中国的海滩岩研究与进展

海滩岩作为海陆交互作用的直接产物之一,对于研究古海平面变化、海岸带演化以及古气候变化等海陆相互作用过程具有重要意义.对我国的海滩岩研究历史与现状进行了分析,对当前的海滩岩研究中存在的一些争议和问题如海滩岩的定义、海滩岩的胶结物及其形成机制、海滩岩的形成时代、研究方法等进行了讨论,并对今后我国海滩岩研究的发展进行了展望.     

西沙群岛海滩岩类型及其油气地质意义

介绍了西沙群岛现代生物礁最新科考成果,在数十个岛屿上发现海滩岩,划分为固结海滩岩、高位海滩岩、坍塌破坏型海滩岩、侵蚀破坏型海滩岩和侵蚀型海滩岩5种类型;描述了它们的手标本特征、赋存分布及岩石类型和作为油气储层的价值;指出甘泉岛淡水资源的存在归因于海滩岩的胶结致密程度。     

福建全新世海滩岩与海平面变化

海滩岩是热带、亚热带砂砾质海岸中特有的一种滨海相沉积岩。海滩岩对海平面变化、地壳构造运动、古气候及古地理环境等方面的研究有着重要意义。过去,人们对福建海滩岩了解甚少,往往视为贝壳砂堤或贝壳砂层。近年来,我们调查了福建海滩岩的分布,研究了其岩石学特征、沉积相及其与海平面变化的关系。一、海滩岩的分布及其地质地貌特征有人认为,我国全新世海滩岩北界在福建东山岛。调查表明,这条界线至少北移至     

福建深沪湾潮间带发现晚更新世牡蛎海滩岩

1986年9月至1987年5月笔者在地壳变形调查时,在福建省晋江县深沪湾发现主要由大量牡蛎化石组成的海滩岩,分布在深沪湾土地寮村边距岸约100m外,通常水深约2-3m的潮间带.牡蛎海滩岩长400余米,宽达60余米,间断分布,厚达20cm,下部被泥沙掩埋(照片1—2).     

华南全新世海滩岩及其古地理意义

闽、粤、桂、琼已发现全新世海滩岩不少于44处.(14)~C测年表明,大部分为中全新世,其中以距今4000—200年的为最多,表明中全新世晚期至晚全新世早期是华南海滩岩的主要形成期.这些全新世海滩岩反映下列四方面的古地理意义:海岸线变迁;海平面变化;动力条件的变化;新构造运动.讨论了海滩岩与海岸沙丘岩的相似性与差异性、明确区别海滩岩与珊瑚礁或沙堤中的贝壳、分清海面升降还是堆积扩展等问题.     

福建笏石半岛—湄洲岛海滩岩与海滨砂丘岩之鉴别

本文根据岩性、沉积结构、胶结物成分、胶结类型和产状等特征区分海滨砂丘岩与海滩岩,从而把福建莆田笏石半岛—湄洲岛地区的海滨砂丘岩从以往所称的海滩岩中划分出来。为了便于鉴别,文中对海滨砂丘岩、潮上带海滩岩和潮间带海滩岩的特征作了对比。     

从广东沿海海滩岩探讨历史时期海平面变化

讨论了广东沿海海滩岩与碳酸盐结岩的关系，结构，物质组分，并从海滩岩的分布高度探讨该区历史时期海平面变化。     

舟山地区晚更新世地层发现疑似古海滩岩

舟山东港地区的钻孔资料揭示,埋深47.5～51.5m的第四纪晚更新世地层,赋存有固结程度较高的薄层砂砾岩,其产状与现代海滩近一致,具有磨圆较好、分选较差、有较多细小孔洞、砾石略定向分布的特点,类似于海滩岩,对此并进行了初步研究。     

关于海滩岩几个问题的初步研究

海滩岩一词见诸文献,已经有百余年的历史,系指一种形成于热带、亚热带潮间带,由碳酸盐矿物胶结的岩石.该术语最先为地理学者应用,近廿年来亦常见于海洋地质学中.但是由于其岩石学涵义过广,在一般沉积岩分类中,并没有它的位置.近十多年来,在国内专业文献中,海滩岩的描述日见增多,但对海滩岩的理解却不尽一致.笔者在海南岛南岸及西沙群岛的调查和冲绳海槽淹没型海滩岩的研究中,接触到许多与海滩岩有关的问题,深感有必要对海滩岩的若干认识做些探讨.不妥之处,欢迎教正.     

神奇的海滩岩

在我国的西沙群岛、海南岛的天涯海角、江苏连云港市的西墅等地,先后发现了狭义的海滩岩,引起了人们的广泛关注。人们对海滩岩的认识是在不断地深化的,随着调查研究的深入,海滩岩已被划分为广义与狭义两大类。在80年代,曾有一些科技人员认为,在海滩上的各种石头,都     

Kr and Xe isotopic compositions of Fe-Mn crusts from the western and central Pacific Ocean and implications for their genesis

Kr and Xe nuclide abundance and isotopic ratios of the uppermost layer of Fe-Mn Crusts from the western and central Pacific Ocean have been determined. The results indicate that the Kr and Xe isotopic composi-tions, like that of He, Ne and Ar, can be classified into two types： low3He/4He type and high3He/4He type. The low3He/4He type crusts have low84Kr and132Xe abundance, while the high3He/4He type crusts have high84Kr and132Xe abundance. The82Kr/84Kr ratios of the low3He/4He type crusts are lower than that of the air, while the83Kr/84Kr and86Kr/84Kr ratios are higher than those of the air. The Kr isotopic ratios of the high-er3He/4He type crusts are quite similar to those of the air. The128Xe/132Xe,130Xe/132Xe and131Xe/132Xe ratios of the low3He/4He type sample are distinctly lower than those of the air, whereas the129Xe/132Xe,134Xe/132Xe and136Xe/132Xe ratios are higher than those of the air. The low3He/4He type samples have the diagnostic characteristics of the MORB, with excess129, 131, 132, 134, 136Xe relative to130Xe compared with the solar wind. The128Xe/132Xe,130Xe/132Xe and131Xe/132Xe ratios of the high3He/4He type samples are slightly higher than those of the air, and the129Xe/132Xe,134Xe/132Xe and136Xe/132Xe ratios are qiute similar to those of the air. The noble gases in the Fe-Mn crusts are derived from the lower mantle, and they are a mixture of lower mantle primitive component, radiogenic component and subduction recycled component. The helium isotopic ra-tios of the low mantle reservoir are predominantly controlled by primitive He （3He） and U and Th radiogenic decayed He （4He）, but the isotopic ratios of the heavier noble gases, such as Ar, Kr and Xe, are controlled to different extent by recycling of subduction components. The difference of the noble isotopic compositions of the two type crusts is the result of the difference of the noble isotopic composition of the mantle source reservoir underneath the seamounts the crusts occurred, the noble gases of the high3He/4He type crusts are     

不平衡铀系和钍系核素的γ谱测定

求解初始时刻子体活度不为零时两个子体级连衰变动力学方程,给出γ谱分析测量不平衡铀系和钍系核素活度的计算公式.作为应用测量了两个沉积物样品中的238U,234Th,226Ra,222Rn,228Ra,228Th,224Ra,212Pb,210Pb和40K的活度.     

厦门近岸210Po和210Pb的大气沉降通量

为揭示中国东南沿海地区210Po和210Pb的大气沉降时空变化特征,探讨该地区气溶胶的停留时间,于2013年1月至2014年12月对厦门地区210Po和210Pb的大气沉降通量进行了时间序列研究。结果发现,210Po和210Pb的平均日沉降通量分别为（65.38±4.79） mBq/（m2·d）（n=54）和（0.78±0.09） Bq/（m2·d）（n=54）,表现出明显的周年变化。东北季风期间,210Po和210Pb的沉降通量较高,而西南季风期间其通量较低。2013年和2014年,210Po的年沉降通量分别为19.29 Bq/（m2·a）和9.25 Bq/（m2·a）,210Pb的年沉降通量分别为159.2 Bq/（m2·a）和189.6 Bq/（m2·a）。两核素的年沉降通量表现出不同程度的年际差异。210Po与210Pb沉降通量之间存在显著的线性正相关关系,揭示了大气中210Po和210Pb具有相同的迁出机制,降雨和大气中核素含量是影响210Po和210Pb沉降通量的主要因素。该研究结果可以为探求台湾海峡海水中210Po与210Pb的收支平衡提供大气来源项。     

Geochemical cycling in the Hooghly estuary, India

U–Th decay series isotopes, δ¹⁸O and Si measurements in the river estuarine waters and sediments of the polluted Hooghly estuary as well as the surface waters of the Bay of Bengal, its high salinity end member, are reported. Dissolved Si indicates that there are probably two mixing regimes, dissolved U behaviour is nonconservative and δ¹⁸O behaves conservatively in the overall estuarine region. Isotopes of reactive elements, viz. ²³⁴Th and ²¹⁰Po, are removed from the estuarine waters in <2 days and <1 month, respectively, which is due to high suspended matter (30–301 mg l⁻¹). ²²⁸Ra and ²²⁶Ra are profusely released into the estuarine waters in the low to mid-salinity regions.As expected, the opposite trend is observed in the case of estuarine sediments and suspended matter. Reactive isotopes of Th, ²¹⁰Pb and ²¹⁰Po are enriched, whereas Ra isotopes are depleted with respect to their parent nuclides in the estuarine sediments and suspended matter. ²³²Th/Al ratio appears well suited to study the distribution and mixing of the bed load sediments of the Ganga–Brahmaputra (G–B) and the Hooghly rivers with those from other rivers on the Bay of Bengal floor.     

南海表层沉积物中铂族元素的地球化学分布特征及其影响因素

报道了南海表层沉积物中铂族元素的丰度及其分布特征。52个表层沉积物中铂族元素(PGE)含量变化范围:钌为0.40×10-9~3.20×10-9,平均值为1.20×10-9;钯为0.01×10-9~13.30×10-9,平均值为4.31×10-9;铱为0.59×10-9~4.49×10-9,平均值为1.21×10-9;铂为1.27×10-9~16.21×10-9,平均值为5.26×10-9;铑为0.05×10-9~0.2×10-9,平均值为0.12×10-9;金为0.43×10-9~27.38×10-9,平均值为6.92×10-9。尽管PGE含量与沉积物平均粒径的关系不是很明显,但是整体上随平均粒径的增大,PGE含量出现逐渐减少的趋势,表现出一定的粒度控制规律。南海全海域表层沉积物铂、钯、钌、铑、铱和金的估算背景值分别为1.168×10-9±0.190×10-9,3.228×10-9±0.403×10-9,1.085×10-9±0.189×10-9,4.432×10-9±0.258×10-9,0.123×10-9±0.023×10-9和4.720×10-9±0.413×10-9,远高于我国大陆东部地壳的,而与深海沉积物的基本处于同一水平,表现出了海洋沉积物富集PGE的固有特征。尽管PGE在大陆架区有所富集,但明显富集区主要分布在吕宋岛以西至中央海盆区域,指示海底火山喷发作用释放的PGE对南海中西部深海盆区沉积物中的PGE可能有重要贡献。     

Fluxes of234Th,210Po and210Pb determined by sediment trap experiments in pelagic oceans

Sediment trap experiments were carried out in two oceans, the eastern Pacific Ocean and the Antarctic Ocean, which have very different biological productivities. The natural radionuclides,²³⁴Th,²¹⁰Po and²¹⁰Pb were used as tracers of reactive metals. Larger particulate fluxes of these radionuclides were found in the seas where total mass fluxes were larger, although the concentrations of these radionuclides in the settling particles were somewhat smaller. The concentrations of²³⁴Th in the settling particles varied widely and irregularly with depth, whereas the concentrations of²¹⁰Po and²¹⁰Pb in the settling particles steadily increased with increasing water depth. The ratios of²¹⁰Po/²¹⁰Pb in the settling particulates were larger than unity which the ratio of²³⁴Th/excess²¹⁰Po as larger than²³⁴Th/²¹⁰Po in the deep water. These results suggest that, when the particles sink through the water column, these radionuclides are being absorbed by settling particles in the order²³⁴Th>²¹⁰Po>²¹⁰Pb. The observed particulate fluxes of²¹⁰Pb are about one eighth of those calculated from the disequilibria between²²⁶Ra and²¹⁰Pb at the stations in the subtropical eastern Pacific, although the observed fluxes are the same as the calculated ones in the northern North Pacific and the Antarctic Ocean. Thus, there must be a horizontal flow carrying these reactive metals from the oligotorophic ocean to the biologically productive ocean where the metals are removed by settling particles even in deep water.     

Radionuclides as tracers of water fronts in the South Indian Ocean—ANTARES IV Results

Anthropogenic ⁹⁰Sr, ^239,240Pu and ²⁴¹Am were used as tracers of water mass circulation in the Crozet Basin of the South Indian Ocean, represented by three main water fronts—Agulhas (AF), Subtropical (STF) and Subantarctic (SAF). Higher ⁹⁰Sr concentrations observed north of 43°S were due to the influence of AF and STF, which are associated with the south branch of the Subtropical gyre, which acts as a reservoir of radionuclides transported from the North to the South Indian Ocean. On the other hand, the region south of 43°S has been influenced by SAF, bringing to the Crozet Basin Antarctic waters with lower radionuclide concentrations. The ²³⁸Pu/^239,240Pu activity ratios observed in water and zooplankton samples indicated that, even 35 years after the injection of ²³⁸Pu to the Indian Ocean from the burn-up of the SNAP-9A satellite, the increased levels of ²³⁸Pu in surface water and zooplankton are still well visible. The radionuclide concentrations in seawater and their availability to zooplankton are responsible for the observed ²¹⁰Po, ^239,240Pu and ²⁴¹Am levels in zooplankton.     

Coupling iodine speciation to primary,regenerated or “new” production: a re-evaluation

In two recent studies (Tian et al., Deep-Sea Res. I 43 (1996) 723–738; Campos et al., Deep-Sea Res. II 43 (1996) 455–466), in order to explain the observed temporal variations in the distributions of the dissolved iodine species at the time-series stations in the Mediterranean Sea, the North Atlantic and the North Pacific, diverse assumptions were invoked on the relationships between changes in the speciation of dissolved iodine in the surface oceans and biological production such that the surface enrichment of I⁻ was linked to both regenerated production and primary production while the surface depletion of [IO₃⁻+I⁻] was linked to “new” production. However, while some of the major conclusions in these studies are critically dependent on these assumptions, the validity of the assumptions has yet to be verified with experimental evidence. On the other hand, while there are still significant unknowns in the understanding of the cycling among dissolved iodine species in the surface oceans, presently available data from laboratory cultures and field observations are consistent with an alternative conceptual model in which IO₃⁻ and NO₃⁻ are taken up at some ratio to each other during NO₃⁻ uptake and almost all of the IO₃⁻ taken up is exuded as I⁻. Thus, the depletion of IO₃⁻ and the enrichment of I⁻ in the surface water are linked to NO₃⁻ uptake. This alternative model is also consistent with the data sets presented by Tian et al. (1996) and Campos et al. (1996). By linking the surface depletion of IO₃⁻ to NO₃⁻ uptake, significantly different biogeochemical behavior of the marine dissolved iodine system may be inferred. The extent to which I⁻ may be oxidized to IO₃⁻ within the euphotic zone during the residence time of the water in the surface ocean is still an open question.     

Exploring the connection between 210Po and organic matter in the northwestern Mediterranean

The disequilibrium between ²¹⁰Po and its grandparent ²¹⁰Pb has been proposed as a tracer of the vertical flux of sinking particulate organic matter in the ocean. The mechanism of association between ²¹⁰Po and organic matter is, however, still unclear. To investigate this association we measured trace metals, minerals, organic carbon, nitrogen, and the natural radioisotopes ²³⁴Th, ²²⁸Th, ²¹⁰Po, and ²¹⁰Pb in sinking particles collected in sediment traps at 200 m in the northwestern Mediterranean. Pigments, fatty acids, and amino acids were used to identify the types and sources of particulate organic matter. Multivariate analyses were used to determine which components of sinking particulate matter are traced by ²¹⁰Po and/or by the ²¹⁰Po/²¹⁰Pb ratio. Statistical analysis of the results indicates that the distribution of polonium in sinking marine particles is influenced by fresh phytoplankton-derived, nitrogen-rich organic matter as well as sulfur-containing amino acids. These findings are consistent with previous laboratory observations that the distribution of ²¹⁰Po in biota parallels the distributions of both sulfur and protein, and indicate that these associations persist as material sinks through the water column. While this research generally supports the use of ²¹⁰Po as a specific tracer of the flux of organic matter, the signals traced by ²¹⁰Po/²¹⁰Pb and ²³⁴Th/²³⁸U are not as distinct in the field as in laboratory experiments. Further work is needed to determine more precisely what ²¹⁰Po/²¹⁰Pb traces in order to increase the correspondence of ²¹⁰Po/²¹⁰Pb measurements to biogeochemically important rates and quantities.     

Basin-scale seawater lead isotopic character and its geological evolution indicated by Fe-Mn deposits in the SCS

Abstract

The geochemical characteristics and Pb isotope variations in Fe-Mn deposits collected from the South China Sea (SCS) were studied in this paper. The mineralogical and chemical composition data indicate that the deposits are almost all hydrogenetic in origin. Compared with the Fe-Mn deposits in other oceans, the SCS Fe-Mn deposits have a significantly higher Pb content because of higher material supply in addition to a lower growth rate of the deposits. Pb isotope ratios in the surface of the SCS Fe-Mn deposits are relatively uniform, with a characteristic of relatively lower ²⁰⁶Pb/²⁰⁴Pb ratio. The Pb isotopic compositions of the SCS Fe-Mn deposits are controlled by the Pacific Deep Water and local inputs, which include eolian dust from the Asian continent and weathering products from Taiwan, Luzon and SCS submarine volcanic rocks. The continuously increasing ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios along the transect of nodule D581 over the past 3.5?Ma are affected by the stepwise closure of the Luzon Strait that reduced volcanic material supply and the deep current strengthen at the same time.