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1.
The ultraslow-spreading Southwest Indian Ridge(SWIR) to the east of the Melville fracture zone is characterized by very low melt supply and intensive tectonic activity. Due to its weak thermal budget and extremely slow spreading rate, the easternmost SWIR was considered to be devoid of hydrothermal activity until the discovery of the inactive Mt. Jourdanne hydrothermal field(27°51′S, 63°56′E) in 1998. During the COMRA DY115-20 cruise in2009, two additional hydrothermal fields(i.e., the Tiancheng(27°51′S, 63°55′E) and Tianzuo(27°57′S, 63°32′E)fields) were discovered. Further detailed investigations of these two hydrothermal sites were conducted by Chinese manned submersible Jiaolong in 2014–2015. The Tiancheng filed can be characterized as a lowtemperature(up to 13.2°C) diffuse flow hydrothermal field, and is hosted by fractured basalts with hydrothermal fauna widespread on the seafloor. The Tianzuo hydrothermal field is an inactive sulfide field, which is hosted by ultramafic rocks and controlled by detachment fault. The discovery of the three hydrothermal fields around Segment #11 which receives more melt than the regional average, provided evidence for local enhanced magmatism providing heat source to drive hydrothermal circulation. We further imply that hydrothermal activity and sulfide deposits may be rather promising along the easternmost SWIR.  相似文献   

2.
3.
Investigations of the diffusion activities both within and outside the seafloor hydrothermal vents, as well as related mineral genesis, have been one of the key focuses of ocean biogeochemistry studies. Many hydrothermal vents are distributed close to the southern Okinawa Trough on the less-than-30-m deep shallow seafloor off Kueishan Tao, northeast of Taiwan Island. Investigations of temperature, pH and Eh at four depths of hydrothermal plume were carried out near Kueishan Tao at the white(24.83°N, 121.96°E) and yellow(24.83°N, 121.96°E) vents. An 87 h of temperature time series observation-undertaken near the white vent showed that tide is the main factor affecting the background environment. Based on the observed data, 3-dimensional sliced diffusion fields were obtained and analyzed. It was concluded that the plume diffused mainly from north to south due to ebb tide. The yellow vent's plume could effect as far as the white vent surface. From the temperature diffusion field, the vortices of the plume were observed. The Eh negative abnormality was a better indicator to search for hydrothermal plumes and locate hydrothermal vents than high temperature and low pH abnormalities.  相似文献   

4.
According to the exploration contract about polymetallic sulfides in the SWIR (Southwest Indian Ridge) signed by China with the International Seabed Authority, to delineate sulfide minerals and estimate resource quantity are urgent tasks. We independently developed our first coincident loop Transient Electromagnetic Method (TEM) device in 2010, and gained the TEM data for seafloor sulfide at South Atlantic Ridge 13.2°S in June 2011. In contrast with the widely applied CSEM (Marine controlled-source electromagnetic) method, whose goal is to explore hydrocarbons (oil/gas) of higher resistivity than seawater from 102 to 103 m below the sea floor, the TEM is for low resistivity minerals, and the target depth is from 0 to 100 m below the sea floor. Based on the development of complex sulfide geoelectrial models, this paper analyzed the TEM data obtained, proposing a new method for seafloor sulfide detection. We present the preliminary trial results, in the form of apparent resistivity sections for both half-space and full-space conditions. The results cor- respond well with the observations of the actual hydrothermal vent area, and the detection depth reached 50-100m below the bed, which verified the capability of the equipment.  相似文献   

5.
Massive sulfide precipitates found in the Southwest Indian Ridge(SWIR) 49.6°E hydrothermal field are enriched in gold.Here,the mineralogy and mineral chemistry of these massive sulfides to constrain the process of gold precipitation were studied.Sulfide samples in this field include lowertemperature Zn-rich sulfides and relative higher-temperature Fe-rich sulfides.Zn-rich sulfides are dominated by sphalerite-pyrite-chalcopyrite assemblages,with concentrations of gold ranging from 9.08 to 17.0 μg/g.Fe-rich sulfides consist mainly of pyrite-marcasite-isocubanite assemblages,with gold concentrations from 2.17 to 3.79 μg/g.The significant enrichment in gold within the lowertemperature Zn-rich sulfides and the effective separation of Zn and Fe in hydrothermal precipitates at the surface of this field are here interpreted to reflect the strong temperature dependence of gold transportation and deposition within the sulfides.In Zn-rich samples,large amounts of isolated native gold grains were identified.They were found mainly as inclusions up to 8 μm in diameter,occupying porous cavities in sphalerite or in the elevated iron content rim of sphalerite.The fineness of the gold ranged from 810 to 830.Unlike previously published results on other hydrothermal fields,these data show a low gold fineness values in SWIR 49.6°E.The FeS content of sphalerite associated with gold grains ranged from 3.2 mole % to 18.9 mole %.This was higher than in other fields,indicating that the sulfur activity is relatively low during the gold precipitation process and that sulfur activity may be one of the main factors affecting gold fineness in the SWIR 49.6°E hydrothermal field.Evidence regarding gold fineness and sulfur activity suggests that gold was quite likely transported as AuHS0 rather than as a Au(HS)-2 complex.  相似文献   

6.
The REE compositions of hydrothermal deposits and basalt samples from the Southwest Indian Ridge (SWIR) were determined with ICP-MS.The results show that there are significant differences between different types of samples although all samples show relative LREE enrichment.The contents of REE in hydrothermal sulfides and alterated rocks samples are lower (from 7.036 × 10 6 to 23.660 × 10 6),while those in the white chimney deposits are relatively higher (ranging from 84.496 × 10 6 to 103.511 × 10 6).Both of them are lower than basalts.Chondrite-normalized REE distribution patterns show that sulfides and alterated rocks samples are characterized by significant positive Eu anomalies.On the contrary,white chimney deposits have obvious negative Eu anomalies,which may be caused by abundant calcite existing in the white chimney samples.Both the content and distribution pattern of REE in sulfides suggest that REE most possibly is originally derived from hydrothermal fluids,but influenced by the submarine reducing ore-forming environment,seawater convection,mineral compositions as well as the constraint of mineral crystallizations.  相似文献   

7.
A seafloor hydrothermal field, named Deyin-1 later, near 15°S southern Mid-Atlantic Ridge(SMAR) was newly found during the 22 nd cruise carried out by the China Ocean Mineral Resources Research Development Association(COMRA). Sulfide samples were collected at three stations from the hydrothermal field during the26 th cruise in 2012. In this paper, mineralogical characteristics of the sulfides were analyzed with optical microscope, X-ray diffractometer, scanning electron microscope and electron microprobe to study the crystallization sequence of minerals and the process of hydrothermal mineralization. According to the difference of the ore-forming metal elements, the sulfide samples can be divided into three types:(1) the Ferich sulfide, which contains mainly pyrite and chalcopyrite;(2) the Fe-Cu-rich sulfide consisting predominantly of pyrite, chalcopyrite and isocubanite, with lesser amount of sphalerite, marmatite and pyrrhotine; and(3) the Fe-Zn-rich sulfide dominated by pyrite, sphalerite and marmatite, with variable amounts of chalcopyrite, isocubanite, pyrrhotine, marcasite, galena and gratonite. Mineral precipitations in these sulfides are in the sequence of chalcopyrite(isocubanite and possible coarse pyrite), fine pyrite,sphalerite(marmatite), galena, gratonite and then the minerals out of the dissolution. Two morphologically distinct generations(Py-I and Py-II) of pyrite are identified in each of the samples; inclusions of marmatite tend to exist in the coarse pyrite crystals(Py-I). Sphalerite in the Fe-Zn-rich sulfide is characterized by a"chalcopyrite disease" phenomenon. Mineral paragenetic relationships and a wide range of chemical compositions suggest that the environment of hydrothermal mineralization was largely changing. By comparison, the Fe-rich sulfide was formed in a relatively stable environment with a high temperature, but the conditions for the formation of the Fe-Cu-rich sulfide were variable. The Fe-Zn-rich sulfide was precipitated during the hydrothermal venting at relatively low temperature.  相似文献   

8.
The 26th Chinese COMRA (China Ocean Mineral Resources Research & Development Association) cruise was an important cruise. The Carlsberg Ridge (CR) of the Northwest Indian Ocean and the North Atlantic Ridge (NAR), in which less investigation has been carried out for hydrothermal activities, were investigated and studied during the first two legs of the 26th COMRA cruise. During the first leg, we found one hydrothermal activity field located in the CR at 3.5 -3.8 N on the Northwest Indian Ocean Ridge (NWIR), and sampled seafloor polymetallic sulfide deposits where only abnormalities were found before. During the second leg, we found a new hydrothermal anomaly field located in the NAR at 4 -7 N. The discovery of two hydrothermal and anomaly fields filled in the gap of hydrothermal investigation and study in the corresponding regions for China.  相似文献   

9.
Polymetalic sulfide is the main product of sea-floor hydrothermal venting, and has become an important sea-floor mineral resources for its rich in many kinds of precious metal elements. Since 2007, a number of investigations have been carried out by the China Ocean Mineral Resources Research and Development Association(COMRA)cruises(CCCs) along the Southwest Indian Ridge(SWIR). In 2011, the COMRA signed an exploration contract of sea-floor polymetallic sulfides of 10 000 km2 on the SWIR with the International Seabed Authority. Based on the multibeam data and shipborne gravity data obtained in 2010 by the R/V Dayang Yihao during the leg 6 of CCCs21, together with the global satellite surveys, the characteristics of gravity anomalies are analyzed in the Duanqiao hydrothermal field(37°39′S, 50°24′E). The "subarea calibration" terrain-correcting method is employed to calculate the Bouguer gravity anomaly, and the ocean bottom seismometer(OBS) profile is used to constrain the two-dimensional gravity anomaly simulation. The absent Moho in a previous seismic model is also calculated.The results show that the crustal thickness varies between 3 and 10 km along the profile, and the maximum crustal thickness reaches up to 10 km in the Duanqiao hydrothermal field with an average of 7.5 km. It is by far the most thicker crust discovered along the SWIR. The calculated crust thickness at the Longqi hydrothermal field is approximately 3 km, 1 km less than that indicated by seismic models, possibly due to the outcome of an oceanic core complex(OCC).  相似文献   

10.
南大西洋沉积物中多环芳香化合物的组成特征研究   总被引:1,自引:0,他引:1  
10 samples of sediments obtained from the South Mid-Atlantic Ridge were measured for the abundances and distributions of polycyclic aromatic compounds(PAHs). The total concentrations of PAHs(∑PAHs) ranged from 2.768 to 9.826 μg/g dry sediment. The ∑PAHs was higher in sample 22V-TVG10 and sample 26V-TVG05 which were close to hydrothermal fields, with the lowest value in sample 22V-TVG14 which was farthest from hydrothermal fields, suggesting a probable hydrothermal origin of ∑PAHs of samples. Approximately nine kinds of PAHs were identified, and low molecular mass tricyclic and tetracyclic aromatic compounds were predominant in the samples. The concentrations of fluoranthene which were typical as hydrothermal alteration compounds were the highest among PAHs with dry weight between 0.913–3.157 μg/g. The phenanthrene homologue was most abundant in the samples, and the ratios between parent phenanthrene and methylphenanthrene which probably reflected the degree of hydrothermal alteration ranged from 0.097 to 1.602. The sample 22V-TVG10 possessing a maximum ratio value showed the intense influence of the hydrothermal alteration on this sample, which might further imply that PAHs in sediments were mainly derived from the hydrothermal alteration.  相似文献   

11.
瞬变电磁法是深海多金属硫化物勘探的有效手段。海底多金属硫化物中高品位的金属组分会引起极强的激电效应,且对瞬变电磁响应产生显著影响。本文通过实验室测量和数值模拟对深海多金属硫化物的激电效应进行了探讨和分析。首先对西南印度洋中脊热液区的岩矿石样品进行了较为系统的电性测试,典型硫化物的复电阻率在频率域有最大达160 mrad相位移动,时间域与频率域的测量结果表明,极化率参数可以很好地区分硫化矿物与围岩。利用Cole-Cole模型对实测复电阻率进行解释,得到复电阻率的特征参数,分析各参数与块状硫化物组分和结构的关系,并根据极化率参数对典型硫化物进行了分类。将典型硫化物的激电参数用于计算层状介质的瞬变电磁响应,计算结果表明,在海底多金属硫化物矿床瞬变电磁法响应的最佳观测时窗内可同时观测到激电效应的影响。虽然在采集时窗晚期瞬变响应发生畸变,但在信号接收早期,激电效应能有效增强瞬变电磁法对深海多金属硫化物的探测能力,为瞬变电磁实测数据提供解释依据。  相似文献   

12.
现代海底热液沉积物的硫同位素组成及其地质意义   总被引:17,自引:0,他引:17  
共收集到现代海底热液沉积物的1264个硫同位素数据,结合我们对冲绳海槽Jade热液区和大西洋中脊TAG热液区中表层热液沉积物的硫同位素研究成果,对比分析了不同地质-构造环境中海底热液沉积物的硫同位素组成特征及其硫源问题.结果表明:(1)现代海底热液沉积物中硫化物的硫同位素组成集中分布在1‰~9‰之间,均值为4.5‰(n=1042),而硫酸盐矿物的硫同位素组成主要分布在19‰~24‰之间,均值为21.3‰(n=217);(2)无论在洋中脊还是在弧后盆地扩张中心,无沉积物覆盖热液活动区中热液沉积物与有沉积物覆盖热液活动区相比,其硫同位素组成的分布范围相对狭窄;(3)各热液活动区中硫化物硫同位素组成的不同,反映出各自硫源的差异性.无沉积物覆盖洋中脊中热液成因硫化物的硫主要来自玄武岩,部分来自海水,是玄武岩和海水硫酸盐中硫不同比例混合的结果,而在弧后盆地和有沉积物覆盖的洋中脊,除了火山岩以外,沉积物和有机质均可能为热液硫化物的形成提供硫;(4)现代海底热液沉积物硫同位素组成的变化和硫源的不同可能归因于海底热液体系中流体物理化学性质的变化、岩浆演化和构造-地质背景的不同.  相似文献   

13.
西南印度洋63.5°E热液区是在超慢速扩张洋脊发现的首个超镁铁质岩热液系统。对取自该区的热液硫化物样品进行了系统的矿物学和地球化学分析,矿物学分析结果表明:该热液区硫化物为富Fe型高温硫化物,且经历了较深程度的氧化蚀变,大量中间态的Fe氧化物充填在硫化物矿物间的孔隙及内部解理中;这些硫化物相以白铁矿为主,其次是等轴古巴矿和少量铜蓝,缺乏黄铁矿、闪锌矿。据推断,该区的热液成矿作用分为4个阶段:低温白铁矿阶段→高温等轴古巴矿阶段→自形白铁矿阶段→后期海底风化阶段(少量铜蓝以及大量的Fe的羟氧化物)。与之相对应,地球化学分析结果表明这些硫化物的Fe含量较高(31.57%~44.59%),Cu含量次之(0.16%~7.24%),而Zn含量普遍较低(0.01%~0.11%);微量元素较为富集Co(328×10-6~2 400×10-6)和Mn(48.5×10-6~1 730×10-6)。该区硫化物中较高含量的Fe、Co与超镁铁质岩热液系统相似,明显高于镁铁质岩热液系统。独特的热液硫化物矿物学特征和元素组成可能与该区普遍出露的地幔岩、橄榄岩蛇纹石化作用以及拆离断层的广泛发育的环境有关。  相似文献   

14.
INTRODUCTIONDuringtheperiodofearly 1 980stomid 1 990s ,withtherapiddevelopmentofexplorationtotheseafloorhydrothermalactivities ,thesulfurisotopiccompositionofhydrothermasedimentsaroundtheworldhadbeencarriedouttosomeextent (ZierenbergandShanks ,1 988;BlumandPuchel…  相似文献   

15.
海底热液活动及其周边环境的调查研究是海洋科学领域的热点之一。海底热液喷口环境的物理化学参数,尤其是浅水型热液,会受到潮汐变化的影响。台湾龟山岛靠近冲绳海槽南端分布有多处浅水型热液喷口(30m)。2010年5月,浙江大学、杭州电子科技大学和台湾中山大学对该海域实施了联合考察,利用电化学传感器获得了低温热液喷口(24.834 14°N,121.961 91°E)连续87h的温度和pH现场观测数据。基于Morlet复小波变换方法,分析了浅水型热液喷口的温度和pH现场观测时间序列的变化周期,并通过与当地潮汐记录数据作比较,获得了其与潮汐信号之间的潜在关系,证实了潮汐变化是海底白色热泉喷口物理化学参数现场观测最主要的影响因素。温度和pH现场观测数据经Morlet复小波变换后的小波系数分别存在规律的12.9h和12.5h变化周期,并且温度的小波系数在准半日周期尺度与潮汐高度呈负相关变化,相关系数为-0.89;pH的小波系数情况相反,相关系数为0.76。  相似文献   

16.
Abstract

Mineralogical, geochemical and S-isotopic studies were carried out on seafloor massive sulfides (SMS) and hydrothermally altered rocks from the mafic-hosted TaiJi field (including TaiJi-1 and TaiJi-2 sites), which is located on the margin of a nontransform discontinuity (NTD) on the Southern Mid-Atlantic Ridge (SMAR). The main hydrothermal precipitates of TaiJi-1 were massive sulfides, while TaiJi-2 produced a large amount of semi-massive sulfides. Significant rock alteration is an important feature of this field, and large amounts of clay minerals (chlorite) occurred in the semi-massive sulfides. Geochemically, notable negative correlations were identified between rock forming elements (Mg) and major hydrothermal metal elements such as Zn?+?Cu and Co in semisulfides. Such mineralogical and geochemical characteristics, together with low Co/Ni ratio (similar to the surrounding rocks) of the semi-massive sulfides and the unique REE features of some altered rocks, tell us that the prominent mineralization mechanism for these semi-massive sulfides was probably related to rock mineralization. Thus, TaiJi-2 appears to differ significantly from the TaiJi-1 in terms of sulfide mineralization mechanism. Moreover, the TaiJi sulfides are remarkable for large δ34S variation (7.2–15.3%). We suggest that seawater corrosion after sulfides precipitation were responsible for 34S enrichment in sulfides. Furthermore, our work sheds some light on the comparison between TaiJi and other NTD-related fields along the Mid-Atlantic Ridge. We argue that rock mineralization may represent an important mineralization type in NTDs.  相似文献   

17.
“潜龙二号”水下自主航行器(QianlongⅡ AUV)为深海资源尤其是海底多金属硫化物调查而设计,其已在西南印度洋脊热液区进行成功的调查运用。本文系统地概述了“潜龙二号”的热液系统探测功能实现、数据管理、快速成图等工作;阐述了如何利用AUV转圈数据有效的校正载体对磁测干扰的。基于“潜龙二号”获取的热液异常,发展了热液喷口快速定位方法。以具体一潜次为例,系统地展示了热液探测数据的处理分析与热液异常定位工作,证实了该方法的有效性。  相似文献   

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