宁南盆地古近纪沉积岩地球化学特征对沉积环境的反映

沉积物元素地球化学特征是盆地沉积环境变化的响应。通过分析沉积岩的微量元素和稀土元素含量变化特征,研究了宁南盆地古近纪气候条件、古盐度和氧化还原环境。Cu、Cs质量分数变化以及Rb/Sr比值、Sr/Cu比值特征,揭示寺口子组沉积时期至少存在一期由潮湿-干旱转变的气候事件,从寺口子组沉积末期到清水营组沉积初期,古气候由干旱变为潮湿。Sr/Ba比值和B/Ga比值反映清水营组沉积水体盐度与寺口子组相差不大,仅在石峡口水库处古盐度值极大,其他地区略有减小。寺口子组沉积过程中,水体盐度有所增加。氧化还原指标V/Cr、Ni/Co、U/Th、V/(V+Ni)、δU、δCe、Ce/La和Ce_anom以及氧化还原敏感元素V、U、Ni、Zn 和Cr 的质量分数变化指示清水营组沉积时期水体氧含量整体小于寺口子组沉积时期。寺口子组沉积环境以氧化环境为主,清水营组沉积水体为氧-贫氧环境。      

来宾地区中泥盆统东岗岭组泥页岩有机地球化学特征

文章分析了桂中坳陷东部来宾地区中泥盆统东岗岭组(以下简称中泥盆统东岗岭组)泥页岩总有机碳含量(TOC)、有机质成熟度(Ro)、饱和烃色谱等有机地球化学特征,对比国内外不同地区富有机质泥页岩的有机地球化学特征,发现中泥盆统东岗岭组泥页岩具有一定的生气基础和勘探潜力。在此基础上,探讨中泥盆统东岗岭组泥页岩的沉积环境和有机质来源,发现中泥盆统东岗岭组泥页岩的沉积环境属于陆棚斜坡相缺氧还原的咸水环境,有机质来源多样,既有陆源高等植物,也有低等水生生物,有机质类型为Ⅰ-Ⅱ_1型。     

古海洋氧化还原地球化学指标研究新进展

古海洋氧化还原条件的恢复一直是地学界的研究热点。许多指标可以用来指示古海洋沉积岩(物)的氧化还原条件。其中地球化学和矿物学方法历来是研究古海洋氧化还原条件的主要手段,前人工作主要集中在单个种类指标(沉积学、矿物学、地球化学等)的单方面研究,缺乏系统研究。但沉积物中的氧化还原指标受很多因素的影响,用单个指标来指示水体的氧化还原条件存在不确定性。主要通过主量元素(总有机碳TOC、有机碳和磷的摩尔比C_org∶P),氧化还原敏感的微量元素(U、V、Mo),黄铁矿类型和草莓状黄铁矿粒径分布以及同位素(黄铁矿硫同位素δ34S_pyrite、钼同位素δ₉₈Mo、铀同位素δ238U)等指标的综合运用来区分硫化、缺氧、次氧化以及氧化等水体条件。在硫化水体中,氧化还原敏感元素和TOC含量均大量富集,尤其是Mo的富集系数(Mo_EF)比U的富集系数(U_EF)更大(Mo_EF>U_EF),有机碳和磷的摩尔比(C_org∶P)也呈现高值;黄铁矿几乎全部呈草莓状,很少出现自形晶,草莓状黄铁矿平均粒径小(常小于5 μm)且变化不大,δ34S_pyrite值偏负,δ98Mo值和海水同位素值接近,约为+2.3‰,δ238U值为+0.2‰,高于海水的同位素值(-0.41‰)。水体环境为氧化的条件下,氧化还原敏感的元素和TOC的量都很缺乏,有机碳和磷的摩尔比(C_org∶P)出现低值,黄铁矿很少,且主要以自形晶的形式出现,平均粒径很大,黄铁矿中的δ34S_pyrite值偏正,δ98Mo值偏负,为-0.7‰,δ238U值为-0.65‰。在缺氧和次氧化水体环境中,各种指标介于硫化和氧化环境之间,氧化还原敏感元素和TOC含量适中,U相对比Mo富集(U_EF>Mo_EF),黄铁矿以草莓状为主,有部分的自形晶出现,黄铁矿平均粒径较大,而且变化范围较大,黄铁矿中的δ ₃₄S_pyrite值、δ98Mo值以及δ238U值均介于氧化和硫化环境之间。最后,还提出在分析古海洋的氧化还原条件时,要综合考虑多种影响因素,清晰认识到每个指标的适用性和局限性,并指出了存在的问题和不足。      

四川龙门山泥盆纪四射珊瑚

本文记述了产于四川龙门山地区中、上泥盆统界线附近观雾山组和土桥子组的四射珊瑚。在大量珊瑚标本鉴定的基础上,建立了中泥盆世晚期至晚泥盆世初期的四个四射珊瑚化石组合。根据四射珊瑚的演化规律,确定以Peneckiella珊瑚类的兴起和Pseudozaphrentis hejiazhaiensis,Temnophyllun(Truncicarinulum)beichua-nensis珊瑚类的消失作为龙门山地区识别中、上泥盆统界线的标志。     

鄂尔多斯盆地延长探区山西组泥页岩沉积地球化学特征及有机质保存条件分析

摘 要:通过主量元素和微量元素分析,应用沉积地球化学方法对采自于鄂尔多斯盆地中部两口页岩气探井的泥页岩沉积地球化学特征和有机质保存条件进行了研究。结果表明:①化学蚀变指数(ＣＩＡ)和Ｓｒ/Ｃｕ比值反映本区山西期为温湿气候,Ｒｂ/Ｚｒ 比值反映本区山西组泥页岩沉积水体较浅;② (Ｔｈ)－(Ｚｒ)、(Ｔｈ)－Ｙ/ Ｈｏ相关性图解以及Ｙ/ Ｈｏ比值更接近于陆源碎屑物质,表明本区山西组泥页岩沉积时主要来源为陆源碎屑物质;③Ｖ/ Ｃｒ 比值、Ｖ/ (Ｖ＋Ｎｉ)比值、δＵ 和Ｔｈ/ Ｕ比值表明山西组泥页岩形成于以弱还原环境为主的弱氧化－弱还原环境;④Ｓｒ/Ｂａ和ＴＯＣ/Ｓ比值反映本区山西组沉积水体以淡水为主,并兼有少量混合水;⑤地球化学综合分析表明,山西组泥页岩沉积水体富氧,缺少有机质保存的还原条件,有机质被氧化分解,不利于后期生烃。      

川东卧龙河地区长兴晚期自然伽马异常及其环境启示意义

目前研究表明,深水环境缺氧团向浅水扩散是导致二叠纪末生物危机事件的重要诱因,然而其作用过程仍存在较大争议。四川盆地东部晚二叠世长兴期主要为台地环境,通过对研究区内卧龙河构造连续沉积的井剖面对比研究发现,在二叠纪末生物大灭绝界线之前的碳酸盐岩地层中自然伽马值整体出现异常正偏。当碳酸盐岩地层中泥质含量、钍和钾的含量相对较少时,自然伽马主要反映铀含量变化,进而指示海水氧化还原条件。长兴晚期区内台地环境显现出不同程度的缺氧效应,并持续发展直至生物大灭绝的来临。区内长兴组自然伽马值异常记录了长兴晚期海洋氧化还原过程,同时也见证了重大地质转折期将至时环境的不稳定性。      

鄂尔多斯盆地西部上二叠统石千峰组沉积环境地球化学表征

在沉积学、生物和地球物理测井相标志研究基础上,运用锶钡质量分数比值和锶钡散点图法,锶钙和钍铀比值法、沉积磷酸盐法、碳氧同位素和氧化-还原电位法等地球化学方法,根据微量元素和稳定同位素的特征对鄂尔多斯盆地西部上二叠统石千峰组沉积时的古盐度和氧化还原条件进行了详细分析.结果表明:石千峰组为淡水沉积,属干旱、炎热、氧化的陆相湖泊环境.其结论与石千峰组的棕红、紫红和紫灰色陆源碎屑岩沉积特别与红色沉积层为特征是相一致的.     

三峡地区前寒武纪-寒武纪转折期黑色页岩地球化学特征及其环境意义

通过对三峡地区秭归滚石坳前寒武纪—寒武纪界线(PC-C)剖面黑色页岩稀土元素、微量元素的地球化学组合特征的分析,对这一特殊转换时期的古海洋演化特征展开了研究,并就岩家河组硅质岩成因做了初步探讨。研究结果表明:岩家河组Ⅰ、Ⅱ、Ⅲ层样品具不同程度的LREE亏损,Ce负异常和Eu正异常;水井沱组样品呈轻微LREE亏损,Ce未见明显异常,Eu具轻微正异常。整个剖面样品稀土元素总量∑REE明显低于PAAS中的含量,其中硅质岩样品的∑REE含量更低,表明硅质对稀土元素含量有稀释作用。样品的氧化还原敏感元素富集系数及V/(V+Ni)、U/Th比值演化趋势显示岩家河组沉积早期(埃迪卡拉纪晚期),海水呈现强烈分层的还原硫化环境,随后到早寒武世Nemakit Daldynian期水体的还原程度及分层状态有逐渐减弱的趋势;水井沱组沉积早期(早寒武世Tommotian早期),广泛的海侵使得水体环境又恢复到分层不强的缺氧甚至硫化环境,到早寒武世Tommotian晚期至Atdabanian期,水体含氧量又逐渐上升,过渡到弱还原-弱氧化或贫氧状态,暗示了这一特殊时期古海水物理化学特征的不稳定性。岩家河组全岩样品Ce负异常可能与海水分层和氧化还原界面波动对区域环境变化的影响有关,而水井沱组全岩样品由前者的Ce负异常迅速上升变为Ce异常不明显,则可能与这一时期陆源碎屑物质对该地区水井沱组细粒沉积物Ce异常起正反馈作用有关。三峡地区PC-C界线附近岩家河组硅质岩地球化学特征显示本期硅质岩具明显热液成因特征。      

陕西谭家沟热水沉积型金矿床地质特征与成因分析

谭家沟金矿产于中泥盆统热水沉积岩中。矿体位于铁白云石硅质岩构造角砾带 ,是以浸染状矿化为主 ,由热水沉积铁白云石硅质岩提供矿质并基本在层内富集成矿的热水沉积改造型金矿床。铅同位素特征表明成矿金属来源于地壳 ;硫同位素组成特征表明硫主要来自海水硫酸盐的还原硫 ;氢氧同位素测试数据表明 ,成矿流体主要为原生建造水。成矿流体为SO4 2 F/Na Ca2 型 ,成矿物理化学条件为弱中等还原环境 ,成矿温度 15 0～ 170℃ ,盐度w(NaCl)为 6 .86 %。     

广西融水地区上泥盆统融县组地层特征

广西融水地区上泥盆统融县组,在广西特别是在北部地区广泛发育,其层型剖面由于年代远久部分层段未能保存下来,长期以来,对该套地层的岩性特征存在较大争议。文章通过对两条剖面岩性组合特征的详细研究,认为广西上泥盆统融县组岩性特征总体由下往上为:白云岩—白云质灰岩—白云质含鲕粒灰岩—鲕粒灰岩—鸟眼灰岩及生物屑灰岩,颜色由浅变深,表明其属于晚泥盆世开阔台地相沉积为主,部分为滩后半局限、局限台地环境下的沉积类型。     

Investigations of natural and artificial radioactive isotopes in seawater and sediments in the Yellow Sea and adjacent southeast area

Investigations of natural and artificial radioisotopes including 90Sr,137Cs, gross B and U carried out in the Yellow Sea and adjacent southeast area in 1963. 1964, 1975 and 1978 showed that radioactive pollution by 90Sr and 137Cs from atmospheric fallout had gradually decreased with time due to the cessation of atmospheric nuclear weapons tests in the 70s. The distributions of natural and artificial radioactive isotopes (U, Ra, Th. 40K and 137Cs) in sediments southwest of Jizhou Island were uniform. The more uniform may be related to the soluble species of U[Uo2(CO3)4] in the seawater.The high value of Th at stations 3 and 6 was related to the sandy clay sediment; the low value at station 8 was related to sandy sediment. The content of 137Cs in the eddy area being less than about half of that in the China inshore area showed that the source of Cs may be insufficient orthat the conditions for enriching " Cs in the circulation eddy area were not favorable.     

Reconstructing environmental changes of a coastal lagoon with coral reefs in southeastern Hainan Island

Coastal lagoons with small catchment basins are highly sensitive to natural processes and anthropogenic activities. To figure out the environmental changes of a coastal lagoon and its contribution to carbon burial, two sediment cores were collected in Xincun Lagoon, southeastern Hainan Island and (210) ~Pb activities, grain size parameters, total organic carbon(TOC), total nitrogen(TN), total inorganic carbon(TIC) and stable carbon isotopes(δ~(13)C) were measured. The results show that in 1770–1815, the decreasing water exchange capacity with outer open water, probably caused by the shifting and narrowing of the tidal inlet, not only diminished the currents and fined the sediments in the lagoon, but also reduced the organic matter of marine sources. From 1815 to 1950, the sedimentary environment of Xincun Lagoon was frequently influenced by storm events. These extreme events resulted in the high fluctuation of sediment grain size and sorting, as well as the great variation in contributions of terrestrial(higher plants, soils) and marine sources(phytoplankton, algae, seagrass). The extremely high content of TIC, compared to TOC before 1950 could be attributed to the large-scale coverage of coral reefs. However, with the boost of seawater aquaculture activities after 1970, the health growth of coral species was severely threatened, and corresponding production and inorganic carbon burial flux reduced. The apparent enhanced inorganic carbon burial rate after 1990 might result from the concomitant carbonate debris produced by seawater aquaculture. This result is important for local government long-term coastal management and environmental planning.     

Geochemical characteristics and sedimentary environment significance of carbonate rocks in Nanfen Formation of Qingbaikou System in Tonghua,Jilin Province

In order to reveal the sedimentary environment of carbonate rocks in Nanfen Formation of Qingbaikou System in Tonghua, Jilin Province, the mineral composition and petrochemistry of carbonate rocks in Nanfen Formation were analyzed. The mineral compositions of five carbonate rock samples in Nanfen Formation mainly consist of calcite, with minor clay minerals and quartz, and the rock type is siliceous marlite. The Mn/Sr va-lues range from 1.52 to 4.08, with an average of 2.64, indicating that the carbonate rocks experienced weak diagenesis; the Sr/Ba values range from 1.26 to 2.51, with an average of 1.93, indicating marine environment; the ratio of Mg/Al ranges from 35.33 to 86.34, with an average of 62.95, indicating the seawater environment, which is consistent with the result from Sr/Ba; the MgO/CaO values range from 0.01 to 0.04, with an average of 0.02, indicating humid environment; the values of V/(V+Ni) range from 0.63 to 0.73, with an average of 0.70, indicating anoxic environment. In summary, geochemical analyses show that the Nanfen Formation carbonate rocks are marine deposits, in a warm, humid, anoxic environment with poor flow of seawater, and subsequently underwent weak diagenetic alteration.     

Records of bulk organic matter and plant pigments in sediment of the “red-tide zone” adjacent to the Changjiang River estuary

Cultural eutrophication caused by nutrient over-enrichment in coastal waters will lead to a cascading set of ecosystem changes and deleterious ecological consequences,such as harmful algal blooms(HABs) and hypoxia.During the past two decades since the late 1990s,recurrent large-scale HABs(red tides)and an extensive hypoxic zone have been reported in the coastal waters adjacent to the Changjiang River estuary.To retrieve the history of eutrophication and its associated ecosystem changes,a sediment core was collected from the "red-tide zone" adjacent to the Changjiang River estuary.The core was dated using the~(210)Pb radioisotope and examined for multiple proxies,including organic carbon(OC),total nitrogen(TN),stable isotopes of C and N,and plant pigments.An apparent up-core increase of OC content was observed after the 1970s,accompanied by a rapid increase of TN.The concurrent enrichment of δ~(13)C and increase of the C/N ratio suggested the accumulation of organic matter derived from marine primary production during this stage.The accumulation of OC after the 1970 s well reflected the significant increase of primary production in the red-tide zone and probably the intensification of hypoxia as well.Plant pigments,including chlorophyll a,p-carotene,and diatoxanthin,showed similar patterns of variation to OC throughout the core,which further confirmed the important contribution of microalgae,particularly diatoms,to the deposited organic matter.Based on the variant profiles of the pigments representative of different microalgal groups,the potential changes of the phytoplankton community since the 1970s were discussed.     

塔里木盆地中央隆起带寒武系-奥陶系白云岩成岩相及其地球化学特征

成岩相识别与划分有助于碳酸盐岩储层分类评价及预测。为了明确塔里木盆地中央隆起带寒武系-奥陶系的白云岩成岩相类型及特征, 通过岩心描述、常规及铸体薄片观察、X衍射分析以及粒度分析等方法, 首先对其岩相学特征进行了详细研究并对成岩相类型进行了划分, 在此基础上, 结合O、C稳定同位素测试方法以及Fe、Mn、Sr、Li、U等常、微量元素测试技术探讨了各类白云岩成岩相的地球化学特征并建立了各类成岩相的模式。研究结果表明, 塔里木盆地中央隆起带寒武系-奥陶系白云岩成岩相可划分为准同生云化亚相(PD-F)、浅埋藏隐伏回流渗透云化亚相(SLRD-F)、浅埋藏活跃回流渗透云化亚相(SARD-F)、表生风化壳岩溶亚相(WK-F)和构造破碎亚相(TF-F)共5类。其中, PD-F模式的白云岩云化流体主要来自咸化海水并受部分淡水影响, 表现出O同位素负偏, Fe、Mn、Sr和Li质量分数明显偏高的特征; SARD-F模式的白云岩基本形成于正常海水, 个别样品受到埋藏溶蚀或重结晶作用以及淡水影响, 整体表现为O同位素值与奥陶纪海水一致, Fe、Mn、Sr质量分数相对较低的特点; SLRD-F模式的白云岩形成环境相对封闭, 受淡水影响较小, 表现为O同位素值与海水一致, Fe、Mn质量分数相对较低, Sr质量分数相对较高的特征; WK-F模式的白云岩样品由于经历表生淡水溶蚀作用和埋藏期的白云化作用, 具有O同位素负偏, Fe、U质量分数较高, Sr质量分数较低的特征; TF-F模式的白云岩样品受到构造热液的影响, 具有O同位素负偏, Fe、Mn、U、Li质量分数低的特征。      

沂水县富锶地下水特征及成因分析

沂水县富锶(Sr)地下水分布广泛,白垩纪沂南序列侵入岩的锶(Sr)含量最高,平均含量1013.64×10^-6,其次为白垩纪火山岩,锶(Sr)平均含量为739.18×10^-6,太古代侵入岩、变质岩中的锶(Sr)平均含量为398.99×10^-6,寒武-奥陶纪灰岩、页岩中的锶(Sr)平均含量为201.54×10^-6;碎屑岩类孔隙裂隙水含水岩组地下水锶(Sr)平均含量为0.99mg/L,喷出岩孔洞裂隙水含水岩组地下水锶(Sr)平均含量为0.95mg/L,碳酸盐岩裂隙岩溶水含水岩组地下水锶(Sr)平均含量为0.76mg/L,块状岩类(侵入岩)裂隙水含水岩组地下水锶(Sr)平均含量为0.48mg/L。碎屑岩类孔隙裂隙水含水岩组、喷出岩孔洞裂隙水含水岩组、块状岩类(侵入岩)裂隙水含水岩组地下水中锶(Sr)主要来源为围岩的风化溶解;碳酸盐岩裂隙岩溶水含水岩组地下水中锶(Sr)主要来源于沂南序列构造破碎带和风化带的风化溶解,其次为寒武-奥陶纪灰岩的风化溶解,锶(Sr)强变异性与不同含水层地下水的混合比例有关。     

四川西部西康群新都桥组碳酸盐岩的锶同位素特征

四川西部松潘—甘孜地区广泛分布一套三叠系黑色砂板岩层系,由于其岩性单调、古生物化石贫乏,给该区地层划分、对比带来极大困难。因此,从锶同位素地层学基本原理出发,对甘孜北部西康群新都桥组中薄层状灰岩样品进行了锶同位素组成测定。结果表明,6件样品的N(87Sr)/N(86Sr)分别为0.708688、0.708659、0.708907、0.708223、0.708341、0.708266,平均为0.708514。表明该地层的碳酸盐岩样品可能遭受了不同程度的成岩蚀变,多数样品的锶同位素组成偏离同时代的全球海水锶同位素组成。     

Studies on marine oil spills and their ecological damage

The sources of marine oil spills are mainly from accidents of marine oil tankers or freighters, marine oil-drilling platforms, marine oil pipelines, marine oilfields, terrestrial pollution, oil-bearing atmosphere, and offshore oil production equipment. It is concluded upon analysis that there are two main reasons for marine oil spills: (I) The motive for huge economic benefits of oil industry owners and oil shipping agents far surpasses their sense of ecological risks. (II) Marine ecological safety has not become the main concern of national security. Oil spills are disasters because humans spare no efforts to get economic benefits from oil. The present paper draws another conclusion that marine ecological damage caused by oil spills can be roughly divided into two categories: damage to marine resource value (direct value) and damage to marine ecosystem service value (indirect value). Marine oil spills cause damage to marine biological, fishery, seawater, tourism and mineral resources to various extents, which contributes to the lower quality and value of marine resources.     

Geochemical studies of U,Th, Ra,40K in seciments of the China Sea and adjacent sea area,and lower reaches of several Chinese Rivers

Geochemical studies of the U, Th, Ra, and⁴⁰K in surface sediments of the China Sea and adjacent sea areas, the lower reaches of the Huanghe and Changjiang Rivers and the estuaries of the Zhujiang and Rongjiang Rivers were carried out with a model 8180-4K multichannel Ge(Li)γ spectrometer in 1981–1985. The mean values of U, Ra, Th,⁴⁰K are about 2.11 ppm, 7.67×10⁻¹³g/g, 11.00 ppm, and 2.33 ppm respectively, in the China Sea, the Okinawa Trough, and the Changjiang and Huanghe River estuaries. The distribution of the four isotopes is uniform in the above zone. The contents of U and Th in the sediments of the Zhujiang and Rongjiang Rivers and the Fujian coast are 1–4 times higher than those of the above zone and are related to the granite and radioactive ore present in the upper reaches of these rivers or the adjacent mountains. The distributions of U, Th, Ra, and⁴⁰K are related to the physico-chemical property, redox state, geological type and grain size of the sediment, and biotic activity. Contribution No. 1408, Institute of Oceanology, Academia Sinica, Qingdao.