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1.
冲绳海槽中段表层沉积物中稀土元素组成及其物源指示意义 总被引：7，自引：0，他引：7
冲绳海槽中段表层沉积物主要是由陆源、火山源和生物源物质按不同比例组成的混合物。研究表明，陆源物质(长江和黄河沉积物)稀土总量最高，轻稀土明显比重稀土富集；火山物质(冲绳海槽火山玻璃)具有较明显的正Eu异常且重稀土相对富集；生物源物质(冲绳海槽有孔虫壳)中稀土富集。3种端员物质的稀土元素组成特征存在显著差异，因此，选择合适的稀土元素特征参数——∑LREE／∑HREE、Eu／Sm及MREE／(LREE HREE)可以分别刻画出冲绳海槽沉积物中陆源、火山源及生物源物质的组成特征。通过与前人对研究区物源定性、定量分区的结果对比，验证了利用稀土元素特征参数刻画冲绳海槽混合沉积物物质来源组成的有效性。 相似文献
2.
锶同位素作为物源示踪剂和计时器在海洋地球化学研究中得到了广泛应用,南海东部海域沉积物中非碳酸盐相物质由慢源型火山物质和陆源硅铝物质组成,两者呈互为消长关系,由北向南陆源物质逐渐减少而慢源物质逐渐增多,海盆内发育的火山喷发是慢源型物质的主要来源,陆源物质主要是中国大陆碎屑物质经台湾海峡进入南海,南海东部海域非碳酸盐相沉积物87Sr/86Sr比值分布特点是:(1)陆架和陆坡边缘沉积物中87Sr/86Sr比值高(0.718 994),向东至深海盆东部边缘逐渐降低(0.713 545);(2)东沙群岛、中沙群岛周围海区87Sr/86Sr比值小(0.709 232);(3)台湾海峡南部87Sr/86Sr比值(0.717 940)接近地壳平均值,黄岩岛附近87Sr/86Sr比值(0.704 241),与幔源物质的锶同位素组成一致,这种分布规律说明中国大陆物质对南海东部海域沉积物的贡献由西向东、由北向南逐渐减小,对幔源基性岩组分和陆源硅铝质组分计算得出,东沙群岛以东、黄岩岛以北海区沉积物中陆源硅铝质组分平均含量为87%,台湾省南部基性岩组分含量不到10%,黄岩岛周围基性岩组分含量接近50%,来自台湾海峡的陆源物流向南一直延伸到17°N左右。幔源基性岩组分和陆源硅铝质组分理论计算值与区内沉积物中火山碎屑、陆源碎屑实际分布相一致。 相似文献
3.
冲绳海槽近3.5万a来陆源物质沉积通量及其对气候变化的响应 总被引：1，自引：1，他引：1
以冲绳海槽DGKS9603孔沉积物为研究对象,利用元素地球化学成分数据因子分析方法把混合源沉积物分离成陆源、火山源和生物源.结合沉积物干样密度和沉积速率对冲绳海槽近3.5万a以来沉积物中陆源物质沉积通量进行了估计,进而揭示陆源物质供应对气候变化的响应规律.研究表明,冲绳海槽的陆源物质主要来源于长江输运的我国大陆物质.在冰期—间冰期时间尺度上,海平面涨落导致的长江与海槽之间距离的伸缩是制约陆源物质通量变化的主要因素;在盛冰期和气候变冷事件(Heinrich事件)期间,东亚冬季风的增强使更多的粉砂级物质进入冲绳海槽,导致陆源物质通量增加.冲绳海槽沉积物记录的Heinrich事件与增强的东亚冬季风密切相关. 相似文献
4.
冲绳海槽北部的全新世火山碎屑沉积 总被引：1，自引：0，他引：1
分析了冲绳海槽北部的CSH1岩芯沉积物中矿物组成、化学元素质量分数和粒度的变化规律,研究结果表明,在全新世期间,日本九州岛发生了2次大规模火山喷发活动,造成大量的火山物质沉积在冲绳海槽北部。从岩芯最上部的沉积物中可识别出2层火山碎屑沉积,它们都具有沉积物粒径突然变粗、SiO2和Na2O等化合物的质量分数突然增加以及粘土矿物、挥发份、Fe2O3、MgO、CaO和Sr的质量分数迅速下降等特征。沉积物粒度数据的端员分析结果表明,冲绳海槽北部全新世沉积物中的硅酸盐碎屑是由陆源碎屑物质和火山灰按不同的比例混合而成的。有火山物质混入的沉积物的粒度分布多呈现双峰模式,粒度众数值分别为74.3和7.81μm。浮游有孔虫壳体的AMS14C测年结果表明,2层火山碎屑所对应的火山喷发年代分别为7 210和10 870 cal.aBP。其中前者与K-Ah火山的喷发时间一致,后者可能与Kuju火山在12~10 cal.kaBP期间的喷发有关。 相似文献
5.
对IODP333航次四国海盆北部地区C0011站位表层样品进行粒度和Sr-Nd同位素分析,并与前人发表的邻近海域同位素数据进行比较。经分离自生碳酸盐组分,四国海盆全新世沉积物呈现较好的陆源、火山源二端元组分特征。从地理位置看,四国海盆北部主要物质来源包括伊豆-小笠原海脊火山物质、日本列岛西南部的混合型沉积物以及由西向风或河流入海洋流输送而来的亚洲陆地沉积物,且日本列岛西南部对于该区域物质贡献最大。对四国海盆北部而言,与海盆中部沉积及日本海沉积相比,源自亚洲大陆的碎屑沉积物具有更多的贡献。沉积物中87Sr/86Sr与εNd、平均粒径的负相关关系反映了沉积物中陆源物质的相对贡献按时间顺序呈现增加、减小、增加、减少的多周期变化趋势。 相似文献
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7.
冲绳海槽Jade热液场烟囱物稀土元素和锶、钕同位素地球化学特征 总被引：5，自引：0，他引：5
热液烟囱物是弧后扩张盆地现代海底热液活动成矿系统的重要产物.冲绳海槽中的伊是名(Izena)海洼Jade热液活动区烟囱物稀土元素特征表现为轻稀土元素相对富集,并具有铕的较强的正异常.87Sr/86Sr和143Nd/144Nd的平均值分别为0.708928和0.512292,介于冲绳海槽海水和海槽酸性浮岩中的值之间.这些特征表明,Jade热液活动区的热液硫化物矿床的成矿物质来源于下伏的酸性火山岩.矿床的成矿机制可描述为:下渗的海水被加热,它与酸性火山岩发生水-岩热化学交换反应时淋滤出大量的成矿物质形成以富含轻稀土元素为特征的热水溶液;当热液喷出并发生快速结晶沉淀时,形成了以具有轻稀土元素相对富集和铕的正异常为特征的铜-锌硫化物和重晶石-非晶质SiO2型矿石. 相似文献
8.
通过对东海周边9条中小型河流沉积物进行锶钕铅(Sr-Nd-Pb)同位素测试,分析了其组成特征及其物源指示意义。结果表明,~(87)Sr/~(86)Sr、~(143)Nd/~(144)Nd、~(206)Pb/~(204)Pb平均值分别为0.719 056、0.512 056和18.614 94。Sr-Nd-Pb同位素组成主要受地质背景和风化作用的制约,空间变化规律明显,可作为区分不同来源河流沉积物的有效指标。统计结果确立出三个端元值,分别为台湾岛东部河流(~(87)Sr/~(86)Sr-0.713 355,ε_(Nd)--8.488)、台湾西部河流(~(87)Sr/~(86)Sr-0.718 804,ε_(Nd)--12.375 7)和大陆东南部河流(~(87)Sr/~(86)Sr-0.722 195,ε_(Nd)--11.944 4)。确立这些端元可为认识中国东部陆架区沉积物"源-汇"过程及陆海相互作用提供科学依据。 相似文献
9.
末次盛冰期以来冲绳海槽中段岩心中黏土粒级沉积物地球化学特征及物质来源的阶段性 总被引：4，自引：2，他引：4
测定了冲绳海槽DGKS9603孔21个样品中黏土粒级沉积物的常、微量元素组分,利用因子分析的方法,识别出对冲绳海槽中段沉积物物源有重要影响的陆源成因因子、生物成因因子及火山作用和海底热液因子.陆源成因因子的元素组合为Fe2O3,Al2O3,V等惰性元素及K2O,MgO等氧化物;生源因子的元素组合为CaO,Sr,Ba,Mn,P;火山和海底热液成因因子的元素组合为Na,Co,Ni.据样品的因子得分将柱样由上而下划分出物源的4个不同阶段:A段生物成因因子得分高,沉积物质主要是本地生物沉积,但也有富含生物成因物质的陆源物质的贡献;B段火山作用所产生的沉积物质特征显著,Na,Co,Ni呈现高含量;C段以陆源物质和生源物质沉积混杂为特征,元素垂向上变化不大;D段主要为陆源物质,其他来源物质相对较少,且可能主要来自在末次冰期最盛期所出露的陆架沉积.提出了冲绳海槽物源具有阶段性的论点.由于末次盛冰期以来全球气候呈现冷暖交替的阶段性变化,本区物源的阶段性变化是这一时期气候和古环境阶段性变化的良好反映. 相似文献
10.
东太平洋铁锰结核的Sr-Nd同位素体系及其对成矿环境的指示意义 总被引：2，自引：0，他引：2
对东太平洋1枚水成结核和2枚成岩－水成混成结核共25个微层样品进行了同位素质谱分析和等离子光谱分析，取得了结核壳层的^87Sr/^86Sr、^143Nd/^144Nd比值以及Mn,Fe,Ti,Al、稀土元素等含量，以此为基础探讨了不同类型结核中Sr-Nd同位素特征及地质意义。在水成结核A99中^87Sr/^86Sr比值与εNd值呈弱正相关，在成岩－水成混成结核5737G和5739G中^87Sr/^86Sr比值与εNd值呈负相关。^87Sr/^86Sr比值与εNd值在A99结核剖面中的分布反应了东太平洋10Ma（晚中新世）以来海水受到了强→弱→强的火山作用影响；^87Sr/^86Sr比值与εNd在5739G结核剖面中的变化表明成岩作用结核的生长起了重要的作用；而5737G结核剖面中的变化则反应了火山作用对结核的成长起了较大作用 。同时所有类型结核的初始壳层都具有较高的εNd值，表明火山作用突然加强可能是结核生长的一个重要驱动机制。 相似文献
11.
Geochemistry of trace elements and Sr-Nd isotopes of foraminifera shell from the Okinawa Trough 总被引：1，自引：0，他引：1
ＩＮＴＲＯＤＵＣＴＩＯＮＰｒｏｖｅｎａｎｃｅｏｆｍａｒｉｎｅｓｅｄｉｍｅｎｔｓｈａｓａｌｗａｙｓｂｅｅｎａｆｏｃｕｓｅｄｐｒｏｂｌｅｍｉｎｍａｒｉｎｅｓｅｄｉｍｅｎｔｇｅ ｏｌｏｇｙ.Ｒｅｃｏｇｎｉｔｉｏｎｏｆｅｎｄｍｅｍｂｅｒｓａｎｄｅｓｔｉｍａｔｉｏｎｏｆｔｈｅｉｒｒｅｌａｔｉｖｅｐｒｏｐｏｒｔｉｏｎｓｆｒｏｍｍｉｘｅｄｓｅｄｉｍｅｎｔｓｈａｖｅｂｅｅｎａｋｅｙｃｏｎｔｅｎｔｉｎｔｈｅｓｔｕｄｙｏｆｐｒｏｖｅｎａｎｃｅ .Ｆｏｒｔｈｉｓａｉｍ ,ｉｔｉｓｎｅｃｅｓｓａｒｙｔｏｓｅｌｅｃｔｅｎｄｍｅ… 相似文献
12.
冲绳海槽有孔虫壳体的微量元素Sr,Nd同位素地球化学 总被引：6，自引：1，他引：6
钙质生物壳的微量元素组合和Sr,Nd同位素组成是识别海底混合源沉积物中生物源物质相对贡献的重要参数.冲绳海槽有孔虫壳体强烈富集Sr,P,Mn和Ba,富集Li,U,Th,Sc,Co,Pb,Zn,Cr,Rb,Y,Sb和轻稀土元素,弱富集V,Ga,Zr,Nb,Cd和中稀土元素,相对贫Ge,Mo,In,Sn,Cs,Hf,Ta,W,Tl,Bi和重稀土元素,海水中微量元素的背景含量和生物活动对微量元素的选择性吸收是有孔虫壳体中微量元素发生富集和贫化的主要机制,冲绳海槽有孔虫壳体的稀土元素配分模式与海水和太平洋有孔虫的有明显差异,表现出中稀土元素相对富集,并具有微弱的负Ce异常.有孔虫壳体的Sr,Nd同位素比值也与大洋海水不同,分别为0.709769和0.512162,前者略高于大洋海水,后者略低于大洋海水,表明冲绳海槽海水明显受大陆河水影响. 相似文献
13.
冲绳海槽西部陆坡地震相模式与沉积体系 总被引：5，自引：3，他引：5
对冲绳海槽西部陆坡上两个航次(95航次和99航次)共计2000多公里的单道地震资料进行分析和解译，对斜坡沉积环境下沉积体系发育、分布特征进行了研究。结果表明：a)冲绳海槽西部斜坡环境下，上新世以来的沉积层均不同程度的变形和错动；b)存在两种斜坡相地震反射模式——退覆模式和叠覆模式，这两种模式都反映了冲绳海槽西部陆坡得到充足的沉积物供给；c)斜坡环境下主要发育陆架边缘三角洲、重力流沉积和水道充填等沉积体系；d)沉积层发育特征表明，冲绳海槽西部陆坡具有北段坡度缓、沉积物供应丰富、构造相对不活跃，中段坡度陡、沉积物供应充足、构造活动强烈，南段坡度陡、沉积供应相对较少、构造和火山活动十分强烈3种主要沉积环境。西部陆坡的沉积特征也揭示了东海陆架向陆坡提供了大量碎屑沉积物质。 相似文献
14.
The shelfbreak of the East China Sea lies in an area with a marked change in gradient between the continental shelf and the slope (west wall of Okinawa Trough), depth ranging from 132 to 162m with an average of about 147 m, and the width ranging from 4 to 18 km. The types of the shelfbreak differ markedly from the north to the south, having an abrupt break in the south and a gradual break in the middle and the north. Without permanent deposition of fine-grained material formed at the shelfbreak zone, it serves only as a temporary resting place for terrigenous sediments moving toward the Okinawa Trough through submarine canyons as important transport conduits. 相似文献
15.
冲绳海槽中部表层沉积物中的放射虫 总被引：7，自引：2，他引：5
1992年7月“向阳红16号”海洋调查船利用大洋50型抓斗在冲绳海槽中部（25°30’－30°N，125°－129°E）区域内获取表层沉积物样品88个。表层沉积物中的放射虫定量分析结果表明；愈近海槽放射虫的数量及属、种丰度值愈高，西侧槽坡离开槽区越远，放射虫数量及属种越渐少。而东侧槽被放射虫数量则表现了高、低值成点状分布的格局。表层沉积物中两大类放射虫的百分含量分别为泡沫虫约占87％，罩笼虫约占13％。另外根据分析结果，把本区分为3个小的沉积区：陆坡上部沉积区；陆被下部沉积区；海槽底部沉积区。 相似文献
16.
冲绳海槽中部伊平屋脊火山岩地球化学和Sr-Nd-Pb同位素组成：对岩石成因和地幔源区的指示 总被引：1，自引：0，他引：1
As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-NdPb isotopic composition data are presented for volcanic rocks from the Iheya Ridge(IR), the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in ~(87)Sr/~(86)Sr(0.703 862–0.704 884), ~(144)Nd/~(143)Nd(0.512 763–0.512 880) and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle(DM) but extends to the enriched mantle(EMII), indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts. 相似文献
17.
Hydrothermal chimney is a product of hydrothermal activity on the seabed. Chimney samples dredged from Jade hydrothermal area in Izena depression of the Okinawa Trough, are characterized by relatively enriched light rare earth elements (LREE) and strongly positive Eu anomalies. 87Sr/86Sr and 143Nd/144Nd of these samples are exactly between those of seawater and of acidic pumice, averaged at 0.708928 and 0.512292, respectively. These characteristics imply that the main source of hydrothermal sulfide at Jade area is possibly the undersurface acidic rocks. The mineralizing mechanism can be summarized as follows: Large amount of mineralized material would be leached out and LREEenriched hydrothermal solution would be subsequently produced as a result of thermo-chemical exchange reaction between acidic volcanic rocks and heated seawater that penetrated in advance from upper water mass. The spurting out from the seabed and quickly crystallizing in the seawater of hydrothermal solution are responsible for the formation of Cu-Zn sulfide and barite-amorphous SiO2 minerals that are characterized by enriched LREE and positively strong Eu anomalies. 相似文献
18.
Hydrothermal chimney is a product of hydrothermal activity on the seabed. Chimney samples dredged from Jade hydrothermal area in Izena depression of the Okinawa Trough, are characterized by relatively enriched light rare earth elements (LREE) and strongly positive Eu anomalies. ^87Sr/^86Sr and ^143Nd/^144Nd of these samples are exactly between those of seawater and of acidic pumice, averaged at 0.708928 and 0.512292, respectively. These characteristics imply that the main source of hydrothermal sulfide at Jade area is possibly the undersurface acidic rocks. The mineralizing mechanism can be summarized as follows: Large amount of mineralized material would be leached out and LREE-enriched hydrothermal solution would be subsequently produced as a result of thermo-chemical exchange reaction between acidic volcanic rocks and heated seawater that penetrated in advance from upper water mass. The spurting out from the seabed and quickly crystallizing in the seawater of hydrothermal solution are responsible for the formation of Cu-Zn sulfide and barite-amorphous SiO2 minerals that are characterized by enriched LREE and positively strong Eu anomalies. 相似文献
19.
对冲绳海槽中段DGKS9603孔134个样品(孔深0~481cm),测试了18种常、微量元素,对该柱样的29个样品(孔深0~488cm)进行了REE测试。对采自长江三角洲的CYm柱样和黄河三角洲的S3柱样中的晚更新统的5个样品进行了常、微量元素和REE测试。分析表明,冲绳海槽中段在全新世、末次盛冰期和末次间冰期的沉积物均以陆源物质为主,生物沉积为次。末次盛冰期以陆源硅质碎屑沉积的大量增加为特征;全新世生物沉积量有较大的增加;末次间冰期介于上述两者之间,但较全新世更富陆源物质。冲绳海槽的物源演化受末次冰期的影响,具有阶段性。对比冲绳海槽与长江和黄河物源的地球化学参数,包括REE、稀有元素、惰性常、微量元素,判识出末次盛冰期冲绳海槽的陆源物质,具有长江源的物质属性,沉积物可能主要来自古长江。 相似文献
20.
Geochemical and isotopic characteristics of volcanic rocks from the northern East China Sea shelf margin and the Okinawa Trough 总被引：8，自引：2，他引：6
ZENG Zhigang YU Shaoxiong WANG Xiaoyuan FU Yongtao YIN Xuebo ZHANG Guoliang WANG Xiaomei CHEN Shuai 《海洋学报(英文版)》2010,29(4):48-61
Volcanic rocks both from the northern East China Sea (NECS) shelf margin and the northern Okinawa Trough are subalkaline less aluminous,and lower in High Field Strength Elements (HFSE).These rocks are higher in Large Ion Lithophile Elements (LILE),thorium and uranium contents,positive lead anomalies,negative Nb-Ta anomalies,and enrichment in Light Rare Earth Elements (LREE).Basalts from the NECS shelf margin are akin to Indian Ocean Mid-Ocean Ridge Basalt (MORB),and rhyolites from the northern Okinawa Trough have the highest 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios.The NECS shelf margin basalts have lower 87 Sr/ 86 Sr ratios,ε N d and σ 18 O than the northern Okinawa Trough silicic rocks.According to 40 K– 40 Ar isotopic ages of basalts from the NECS shelf margin,rifting of the Okinawa Trough may have been active since at least 3.65–3.86 Ma.The origin of the NECS shelf margin basalt can be explained by the interaction of melt derived from Indian Ocean MORB-like mantle with enriched subcontinental lithosphere.The basalts from both sides of the Okinawa Trough may have a similar origin during the initial rifting of the Okinawa Trough,and the formation of basaltic magmas closely relates to the thinning of continental crust.The source of the formation of the northern Okinawa Trough silicic rocks was different from that of the middle Okinawa Trough,which could have been generated by the interaction of basaltic melt with an enriched crustal component.From the Ryukyu island arc to East China,the Cenozoic basalts have apparently increasing trends of MgO contents and ratios of LREE to Heavy Rare Earth Elements (HREE),suggesting that the trace element variabilities of basalts may have been influenced by the subduction of the Philippine Sea plate,and that the effects of subduction of the Philippine Sea plate on the chemical composition of basaltic melts have had a decreasing effect from the Ryukyu island arc to East China. 相似文献