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1.
尖顶海山和平顶海山是洋底海山的两种类型,同时也是富钴结壳资源赖以成长的主要载体,两者在地形上具有显著差别,资源状况和分布也不尽一致。以地形分类为基础,就中太平洋海山区两类海山结壳的成矿特征、宏微观构造、矿物和化学组成以及空间分布等进行了比对研究。研究认为,尖顶海山体积虽小,但地形演化连续,底层流及环境氧化性较强,有利于结壳的长期稳定生长,结壳厚度总体较大,富成矿元素和生物组分,远景成矿区域连续绵长。平顶海山山体巨大,顶部和斜坡陡崖区不利于结壳成长,底流活动只在山顶边缘和山脊地带表现突出,环境氧化性整体较弱,后期构造活动相对频繁,结壳总体厚度较小,铁,碎屑和热液组分含量较高,远景矿区相对狭窄。 相似文献
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中太平洋海山富钴结壳与基岩关系的研究 总被引：13，自引：5，他引：13
对我国首次取得的中太平洋海山基岩和富钴结壳样品的结构构造、矿物和化学组成特征的研究表明,该区主要基岩类型为碱性玄武岩、磷块岩、磷酸盐化碳酸盐岩和燧石等,碱性玄武岩分布最广,并均有不同程度的风化.观察表明,富钴结壳的载体可以是各种岩性的基岩.玄武岩、风化火山岩和磷块岩上的结壳厚度比燧石的大,有较高的经济价值,是选矿冶炼的主要对象.对于调查区内富钴结壳形态总体上可分为三种类型:板状、砾状和结核状结壳.从以下四个方面探讨结壳与基岩之间的关系:(1)海水、基岩和结壳中主要金属元素含量特点;(2)通过聚类分析方法探讨结壳与基岩之间的亲疏程度;(3)结壳的分布特征;(4)不同基岩类型对结壳生长的影响.分析结果表明,调查区内的火山岩及磷块岩对结壳形成的贡献大(比其他类型岩石). 相似文献
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A widespread distribution of hydrothermal and hydrogenetic manganese deposits is described in the results of the Hakurei‐Maru cruises conducted in the Bonin Arc areas of the West Pacific from 1984 to 1989. Manganese deposits occur in the active volcano chains, back‐arc basins, remnant back‐arc ridges, and oceanic seamounts. The hydrogenetic iron‐manganese deposits commonly form earthly black crusts and nodules on the topographic highs of inactive ridges and old seamounts, sometimes as thick as 10 cm. They are always composed of the iron‐manganese mineral vernadite. Co and Ni contents are relatively high in the crusts from the seamounts in the open Pacific Ocean (up to 1.1% Co and 1.0% Ni). Two generations of distinct chemistry and texture are typical of these crusts, which can be compared to reported thick crusts from the Central Pacific seamounts. The hydrothermal deposits, characterized by dense, submetallic, and gray appearance, are dominant in the recent and also in past submarine volcanoes of the island‐arc systems. Evidence of past hydrothermal activity was ascertained as fossil hydrothermal manganese deposits inside the hydrogenetic nodules or beneath the hydrogenetic crusts over the Tertiary island arc. Their component minerals are considered to be todorokite and bimessite (stable and contractible upon dehydration), having almost negligible amounts of Fe, Si, Al, Ni, Co, Zn, Pb, Cu, etc. In the small model site, the Kaikata Seamount hydrothermal area, the presumably recent hydrothermal activity has yielded thin slabs of pure manganate deposits growing downward within volcanic and sand layers. Early diagenetic influence is negligible on nodules of this area. 相似文献
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The Magellan seamounts began forming as large submarine shield volcanoes south of the equator during the Cretaceous. These
volcanoes formed as a cluster on the small Pacific plate in a period when tectonic stress was absent. Thermal subsidence of
the seafloor led to sinking of these volcanoes and the formation of guyots as the seamounts crossed the equatorial South Pacific
(10–0°S) sequentially and ocean surface temperatures became too high for calcareous organisms to survive. Guyot formation
was completed between about 59 and 45 Ma and the guyots became phosphatized at about 39–34 and 27–21 Ma. Ferromanganese crusts
began formation as proto-crusts on the seamounts and guyots of the Magellan Seamount cluster towards the end of the Cretaceous
up to 55 Ma after the formation of the seamounts themselves. The chemical composition of these crusts evolved over time in
a series of steps in response to changes in global climate and ocean circulation. The great thickness of these crusts (up
to 15–20 cm) reflects their very long period of growth. The high Co contents of the outer parts of the crusts are a consequence
of the increasing deep circulation of the ocean and the resulting deepening of the oxygen minimum zone with time. Growth of
the Co-rich Mn crusts in the Magellan Seamount cluster can be considered to be the culmination of a long journey through time. 相似文献
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富Co铁锰结壳铂族元素与铼-锇同位素组成及其意义 总被引：13，自引：0，他引：13
用ICP－MS测定了太平洋富Co铁锰结壳铂族元素和铼－锇同位素组成。富Co铁锰结壳不仅异常富集铂族元素，而且铂族元素及其它亲铁元素的配发与陨石特征非常相似。铁锰结壳的铼－锇同位素组成明显有别于大陆地壳岩石，和K－T界线沉积物相似，接近陨石值。世界大洋范围内的富Co铁锰结壳均产于远离海底构造热液活动区，几乎不可能受到地幔源热液作用的直接影响。因此，富Co铁锰结壳中的铂族元素可能部分来源于地外物质。 相似文献
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Pavements of manganese nodules and crusts and outcrops of Miocene limestones were observed on the flanks and flat top of the Tenpo Seamount during three Shinkai 2000 dives. The pre‐Miocene volcano supplied nuclei of volcanic rocks and hydrothermal manganese deposits, and subsequent slow or no sedimentation promoted deposition of abundant hydrogenetic nodules and crusts, mainly on the upper flank of the seamount. Nodule pavements generally cover calcareous sand surface sediments, while crusts cover hard outcrops composed probably of volcanic rocks. The fields of crusts and nodules are sparsely distributed with each other on scales of meters to tens of meters. The on‐site observation suggests the deposits have encountered tectonic and/or mass movements that resulted in unusual occurrences of densely stacked nodules and occasionally the nodules resting directly on crusts or hard substrates. Mineralogical and chemical compositions reveal that for nodules and crusts the encrusting manganese layers of around 1 cm thickness are composed of hydrogenetic vernadite, and diagenetic influence is negligible. 相似文献
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P. Stoffers G. P. Glasby D. Stuben R. M. Renner T. G. Pierre J. Webb 《Marine Georesources & Geotechnology》2013,31(1):45-86
Abstract Hydrothermal iron‐rich crusts have been recovered from a number of hot spot volcanos including Crough Seamount, Pitcairn Volcanos 2 and 1, Cyana Seamount, Teahitia, Moua Pihaa, and Macdonald Seamount in the S. W. Pacific. Mineralogically, the crusts consists of ferrihydrite with traces of the weathering products of volcanic ash (feldspar, nontronite, pyroxene, and serpentinite). The iron oxyhydroxide phase has a mean particle size of 3–4 nm indicating rapid deposition. Electron microprobe studies have revealed the presence of filamentous iron‐silica deposits within the crusts reflecting the possible bacterial oxidation of iron from the hydrothermal fluids. The crusts display wide variability in composition both between individual sampling stations and between seamounts. Endmember analysis shows that the compositional data can be resolved into three endmembers: a Fe‐rich endmember, a light and heavy rare earth element endmember, and a Ba (barite)‐rich endmember. The Fe‐rich endmember appears to contain very low concentrations of most trace elements. For bulk samples, the composition of the iron‐rich crusts reflects dilution of the iron oxyhydroxide phase by volcanic ash and, to a lesser extent, a hydrogenous component. This is illustrated by the wide variability in SiO2 (11.1–71.3%) and Mn (0.01–1.21%) contents of the crusts. For iron‐rich crusts containing greater than 40% Fe, the Pitcairn crusts display lower contents of Pb, Ba, Mo, U, Th, As, and rare earth elements (REE) and lower cerium anomalies than those from Teahitia. REE profiles of crusts from each of the hot spot volcanoes are characterized by small negative cerium anomalies but pronounced positive europium anomalies. The low average La/Fe ratios of the crusts from the various seamounts (47–572 X 10‐6) and positive Eu anomalies of the crusts suggest rapid deposition of the iron oxyhydroxide near the hydrothermal vent. The high Fe/Mn ratio of vent fluids at hot spot volcanoes (8.5–5.6) may account for the formation of these iron‐rich crusts. The present data indicate that there may be differences in the nature of the iron‐rich crusts based on the depth of occurrence. This influences the temperature of the venting hydrothermal fluids and the possibility of occurrence of submarine phreatomagmatic eruptions. 相似文献
9.
A method is proposed for identifying seamounts in the northwest sector of the Pacific based on the following criteria: a closed, close to isometric contour of the isobaths at the base of a structure, its quasi-conical shape, and angles of slope exceeding 5° within the limits of the closed contour. A catalog of the mountains has been compiled, consisting of 1995 objects and their quantitative characteristics. The catalog data were statistically processed, and the following was calculated: the correlation between the number of seamounts from the radius of their base and volume, the distribution of the number of mountains, and the total volume within the study area. It is shown that seamounts are characterized as multiscale, and they are located very unevenly: areas with and without their accumulation are distinguished, and the composition of volcanic rocks is typically isotopically and geochemically heterogeneous. It is concluded that currently there is no single geodynamic model that can explain the revealed phenomena in their entirety. At the same time, the data suggest that the nature of some magma chambers that feed intraplate volcanoes is caused by transformation of energy in the lithosphere as a nonlinear open system. 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