Petrological Characteristics and Genesis of the Central Indian Ocean Basin Basalts

The Central Indian Ocean Basin （CIOB） basalts are plagioclase-rich, while olivine and pyroxene are very few. The analyses of 41 samples reveal high FeOT （～10-18 wt%） and TiO 2 （～1.4-2.7 wt%） indicating a ferrobasaltic composition. The basalts have high incompatible elements （Zr 63-228 ppm; Nb ～1-5 ppm; Ba ～15-78 ppm; La ～3-16 ppm）, a similar U/Pb （0.02-0.4） ratio as the normal midoceanic basalt （0.16±0.07） but the Ba/Nb （12.5-53） ratio is much larger than that of the normal midoceanic ridge basalt （～5.7） and Primitive Mantle （9.56）. Interestingly almost all of the basalts have a significant negative Eu anomaly （Eu/Eu＊=0.78-1.00） that may have been a result of the removal of feldspar and pyroxene during crystal fractionation. These compositional variations suggest that the basalts were derived through fractional crystallization together with low partial melting of a shallow seated magma.

Physical Properties,Morphology and Petrological Characteristics of Pumices from the Central Indian Ocean Basin

About 400 pumice clasts collected from the Central Indian Ocean Basin（CIOB）were studied for their morphology and were classified based on their shape and size.A majority of the samples range between1 cm and 36 cm and in the Zinggs shape diagram plot in the equant and oblate fields.The Corey Shape Factor for most of the samples is close to 0.7,which is common for volcaniclastic material. The physical properties such as density,specific gravity,void ratio,porosity,moisture content and degree of saturation,were determined for 30 pumice samples.Density varies from 0.21 to 0.74 g/cm^3 specific gravity 1.84 to 3.27,void ratio 2.21 to 10.67,porosity 67%to 91%,moisture content during sinking 0.44 to 2.35 and degree of saturation varies from 26.5%to 86%.Binocular and electron microscopy studies reveal that 60%of the vesicles are elongated,30%are spherical and 10%are fibrous.Petrography of the pumices exhibits vitrophyric texture with phenocrysts of feldspars and clinopyroxenes.X-ray diffractrogram and mineral analyses confirm plagioclase to be a major phase, while quartz and orthoclase are not uncommon.Todorokite is commonly present in the ferromanganese oxide coating present over some of the pumices.This paper also delves into some details concerning the controversial origin of the pumices and glass shards in the CIOB.

Implications of REE incorporation and host sediment influence on the origin and growth processes of ferromanganese nodules from Central Indian Ocean Basin

This study presents new major,trace and REE data for thirty-five ferromanganese nodules recovered from areas representing three different sediment types(siliceous,red clay and their transition zone)in the Central Indian Ocean Basin(CIOB)to address their genetic aspects,classification,growth rate,nature of host sediments and influence of REE in the processes of nodule formation.The nodules from CIOB are mostly either hydrogenetic(metals coming from oxygenated bottom water)and diagenetic(metals coming from suboxic sediment pore water)or a combination of both,depending on the source of supply of metal.However,a number of biogeochemical processes mediate this supply of metals which again changes from time to time,making the nodule growth process highly dynamic.This study suggests that at the initial stage of nodule growth,host sediments do not play much role in controlling the growth processes for which REEs can enter both Mn and Fe oxyhydroxide phases equally.Thus,the bottom water signature is imprinted in these early formed nodules irrespective of their host sediment substrate but with gradual growth and burial in the sediment,the main mode of metal enrichment becomes diagenetic through sediment pore water.This tends to increase the concentration of Mn,Ni and Cu over other elements which are retained in the sediment fraction.Among the REEs,Ce concentration of the nodules shows significant positive anomaly due to variation in redox potential and hence its magnitude can be used to get an idea about the metal enrichment procedure and the genetic type of the nodules.However,based on host sediment only,not much difference is found in the magnitude of Ce anomaly in these nodules.On the other hand,discrimination diagram,based on HFSE and REY chemistry,indicates that most of these nodules are of diagenetic origin under oxic condition with a trend towards hydrogenetic field.Further,the genetic type of the ferromanganese nodules from the CIOB are more effectively differentiated by a combination of their major and trace element concentrations rather than solely based on their REE or HFSE chemistry or host sediment substrate.

Lithospheric Structure Model of Central Indian Ocean Basin Using Ocean Bottom Seismometer Data

The intense deformation zone in the central Indian Ocean, south of Indian continent is one of the most complex regions in terms of its structure and geodynamics. The deformation zone has been studied and debated in 1990s for its genesis. It was argued that deformation is mainly confined to sedimentary and oceanic crustal layers, while the large wave length geoidal anomalies, on which the deformation region lies, called for deeper sources. The inter connection between deeper and the shallower sources is found missing. The current study focuses on the complexities of this region by analyzing OBS （ocean bottom seismometer） data. The data acquired by five OBS systems along a 300 km long south-north profile in the CIOB （central Indian Ocean basin） have been modeled and the crustal and sub-crustal structure has been determined using 2-D tomographic inversion. Four subsurface layers are identified representing the sediment column, upper crustal layer, lower crustal layer and a sub-crustal layer （upper mantle layer）. A considerable variation in thickness as well as velocity at all interfaces from sedimentary column to upper mantle is observed which indicates that the tectonic forces have affected the entire crust and sub-crustal configuration. The sediments are characterized by higher velocities （2.1 kin/s） due to the increased confining pressure. Modeling results indicated that the velocity in upper crust is in the range of 5.7-6.2 km/s and the velocity of the lower crust varies from 7.0-7.6 km/s. The velocity of the sub-crustal layer is in the range of 7.8-8.4 km/s. This high-velocity layer is interpreted as magmatic under-plating with strong lateral variations. The base of the 7.0 km/s layer at 12-15 km depth is interpreted as the Moho.

The Relationship Between Fat Content and Biological Parameters of Bigeye Tuna(Thunnus obseus) in the Western Central Indian Ocean

Comparing fat content with physiological status can throw light on the reproduction and feeding behavior of the fish. The biological data of 586 bigeye tuna were collected from the longline fishery in the waters of Western Central Indian Ocean from November, 2012 to March, 2013. The spatial or temporal distribution of the fat content, and the relationships of fat content with gender, round weight, gonadal maturity and fork length were analyzed. A generalized additive model(GAM) was used to analyze the relationships between fat content and fork length(FL), gonadosomatic index(GSI), condition factor(K), and somatic index(SI). Results showed that: 1) the fat content of bigeye tuna was in the range of 3.1%–27.1% with the average 12.8%; 2) there were no significant geographical differences of average fat content(P > 0.05) among 1? squares in general; 3) there were no significant differences(P > 0.05) of the fat content for different genders, months, or gonad maturity stages; 4) there was an extremely significant correlation(P = 0.000) between fat content and FL and GSI. There was no significant correlation(P = 0.051) between fat content and K. There was a significant correlation(P = 0.003) between fat content and SI. The results of this study suggest that the fat content of the matured fish was relatively stable. The survey area was in a spawning region, and the survey period was the spawning season for bigeye tuna.

Geochemical characteristics of REY-rich pelagic sediments from the GC02 in central Indian Ocean Basin

As a potential mineral resource, the clay minerals enriched in rare earth elements including yttrium（REY） in the deep sea have been attracting great attention. However, the enrichment mechanism of REY remains unclear. To understand the geochemical characteristics and factors controlling REY enrichment in zeolite clay in the deep sea, we conducted mineral identification by XRD, major and trace element measurements by XRF and REY analyses by ICP-MS on a 1.4-m-long sediment core（GC02） located in the Central Indian Oceanic Basin（CIOB）. The main findings include：（1） the core sediments in GC02 possess elevated REY contents and exhibited a strong negative Ce anomaly, an apparent MREE bulge and positive Y anomaly. These were comparable with typical REY-rich clays in the Pacific Ocean, indicating the similar REY enrichment mechanism and the presence of REY-rich clays in the CIOB;（2） in comparison with the dataset from the Wharton Basin and DSDP site 213, the higher content of REY and stronger PAAS（Post Archean Australian Shale） normalization patterns in the GC02 sediments were likely caused by the weaker impact of terrigenous materials of GC02. The CIOB was suggested to be a promising place hosting REY rich pelagic sediments.

印度洋中西部水域黄鳍金枪鱼的食性及其季节性变化

根据2003年12月至2004年6月及2005年9月至12月在印度洋中西部水域调查所获得的数据，利用两因子列联表及单因子方差分析等统计分析方法，对印度洋中西部水域黄鳍金枪鱼的食物组成及其随月份和体长的变化、摄食强度及食物组成的生态位宽度进行了初步研究。结果表明，印度洋中西部水域黄鳍金枪鱼食物组成包括帆蜥、鲣、鳞鲍、沙丁鱼、鲐鱼、虾、蟹、鱿鱼、章鱼、竹荚鱼及未辨认甲壳类等饵料类群，其中主要食物为鱿鱼、鲐鱼以及蟹。大部分月份黄鳍金枪鱼摄食率相对较高，基本上维持在70％以上；除2月和6月外，其余月份黄鳍金枪鱼饵料种类数更替率均低于50％。各叉长细黄鳍金枪鱼摄食率基本维持在70％以上；当叉长在106～155cm之间，饵料种类数更替率低于40％。黄鳍金枪鱼摄食强度各月差异显著，但各叉长组摄食强度并不存在显著性差异。各月饱满指数存在显著性差异。黄鳍金枪鱼的食物组成随月份和叉长有明显变化。鱿鱼、鲐鱼和蟹基本上为不同叉长组黄鳍金枪鱼所摄食。黄鳍金枪鱼食物组成各月Shannon—Weiner多样性指数H’波动较大，且存在显著性差异；Pielou均匀度指数j’基本上维持在0．80～1．00之间，但各月间存在显著性差异。印度洋中西部水域黄鳍金枪鱼各叉长组食物组成Shannon—Weiner多样性指数H’变化较大，但在106145cm期间相对保持稳定，而Pielou均匀度指数J’波动较大。印度洋中西部黄鳍金枪鱼食物组成各月和各叉长组均存在显著性差异。

印度洋中西部和大西洋西部水域大眼金枪鱼的食性比较

根据2004年8月至2005年3月大西洋西部水域及2003年12月份至2004年5月份在印度洋中西部水域金枪鱼延绳钓渔业所获取的大眼金枪鱼数据，对两个诃查区域内的大眼金枪鱼食性进行了研究。结果表明，印度洋中西部水域大眼金枪鱼的食物组成包括沙丁鱼、鱿鱼、乌贼等13个饵料类群，其中主要摄食鱿鱼和沙丁鱼；大西洋西部水域大眼金枪鱼主要摄食沙丁鱼、鱿鱼、虾类等13种饵料类群，主要以沙丁鱼为饵，其次为鱿鱼。印度洋中西部水域大眼金枪鱼空胃率非常高，基本上维持在60％以上；大西洋西部水域大眼金枪鱼空胃率相对较低，基本上都在30％以下。印度洋中西部水域大眼金枪鱼平均饱满指数变化不大，基本上维持在0．40～0．55之间。大西洋西部水域大眼金枪鱼平均饱满指数变化也不太大。印度洋中西部水域大眼金枪鱼各月平均饱满指数高于大西洋西部水域，且各月空胃率高于后者。印度洋中西部和大西洋西部水域大眼金枪鱼Shannon-Weiner多样性指数H’基本上都1．50～2．00之间变化。相同调查月份内，印度洋中西部水域大眼金枪鱼食物Pielou均匀度指数J’均高于大西洋西部水域。

印度洋中西部水域大眼金枪鱼的食性

根据2005年9月至2005年12月及2003年12月至2004年5月在印度洋中西部水域调查所获得的数据，对大眼金枪鱼食性进行了初步研究。结果表明，印度洋中西部水域大眼金枪鱼食物组成包括鱿、鲐、沙丁鱼、乌贼、蟹、竹笑鱼、蛇鲭、乌鲂、刺鲷、虾、帆蜥、鳞钝、水母和杂鱼等饵料，其中主要食物为鱿（IRI=50．84％）、鲐（IRI=17．70％）以及虾类（IRI=9．49％）。空胃率较高，雄性大眼金枪鱼的空胃率高达52．2％，而雌性大眼金枪鱼的空胃率则为47．7％。食物组成有明显的月份变化，各月大眼金枪鱼食物中鱿所占比重均较大，其次是鲐、沙丁鱼、虾以及蟹。食物中平均饵料重量及平均饵料个数的月变化较为显著，且趋势较为一致。各体长组大眼金枪鱼食物中鱿重量均占有一定的比例，鲐和沙丁鱼所占比重也较大，蟹类以及虾类在大眼金枪鱼的食物中也占有一定的比重。各体长组大眼金枪鱼食物中平均饵料重量及平均饵料个数的变化显著，且趋势较为一致，110-140cm体长范围内的大眼金枪鱼摄食量较大。各月Shannon-Weiner多样性指数H’基本上都在1．50～2．00之间变化，各月Pielou均匀度指数J’均在0．80～1．00之间。各体长组Shannon-Weiner多样性指数H’变化较大，各体长组Pielou均匀度指数J’均在0．85～1．00之间。

印度洋中南部大眼金枪鱼生物学特性研究

根据2008年9月~2009年4月在印度洋中南部金枪鱼延绳钓渔场调查期间收集的大眼金枪鱼生物学数据,对其基本的生物学特征进行了研究。结果表明：（1）叉长范围为57~184 cm,优势叉长组为101~110cm和121~130 cm,约占总数的41.7%,平均叉长为119.5 cm;（2）不分性别大眼金枪鱼叉长（FL）与加工后重（DW）的关系可表达为：DW=2.407 6×10-5FL2.931 6,雌雄个体差异不显著（F=0.207,P〉0.05）;（3）调查期间,大眼金枪鱼雄性比例为56.55%,当叉长大于140 cm时,雄性占优势;调查期间,该海域大眼金枪鱼的繁殖期为10月~翌年4月,繁殖峰期为10月~翌年1月;（4）摄食种类中柔鱼、帆蜥鱼和虾类所占比重较高,分别占36.0%、20.1%和18.0%;各月份摄食等级1~4级分布呈显著性差异（χ2=191.20,P〈0.01）,各叉长组大眼金枪鱼摄食等级变化无显著性差异（χ2=41.08,P〉0.05）。

赤道印度洋中部断面东西水交换的季节变化及其区域差异

采用海洋再分析资料和实测资料研究了热带印度洋中部东西水交换特征。结果表明存在两个相互独立的过程,即北印度洋过程(4°～6°N)和赤道过程(2°S-2°N)。北印度洋过程受季风影响显著,11月至翌年3月冬季风期间表现出很强的低盐水向西输送,5-9月夏季风期间则为高盐水向东输送;由于冬季风期间的输送较强,年平均表现为低盐水向西输送。赤道过程分为表层过程和次表层过程。表层赤道过程受局地风场驱动,有明显的半年周期;4-5月和10-11月的东向流将赤道西印度洋的高盐水向东输送,其余月份相反;向东的输送较强,年平均表现为净高盐水向东输送。在次表层赤道过程没有明显的季节变化,海流全年一致向东,将海盆西部的高盐水向东输送。

中印度洋海盆多金属结核地质特征

利用"大洋一号"2007年在中印度洋海盆采集的多金属结核和沉积物样品,采用X射线衍射、穆斯堡尔谱、X荧光分析、ICPMS等方法,对样品进行了矿物学和化学成分分析,并与东太平洋海盆我国开辟区多金属结核进行了对比。印度洋结核区海底沉积为含黏土硅质软泥,结核呈菜花状、碎屑状、杨梅状和连生体4种类型产出,大小为0～6cm,平均丰度4.213kg/m2,矿物有钙锰矿、水羟锰矿、水钠锰矿、针铁矿,其次为钙十字沸石、石英等,平均品位(Cu+Co+Ni)2.39%,菜花状结核富Mn、Ni、Cu(Mn/Fe=5.09～6.33),连生体状结核富Fe、Co(Mn/Fe=1.03～1.36),结核的页岩标准化稀土元素配分模式基本一致,表现为轻稀土富集、正Ce异常,但连生体状结核稀土总量和Ce的异常远远高于菜花状结核。中印度洋海盆结核与东太平洋海盆结核具有类似的矿物组成和稀土配分模式,可能具有类似的成因模式,但前者的平均丰度和品位均低于后者。

印度洋中西部大眼金枪鱼资源生物学的初步研究

根据2003-2004年1～6月份印度洋海域金枪鱼延绳钓生产实践及调查．对所捕获的大眼金枪鱼群体的构成、性比和胃含物等基本生物学特征进行了初步探讨及简单比较。结果表明。渔获中大眼金枪鱼体重范围为7～136kg（2003年）及14～100kg（2004年）。2003年，雌性个体所占比例基本上维持在0．45左右；2004年，雌性个体所占比例较2003年大。2003-2004年渔获中大眼金枪鱼分别由又长69～201cm及55～190cm的个体组成。2003年及2004年各月份1级所占比较均较大．1级以后胃饱满度频次基本上呈下降趋势。3～6月为印度洋中修补大眼金枪鱼的产卵期。体长一体重关系为W=3×10^-5L^2.8838。

印度洋中南部水域金枪鱼延绳钓钓钩钩型对钓获对象的选择性

基于2008年9月至2009年4月在印度洋中南部水域金枪鱼延绳钓渔场收集的数据,研究分析和比较了3种钓钩钩型(传统金枪鱼钩、"J"形钩和圆形钩)的渔获效益及对钓捕对象的选择性。结果表明:(1)从渔获种类上看,大眼金枪鱼和大青鲨金枪鱼钩钓获比例最高,"J"形钩和圆形钩的钓获比例相当;而长鳍金枪鱼则为金枪鱼钩钓获比例最高,其次为"J"形钩和圆形钩。(2)大眼金枪鱼存活率以金枪鱼钩最高,"J"形钩最低;长鳍金枪鱼则为"J"形钩稍高于圆形钩,金枪鱼钩最低;大青鲨则以圆形钩最高,"J"形钩最低。(3)"J"形钩钓获的长鳍金枪鱼和鲨鱼平均叉长较金枪鱼钩和圆形钩稍大;而金枪鱼钩钓获的大眼金枪鱼平均叉长较圆形钩和"J"形钩稍大。(4)3种钩型钓获的长鳍金枪鱼、大眼金枪鱼和大青鲨叉长分布均不存在显著性差异。

印度洋中南部长鳍金枪鱼生物学特性的研究

根据2008年9月—2009年4月印度洋中南部金枪鱼延绳钓渔场所捕获的长鳍金枪鱼Thunnus alalun-ga数据,对该鱼种的生物学特征进行了分析。结果表明：1）叉长为74~120 cm,优势叉长为105~110cm,约占总数的47.8%,平均叉长为（107.2±4.99）cm。2）长鳍金枪鱼叉长（LF,cm）与加工后重（WD,kg）的关系可表达为WD=1.7146×10-5LF3.0197（总体）,WDM=7×10-5L2F.M7229（雄性）,WDF=2×10-6L3F.F5354（雌性）。3）调查期间,长鳍金枪鱼性腺成熟度以Ⅳ级为主,约占总数的43.1%。4）当长鳍金枪鱼叉长小于100 cm时,摄食等级以0级和2级为主;当叉长为100~120 cm时,空胃率达39%以上,且随叉长的增长而递增。当叉长为91~110 cm时,摄食饱满指数随叉长增长而上升;当叉长为111~120 cm时,饱满指数随叉长递增而降低。

印度洋中西部大眼金枪鱼繁殖生物学的初步研究

根据2003年1—6月由中国农业部渔业局资助项目收集的渔业观察员数据和2004年1—6月印度洋中西部海域中国金枪鱼延绳钓生产调查数据，对所捕获的大眼金枪鱼繁殖生物学特征进行了初步研究。结果表明，渔获中性比均值为0．8，各月间的性比差异不显著。叉长小于85cm或大于185cm时，渔获个体均为雄性；叉长为85—170cm时，性比约为1．0。各月份大眼金枪鱼雌雄个体的性腺指数变动基本上保持一致，性腺指数随着月份增加而呈下降趋势。

印度洋中西部大眼金枪鱼年龄与鱼体脂肪含量的关系

本文根据2012年10月—2013年3月在印度洋中西部海域金枪鱼延绳钓渔业调查所获得的样本,利用其脊椎骨鉴定了334尾大眼金枪鱼(Thunnus obesus)的年龄,并利用鱼类脂肪含量仪测定了其肌肉的脂肪含量,进而对年龄与脂肪含量的关系进行了研究。结果表明样本金枪鱼的特征如下:(1)年龄组成为1—9龄,其中4—6龄比例最大,约占样本总数的66.4%;(2)脂肪含量范围为3.1%—29.8%,平均为13.4%,优势范围在7.0%—17.0%之间,其中13.0%—17.0%的比例最高达51.4%;(3)通过比较不同年龄组的脂肪含量发现,鱼体脂肪含量1—3龄随年龄增加而下降。4—5龄脂肪含量较高,6龄急剧下降到最低,7—9龄又呈升高的趋势;(4)雌性和雄性大眼金枪鱼的新陈代谢变化无明显差异,雌性比雄性的性成熟年龄要早1年左右,雌性3—4龄时性成熟,而雄性为4—5龄时性成熟;(5)脂肪含量的变化可能与大眼金枪鱼生长、繁殖、衰老等过程中的新陈代谢变化相吻合。

印度洋中脊多金属硫化物矿产资源定量预测与评价

大洋钻探资料证实,现代海底多金属硫化物分布范围广泛、储量大,是具有巨大开发潜力和远景的海底矿产资源。根据水深、地质构造、扩张速率、地球物理以及火山地震等区域性调查数据,分析了印度洋中脊多金属硫化物成矿地质条件、控矿因素和地球物理异常信息,提取了9项找矿证据因子,建立了区域找矿有利条件组合模型。运用证据权重法,对印度洋中脊多金属硫化物资源进行了基于数据驱动的定量预测与评价。研究认为,最有利区(Ⅰ类)占工区面积的29.77%,比较有利区(Ⅱ类)占18.12%。

印度洋中西部黄鳍金枪鱼生物学特性的初步研究

根据2003—2004年1—6月我国农业部印度洋金枪鱼延绳钓观察员项目所收集的有关数据，对印度洋中西部黄鳍金枪鱼的基本生物学特征进行了研究。结果表明，2003年和2004年渔获物中黄鳍金枪鱼加工后体重范围分别为7—81kg和20～78kg，优势组分别为20—50kg和30—60kg。叉长范围分别为70—180cm和110～170cm。2003年渔获物雌雄性比的平均值为0.71，月间性比组成差异较小；而2004年渔获雌雄性比的平均值为1．00，月间性比组成差异较大。2003年各月的摄食等级以1—2级为主，月间差异较小；而2004年摄食等级以1级为主，并且月间各等级组成差异大。体长与体重关系为W=2．1890×10^-5L^2.9269。

印度洋黄鳍金枪鱼生物学特性的初步研究(英文)

根据2003—2004年1—6月印度洋中西部海域金枪鱼延绳钓所捕获的黄鳍金枪鱼数据，对其基本的生物学特征进行了研究。结果表明，2003年和2004年渔获物中黄鳍金枪鱼加工后体重分别为7～81kg和20～78kg，优势组分别为20～50kg和30～60kg。叉长范围分别为70～180cm和110～170cm。2003年渔获物雌雄性比的平均值为0．71，月间性比组成差异较小；2004年渔获雌雄性比的平均值为1．00，月间性比组成差异较大。2003年各月的摄食等级以1—2级为主，月间差异较小；2004年摄食等级以一级为主，并且月间各等级组成差异大。当渔获个体的叉长小于100cm时，其性比组成波动较大；当渔获个体的叉长范围在100～150cm之间时，性比组成的变化相对较小，基本上维持在0．5左右，也就是说雌雄个体数量大体保持平衡；当渔获个体的叉长大于160cm时，所有样本个体均为雄性。体长与体重关系为W=2×10^-5L2.