西南印度洋中脊表层沉积物中存在热液组分的地球化学证据

Hydrothermal materials in deep-sea sediments provide a robust tracer to the localized hydrothermal activity at mid-ocean ridges. Major, trace and rare earth element(REE) data for surface sediments collected from the ultraslow spreading Southwest Indian Ridge are presented to examine the existence of hydrothermal component.Biogenic carbonate oozes dominate all the sediment samples, with CaO content varying from 85.5% to 89.9% on a volatile-free basis. The leaching residue of bulk sediments by ~5% HCl is compositionally comparable to the Upper Continental Crust(UCC) in SiO_2, Al_2O_3, CaO, MgO, alkali elements(Rb, Cs) and high field strength elements(Nb, Ta, Zr, Hf, Ti). These detritus-hosted elements are inferred to be prominently derived from the Australian continent by means of eolian dust, while the contribution of local volcaniclastics is insignificant. In addition, the residual fraction shows a clear enrichment in Fe, Mn, and Ba compared with the UCC. Combining the positive Eu anomaly of residual fraction which is opposed to the UCC but the characteristic of hydrothermal fluids and associated precipitates occurred at mid-ocean ridges, the incorporation of localized hydrothermal component can be constrained. REE mixing calculations indicate that more than half REE within the residual fraction(~55%–60%) are derived from a hydrothermal component, which is inferred to be resulted from a diffuse fluid mineralization. The low-temperature diffuse flow may be widely distributed along the slow-ultraslow spreading ridges where crustal faults and fissures abound, and probably have a great mineralization potential.     

海底天然气水合物及冷泉流体渗漏的原位观测技术

海底天然气水合物藏是天然的巨型碳储藏库,是深部甲烷等烃类气体运移至海底过程中暂时的碳储,是地球碳循环过程的重要一环。冷泉通常与海底天然气水合物藏分解密切相关,是深源或浅层气及水合物分解气在海底发生渗漏的现象。该文根据国内外天然气水合物及冷泉系统勘查的最新动向,综述了与水合物及冷泉流体渗漏相关的羽状流、运移通道、海底微地形地貌等要素的海底原位观测技术,主要包括：走航式及坐底式原位观测、海面及低空渗漏甲烷观测、海底可视化观测、与水合物及冷泉相关的海底观测网络等。综合使用原位观测技术可以更细致、全面地描绘水合物和冷泉系统的时空“景象”,更好地协助厘清海底渗漏甲烷的归趋,拓展人类对深海独特生命绿洲的认知。     

锂同位素地球化学及其在热液活动研究中的应用

在前人研究资料及成果的基础上,探讨了海底热液活动区锂和锂同位素地球化学组成及应用前景。与海底热液活动相伴的锂元素是海洋锂库的重要来源。海底热液系统中各部分锂及其同位素组成具有显著差异,热液流体中锂含量为20~1 421μmol/kg,δ7Li值为 2.6‰~ 11.6‰;孔隙水中锂含量为9.0~5 720μmol/kg,δ7Li值为 4.5‰~ 43.7‰;热液活动区沉积物中锂含量为(4.8~76)×10-6,δ7Li值为-4.31‰~ 9.36‰;风化玄武岩中锂含量为(6.97~75.5)×10-6,δ7Li值为 7.5‰~ 13.7‰;高温变质玄武岩中锂含量为(0.60~4.61)×10-6,δ7Li值为-2.1‰~ 4.8‰。因此,锂及其同位素组成能提供热液系统中有关水-岩反应、水-沉积物反应、物质来源及流体循环的信息,是洋壳岩石蚀变及海底热液循环非常有效的指示剂。热液系统锂及其同位素组成能预测海底水岩比率,是海底热液矿床规模预测的有效参数。     

矿山地质环境问题及防治对策

论述了矿业开发对大气环境、水文系统、土地资源的影响及引起的地质灾害，根据矿山地质环境质量评价，提出保护与防治矿山地质环境。实施清洁生产工艺，预防和减少污染。采用先进治理技术修复环境污染，走绿色矿业之路。     

西南印度洋中脊热液硫化物成矿物质来源探讨:同位素证据

报道了西南印度洋中脊47°E~55°E洋脊段热液区硫化物中He、Pb和Cu同位素特征,探讨了热液硫化物成矿物质来源特征。结果表明:硫化物N(3 He)/N(4 He)值变化范围较大(R/Ra=0.85~7.02),显示洋中脊玄武岩和海水对He来源具有不同贡献,硫化物中He主要来源于洋中脊玄武岩,也有部分放射性成因He的混入;热液硫化物Pb同位素比值变化范围很小(N(206 Pb)/N(204Pb)=18.196~18.239,N(207 Pb)/N(204 Pb)=15.479~15.490和N(208 Pb)/N(204 Pb)=37.951~38.023),与西南印度洋中脊玄武岩Pb同位素比值较大的变化范围相比,热液流体循环过程中Pb同位素发生了明显均一化;硫化物单矿物Cu同位素组成均为正值(δ(64 Cu)=(0.02~0.52)×10-3),显示西南印度洋中脊热液硫化物呈现略微富集Cu重同位素特征;西南印度洋中脊热液硫化物中He、Pb和Cu同位素记录了热液喷口流体和金属源区特征,热液硫化物成矿物质主要来源于洋中脊玄武岩和海水,但明显经历了热液流体再循环和后期改造过程。     

Chemical composition and petrogenesis of plagioclases in plagioclase-phyric basalts from the Southwest Indian Ridge(51°E)

Electron microprobe analysis was conducted on plagioclase from the plagioclase ultraphyric basalts(PUBs)erupted on the Southwest Indian Ridge(SWIR)(51°E) to investigate the geochemical changes in order to better understand the magmatic processes occurring under ultraslow spreading ridges and to provide insights into the thermal and dynamic regimes of the magmatic reservoirs and conduit systems. The phenocryst cores are generally calcic(An_(74–82)) and are depleted in FeO and MgO. Whereas the phenocryst rims(An_(67–71)) and the plagioclase in the groundmass(An_(58–63)) are more sodic and have higher FeO and MgO contents than the phenocryst cores. The crystallization temperatures of the phenocryst cores and the calculation of the equilibrium between the phenocrysts and the matrix suggest that the plagioclase cores are unlikely to have crystallized from the host basaltic melt, but are likely to have crystallized from a more calcic melt. The enrichment in incompatible elements(FeO and MgO), as well as the higher FeO/MgO ratios of the outermost phenocryst rims and the groundmass, are the result of plagioclase-melt disequilibrium diffusion during the short residence time in which the plagioclase crystallized. Our results indicate that an evolved melt replenishing under the SWIR(51°E) drives the eruption over a short period of time.     

现代海底热液流体和硫化物Fe同位素组成特征及其地质意义

<正>非传统稳定同位素体系地球化学及其应用近十多年来得到了快速发展,特别是低分辨率下Fe同位素的MC-ICP-MS高精度测试技术使得Fe同位素在地球科学领域得到广泛应用(Belshaw et al.,2000;Zhu et al.,2002;朱祥坤等,2013)。前人对地球上不同储库的Fe同位素组成进行了大量研究,     

拆离断层与大洋核杂岩: 一种新的海底扩张模式

近年来, 一种新的海底扩张模式引起了广大科学家的重视.它与一般的岩浆型洋中脊扩张不同, 属于一种非岩浆或贫岩浆的海底扩张方式, 扩张作用主要通过拆离断层的滑移来实现.拆离断层使下盘的深部洋壳或上地幔岩石出露到海底, 形成了大洋核杂岩, 通常表面呈现龟背似的波瓦状穹隆, 或称巨型窗棱构造.从拆离断层、大洋核杂岩等基本概念入手, 综述这种新型海底扩张模式的特征, 总结归纳大洋核杂岩的分布状况及识别手段, 探讨其地质意义以及对海底热液活动、成矿的积极影响.      

制度变迁下农垦城镇空间演化及其动力机制研究——以湖北省五三农场为例

制度变迁是城镇空间演化的重要驱动,农垦城镇作为一类特殊且重要的城镇类型,受制度因素影响更直接、更显著。鉴于现有研究较少基于制度变迁探究农垦城镇空间演化,论文系统梳理了农场制度变迁的总体情况,并以湖北省五三农场为例,采用综合研究方法,揭示了制度变迁下农垦城镇空间演化及其动力机制。研究发现：① 农垦城镇空间演化主要体现在空间形态、空间关系和功能结构3个方面,即空间形态从缓变到剧变,空间关系从生产协作关系转为城乡关系,功能结构不断从公办到私营、从生产主导到消费主导、从单一化到多元化;② 制度变迁通过改变农场身份、利益关系和资源配置推动农垦城镇空间演化,其中农场身份变化直接影响农垦城镇空间的发展方向,利益关系变化促使农垦城镇空间产业化、市场化,资源配置变化通过改变资源配置主体、类型、尺度和速度作用于农垦城镇空间演化。通过研究,以期能更有针对性地指导农垦城镇在新时期的发展,同时也可丰富城镇空间演化的理论内涵。     

西南印度洋中脊热液产物稀土元素组成变化及其来源

对西南印度洋中脊热液区不同热液产物稀土元素(REE)进行了分析,探讨了热液产物形成过程中稀土元素组成变化及其来源。研究结果表明:不同热液产物稀土元素总量变化范围从3.47×10-7到4.80×10-5,轻重稀土比值(LREE/HREE)从2.06到6.16,表明轻重稀土有较大程度分异,δEu异常(δEu=0.86~3.88)和δCe异常(δCe=0.40~0.86)显示热液产物中REE呈Eu富集和Ce亏损特征。稀土元素球粒陨石标准化模式呈现两种类型:(1)呈轻微富集LREE的平坦模式,REE大于2×10-5;(2)呈显著富集LREE和正Eu异常模式,REE小于5×10-7。模式1类似于洋壳火山岩REE配分模式,而模式2与西南印度洋中脊黑烟囱REE模式相似,也与典型洋中脊热液喷口流体和硫化物LREE富集和正Eu异常模式类似。热液产物中稀土元素含量变化和模式特征以及Mg与LREE极强正相关关系可能反映了西南印度洋中脊硫化物形成在热液流体与海水混合沉淀的初始阶段,后期经历了广泛的热液流体再循环和海水蚀变过程。