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在对CA海山玄武岩CAD21样品岩相学研究基础上,运用电子探针和X-荧光光谱法(XRF)对中太平洋CA海山斜长石斑晶中的环带、斜长石微晶和玄武岩中的硅酸盐进行了化学成分研究。CA海山玄武岩为地幔柱成因的板内玄武岩;斜长石斑晶具有环带结构,环带核部与边部为不连续消光,是不连续环带;环带核部为培长石,边部为拉长石,是岩浆演化过程中形成的正环带,其成因受岩浆演化过程中熔体组分及温、压条件的共同制约。斜长石斑晶核部、边部及斜长石微晶估算温度平均值分别为1 281,1 198和1 071 ℃,分别代表了岩浆源区、岩浆房及岩浆喷发温度,三者温度差值较小,这和洋岛玄武质岩浆的形成及喷发特点相吻合。 相似文献
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麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征 总被引：3，自引：2，他引：1
麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征研究表明,岩性为蚀变玄武岩、橄榄玄武岩等;结构为基质具间隐、间往结构及拉斑玄武结构的斑状结构;矿物组成为斜长石、橄榄石、辉石及脱玻化玻璃等。按岩石化学成分分类属碱性玄武岩,而稀土分配模式属洋岛碱性玄武岩类型。 相似文献
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海底熔岩风化作用过程的研究对于澄清元素地球化学迁移具有重要的意义。首先简要介绍了海底熔岩风化作用及鉴定标志。在细致的岩相学工作前提下,利用指示风化程度的特征风化矿物如橙玄玻璃、黏土矿物(蒙脱石和蒙皂石)、沸石(钙十字沸石)以及铁的氧化物和氢氧化物,结合烧失量(L.O.I),K_2O/(K_2O+Na_2O)比值和Fe_2O_3/(FeO+Fe_2O_3)比值等识别风化岩石的化学鉴别指标,辨识了马里亚纳海槽熔岩(弧后盆地玄武岩,BABB)和火山玻璃、西太平洋海山省(白垩纪碱性洋岛玄武岩,OIB)及中生代洋壳(洋脊玄武岩,MORB)的风化程度,探讨了风化作用的原因及其对岩石地球化学数据的影响。结果表明,与超过5 Ma的海山和洋壳玄武岩相比,马里亚纳海槽玄武质熔岩风化程度很低,仅基质中的隐晶质和玻璃质及玄武岩的玻璃质边缘略微橙玄玻璃化,其余基本保持新鲜岩石结构。马里亚纳海槽熔岩和火山玻璃的很低的风化程度是因其在海底经历的风化作用时间很短。最后,我们指出,马里亚纳海槽处海底熔岩风化作用没有造成显著的元素迁移,对精确获得其全岩的元素和同位素地球化学数据不产生明显影响,而对超过5 Ma的海底熔岩的地球化学数据解释时要谨慎。 相似文献
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全球三大洋海山钴结壳资源量估算 总被引：8，自引：0，他引：8
钴结壳具有Co、Ni、Cu和Mn及其他金属的潜在矿产资源和储存在结壳层中古环境信息的双重意义。与深海多金属结核和热液硫化物矿床相比,具有较高Co、Ni和Pt含量的海山钴结壳有可能成为商业勘探的潜在目标。为合理地估算出全球三大洋海山钴结壳资源量,基于我国西太平洋海山钴结壳拖网采样调查资料和对太平洋海山钴结壳资源分布规律和钴结壳矿区圈定参数指标的深入研究,按海山不同高度、不同洋壳年龄赋予不同结壳厚度,进而计算出全球三大洋海山钴结壳分布面积为3 039 452.14km2和干结壳资源量为(1 081.166 1~2 162.332 2)×108 t。太平洋海山钴结壳分布面积为2 123 087.12km2和干结壳资源量为(513.244~1 026.488)×108 t,大西洋海山钴结壳分布面积为512 509.74km2和干结壳资源量为(116.503 2~233.006 4)×108 t,印度洋海山钴结壳分布面积为403 855.28km2和干结壳资源量为(81.484 9~162.969 8)×108 t。三大洋海山钴结壳的Mn、Co、Ni和Cu金属量分别为(138.848 0~277.696 0)×108 t,(3.967 6~7.935 2)×108 t、(2.793 6~5.587 2)×108 t和(0.825 1~1.650 2)×108 t。根据钴结壳的Co含量、Co通量和厚度相关分析,所赋予的钴结壳厚度占理论推测厚度的6.10%~12.20%,这与Ku等得出"钴结壳生长时间约占其整个生命史4%"的认识非常相近。三大洋海山钴结壳实测厚度与赋值厚度对比分析表明,太平洋海山钴结壳赋值厚度平均值为1.87cm,实测厚度平均值为1.77cm,相对误差为5.35%,大西洋和印度洋相对误差分别为18.18%和23.23%。研究数据表明按海山高度和洋壳年龄所赋的钴结壳厚度基本合理,估算出的钴结壳资源量基本可靠。本文首次估算出三大洋海山钴结壳资源量,为整个海盆和三大洋海山钴结壳资源量估算提供了新方法。 相似文献
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南海东部海盆海山磁性对比 总被引：1，自引：0，他引：1
根据 1 980年～ 1 987年在南海海盆进行地球物理调查获取的海山地形和地磁异常资料 ,运用虚源法 ,对南海东部海盆区域的 9座海山作了磁性计算及对比。结果表明 :(1 )每座海山非均匀磁性反演的磁异常形态比均匀磁性反演的磁异常形态更接近观测异常 ,海山为非均匀磁化。 (2 )每座海山的非均匀磁化计算的拟合度参数值 (GFR值 )大于均匀磁化计算的拟合度参数值 (GFR0 值 ) ,平均每座海山增加 3 .7。 (3 )海山形成后均向北运移 ,位于东部海盆北侧的5座海山沿纬向位移的平均距离为 9.2 1°,南侧 4座海山沿纬向位移的平均距离为 3 .6 7°;海山均呈逆时针旋转 ,但旋转的角度存在区域性差异 ;东部海盆的运移方式与东邻的吕宋岛、西菲律宾海盆和台湾岛相一致。 (4)海山的磁化强度呈明显的分区性 ,北侧 5座海山的磁化强度大于南侧 4座海山的磁化强度 ,推测东部海盆形成过程中整体向北运动 相似文献
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南海海盆15°N附近呈东西向展布的珍贝-黄岩海山被认为是32~17Ma前南海海盆的残留扩张中心.对采自黄岩海山的两个火山岩样品(9DG,9DG-2)进行了岩石学、地球化学和年代学研究.两个样品的SiO2含量分别为60.3%和63.6%,Al2O3含量分别为17.56%和17.55%,TiO2含量分别为0.48%和0.31%,碱度率分别为3.88和3.62.根据岩石学和岩石化学分类,样品属碱性系列的粗面岩.对稀土元素和微量元素分析表明岩石具有洋岛玄武岩(OIB)型配分型式,轻重稀土总量比(∑c(LREE)/∑c(HREE))和球粒陨石标准化镧镱比((La/Yb)N)分别高达17.22和27.23,并具有铕负异常和锶、磷、钛亏损的特点.样品9DG的锶-钕-铅同位素分析结果为锶-87的含量与锶-86的含量之比值为0.704183,钕-143的含量与钕-144的含量之比值为0.512827,铅-206的含量与铅-207的含量之比值为18.68668,铅-207的含量与铅-204的含量之值为15.67962,铅-208的含量与铅-204的含量之比值为39.00261,表明初始岩浆来自软流圈地幔,具有与珍贝海山玄武岩相似的同位素组成.经钾-氩法测年,粗面岩的年龄为(7.77±0.49)Ma,略晚于珍贝海山玄武岩的年龄[(9.1±1.29)~10.0±1.80Ma],属于南海扩张期后晚中新世火山活动的产物.对比珍贝海山玄武岩的地球化学和同位素特征,认为两者有相同的岩浆源区,但是它们经历了不同程度的结晶分异过程,在晚中新世期间珍贝-黄岩海山可能有地幔柱活动. 相似文献
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2017年8月中国科学院海洋研究所在西太平洋低纬度海区的卡罗琳洋脊CM4海山开展了多学科综合调查,发现该海山山体表面分布着大量的铁锰结壳。本文对该海山的5个铁锰结壳样品进行了矿物学和地球化学研究,利用X射线衍射(XRD)、电感耦合等离子光谱及质谱(ICP-OES、ICP-MS)等测试技术分析了铁锰结壳的矿物组成、主微量元素和稀土元素含量,并进一步探讨了铁锰结壳的成因类型。结果表明,该海山铁锰结壳的矿物组成以水羟锰矿为主,含有少量钡镁锰矿、水钠锰矿、针铁矿、纤铁矿、石英和方解石。该海山铁锰结壳的Mn、Fe、Co、Ni、Cu元素平均含量分别为24.24%、15.14%、0.16%、0.34%、0.01%。与全球各大洋海山区铁锰结壳相比,该海山样品的Cu含量很低。该海山铁锰结壳的稀土元素(REY)含量相对偏低,总体为轻稀土(LREE)富集;稀土(REY)配分模式显示相对平坦的特征,呈明显的Ce正异常,轻微的Y负异常和Ho正异常。样品的矿物组成、元素比值、元素组合等都表明该海山铁锰结壳属于水成成因,未受明显的成岩作用影响。 相似文献
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大洋富钴结壳成因机制的探讨——水成因证据 总被引：3，自引：0，他引：3
根据对大洋富钴结壳的分层与年龄、分层与生长速率、生长间断等观测事实,以及大洋富钴结壳主量元素锰、铁元素及钴元素、铂元素、稀土元素、氦同位素、锇同位素等的水成富集,指出大洋富钴结壳是水成因的,进而指出富钴结壳的形成与基岩无关,水动力条件、最低含氧带、生物作用等可能对富钴结壳的形成有控制作用。同时,富钴结壳不一定只生长在岩石裸露的海山上,在沉积物覆盖的海山区也有可能找到富钴结壳。 相似文献
12.
《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(6):1125-1139
Three seamounts flanking the oceanic island of Bermuda were sampled for hydroids. Collecting was undertaken by submersible (SDL-1) and by dredge at depths between 48 and 107 m on the summits of Argus and Challenger banks. A shallower collection (<20 m) from the pilings of a tower on Argus Bank was made using SCUBA. Major bottom types on both banks were aggregations of rhodoliths, limestone reefs, and areas of calcareous sand. Hydroids were ubiquitous, but quite sparse, on firm substrata. None was collected on sandy bottoms. Of 45 species identified from the two oceanic banks, over half (25) were found on both. On Bowditch Seamount, samples were obtained at depths between 1285 and 1381 m by dredge and grab. Of four species found, only one (Filellum serratum) occurred in shallower collections from Argus and Challenger banks. Most species (43 of 48) from the three seamounts have been reported elsewhere in the Western Atlantic Tropical region, and many (38 of 48) are known from Bermuda. No endemics were discovered, and no relicts or exotics were recognized. Gonophores in >70% of the species are fixed sporosacs instead of free medusae. This conforms with a hypothesis that invertebrates of oceanic islands and seamounts tend to have short-lived pelagic larval stages, ensuring the greatest retention and conservation of propagules. 相似文献
13.
中国第四系研究中的几个问题 总被引：3，自引：0，他引：3
王强 《海洋地质与第四纪地质》1992,(3)
在第四系地层典着手编写之际,本文对第四系研究的一些基本问题进行了讨论。第四系长期以来的“四分”及相应的符号,将下、中、上更新亚统与全新统并列而应废止;且由于全新统资料已很丰富,可以再予细划分,则在取Q_p和Q_h作更新统和全新统代号后,再行划分,并在其右上角做亚统标记。从多重标准划分地层后,为求得国际可使用的对比基础,应尽量使用时间标尺。西部依构造期划分的地层,未能精确地确定地质时代,除非对构造期及相应地层做测年,否则,与东部沉降地区地层对比将有很多困难。应严格组的内容、概念、延伸性的研究。 相似文献
14.
利用重磁计算解释南海海盆中部地壳结构特征 总被引：11，自引：0，他引：11
以南海海盆中部3个海盆的交汇处为研究区，通过对重磁异常场的向上延拓计算及对重力异常的重反演拟合计算，并结合地质资料，进行综合分析和解释来揭示此区域的地壳结构特征。结果表明研究区地壳结构复杂，三种性质的地壳均有分布。各海山形成过程和岩石组成及地壳结构不尽相同，区内有年轻的大洋玄武岩海山，也有包含了大陆玄武岩的“双性”海山。综合各种地质、地球物理现象，认为南海海盆可能是多种机制联合作用的结果，西南、西北两海盆的形成时间要早于中央海盆。 相似文献
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Georgia Pe-Piper Shawn Meredyk Yuanyuan Zhang David J. W. Piper Evan Edinger 《Geo-Marine Letters》2013,33(6):433-447
The Early Cretaceous separation of Newfoundland from Iberia–Ireland is a classic example of a magma-poor continental margin with hyperextension and with widespread minor magmatism resulting in seamounts. This study defines the distribution of seamounts east of Orphan Knoll, and documents and interprets the geochemical character of the one recovered lava sample. Video imagery of lava outcrops, and the sample, were obtained by ROV from Orphan seamount, one of a linear series of small seamounts overlying transitional thinned continental crust on the seaward side of Orphan Knoll. New multibeam bathymetry and legacy seismic data show several seamounts that extend irregularly along the fault-bound NE margin of Orphan Knoll. Whole rock geochemistry shows the sample to be highly alkaline basanite or possibly tephrite. Diopside–hedenbergite, kaersutite and K-feldspar phenocrysts were analyzed by electron microprobe and scanning electron microscope, and alteration minerals including kaolinite were identified by X-ray diffraction. The highly alkaline character of the basanite is similar only to Early Cretaceous volcanic and sub-volcanic rocks erupted through thick continental crust of the Mesoproterozoic Grenville Orogeny. The location of the linear set of seamounts is related to margin-parallel faults on the seaward side of Orphan Knoll that provided a pathway for magma, although ENE-trending lineaments in individual seamounts or seamount groups suggest the influence of oceanic fracture zones. A lower gradient crest to Orphan seamount above 2,200 m suggests subaerial erosion, consistent with the presence of kaolinite as an alteration product and the absence of lava pillows at and above this depth. 相似文献
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The diverse geodynamic conditions of the parental magma??s melting are responsible for the compositional diversity of the alkaline volcanics near the southwestern margin of Iberia. The petrological-geochemical data show that the volcanics of the Gorringe Bank originated within the continental plate. The parental melilitite melts depleted in silica and anomalously enriched with trace elements could have been generated only in deep settings with a low degree of metasomatically enriched mantle matter melting. The volcanic melilitite-nephelinite-phonolite series is widespread in alkaline provinces of the Eurasian, African, and other continental plates. The Ampere, Josephine, and other seamounts and islands of the region are largely composed of volcanic rocks belonging to the picrobasalt-hawaiite-mugearite association. Their parental magmas were generated within the oceanic plate at shallower depths under a higher degree of moderately enriched oceanic lithospheric mantle melting. Both series of volcanics were formed under the influence of mantle plumes. 相似文献
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Valrie Allain Julie-Anne Kerandel Serge Andrfouët Franck Magron Malcolm Clark David S. Kirby Frank E. Muller-Karger 《Deep Sea Research Part I: Oceanographic Research Papers》2008,55(8):1035-1047
Seamounts are habitats of considerable interest in terms of conservation and biodiversity, and in terms of fisheries for bentho-pelagic and pelagic species. Twenty previously compiled datasets including seamount/underwater feature lists, bathymetric maps and emerged feature maps from different sources (ship-derived and satellite altimetry-derived) at different spatial scales (from individual cruise to worldwide satellite data) were gathered in order to compile an enhanced list of underwater features for parts of the western and central Pacific Ocean (WCPO). The KL04 dataset [Kitchingman, A., and Lai, S., 2004. Inferences on potential seamount locations from mid-resolution bathymetric data. Fisheries Centre Research Reports 12 (5), 7–12], listing seamount positions and depths as calculated from satellite altimetry-derived bathymetry, provided the baseline data for this study as it covered the entire region of interest and included summit depth information. All KL04 potential seamounts were cross-checked with other datasets to remove any atolls and islands that had been incorrectly classified as seamounts, to add seamounts undetected by KL04, to update the overall database (geolocation, depth, elevation, and name) and to compile a 12-class typology of the different types of underwater features. Of the 4626 potential seamounts identified in KL04, 719 were multiple identifications of the same large underwater features and 373 (10%) were actually emerged banks, atolls and islands, leaving 3534 actual underwater features. Conversely, 487 underwater features were documented in other datasets but not registered by KL04. The screening of all the potential WCPO seamounts produced a final list of 4021 underwater features with agreed upon position and information. This enhanced list should have many applications in oceanography, biodiversity conservation and studies of the influence of seamounts on pelagic ecosystems and fisheries. 相似文献
18.
断裂和白垩纪岩浆活动对中西太平洋海山区海山形成的影响 总被引：6，自引：0，他引：6
断裂和岩浆活动影响着海山的形成及其基岩的分布类型。在总结中、西太平洋海山区的海山与构造分布特征、白垩纪大规模岩浆喷发事件、海山形成年代分布、海山与海底高原的岩性分布和GEOROC数据库样品的年代时序对比的基础上,分析了断裂和白垩纪岩浆活动的特点及其对中、西太平洋海山区海山形成的影响作用。研究认为:中、西太平洋海山区的洋壳在海山形成前受断裂带改造;受白垩纪大规模岩浆活动的影响,中、西太平洋海山区的海山约在87~89 Ma和120~123 Ma出现两个生长高峰期,并且在岩性上表现出与同期生成的海底高原相近。 相似文献
19.
Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province(WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new ~(40)Ar/~(39) Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt(OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element(REE) patterns and a spider diagram of the samples in this study show OIB(Ocean Island Basalt) like behavior. The range of ~(87)Sr/~(86) Sr values is from 0.704 60 to 0.706 24, the range of ~(206)Pb/~(204) Pb values is from 18.241 to 18.599, and the range of ~(143)Nd/~(144) Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMII. Finally, new ~(40)Ar/~(39) Ar age data show that these seamounts formed at ～97 and ～106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins. 相似文献
20.
The Canary and Cape-Verde archipelagos are two groups of volcanic islands often cited as case examples of the surface expression
of two distinct hot-spot plumes. However, several considerations that␣we enumerate suggest a link between the two archipelagos.
Using seismic profiles we describe a continuous morphological basement ridge that exists between the two archipelagos. We
then examine the stratigraphic record available from field data on Fuerteventura Island (Canary) and Maio Island (Cape-Verde)
and from a few Deep Sea Drilling Project (DSDP) holes. The geological history of these volcanic islands is very similar since
the formation of their oceanic basement during the Late Jurassic. They share the same and synchronious sedimentary evolution
(subsidence, uplift and emersion) as well as very similar timing of volcanism and deformation. The two distinct hot-spots
model does not appear adapted to account for the formation of these structures as it ignores the existence of the ridge, as
well as most of the geological coincidences. By describing the coinciding geological incidents, we argue that it is misleading
to treat these two regions apart. 相似文献