稳定碳同位素δ13C1在煤层气田勘探中的应用

煤层气分布状态主要受控于两种地质效应：一种是热动力学机制控制下的同位素分馏效应，存在于煤层气生成期；另一种是甲烷δ^13C1解吸一扩散一运移效应，存在于煤层气生成后，源于埋深变浅而造成的泄压条件下。文中以沁水煤层气田为例，探讨了沁水煤层气田煤层气δ^13C1解吸-扩散-运移效应。认为可以利用煤层气δ^13C1特征来评价煤层气保存条件和开采稳定性，指导煤层气田的勘探和开发。     

树轮α-纤维素δ13C角分布及其气候含义

利用从中国天目山和庐山采集的4株树轮样，分析了树轮沿不同方位δ^13C的变化特点，讨论了角分布的成因。结果表明，树轮在不同方位上的木质α－纤维素δ^13C值不同，而且各方位上δ^13C的差异与分析期间历年平均值的年际差异在量级上大致相当。对各方位δ^13C作方差分析表明，各方位存在显性差异。说明δ^13C的角分布具有独立意义。对其中一棵柳杉树轮δ^13C角分布与气候要素的相关分析表明，不同方位的δ^13C值与年、季节和朋降水及温度相关，从而使树轮可记录住处分辨率提高、信息量增大。用树轮δ^13C的角分布重建的气候要素更能反映气候要素的实际变化情况。     

Variations of organic carbon isotopic composition and its environmental significance during the last glacial on western Chinese Loess Plateau

The last glacial period is characterized by a cold and dry climate with low atmospheric CO2 concentration. The relatively arid climate and low CO2 concentration are favorable to the growth of C4 plants, but the low temperature limits the development of th…     

Climate as the dominant control on C3 and C4 plant abundance in the Loess Plateau： Organic carbon isotope evidence from the last glacial-interglacial loess-soil sequences

Abundance of C3 and C4 photosynthesis plants can be inferred relatively from stable carbon isotopic composition of organic matter in soils. The samples from five sequences of the last glacial-interglacial loess-soil in the Chinese Loess Plateau have been measured for organic carbon isotopic ratios (613Corg). The organic carbon isotope data show that relative abundance (or biomass) of C4 plants was increased ca. 40% for each sampling site from the last glacial maximum (LGM) to Holocene optimum, and increased southeastward on the Loess Plateau during both periods of LGM and Holocene. Statistic analyses on the steady maximum δ^13Corg values of Holocene soils and modern climatic data from the Loess Plateau and Inner Mongolia indicate that the C4 plant abundance increases with increasing temperature and decreasing precipitation. The C4 plant abundance is related much closer with mean April temperature and precipitation than annual. These results lead us to deduce following conclusions. First, temperature is the major factor for control on variations in C4 plant abundance in the Loess Plateau from the last glacial to interglacial. In the absence of favorable temperature condition, both of low moisture and low atmospheric CO2 concentration are insufficient to drive an expansion of the C4 plants in the plateau. Second,δ^13Corg in the loess-paleosol sequences, as a proxy of the relative abundance of C4 plants in the Loess Plateau, could not be used as an indicator of changes in the summer monsoon intensity unless the temperature had changed without great amplitude. Since all C4 plants are grasses, finally, the increase of the C4 plants supports that forest has not been dominant in the ecosystem on the Loess Plateau during Holocene although precipitation and atmospheric CO2 were largely increased relative to those during LGM.     

Response of the northwestern Pacific upper water δ~(13)C to the last deglacial ventilation of the deep Southern Ocean

The deglacial δ~13C minimum events that originated from the ventilation of the deep Southern Ocean around Antarctica, have been recorded in a range of marine sediments from the southern to tropical oceans in late Pleistocene. However, the broad δ~13C minimum event was also reported as far as to the northern middle latitudes, in northwestern Pacific marginal sea areas, during the last deglaciation. In the northwestern Pacific, forcing from the northern high latitudes is strongly expressed, while the records of in- fluence from the southern high latitudes are few. The Kuroshio Source Region (KSR) forms a boundary between the northwestern Pacific and the southern, tropical Pacific. So, high-resolution planktonic foraminiferal records in core MD06-3054 from the KSR are well positioned to identify signals from the southern hemisphere in the northwestern Pacific. Planktonic foraminiferal tests from the upper 1030 cm of the core were subject to AMS14C, carbon and oxygen isotopic measurements. A negative excursion was found to occur from about 20.0-6.0 ka BP in δ~13C records of both surface (Globigerinoides ruber) and subsurface (Pulleni- atina obliquiloculata) dwellers, but the overall trends of the two curves have reversed since 26.5 ka BP. Moreover, the δ~13C rec- ord of G. ruber (the surface dweller) shows a robust link to the record of atmospheric CO2, and its changes precede the records of P. obliquiloculata (the subsurface dweller). According to the hydrologic conditions, the broad δ~13C minimum event recorded in the KSR is also a response to the increasing ventilation of the deep Southern Ocean around Antarctica during the last deglaciation. The inconsistency between the records of the surface and subsurface dwellers was possibly caused by the ways that the low δ~13C signal was transmitted. Subsurface water primarily received the low δ~13C signal from the Antarctic Intermediate Water (AAIW), whereas the surface water was probably mainly impacted by atmospheric CO2 in the KSR. The records from the KSR confirm the deduction that the broad δ~13C minimum event in the Okinawa Trough was due to the impact of tropical Pacific surface water dur- ing the last deglaciation, and suggest that signals from the southern high latitudes also can be delivered to the northern middle latitudes.     

Foliar δ^13C and δ^15N values of C3 plants in the Ethiopia Rift Valley and their environmental controls

The foliar C and N stable isotopic compositions （δ^13C and δ^15N） and the relationships between these compositions and environmental factors of C3 plants in the Ethiopia Rift Valley were investigated. There were three distribution patterns for foliar δ^13C with mean values of -26.7‰±0.4‰, -29.7‰ ±0.6‰ , and -26.9‰± 1.2‰ in cold-moist, temperate-moist, and arid-hot environments, respectively. The δ^15N values ranged from -1.4‰ ±1.7‰ to 14.3‰ ± 0.1‰, with higher values under arid-hot conditions and the lowest values in plants growing at higher altitudes under cold-moist conditions. A strong negative relationship between mean annual precipitation and δ^15N explained more than half of the observed variation in the δ^15N values （r2= 0.54, P 〈 0.001）; a modest positive relationship was also found between δ^15N and temperature （r2 = 0.32, P 〈 0.01）. A weakly positive relationship existed between δ^13C and temperature, and changes in δ^13C values with precipitation and altitude followed quadratic curves. This suggests a shift in the effects of water and heat conditions caused by altitude on carbon isotopic discrimination.     

C-isotope composition and correlation of the Upper Neoproterozoic in Keping area, Xinjiang

C-isotope analysis of the carbonates in the Upper Neoproterozoic in Keping, Xinjiang indicates that the Qigebrak Formation and the Upper Sugaitbrak Formation mainly record positive C-isotope values, and a distinct positive excursion occurs in the lower part of the Qigebrak Formation. There are three negative excursions in the boundary between the Qigebrak Formation and the Cambrian, the uppermost and lowermost Upper Sugaitbrak Formation. These characters resemble those of the Upper Neoproterozoic in the Three-Gorge area, which suggests that the Upper Sugaitbrak Formation and Qigebrak Formation can be correlated with the middle and upper parts of the Doushantuo Formation and Dengying Formation, respectively. The negative excursion at the top of the Upper Sugaitbrak Formation corresponds to that at the top of the Doushantuo Formation, while the negative excursion at the bottom of the Sugaitbrak Formation can be correlated with that at the middle part of the Doushantuo Formation in the Three-Gorge area and that at the top of the Hangelchaok diamictites in the Quruqtagh area.     

Carbon isotopic record of foraminifers in surface sediments from the South China Sea and its significance

Since the 1990s, the papers and data involved withthe South China Sea (SCS) have been emerging in largenumbers in the world as people pay more attention to thepaleoceanography of the SCS. There have been more than100 cores mentioned in papers containing p…     

Effect of land use on microbial biomass－C, －N and －P in red soils

Eleven red soils varying in land use and fertility status were used to examine the effect of land useon microbial biomass -C, -N and -P. Microbial biomass-C in the red soils ranged from about 68 rag C/kg to 225 mg C/kg, which is generally lower than that reported from other types of soil, probably because of low or-ganic matter and high acidity in the red soils. Land use had considerable effects on the amounts of soil Cmic.The Cmic was the lowest in eroded fallow land, followed by woodland, tea garden, citrus grove and fallow grassland, and the highest in vegetable and paddy fields. There was significant correlation between Cmic and organic matter content, suggesting that the influence of land use on Cmie is mainly related to the input and ac-cumulation of organic matter. Microbial biomass-N in the soils ranged from 12.1 Nmg/kg to 31.7 Nmg/kg andwas also affected by land use. The change of Nmic with land use was similar to that of Cmic. The microbial C/N ratio ranged from 5.2 to 9.9 and averaged 7.6. The Nmic was significantly correlated with soil total N and available N. Microbial biomass-P in the soils ranged from 4.5 mg P/kg to 52.3 rag P/kg. The microbial C/P ratio was in the range of 4-23. The Pmic was relatively less affected by land use due to differences in fertili-zation practices for various land use systems.     

中扬子区上震旦统层序地层研究

以中扬子区上震旦统为对象,研究了层序界面和体系域特点,分析了层序样式的基本类型及其特征,共划分出2个二级层序,8个三级层序.陡山沱组划分了1个二级层序(SS1),四个三级层序(ZSQ1～ZSQ4),平均延时12.5 Ma;体系域颜色普遍较深,泥质含量较高,是一套良好的烃源岩;T型样式和H型样式为主,并且T型样式较多,反映陡山沱期水体较浅.灯影组划分出1个二级层序(SS2),四个三级层序(ZSQ5～ZSQ8),平均延时约20Ma;体系域颜色普遍较浅,云质含量较高,是一套良好的储集层;T型样式和H型样式为主,并且H型样式较多,反映灯影期水体也较浅.二级层序体系域和三级层序体系域都表现出明显的南北向差异性.     

塔里木板块东北缘霍布哈尔白山组流纹岩地球化学特征及构造意义

探讨塔里木板块东北缘额济纳旗霍布哈尔地区上石炭统白山组流纹岩的形成环境、厘定晚石炭世雅干地区的古大地构造环境。对白山组流纹岩样品开展了岩相学分析以及主元素、痕量元素地球化学分析,结果显示流纹岩SiO_2平均质量分数为75.63%,K_2O/Na_2O比值平均为1.09,里特曼指数δ平均为2.05,属于高钾钙碱性岩石。TiO_2、MgO含量较低(质量分数分别为0.06%～0.17%、0.12%～0.29%),显示壳源岩浆岩的特点。高场强元素Nb、Ta、Ti和P强烈亏损,大离子亲石元素K、Rb、Th和U相对富集,轻重稀土元素分异明显,具明显负铕异常,流纹岩具有大陆边缘火山弧的地化特征。综合岩石组合特征及与西侧白山岩浆弧的对比,认为晚石炭世霍布哈尔地区为大陆边缘火山弧环境。     

震旦纪至寒武纪转折时期湘西北地区黑色岩系元素地球化学特征及其意义

黑色岩系作为地质历史时期特殊环境的产物,对研究地质历史与环境演化具有重要意义。本文以湘西北地区新元古代晚期至寒武纪早期典型剖面中的黑色岩系为研究对象,对震旦系灯影组白云岩、寒武纪牛蹄塘组硅质岩、磷块岩、黑色页岩等,开展了常规的元素地球化学特征研究,结果表明,研究区黑色岩系明显富集Mo、U、V、Cd、Tl,相对富集Cu、Ni、Zn,亏损Co、Mn、Ge 等元素;稀土元素总量较低,总体表现出轻稀土相对富集、重稀土相对亏损,δCe 呈明显负异常特征,显示出黑色岩系具海相热水沉积特征：黑色页岩、白云岩以正常海相沉积为主,兼有热水作用参与;硅质岩、磷结核受海水热液作用强烈。结合氧化还原特征元素比值U/Th、V/Cr、Ni/Co、V/Sc、V/(V+Ni),MoEF-UEF协变关系及δCe 异常值在剖面上的分布规律,分析得出剖面自底部而上沉积环境经历了弱氧化→氧化→还原(硫化)→缺氧→贫氧的变化。     

塔里木河水系变迁遥感研究

本文采用陆地卫星ＭＳＳ数字磁带，经过增强处理，提取了塔里木河水系变迁信息．经研究认为：现代塔里木河水系是由南北两大水系合并而成的，水系变迁的主要原因是冰后期大气环流调整和新构造运动影响．     

塔北隆起北部正断层的成因机制及地质意义

塔里木盆地自中生代以来一直处于挤压构造背景,而塔北隆起北部正断层的出现却引起众多学者的关注.本文对塔北隆起北部正断层的成因机制进行了分析探讨.分析认为,根据正断层发育完全受基底古构造格架的控制,其成因源于再生前陆盆地挤压背景下基底构造活动对上覆构造层的影响,具体表现为:①基底受挤压强烈翘曲导致上覆脆性地层引张构造变形;②先存基底断块隐伏活动诱导上盘层系引起构造变形.得出正断层自西向东的持续发育随前陆盆地沉降中心的迁移而有规律性变化的结论.塔北隆起北部正断层的成因模式揭示了塔里木盆地北部基底—盖层统一构造变形的关系,对解释中国西北地区挤压构造背景下沉积盖层局部引张构造变形具有重要的地质意义.     

塔里木盆地西北缘石炭-二叠系浊积岩的沉积特征及其构造意义

目的研究塔里木盆地西北缘晚石炭世晚期—中二叠世早期(逍遥—栖霞期)浊积岩沉积特征及其构造意义。方法对塔里木盆地西北缘上石炭统上部—中二叠统下部的浊积岩进行岩石、岩相和时空变化特点的分析。结果从晚石炭世晚期—早二叠世早期到中二叠世早期,浊积岩的沉积范围显著减小,沉积区域在向西南方向收缩的同时水体则进一步加深。结论这种沉积-构造特点反映当时南天山造山带内部处于强烈的构造活动状态,南天山造山带向塔里木地块的冲断推覆可以导致这种沉积-构造格局;从沉积学的角度提出南天山造山带在晚石炭世晚期—中二叠世早期可能处于碰撞造山作用的晚期阶段。     

欧洲近代史学与傅斯年的学术思想

欧洲近代史学作为一种舶来品,对于中国史学从传统走向现代,起到了至为重要的推动作用。在欧洲近代史学东传的过程中,傅斯年穿针引线,对欧洲近代史学的引介不遗余力,贡献尤著。尤其是,他对巴克尔史学的借鉴、兰克治史理念的宣扬,以及德国"种族-文化"观念的运用,不仅成为其取得重要史学成就的学术渊源,而且为转型期的中国史学创辟了一条新路径。同时,欧洲近代史学经由傅斯年输入国内,开阔了中国学者的国际视野,为中国史学走向世界,取得国际学术话语权奠定了基础。     

塔中西北部奥陶系异常压力成因及地质意义

塔中西北部地区奥陶系地层中存在异常压力,研究认为该异常压力的形成主要与油气聚集增压机理有关,其次为构造增压和流体热膨胀增压机理,火成岩侵入也是一种辅助的增压机理.异常压力的存在可以表征良好的储层和盖层的封盖能力,也与油气藏的分布有一定的关系,异常压力层的发育层位往往指示一定丰度的油气层,而油气层并不一定都是异常压力层.     

Geochemical significance of pyrrolic nitrogen compounds in various kinds of crude oils from the Tarim Basin

This is a report of the differences in abundances of pyrrolic nitrogen compounds and distribution of alkylated carbazoles among various oils from the Tarim Basin. At the same time, their geochemical significance is discussed.