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1.
Shikui Zhai Kun Guo Tong Zong Zenghui Yu Shujie Wang Zongwei Cai Xia Zhang 《中国海洋大学学报(英文版)》2017,16(2):233-242
Pumice, the most widely distributed volcanic rock in Okinawa Trough, is loose and porous. Since its formation, it has definitely suffered from the denudation of the sea to different degrees. In order to truly reveal the geochemical features of pumice, we choose the method of mineral separation. Firstly, the phenocryst is separated from glass. Then the phenocryst is divided into light and heavy mineral compositions. By ICP-MS (inductively coupled plasma mass spectrometry) analytical technology, the contents of trace and rare earth elements in the whole pumice, the glass and the heavy and light mineral compositions are determined respectively. By researching the elemental geochemical features, the magma dynamic processes are found. It shows that the initial magma for the pumice in Okinawa Trough came from the depleted mantle, from which the N-MORB (normal type of mid-ocean ridge basalt) is formed, homologous with the local basalts. But they are formed in different periods of magma crystal fractionation. Featured with sufficient crystal fractionation for pumice, it is found that the earlier crystallizing minerals are olivine, plagioclase and pyroxene. The pumice magma, formed from the depleted mantle, was mixed with additional subduction-related materials (components), and contaminated with the mass from upper crust when it rose up into the crust. As the Okinawa Trough is a back-arc basin in its early back-arc spreading stage, its magmatism has a series of its own unique characteristics, different from not only the mid-ocean ridge expansion, but also the mature back-arc basin. 相似文献
2.
李乃胜 《中国海洋湖沼学报》2001,19(3):255-264
The Okinawa Trough is a very active tectonic zone at the margin of the Northwest Pacific and is typical of back-arc rifting at the young stage of tectonic evolution. Many scientists from Japan,China, Germany, France, the U. S.A. and Russia have done a lot of geologic and geophysical investigations there. It is well known that the Okinawa Trough is an active back-arc rift with extremely high heat flow, very strong hydrothermal circulation, strong volcanic and magmatic activity, frequent earthquakes,rapid subsidence and rifting, well-developed fault and central graben. But up to now, there are still some important tectonic problems about the Okinawa Trough that require clarification on some aspects such as the type of its crust, its forming time, its tectonic evolution, the distribution of its central grabens, the relationship between its high heat flow and tectonic activity. Based on the data obtained from seismic sur-vey, geomagnetic and gravity measurements, submarine sampling and heat flow measurements in the last 15 years, the author discusses the following tectonic problems about the Okinawa Trough: (1) If the Okinawa Trough develops oceanic crust or not. (2) Is the South Okinawa Trough tectonically more active than the North Okinawa Trough with shallower water and few investigation data on it. (3) The formation time of the Okinawa Trough and its tectonic evolution. The Okinawa Trough has a very thin continental crust. Up to now, there is no evidence of oceanic crust in the Okinawa Trough. The North, Middle and South Okinawa Trough are all very strongly active areas. From 6 Ma B.P. , the Okinawa Trough began to form. Since 2 Ma, the Okinawa Trough has been very active. 相似文献
3.
This article presents the evidence in support of the direct magma degassing as the principal mechanism of volatiles releasing
into the hydrothermal fluids in the Okinawa Trough, as contrasted to the argument for the hydrothermal stripping of volatiles
from the volcanic rocks.
Laser Raman microprobe and stepped-heating techniques are employed to determine the compositions and contents of the volatiles
in pumices in the middle Okinawa Trough. The results show that the volatiles are similar to the gases in the hydrothermal
fluids and hydrothermal minerals in composition, the mean percent content of each component and variation trend. This indicates
the direct influence of magma degassing on the hydrothermal fluid. In addition, the contents of volatiles in pumices are rather
low and do not support the hydrothermal stripping as the main mechanism to enrich the fluids with gases. The results are consistent
with the idea that the direct magma degassing is more important than hydrothermal stripping in supplying gases to the hydrothermal
fluids in the Okinawa Trough. 相似文献
4.
The tectonics beneath the Okinawa Trough 总被引：1，自引：0，他引：1
Jin Xianglong 《中国海洋湖沼学报》1984,2(1):73-80
The nature of the crust of the Okinawa Trough is different from that of the continental shelf in the East China Sea. The crust
beneath the Trough is in transformation from continental to oceanic and the depth of MOHO in the northern section of the Trough
is deeper than in the southern section. Thick sedimentary strata of Neogene and Pleistocene ages are deposited in the Okinawa
Trough, and divided into three layers: the upper horizontal layer, the middle layer lightly folded and the lower deformed
layer. They were formed in Pleistocene, Pliocene, and Miocene to Paleogene, respectively. The tectonic movement in the southern
section is stronger than that in the northern section. Some volcanic seamounts appear on the bottom of the Trough. On both
slopes of the Trough are developed many normal faults and the intrusive igneous rocks. The Okinawa Trough, the back-arc basin,
is an embryonic marginal basin in rifting and spreading. The formation of the Okinawa Trough started in the early Pliocene.
The transformation of crust and the growth of the Trough progressed from the southern to the northern section. The southern
section is a true trough in tectonic sense.
Contribution No. 986 from the Institute of Oceanology, Academia Sinica.
The paper was presented in the PS-11 of IAPSO Symposium, 18th General Assembly IUGG, Hamburg, 22 August 1983. 相似文献
5.
To investigate the relationship between volcanic activity and sediment record on regional and temporal scales,158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT),and two cores recovered in the northern and southern OT,respectively.Mineralogy,grain-size,and geochemical analyses of those samples show that:1) volcanic glass,volcanic-type pyroxene,hypersthenes,and magnetite increase in sediment influenced by volcanic activity;2) sediment grain sizes (and... 相似文献
6.
7.
Zuxing Chen Zhigang Zeng Xiaoyuan Wang Yuxiang Zhang Xuebo Yin Shuai Chen Yao Ma Xiaohui Li Hanyan Qi 《中国海洋大学学报(英文版)》2017,16(6):1097-1108
To reveal the petrogenesis of rhyolite from the southwestern Okinawa Trough, the mineral chemistry of plagioclase, orthopyroxene, amphibole, quartz and Fe-Ti oxide phenocrysts were analyzed using an electron microprobe, and in suit Sr and Ba contents of plagioclase analysed by LA-ICPMS were chosen for fingerprinting plagioclases of different provenances. Results indicate an overall homogeneous composition for each of the mineral phases except for plagioclase phenocrysts which have a wide range of composition(An=39~88). Plagioclase crystals characterized by An contents of 70 are not in equilibrium with their whole-rock compositions, and coarse-sieved plagioclase phenocryst interiors record high An contents(70) and Sr/Ba ratios(7), which are similar to the those of plagioclase crystals in basalt. Therefore, these crystals must have been introduced to the rhyolitic magma from a more mafic source. Equilibrium temperatures estimated using orthopyroxene-liquid, iron–titanium oxide, titanium-in-quartz and amphibole geothermometers show consistent values ranging from 792 to 869℃. The equilibrium pressure calculated using amphibole compositions is close to 121 MPa which corresponds to an approximate depth of 4 km. The fO_2 conditions estimated from Fe-Ti oxides and amphiboles plot slightly above the NNO buffer, which indicates that the rock formed under more oxidized conditions. Our results suggests that petrogenesis of the rhyolite due to basaltic magma ascend with the high An and Sr/Ba plaigoclases from deep magma chamber into the shallow chamber where the fractional crystallization and crustal assimilation happened. It also indicates that a two-layer magma chamber structure may occur under the southwestern Okinawa Trough. 相似文献
8.
The Ryukyu trench-arc system can be divided into two types according to its subduction model. The normal subduction in the
northern part of the Philippine Sea plate creates a hinge sedimentary wedge with large deformation at the collision front,
while the oblique subduction in the southern part gives rise to a smaller accretion with small deformation than that in the
northern part. The mechanisms that cause distinction between these two types have been analysed and calculated by using gravity
data based on the lithosphere rheology and the stress state of the lithosphere in the subduction boundary. The two types of
subduction model are associated with the internal extension in the southern Okinawa Trough and the small extension in the
northern part. The difference of the stress state between the two types of subduction model is also manifested in other tectonic
features, such as topography, volcanic activity and crust movement. Modeling bathymetric and gravity data from this area suggests
that the oblique subduction of low angle, together with smooth geometry of the overlying plate crust, results in small stress
released on the south of the trench by the subduction plate. The intraplate faults in the southern Okinawa Trough behind the
trench stand in surplus intensive stress. On the other hand, the normal subduction of high angle, together with strong undulation
geometry of the overlying crust, results in more intensive stress released in the northern Ryukyu Trench than that in the
south. The intraplate faults in the northern Okinawa Trough behind the northern Ryukyu Trench stand in small stress. 相似文献
9.
通过邹平火山岩盆地不同岩石类型岩石化学特征的对比分析:认为火山活动总的趋势是由弱到强,爆发指数为38—68—92;火山岩3个亚组SI值均<40,表明母岩浆可能是由幔源岩浆经分异演化或同化而形成的;侵入岩σ介于2.39～4.99,属钙碱性-碱性岩系;DI为65.15～88.98,岩浆分异演化程度相对较高;A/NKC为0.96～1.02,岩石为弱过铝质。该区岩浆岩属壳幔型中性岩—壳幔型和铝质地壳过渡区中酸性岩—酸性岩的岩浆岩区。铜多金属对构造-岩浆事件的响应可描述为:长期继承性活动的区域性构造和振荡性的岩浆侵入活动,致使富碱质岩浆热液与已结晶的二长质岩石在地球化学界面发生交代蚀变,并进行了物质交换。 相似文献
10.
11.
Characteristics and tectonic setting of volcanic rocks in Early Cretaceous Baiyingaolao Formation of Keyouzhongqi area，Inner Mongolia 总被引：1，自引：0，他引：1
The authors studied zircon LA-ICP-MS U-Pb dating,the zircon Hf isotope and geochemistry of acidic volcanic rocks in Baiyingaolao Formation of Keyouzhongqi area,Inner Mongolia,and discussed the chronology, source region and tectonic setting of the volcanic rocks in the studied area． The clear oscillatory zoning of zir- cons indicates a typical magmatic origin,and the results of dating show that the volcanic rocks of Baiyingaolao Formation were formed in Early Cretaceous (121.5 ±1.0 Ma)． The features of major and trace elements show that the rocks are alkali-rich,poor in calcium and magnesium with enrichment in LILEs like Th,U,K and Gd and depletion in HFSEs,e.g. Nb,Ta,Sr and Ti． The fact implies that they were the products of partial melting of the crust． εHf(t) = ( +6.30--+9.06) and TDM2=600--835 Ma,suggest the magma originated from par- tial melting of the young crust． Combined with the evolution of regional tectonic structure,the authors conclude that the acidic volcanic rocks of Baiyingaolao Formation may be formed under the extensional environment relat- ed to the subduction of Paleo-Pacific Plate． 相似文献
12.
1 INTRODUCTIONA large-scale volcanic eruption can injectenormous amount of ash and dust into the atmos-phere, leading to local and short cooling due toshielding incoming radiation. During the past 2 to 3decades, accumulated evidence indicated thatlarge-scale volcano eruptions or series of volcanicactivity appears to coincide with climatologicaltransitions. For example, Robock (1979) indicatedthat volcanic eruptions played a role in forcing "Lit-tle Ice Age". Well-dated high-resolution co… 相似文献
13.
To investigate the relationship between volcanic activity and sediment record on regional and temporal scales, 158 surface
sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT), and two cores recovered
in the northern and southern OT, respectively. Mineralogy, grain-size, and geochemical analyses of those samples show that:
1) volcanic glass, volcanic-type pyroxene, hypersthenes, and magnetite increase in sediment influenced by volcanic activity;
2) sediment grain sizes (and also silt content) increase in ash layers; and 3) the contents of Na2O and Zr are higher, while terrigenous elements, e.g., TFe2O3 and K2O, and biogenous compositions, e.g., CaO and Sr, are relatively lower in ash layers than those of non-ash layers. The distribution
of volcanic ash has three distinguishing characteristics: 1) volcanic ash is more abundant in the northern and central OT
than the southern OT; 2) volcanic ash increases from continental shelf to the trough; 3) the sediment during the last 12 000
a suggests stronger volcanic events than during 15 000–12 000 a. The eruptive locations, frequency, and volume of calderas
are among the most important factors controlling the distributions of volcanic ash. In addition, the main Kuroshio warm current
that extends northward probably impeded the diffusion of volcanic ash to the west and south in the OT. However, a southward
current probably carried some volcanic ash toward southern OT. 相似文献
14.
《中国海洋湖沼学报》2021,(3)
Deep-sea sediments are now recognized as a home for rich and largely microbial community. Recently, it has been believed in an increasing number of studies that bacteria could be abundant in deepsea sediments of many types; however, fungi in deep-sea sediments remain relatively unknown. The phylogenetic diversity and bioactivity of culturable deep-sea-derived fungi from Okinawa Trough sediments were investigated in traditional method combined with fungal identification of molecular biology in this study. A total of 76 isolates belonged to 15 fungal taxa were recovered in a harsh condition of low nutrient and low temperature, indicating that the fungal communities in deep-sea sediments from Okinawa Trough were relatively abundant and diversified. Aspergillus, Cladosporium, and Penicillium were the dominant fungal genera, while Mycosphaerella, Purpureocillium, and Schizophyllum were relatively rare in the deep-sea sediments from Okinawa Trough. Among the six genera recovered, Mycosphaerella was firstly recovered from deep-sea sediments in this study. Moreover, about 75% of the extracts from the 15 fungal representative isolates displayed distinct bioactivity against at least one indicator bacterium or marine macrofouler, emphasizing the potentials of these deep-sea-derived fungi from Okinawa Trough as producers of bioactive metabolites. Notably, isolates Cladosporium oxysporum SCSIO z001 and Penicillium citrinum SCSIO z049 displayed a wide spectrum of bioactivities, isolates Cladosporium cladosporioides SCSIO z015, Cladosporium sphaerospermum SCSIO z030, and Penicillium verruculosum SCSIO z007 exhibited a strong anti-bacterial-growth activity, and isolate Penicillium chrysogenum SCSIO z062 displayed a strong anti-larval-settlement activity. These results suggest that these isolates deserved further study as potential sources of novel bioactive metabolites. 相似文献
15.
该文在野外地质调查基础上,对备战铁矿区内的火山岩和矿石进行了详细的矿物学和岩石地球化学研究,并深入讨论了矿床成因。研究表明,该区的主要赋矿围岩为火山岛弧玄武岩,其与磁铁矿有着类似的稀土元素配分模式,说明二者有成因上的联系。成矿物质可能来源于北天山洋块向伊犁板块之下俯冲过程中软流圈上涌形成的富铁玄武质岩浆。受洋块俯冲作用影响,富铁玄武质岩浆沿北天山压扭性深大断裂底侵,并经历了一定的结晶分离或同化混染作用,最后在中地壳形成一套演化的玄武质(安山质)岩浆,并在岩浆晚期阶段发生富铁岩浆和硅酸盐岩浆的分离,此时,火山岩中的普通辉石受岩浆晚期的热液作用影响蚀变为透辉石,发生了Si,Ca,Mg的富集和Fe,Al,Ti的缺失,一定程度上促进了含铁矿浆的富集。 相似文献
16.
华北地块北缘是我国金矿的主要产地之一。其金的成矿地质背景复杂,主要可分为变质基底区、地槽区、盖层区、中生代火山断陷盆地、构造－岩浆活动带５种类型。该区大部分金矿床与中生代构造岩浆活动有关。以成矿作用为主要依据将华北地块北缘金矿床划分为三大类：一类是侵入岩浆热液型金矿床;一类是火山－热液型金矿床;第三类是沉积－改造型金矿床。结合成矿地质背景分析和矿床类型的划分,将华北地块北缘金矿床划分为三个系列组合,即侵入岩浆热液金成矿系列组合、火山－次火山热液金成矿系列组合及沉积－改造金成矿系列组合。 相似文献
17.
通过论述中—晚元古代碧口火山岛弧岩浆建造（喷发、侵入）特征、成岩成矿时代、成矿作用类型，探讨了碧口地体古岛弧岩浆带构造演化与成矿作用类型和矿床成矿系列的关系。中—晚元古代碧口火山岛弧构造演化期，约为１０亿年。可以分为武陵期（１８００～１４００Ｍａ）、四堡期（１４００～１０００Ｍａ）和晋宁期（１０００～８００Ｍａ）。碧口地体经过这三个时期完成了从岩浆岛弧的形成与发展，到板块俯冲和碰撞造山的连续演化过程。武陵期是该区岛弧火山岩带的发育期，生成与蛇绿岩有关的铬铁矿、熔离硫化镍矿床及与细碧－角斑岩有关的块状硫化物矿床。四堡期，主要表现为中酸性深成岩体与钠质辉绿岩的侵入活动，生成岩浆热液及接触交代型铁、铜矿床。晋宁期为碧口地体与扬子板块强烈碰撞造山期，除了生成与中酸性岩浆活动有关矿床外，主要生成与韧性剪切、构造动力变质热液成矿作用有关的金、银矿床。 相似文献
18.
19.
阿吾拉勒山体西段发育了厚度巨大的下二叠统火山岩,这些火山岩均属碱性玄武岩系列,以钾质类型为主,钠质类型次之,岩浆演化呈现出跨越B型趋势。这种火山活动是在大陆地壳内部产生的,代表了陆内裂谷演化的早期阶段。在早二叠世末期,由于受到新源运动的影响,这种火山活动被终止了。 相似文献
20.
华北地块北缘金、多金属成矿地质背景 总被引：1，自引：0，他引：1
华北地块北缘是我国重要的金、多金属成矿带。根据区域地质建造特点、构造性质将研究区划分为５种成矿地质背景。不同的区域成矿地质背景有不同的成矿特点：变质基底区,主要形成沉积变质改造型ＣｕＦｅＡｕＰｂＺｎ成矿系列;盖层区,主要在中晚元古代沉降区形成ＰｂＺｎ（Ａｇ）沉积成矿系列、ＰｂＺｎ（ＡｇＡｕ）沉积改造成矿系列;地槽区,主要形成中酸性岩浆热液多金属成矿系列,火山－次火山热液金、多金属成矿系列,基性－超基性岩浆ＣｕＮｉ成矿系列;中生代火山断陷盆地,主要形成中酸性火山－次火山金、多金属成矿系列;构造岩浆活动带则广泛形成中酸性岩浆热液金、多金属成矿系列。 相似文献