滇西实验场区主要活动断裂地球化学特征

本文论述了滇西实验场区五条主要活动断裂的地球化学特征,分析了活动断裂的地球化学特征与断裂的活动方式、活动强度和切割深度等构造因素之间的内在联系。提出洱源盆地西北部地壳内约5.4—6.2公里深度范围内发育有较大规模的热动力变质带,洱源地区高温温泉群的形成与这一变质带有关,其流体地球化学组分和同位素组成都具有热动力变质特征。红河断裂(北段)沿线温泉中含有较多的幔源挥发性组分,是典型的深循环增温型温泉     

泌阳凹陷古近纪含碱岩系地球化学特征对成碱作用的指示意义

位于南襄盆地东部的泌阳凹陷为南断北超型断陷盆地,其古近纪核桃园组发育有世界上已知的最老沉积碱矿之一,即安棚碱矿.该含碱岩系包括细碎屑岩、泥质白云岩和层状碱矿层,其中碱矿层以重碳钠盐为主,含少量天然碱、芒硝和石盐.核桃园组三段上部-核二段含碱岩系中,白云质泥岩、泥质白云岩和碱矿层在Al2O3,TiO2,Na2O,MgO＋CaO和LOI含量上具有明显差别.Na2O/（MgO＋CaO）可用以指示Na碳酸盐相对于Mg-Ca碳酸盐的富集程度,据此可将泥质白云岩可分为〈0.6和〉0.6的两组.前者Na2O/（MgO＋CaO）与Al2O3＋TiO2含量呈正相关,随碎屑物质的减少倾向于形成纯的Mg-Ca碳酸盐岩,反映湖水蒸发量≤补给量,指示较潮湿气候;而后者中Na2O/（MgO＋CaO）与Al2O3＋TiO2含量呈反相关,随碎屑物质的减少向成碱方向发展,反映湖水蒸发量〉补给量,指示较干旱气候.以Al作为标准,从泥质白云岩到碱矿层,随Na2O/（MgO＋CaO）比值增大,Zr,Ti,La,K,Rb和Ba在碱矿层中明显相对富集,且PAAS（后太古宙平均页岩）标准化的Eu正异常也显著增强.结合碱矿层的高B含量及硅硼钠石的报道和区域伸展性构造背景的认识,该地球化学特征指示有深源热液流体通过边界深大断裂进入盆地而参与成碱过程.     

人类活动影响下的云南阳宗海近百年有机碳与黑炭湖泊沉积记录

利用我国云南省昆明市阳宗海湖心40 cm沉积岩芯,分析总氮(TN)、有机碳(TOC)、黑炭(BC)含量和黑炭同位素(δ~(13)CBC)等多环境指标,采用~(137)Cs和~(210)Pb定年方法建立沉积岩芯年代序列,探讨阳宗海近百年来TOC以及BC沉积变化特征及其对区域人类活动的响应.结果表明:(1)阳宗海沉积岩芯中TN、TOC和BC含量分别为0.76~5.07、4.95~42.65和0.69~11.16 mg/g;δ~(13)CBC值为-31.03‰~-25.45‰,均值为-27.18‰;(2)TN、TOC含量自下而上同步增长,TOC/TN摩尔比值在1994年左右增长到最大值后逐渐减小,反映了流域内人为活动导致的外源性TOC增加,阳宗海水体逐渐富营养化;(3)阳宗海沉积岩芯中BC含量及其同位素的时间序列变化,反映了当地能源结构的变化,工业源和居民消费源成为阳宗海BC的主要来源,BC与人口数量和能耗间呈显著相关.     

过去5000 a以来抚仙湖沉积物有机质碳同位素的古环境指示意义

通过测定抚仙湖沉积物全有机样品的稳定碳同位素组成(δ~(13)C_(org))、总氮、总有机碳含量指标并计算碳氮比值,对过去5000 a以来抚仙湖沉积物有机质来源、δ~(13)C_(org)的影响因素及其所指示的古环境意义进行分析.结果表明:在过去的5000 cal a BP里,抚仙湖沉积物有机质主要来源发生明显变化,沉积物有机质输入由内源水生生物和陆生C_3植物共同输入(5000-2300 cal a BP阶段)转变为以内源沉水植物、浮游植物和藻类等输入为主(2000 cal a BP至今阶段);有机质来源发生变化是造成抚仙湖沉积物δ~(13)C_(org)值变化的主要原因;2000 cal a BP以来,陆源有机质输入的锐减与人类活动的影响密切相关;在2300-2000 cal a BP阶段,抚仙湖沉积物δ~(13)C_(org)值的快速变化可能指示了抚仙湖流域的古环境在这一时期经历了快速变化的气候事件.     

乌梁素海悬浮颗粒物和沉积物有机碳同位素特征及来源

悬浮颗粒物和沉积物是湖泊有机污染物的主要承载物质,其稳定同位素研究对有效识别有机质污染导致的湖泊富营养化具有重要意义.本研究选取乌梁素海为研究区,于2019年4月（融冰期）、7月（夏灌期）和10月（秋灌期）对湖区及入湖渠道的表层沉积物和悬浮颗粒物中有机碳的δ¹³C、C/N比及总有机碳（TOC、POC）和总氮（TON、PON）含量进行测定分析,联合采用δ¹³C、C/N及同位素多元混合模型研究湖泊有机碳来源及其贡献率.结果表明,乌梁素海悬浮颗粒物有机碳δ¹³C_POC的变化范围为-23.29‰~-29.75‰,呈现10月>4月>7月、入湖渠道>湖区的趋势,悬浮颗粒物POC/PON比变化范围为4.10~21.35,呈现出4月<7月<10月的时间变化,悬浮颗粒有机质主要来源于浮游植物（51.59%）、入湖渠道泥沙（34.60%）和大型水生植物（13.76%）.沉积物有机碳δ¹³C_TOC变化范围为-27.58‰~-22.68‰,呈现4月<10月<7月的变化,沉积物TOC/TON比变化范围为3.06~23.77,时空变化明显,沉积物有机质则主要源于入湖渠道挟带的泥沙,贡献达72.79%以上,而浮游植物与大型水生植物的贡献率相差较小,分别为11.85%和15.36%.本研究可以初步判定受入湖渠道影响的富营养化湖泊中悬浮颗粒物和沉积物有机碳来源,为改善湖泊有机污染和研究有机碳来源提供更多理解.     

南四湖沉积剖面中色素与有机碳同位素特征的古环境意义

湖泊沉积物中的色素含量与种类是研究湖泊初始生产力和湖泊环境的有效手段之一．而有机碳同位素比值反映了沉积有机物来源信息．本文在对南四湖沉积剖面中总有机碳含量分析的基础上,测定了有机碳的同位素比值,同时通过剖面中色素指标的分析,揭示该湖泊环境演化历史．研究表明,南四湖成湖时代为2．45kaB．P,成期水体主要来自黄河泛滥;其次,南四湖东西沉积环境差异较大,西部（微山湖）主要受黄河泛滥影响,东部（独山湖）则为山麓碎屑沉积;近代南四湖中蓝藻大量繁盛,湖泊具有逐步向富营养化发展的趋势．     

洱海悬浮颗粒物和表层沉积物有机碳氮同位素来源特征及水质指示意义

为探究湖泊水体悬浮颗粒物和沉积物有机碳、氮来源及水质指示意义,分析了2013-2014年洱海悬浮颗粒物和表层沉积物有机碳同位素(δ13C)、氮同位素(δ15N)和C/N比值时空变化特征及与水质的关系.结果 表明:①洱海悬浮颗粒物δ13C、C/N、δ15N在旱、雨季差异显著(P＜0.05),旱季变化范围分别为-31.75...     

东部油气区天然气中幔源挥发份的地球化学——Ⅱ.幔源挥发份中的氦、氩及碳化合物

讨论了壳源及幔源氦、氩同位素组成特征的“横人字型”模式、二氧化碳丰度分布、同位素组成及其成藏和80年代以来地学研究热点之一的幔源甲烷等有关问题。     

陇县—宝鸡断裂带CO2气体地球化学特征及成因

陇县—宝鸡断裂带位于青藏块体东北缘,属于鄂尔多斯块体西南缘弧形断裂束的最南段。为对比分析该断裂带的分段活动性强弱特征,利用断裂带逸出气CO₂的地球化学特征进行反演。布设6条跨断层土壤气CO₂测线,进行2期测量,共计获取150个土壤气CO₂组分浓度,计算了气体的相对活动强度;收集了60件CO₂气体样品,测试了其碳同位素组成。结果表明：岐山—马召断裂的气体活动强度（1.56～2.70）比固关—虢镇断裂的气体活动强度（1.73～1.75）大,且岐山—马召断裂上的CO₂碳同位素组成比固关—虢镇断裂上的CO₂更靠近深部物质端元。位于南段的岐山—马召断裂的地下构造连通性较好,断裂闭锁程度较低,而位于北段的固关—虢镇断裂气体活动性较弱,闭锁程度较高,未来发生地震的危险性较高。     

鄂尔多斯盆地上、下古生界和中生界天然气地球化学特征及成因类型对比

鄂尔多斯盆地位于中国中部,是中国第二大沉积盆地,天然气类型多样、分布广泛,在上、下古生界都有找到千亿立方米以上的大气田,中生界也找到一些气藏.通过对上、下古生界和中生界200多个气样的组分及碳同位素的对比分析,对不同层位天然气的类型进行研究,并分析其气源.上古生界天然气烷烃碳同位素值较重,显示煤成气的特征;各气田天然气发生单项性碳同位素倒转,这主要是同源不同期煤成气混合的结果.下古生界天然气δ13C1值重,δ13C2和δ13C3值较轻,属于煤成气为主油型气为辅的混合气;有多项性碳同位素倒转,更有少见的δ13C1>δ13C2,这是由于高(过)成熟阶段的煤成气和油型气混合造成的.中生界天然气碳同位素值较轻,显示油型伴生气的特征;少数气样发生δ13C3>δ13C4倒转是由于细菌氧化作用和不同期次油型气混合所致;丁烷碳同位素出现δ13iC4>δ13nC4,与上古生界相反,这可能是与干酪根类型不同有关.通过δ13C1-Ro的判别以及奥陶系碳酸盐岩有机碳含量低,否定了奥陶系碳酸盐岩是下古生界油型气的主要来源,认为下古生界油型气主要来自上古生界海相石灰岩,可能有少量奥陶系碳酸盐岩的贡献.     

The spatial distribution of sedimentary compounds and their environmental implications in surface sediments of Lake Khar Nuur (Mongolian Altai)

Lake sediments are valuable natural archives to reconstruct paleoclimate and paleoenvironmental changes which consist of inorganic and organic sediment compounds of allochthonous origin from the catchment and of autochthonous production in the lake. However, for robust paleo-reconstructions it is important to develop a better understanding about sedimentation processes, the origin of inorganic and organic sediment compounds and their distribution within the lake. In this context, modern process studies provide important insights, although environmental and anthropological changes can affect the spatial distribution of sediment compounds through time. Therefore, in this study the spatial distribution of grain size and geochemical proxies in 52 surface sediment samples from Lake Khar Nuur, a small high-altitude lake in the Mongolian Altai with a small and anthropogenically used hydrological catchment, is investigated. The results show a distinct sediment focussing in the two deep basins of the lake, which therefore act as accumulation zones. In those accumulation zones, total organic carbon (TOC), total nitrogen (N) and their isotopic composition (δ¹³C_TOC, δ¹⁵N) as well as n-alkanes indicate that organic sediment compounds are a mixture of both allochthonous and autochthonous origin. While the recent catchment vegetation consists of grasses/herbs and the shrub Betula nana (L.) with distinct differences in their n-alkane homologue patterns, those differences are not reflected in the sediment surface samples which rather indicates that grass-derived n-alkanes become preferentially incorporated in the lake. Extensive anthropogenic activity such as grazing and housing in the southern part of the catchment causes soil erosion which is well reflected by high TOC, N and sulphur (S) contents and ¹⁵N depleted δ¹⁵N values at the central southern shore, i.e. increased allochthonous sediment input by anthropogenically-induced soil erosion. Overall, the surface sediments of Lake Khar Nuur origin from allochthonous and autochthonous sources and are focussed in the accumulation zones of the lake, while their distribution is both environmentally and anthropogenically driven.     

Origin and chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta,Botswana

The origin and the chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta in semi-arid Botswana were investigated using DIC and major ion concentrations and stable oxygen, hydrogen and carbon isotopes (δD, δ¹⁸O and δ¹³C_DIC). The δD and δ¹⁸O indicated that groundwater was recharged by evaporated river water and unevaporated rain. The river water and shallow (<10 m) groundwater are Ca–Na–HCO₃ type and the deep (≥10 m) groundwater is Na–K–HCO₃ to HCO₃–Cl–SO₄ to Cl–SO₄–HCO₃. Compared to river water, the mean DIC concentrations were 2 times higher in shallow groundwater, 7 times higher in deep groundwater and 24 times higher in island groundwater. The δ¹³C_DIC indicate that DIC production in groundwater is from organic matter oxidation and in island groundwater from organic matter oxidation and dissolution of sodium carbonate salts. The ionic and isotopic evolution of the groundwater relative to evaporated river water indicates two independent pools of DIC.     

Model simulations of tidal changes in a coastal lagoon,the Ria de Aveiro (Portugal)

Tidal changes in the Ria de Aveiro lagoon, Portugal, show an average increase of 0.245 m in M₂ amplitude and an average 17.4° decrease in M₂ phase, over 16 years (1987–2004). This paper investigates the causes of these changes using: (a) an analytical model and (b) hydrodynamic (vertically integrated) model of the Ria de Aveiro lagoon.     

Contrasting carbon export dynamics of human impacted and pristine tropical catchments in response to a short‐lived discharge event

Utilising newly available instrumentation, the carbon balance in two small tropical catchments was measured during two discharge events at high temporal resolution. Catchments share similar climatic conditions, but differ in land use with one draining a pristine rainforest catchment, the other a fully cleared and cultivated catchment. The necessity of high resolution sampling in small catchments was illustrated in each catchment, where significant chemical changes occurred in the space of a few hours or less. Dissolved and particulate carbon transport dominated carbon export from the rainforest catchment during high flow, but was surpassed by degassing of CO₂ less than 4 h after the discharge peak. In contrast, particulate organic carbon dominated export from the cleared catchment, in all flow conditions with CO₂ evasion accounting for 5–23% of total carbon flux. Stable isotopes of dissolved inorganic carbon (DIC) in the ephemeral rainforest catchment decreased quickly from ~1.5 ‰ to ~ ?16 ‰ in 5 h from the flood beginning. A two‐point mixing model revealed that in the initial pulse, over 90% of the DIC was of rainwater origin, decreasing to below 30% in low flow. In the cultivated catchment, δ¹³C_DIC values varied significantly less (?11.0 to ?12.2 ‰) but revealed a complex interaction between surface runoff and groundwater sources, with groundwater DIC becoming proportionally more important in high flow, due to activation of macropores downstream. This work adds to an increasing body of work that recognises the importance of rapid, short‐lived hydrological events in low‐order catchments to global carbon dynamics. Copyright © 2013 John Wiley & Sons, Ltd.     

Distribution and composition of organic matter in surface sediments of coastal Southeast Alaska

Total organic carbon (TOC) and biogenic silica (opal) content, elemental (C/N) and isotopic (δ¹³C, δ¹⁵N) composition of organic matter and the content of lipid biomarkers derived from both marine and terrestrial sources constrain relative contributions from marine productivity and continental erosion to surface sediments throughout coastal SE Alaska (54°N to 61°N). TOC and opal content are very high (up to 8% and 33% by weight, respectively) in fjords and inlets south of Icy Strait (∼58°N) and uniformly low at offshore sites to the south, and at both offshore and inland sites to the north (averaging 0.6±0.3% and 2.3±1.8%, respectively). TOC and opal mass accumulation rates (MARs, based on bulk density and ²¹⁰Pb-derived sediment MAR) suggest dilution with terrigenous, inorganic detrital materials accounts for the low concentrations of both biogenic phases in sediments from the glacial tidewater fjords of Muir and Yakutat Bays but not elsewhere. C/N, δ¹³C, and δ¹⁵N indicate a dominant marine origin for organic matter deposited at most sites. This conclusion implicates elevated primary productivity in inland waters to the south with diatoms, based on opal results, being the dominant contributor. A very significant terrestrial organic fraction (25–50%) is contained in sediments deposited on the continental shelf to the north of 58°N. Hydrocarbon biomarkers indicate the terrestrial fraction in sediments from this region is represented by old organic matter (kerogen) likely contained within riverborne particles eroding from now heavily glaciated adjacent landscapes. In sediment to the south, the terrestrial fraction is traced to modern soil organic matter eroded from the now non-glaciated, heavily forested adjacent landscape. Our study provides a framework to guide future investigations of short- (anthropogenic) to long- (Holocene) term environmental and/or climate change in this region through down-core, stratigraphic analysis.     

Driving factors behind the distribution of dinocyst composition and abundance in surface sediments in a western Mediterranean coastal lagoon: Report from a high resolution mapping study

Species composition and abundance of dinocysts in relation to environmental factors were studied at 123 stations of surface sediment in Bizerte Lagoon. Forty-eight dinocyst types were identified, mainly dominated by Brigantidinium simplex, Votadinum spinosum, Alexandrium pseudogonyaulax, Alexandrium catenella, and Lingulodinum machaerophorum along with many round brown cysts and spiny round brown cysts. Cysts ranged from 1276 to 20126 cysts g⁻¹ dry weight sediment. Significant differences in cyst distribution pattern were recorded among the zones, with a higher cyst abundance occurring in the lagoon’s inner areas. Redundancy analyses showed two distinct associations of dinocysts according to location and environmental variables. Ballast water discharges are potential introducers of non-indigenous species, especially harmful ones such as A. catenella and Polysphaeridium zoharyi, with currents playing a pivotal role in cyst distribution. Findings concerning harmful cyst species indicate potential seedbeds for initiation of future blooms and outbreaks of potentially toxic species in the lagoon.