Mineralogical characteristics of polymetallic sulfides from the Deyin-1 hydrothermal field near 15°S,southern Mid-Atlantic Ridge

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.     

南大西洋沉积物中多环芳香化合物的组成特征研究

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.     

Robust LS-SVM regression for ore grade estimation in a seafloor hydrothermal sulphide deposit

Due to the geological complexities of ore body formation and limited borehole sampling, this paper proposes a robust weighted least square support vectormachine (LS-SVM) regression model to solve the ore grade estimation for a seafloor hydrothermal sulphide deposit in Solwara 1, which consists of a large proportion of incomplete samples without ore types and grade values. The standard LS-SVM classification model is applied to identify the ore type for each in complete sample. Then, a weighted K-nearest neighbor (WKNN) algorithm is proposed to interpolate the missing values. Prior to modeling, the particle swarm optimization (PSO) algorithm is used to obtain an appropriate splitting for the training and test data sets so as to eliminate the large discrepancies caused by randomdivision. Coupled simulated annealing (CSA) and grid search using 10-fold cross validation techniques are adopted to determine the optimal tuning parameters in the LS-SVM models. The effectiveness of the proposed model by comparing with other well-known techniques such as inverse distance weight (IDW), ordinary kriging (OK), and back propagation (BP) neural network is demonstrated. The experimental results show that the robust weighted LS-SVM outperforms the othermethods, and has strong predictive and generalization ability.     

东太平洋海隆热液区嗜热深海偏顶蛤 （Bathymodiolus thermophilus）的形态和分布特征

在2009-2010年的中国大洋第21航次环球科学考察中,"大洋一号"考察船对东太平洋海隆1.2°N周边新发现的"宝石山"热液区进行了综合调查,并利用我国自主研发的电视抓斗采集到了贻贝类样品,经形态学研究鉴定为嗜热深海偏顶蛤Bathymodiolus thermophilus,Kenk&Wilson,1985,这是此物种在该区域分布的新纪录。文章对样品进行了详细描述,并与其它海区发现的B.thermophilus进行了形态学上的比较和讨论。     

大洋中脊热液活动与轴部岩浆房的分布、深度以及熔融程度之间的关系

热液活动,特别是高温流体释放,通常与轴部存在岩浆房（AMC）有关,然而这种关系尚未得到系统的验证。通过对6个区域性较长（长度在170—560km之间）的洋脊段进行连续的AMC以及热液羽流调查,就有可能定量比较热液活动的分布、强度与AMC范围、深度以及在部分站位岩浆熔融程度之间的关系。这六个区域性洋脊的扩张速率在55—145mm／a之间,共包含20个次级的洋脊段。在洋脊段尺度上（除去受到热点影响的加勒帕戈斯扩张中心）,热液羽流的发生率随着AMC的发生率（AMCr,r^2=0．64）增加而线性增加。对所研究的6个区域性洋脊段而言,热液羽流的发生率随着AMC的深度减小而增加（AMCZ,r^2=0．66）。在次级洋脊段尺度上,热液羽流的发生率与AMCr（r^2=0．12）以及AMCz（r^2=0．25）相关性很差。最后在亚段尺度上,或者在局部尺度上（0．75km长的区间内）,热液羽流的强度随着AMCz的变浅而增强（r^2=0．85）。羽流强度越强的区间也就越接近它们的海底来源,其中68±13％直接位于AMC之上。这种分布与现在已知的40个高温喷口场中至少有37个位于AMC之上的分布相似。现在的数据能够允许我们验证AMC与热液活动相互之间关系的假设。尽管现存的数据很少,不支持如下假设：熔融富集的岩浆透镜体优先发育强烈的、持续周期长的热液喷发。同时,在任何洋脊段也未能为如下提议找到证据：在段尺度上,热液冷却的增加可以在局部亚段上降低AMCz。在慢速洋脊,岩浆房存在的证据相当稀少,然而这些数据却与那些具有更快扩张速率洋脊的数据相一致。对所有扩张速率洋脊的观察结果表明,几乎所有的高温热液场均与岩浆或者推断的岩浆有关;而“热岩”或者非岩浆热源不足以引起高温热液喷发。     

构造-岩浆作用对热液活动的控制机理: 马努斯海盆为例

综述了马努斯海盆热液区构造特征、基底差异, 结合马努斯海盆热液区热液活动与构造-岩浆特征, 探讨了二者的耦合关系, 以及构造-岩浆作用对热液活动的影响和控制。马努斯海盆位于西南太平洋俾斯麦海的东北部, 是世界上扩张速度最快的海盆之一。马努斯海盆西部(马努斯扩张中心, Manus Spreading Center, MSC)主要由海盆扩张成熟期产生的大洋中脊玄武岩组成, 属于成熟弧后扩张中心,发育Vienna Woods热液区; 海盆东部(东南裂谷, Southeast Rift, SER)则是一个拉张裂谷, 处于扩张的早期阶段, 属于不成熟弧后扩张中心, 发育PACMANUS、DESMOS、SuSu Knolls三大热液区。MSC与大洋中脊的热液活动相似, 而SER因受到火山、俯冲作用影响更为显著, 其热液流体具有岩浆流体和俯冲流体的特征。与Vienna Woods热液压相比, PACMANUS、DESMOS以及SuSu Knolls三个热液区的水深相对较浅(1 150～1 740 m), 是地球内部热物质由内向外迁移的结果, 其下部岩浆作用强烈。此外,岩浆脱气作用和数值模拟结果表明, PACMANUS热液系统中具有岩浆流体的输入。与Vienna Woods热液区相比, PACMANUS、DESMOS、SuSu Knolls热液区的热液活动强度及流体组成主要受控于岩浆作用。     

冲绳海槽中部热液区及典型喷口区地形地貌特征

利用最新测量的高精度深水多波束资料,对冲绳海槽中部热液活动区的地形地貌特征进行了系统的分析后发现,研究区地形情况相当复杂,起伏变化较大,总体上呈沿SW—NE向延伸的裂谷地势,裂谷水深范围约在1 500~1 800 m,大量呈SW—NE向的线性海山链和裂谷、洼地地貌交错出现,分析认为其形成可能与冲绳海槽的弧后扩张作用有关。另外,通过ROV(Remotely Operated Vehicle)上获得的影像,结合浅表层沉积物和岩石样品分析发现,2处喷口地形地貌情况明显不同,Iheya North喷口区地形起伏变化大,具有较多烟囱体、丘体,周围沉积物以硫化物砂为主;Iheya Ridge则以裂隙式溢流为主,分布范围广,地形倾斜平整,少见烟囱体、丘体,底质较硬,热液沉积物分布较少。     

海底热液沉积物中流体包裹体的研究进展

最近几个新兴起的海底热液沉积物中流体包裹体的研究可以解决许多利用常规矿物学和地球化学方法无法解决的重要科学问题,本文总结了该领域研究工作的进展,探讨了技术手段或方法上的发展及局限性,提出对热液沉积物中透明矿物的大范围显微测温对比分析和非透明矿物分温度段释放包裹体气候相结合,从而获取不同类型和不同成矿阶段包裹体物化指标及成分特征,进而研究热液循环机制及成矿作用过程的思路,对热液沉积物中流体包裹体研究     

冲绳海槽南段沉积物的元素赋存状态及其热液活动记录

为了解冲绳海槽南部沉积物的元素赋存状态以及热液活动对沉积物中元素组成的影响,对冲绳海槽南部沉积物岩芯HOBAB4-S2进行了全岩样及顺序提取分析,探讨了该沉积物岩芯中Al、Ti、K、Fe、Mn、Cu、Zn、Pb、Co、Ni及稀土元素的赋存状态,结果表明残留相与碳酸盐相是岩芯沉积物中元素的重要赋存形式,典型的碎屑组分Al、K、Ti在残留相中比例极高。铁锰氧化物相和有机结合相中各元素含量均相对较低,但在铁锰氧化物相中,与热液活动相关的金属元素在岩芯的萃取比例及含量上随着深度变化具有一致性,同时在4个层位出现了异常高值,表明在该层位对应的时期出现了热液活动对元素组成的显著影响,稀土元素总量变化上也可看出明显相同的变化趋势。沉积物的球粒陨石标准化稀土元素配分模式整体显示了轻稀土元素相对重稀土元素更富集的特征,具有极其轻微的Ce正异常和明显的Eu负异常,与南大西洋受热液活动影响较小的沉积物中铁锰氧化物相的配分模式类似,表明其受到热液流体的影响,是铁锰颗粒吸附海水与热液流体中稀土元素的结果。