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1.
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
2.
冲绳海槽中段热液活动区表层沉积物的主、微量和稀土元素分析结果表明:区内沉积物主要由陆源物质与热液源物质组分组成,Hg、Au、Sb、Cu、Pb、Zn、Ba、As、Fe和Co等微量元素富集;沉积物的化学风化程度中等,A-CN-K图解表明其暂未受到钾交代影响,且其母岩成分接近花岗闪长岩;北美页岩标准化稀土配分模式曲线整体较为平坦,轻重稀土分馏较弱,部分样品具有与热液流体类似的明显正铕异常.受热液活动影响,部分沉积物中的Fe、Cu、As、Pb和Zn显著富集,结合样品所处站位,整体显示含金属沉积物-过渡沉积物-正常沉积物的空间分配模式.结合(La/Sm)N、(La/Yb)N比值指示区内沉积物的陆源物质主要来自于黄河与台湾岛河流. 相似文献
3.
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
4.
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
5.
对新近(2014年)采自冲绳海槽南部Yonaguni Knoll IV热液活动区和中部伊平屋热液活动区的金属硫化物样品分别进行了X射线荧光光谱(XRF)和等离子体质谱(ICP-MS)分析,旨在通过对比分析两个热液活动区金属硫化物的元素地球化学特征,探讨两个不同热液活动区成矿元素的富集规律、热液成矿的作用过程及其区域差异。研究结果表明:在冲绳海槽中部和南部热液区分布有两种金属硫化物,分别为富Fe-Zn型硫化物和Ba-Zn-Pb型硫化物(+硫酸盐);相较于大洋中脊和其它弧后盆地的热液硫化物,研究区硫化物中Pb的含量明显较高,而Cu和Fe的含量相对较低,这与冲绳海槽存在较厚的沉积盖层有关;无论是常量元素、微量元素、还是稀土元素(REE),其含量和相关的特征值都变化较大,表明研究区热液硫化物形成于不同的热液成矿阶段;富Fe-Zn型硫化物是在高温热液活动阶段形成的,而Ba-Zn-Pb型硫化物(+硫酸盐)则形成于热液喷出海底与海水混合的过程中,成矿温度较低;即使在同一热液活动区,成矿环境也有较大变化,主要表现在成矿温度的波动上;研究区热液硫化物中REE的配分模式特征表明硫化物中REE的物源相同,但经历的过程(REE的迁移和富集)有所不同,反映了热液硫化物形成于不同的热液成矿阶段;热液成矿作用存在区域性差异,海槽南部的成矿温度较中部低,成矿物质来源方面,南部热液区硫化物的Pb含量较中部高,表明其成矿物质可能部分来源于沉积物。 相似文献
6.
冲绳海槽中段表层沉积物物质来源的定量分离:Sr-Nd同位素方法 总被引：16，自引：2，他引：16
利用1994年85－904航次获取的冲绳海槽中段表层沉积物样品，测定其硅酸盐相的^87Sr/^86Cr和^143Nd/^144Nd比值，以定量研究冲绳海槽中段表层沉积物硅酸盐物质的来源，结果表明，冲绳海槽中段陆坡区表层沉积物硅酸盐相的^87Sr/^86Sr/^143Nd/^144Nd与东海陆架沉物硅酸盐相的^87Sr/^86Sr和^143Nd/^143Nd相当，槽底和东坡沉积物硅酸盐相的^87Sr/^86Cr和^143Nd/^144Nd值介于中国大陆硅酸盐物质和海槽水山碎屑的^87Sr/^86Sr,^143Nd/^144Nd比值之间，并大致具有两端员混合特征，利用以Sr同位素为参数的二端员混合方程进行物源定量分析的结果表明，冲绳海槽中段的西坡和槽底表层沉积物硅酸盐相以陆源物质为主，最大值为91．07％，由西向东，陆源物逐渐减少，在海槽东坡含量最小，最小值为9．93％，火山源物质在东坡含量最高，量大值为64．92％，由东向西，由北向东，火山源物质逐渐减少为零。 相似文献
7.
冲绳海槽中南部不同环境表层沉积物质来源 总被引：1，自引：0，他引：1
对冲绳海槽中南部3种不同沉积环境(东海外陆架、东海陆坡和冲绳海槽)表层沉积物进行了稀土等元素地球化学分析,结果显示,冲绳海槽和陆坡表层沉积物具有与台湾物质来源类似的稀土元素配分模式,La/Sm-Gd/Yb散点图也显示海槽和陆坡沉积物主要分布在台湾物源端元区,表明冲绳海槽中南部海槽和陆坡表层沉积物主要来源于台湾,而外陆架沉积物明显的重稀土亏损与大陆河流(特别是长江、黄河)沉积物来源较为一致。为进一步判断外陆架表层沉积物来源,对外陆架沉积物重矿物进行分析鉴定,结果显示,外陆架沉积物重矿物以普通角闪石-绿帘石-石榴石-赤褐铁矿为组合特征,与长江沉积物重矿物组成特征类似,其明显缺乏台湾河流来源的典型重矿物锆石、黄河来源典型重矿物云母、浙闽沿岸来源典型重矿物磁铁矿,说明台湾、黄河和浙闽沿岸并非研究区外陆架表层沉积物主要物源。根据以往测年等研究成果,研究区外陆架沉积物年代较老,应为古长江物质经东海现代环流体系不断改造而成。 相似文献
8.
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
9.
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
10.
For the first time, an element abundance table of China Shelf Sea sediments is published based on 286 samples from the continental shelf of China analyzed for 62 chemical elements. The shelf sediments result from the redistribution of sediments from China over the continental shelf. On the basis of comparison of element abundances among the China shelf samples, hemipelagic Okinawa Trough samples, and pelagic brown clay from the West Pacific, it is clear that each has its own elemental characteristics. Hg anomaly enrichment in Okinawa Trough sediments may be used as an indicator of hydrothermal activity. 相似文献
11.
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
12.
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
13.
Xiang Rong Li Tiegang Yang Zuosheng Yan Jun Cao Qiyuan College of Marine Geosciences Ocean University of China 《海洋学报(英文版)》2003,(1)
Benthic foraminiferal analysis of 29 samples in surface sediments from the southern Okinawa Trough is carried out. The results indicate that benthic foraminiferal abundance decreases rapidly with increasing water depth. Percentage frequencies of agglutinated foraminifera further confirm the modern shallow carbonate lysocline in the southern Okinawa Trough. From continental shelf edge to the bottom of Okinawa Trough, benthic foraminiferal fauna in the surface sediments can be divided into 5 assemblages: (1) Continental shelf break assemblage, dominated by Cibicides pseudoungerianus, corresponds to subsurface water mass of the Kuroshio Current; (2) upper continental slope assemblage, dominated by Cassidulina carinata , Globocassidulina subglobosa, corresponds to intermediate water mass of the Kuroshio Current; (3) intermediate continental slope assemblage, dominated by Uvigerina hispi-da, corresponds to the Okinawa Trough deep water mass above the carbonate lysocline; (4) lower continental slope- trough b 相似文献
14.
冲绳海槽南部流纹岩中角闪石的化学特征及其对岩石成因的指示 总被引：2，自引：0，他引：2
为了揭示冲绳海槽西南端流纹岩成因,利用电子探针和LA-ICP-MS对该流纹岩中角闪石进行了主量和微量元素测定。所有角闪石主量元素成分变化范围小,晶体化学特征主要表现为:CaB>1.60,CaA=0,（Na+K）A<0.33,NaB介于0.23~0.39之间,均为钙质镁闪石。微量元素以富集Sc、V、Cr、Co、Ni和REE,亏损Rb、Sr、Ba、Zr、Th、U和Pb为特征,这些元素的富集与亏损与复杂的类质同象作用有关。由角闪石温压计得出其结晶时的温度范围为775~839℃,压力为0.12 GPa,大致相当于4 km的深度。角闪石的成因矿物学研究显示该流纹岩中角闪石为壳-幔混合成因,进一步表明冲绳海槽南部流纹岩由幔源玄武质岩浆与壳源长英质岩浆混合形成的中基性岩浆在浅层岩浆房中结晶分异而形成,且壳幔混合源很可能是冲绳海槽西南端火山岩岩浆的主要来源。 相似文献
15.
冲绳海槽是因菲律宾海板块俯冲于欧亚板块之下,在陆壳上发育起来的一个初始的弧后盆地,是研究弧后扩张作用早期盆地演化、岩浆作用和壳幔过程的天然实验室。尽管迄今对冲绳海槽已经做了大量的调查研究工作,但仍存在一些颇有争议或亟待解决的科学问题,如:冲绳海槽酸性浮岩与基性玄武岩之间的成因联系,冲绳海槽不同区段构造背景对岩浆作用的控制,冲绳海槽岩浆源区地幔的特征,俯冲板块组分(流体+熔体)对地幔楔部分熔融的贡献等。本文在系统收集和整理(剔除了一些存疑数据)了迄今已有冲绳海槽火山岩主量元素、微量元素(包括稀土元素)与Sr-Nd-Pb同位素数据的基础上,通过对资料的系统分析,进一步确认了酸性浮岩与基性玄武岩的岩浆同源性;认为在冲绳海槽北段与中段主要分布有酸性浮岩和中性安山岩,应该是两段区域目前正处于裂谷阶段的反映,而南段广泛分布的基性玄武岩说明在构造性质上已接近成熟性弧后盆地;冲绳海槽的火山岩岩浆源区具有II型富集地幔（EMII型）Dupal异常特征,岩浆源于流行地幔（PREMA）和EMII型地幔端元混合的源区地幔,其中EMII约占比15%,PREMA贡献率在85%左右;源于俯冲的菲律宾海板块(俯冲洋壳或沉积物)的流/熔体的加入是导致冲绳海槽下伏地幔具有EMII型特征的原因,这一点不同于Dupal异常源于壳幔相互作用的观点。 相似文献
16.
深海沉积物中有孔虫壳体的微量元素、同位素测试技术已较为成熟，而河口近海沉积物中有孔虫壳体元素微区测试却鲜有报道。本文报道了一种利用激光剥蚀电感耦合等离子体质谱（LA-ICP-MS）分析法测试取自长江口外沉积物中的有孔虫壳体元素/钙比值的技术，研究了氦气载气流量、能量密度、束斑大小、激光剥蚀频率等参数对测试结果的影响，优化了活体有孔虫原位分析方法。应用确定的测试条件对2016年7月取自长江口外的底栖有孔虫优美花朵虫样品（Florilus decors）进行测试，发现Mg、Sr等元素/钙比值在壳体不同位置上无显著差异，而Mn的数据较为离散，可能与有孔虫生长过程中经历的水环境及其变化有关。 相似文献
17.
Presentaddress:NanjingInstituteofGeologyandPaleontology,ChineseAcademyofSciences,Nanjing210008,ChinaINTRODUCTloNTheOkinawaTrough(NNE-SSW),thedeeperwaterbasinoftheEastChinaSea,liesbe-tween24'~3O"N,122"~13o'E(seeFig.l).Itssouthernpartiswideranddeeperthanthenorthernpart,withthemaximumwaterdepthof2719metersinthesouthwest.ThemostimPOrtanthydrographiccharacteristicinthisareaistheKuroshiocurrentwhichflowsalongthewestbankoftheokinawaTrough-(about2oo~5oometersindepth).Itinnu-encesthedep… 相似文献
18.
冲绳海槽岩浆源的三分量混合模型 总被引：1，自引：0，他引：1
综合分析了冲绳海槽玄武岩中微量元素的地球化学特征，发现最少要求三分量混合作用来解释其岩浆源成分，并通过最大方差因子分析估算了3个分量的贡献比例。亏损型地幔是海槽岩浆源的主体，但其中舍有富集型地幔的成分，尤其是海槽中部玄武岩岩浆源中这种富集型地幔成分的特征表现得更为明显。俯冲组分是岩浆源中的另一个主要成分，贡献量为20％左右，是造成海槽区玄武岩中Pb强烈富集的重要原因。 相似文献
19.
Benthic foraminiferal analysis of 29 samples in surface sediments from the southern Okinawa Trough is carried out.The results indicate that benthic foraminiferal abundance decreases rapidly with increasing water depth.Percentage frequencies of agglutinated foraminifera further confirm the modern shallow carbonate lysocline in the southern Okinawa Trough.From continental shelf edge to the bottom of Okinawa Trough,benthic foraminiferal fauna in the surface sediments can be divided into 5 assemblages:(1) Continental shelf break assemblage,dominated by Cibicides pseudoungerianus,corresponds to subsurface water mass of the Kuroshio Current;(2) upper continental slope assemblage,dominated by Cassidulina carinata,Globocassidulina subglobosa,corresponds to intermediate water mass of the Kuroshio Current;(3) intermediate continental slope assemblage,dominated by Uvigerina hispida,corresponds to the Okinawa Trough deep water mass above the carbonate lysocline. 相似文献