zircon in thin section.The Gouap BIFs were probably deposited at 2422±50 Ma in a region where sediments extended from continental shelf to deep-water environments along craton margins like the Caue Formation of the Minas Supergroup,Brazil.The studied BIFs have experienced regional hydrothermal activity and metamorphism at 2089±8.3 Ma during the Eburnean–Transamazonian orogeny.These findings suggest a physical continuity between the protocratonic masses of both Sao Francisco and Congo continents in the Rhyacian Period. 相似文献
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Wonn Soh 《Progress in Oceanography》2003,57(1):109-124
Sagami Bay is a deep-water foreland basin with an average sedimentary rate of approximately 0.1 g/cm2/year. It is an appropriate area to study for better understanding of sedimentary processes in a setting with a high sedimentation rate. Seven multiple core samples, 30-50 cm thick, were obtained from Sagami Bay. Four of the core samples were taken from the Tokyo submarine fan system (Tokyo canyon floor, Tokyo fan valley and its levee, the distal fan margin). Two samples were obtained from the Sakawa fan delta and the adjacent topographic high. The remaining one was from an escarpment of the Sagami submarine fault. Variations in chemical composition can be recognized at every coring site. They show two different sediment sources: the sediments of the Tokyo submarine fan system and those from Sakawa fan delta. Further, there are differences in chemical composition between canyon floor and levees even within the Tokyo submarine fan system. The results suggest that the sedimentary process is strongly controlled not by vertical particle settling but by a hyperpycnal flow process. The proxies obtained from the core samples do not reflect conditions in the water column immediately overlying the sea floor. Rather, they are controlled by conditions on the adjacent continental shelf or/and shallow basins, which are the areas of primary accumulation. 相似文献
13.
Hiroshi Kitazato Takeshi NakatsukaMotohiro Shimanaga Jota KandaWonn Soh Yoshihisa KatoYoshihiro Okada Akio YamaokaToshiyuki Masuzawa Koji SuzukiYoshihisa Shirayama 《Progress in Oceanography》2003,57(1):3-16
Deep-sea benthic ecosystems are mainly sustained by sinking organic materials that are produced in the euphotic zone. “Benthic-pelagic coupling” is the key to understanding both material cycles and benthic ecology in deep-sea environments, in particular in topographically flat open oceanic settings. However, it remains unclear whether “benthic-pelagic coupling” exists in eutrophic deep-sea environments at the ocean margins where areas of undulating and steep bottom topography are partly closely surrounded by land. Land-locked deep-sea settings may be characterized by different particle behaviors both in the water column and in relation to submarine topography. Mechanisms of particle accumulation may be different from those found in open ocean sedimentary systems. An interdisciplinary programme, “Project Sagami”, was carried out to understand seasonal carbon cycling in a eutrophic deep-sea environment (Sagami Bay) with steep bottom topography along the western margin of the Pacific, off central Japan. We collected data from ocean color photographs obtained using a sea observation satellite, surface water samples, hydrographic casts with turbidity sensor, sediment trap moorings and multiple core samplings at a permanent station in the central part of Sagami Bay between 1997 and 1998. Bottom nepheloid layers were also observed in video images recorded at a real-time, sea-floor observatory off Hatsushima in Sagami Bay. Distinct spring blooms were observed during mid-February through May in 1997. Mass flux deposited in sediment traps did not show a distinct spring bloom signal because of the influence of resuspended materials. However, dense clouds of suspended particles were observed only in the spring in the benthic nepheloid layer. This phenomenon corresponds well to the increased deposition of phytodetritus after the spring bloom. A phytodetrital layer started to form on the sediment surface about two weeks after the start of the spring bloom. Chlorophyll-a was detected in the top 2 cm of the sediment only when a phytodetritus layer was present. Protozoan and metazoan meiobenthos increased in density after phytodetritus deposition. Thus, “benthic-pelagic coupling” was certainly observed even in a marginal ocean environment with undulated bottom topography. Seasonal changes in features of the sediment-water interface were also documented. 相似文献
14.
Jina Oh Sung Kim Choong-Gon Kim Ho Young Soh Dawa Jeong Youn-Ho Lee 《Ocean Science Journal》2006,41(1):53-57
A specimen ofAetobatus flagellum was collected at Uljin in June 2005 for the first time in Korea. This specimen is characterized by the cephalic fin, the
long snout, the dorsal fin between pelvic fins, spiracles on the dorsal side of the disc, the deeply notched nasal curtain
and the one row of the teeth in the lower and the upper jaws. And unlikeAetobatus narinari, it does not have any spots on the its dorsal side of the disc. We report this specimen as the first record from Korea and
name it ‘Bak-jui-ga-o-ri’ in Korean. 相似文献
15.
Hideki Mukoyoshi Tetsuro Hirono Hidetoshi Hara Kotaro Sekine Noriyoshi Tsuchiya Arito Sakaguchi Wonn Soh 《Island Arc》2009,18(2):333-351
To understand the characteristics of deformation of an out-of-sequence thrust (OST) and the style of fluid flow along it, we investigated the Nobeoka Tectonic Line, which has been interpreted as a deep OST (7–9 km), in the Shimanto accretionary complex, Southwest Japan. The shear zone in the footwall differs significantly in the along-strike direction not only in thickness, which varied from 100 to 300 m, but also in lithology and mineral vein development. These variations might reflect primarily differences in lithology; that is, the sandstone-dominant shear zone with a large amount of mineral veins precipitated in microcracks is relatively thick, whereas the shale-dominant shear zone with a small amount of veins and with textures indicating highly pressurized pore fluid, is thinner. By comparison with characteristics of a shallow OST (3–5 km), we conclude that the shallow OST has experienced repeated brittle failure with rapid slip and focused fluid flow whereas the deep OST has experienced both brittle and ductile deformation, followed by fluid flow of various styles, depending on the lithology. 相似文献
16.
Shin Hyeon Ho Li Zhun Seo Min Ho Soh Ho Young Lim Weol Ae Park Jong Woo 《Ocean Science Journal》2019,54(4):685-691
Ocean Science Journal - There have been controversies regarding the taxonomy of Prorocentrum donghaiense, however Zhang et al. (2016) recently developed a probe with a quantitative real-time PCR... 相似文献
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Abstract
Oncaea venusta Philippi, 1843 has been known as having some different size groups, but recent genetic study for cyt b and ITS 1 (Elverset al. 2006) suggests that these size groups can be considered as different species. Of these size groups, the largestO. venusta Philippi and the smallestO. venella Farran, 1929 were first described in Korean waters. The latter is easily distinguishable from the former in the following
characteristics in addition to its small size: (1) length to width ratio of genital double somite of two genders smaller,
and (2) female second pediger bearing inconspicuous dorso-posterior swelling.Oncaea venusta andO. venella co-occur in Korean waters during spring to fall, but their occurrence patterns seasonally differ: the former shows higher
density in fall while the latter does in summer. 相似文献
19.
Although structural mechanical impedance is a direct representation of the structural parameters, its measurement is difficult at high frequencies owing to practical considerations. This paper presents a new method of damage diagnosis by means of changes in the structural mechanical impedance at high frequencies. The mechanical impedance is extracted from the electro‐mechanical admittance signatures of piezoelectric‐ceramic (PZT) patches surface bonded to the structure using the electro‐mechanical impedance (EMI) technique. The main feature of the newly developed approach is that both the real as well as the imaginary component of the admittance signature is used in damage quantification. A complex damage metric is proposed to quantify damage parametrically based on the extracted structural parameters, i.e. the equivalent single degree of freedom (SDOF) stiffness, the mass, and the damping associated with the drive point of the PZT patch. The proposed scheme eliminates the need for any a priori information about the phenomenological nature of the structure or any ‘model’ of the structural system. As proof of concept, the paper reports a damage diagnosis study conducted on a model reinforced concrete (RC) frame subjected to base vibrations on a shaking table. The proposed methodology was found to perform better than the existing damage quantification approaches, i.e. the low‐frequency vibration methods as well as the traditional raw‐signature based damage quantification in the EMI technique. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
20.
Yu'suke?KuboEmail author Wonn?Soh Hideaki?Machiyama Hidekazu?Tokuyama 《Geo-Marine Letters》2004,24(1):1-7
Current-generated bedforms were found on sandy seafloor at water depths of 200–400 m on the northern Izu Ridge, where the Kuroshio Current encounters and passes over the ridge. The observed bedforms include large dunes and sand ribbons and are interpreted to be products of present-day oceanographic conditions and to indicate intensive flow activity controlled by local topography. A comparison between the surface flow velocity estimated from empirical relationships for dune formation and the observed flow velocity suggests that the dunes are generated when the main axis of the meandering Kuroshio Current passes through this area, and that subsequent current velocities are sufficiently high to maintain the dunes up to the next event. 相似文献