五台山晚太古代花岗岩的成因及其动力学意义

五台山晚太古代花岗岩（～2.540 Ga）,主要由花岗闪长岩、二长花岗岩、少量的英云闪长岩、奥长花岗岩组成,全岩化学分析表明它们具有中～高钾钙碱性花岗质岩浆性质,LILE富集和高的 w(Rb)/w(Sr) (即: Rb/Sr)比值,相对较低的 w(Sr)/w(Y)、w(La)_n/w(Yb)_n、w(Nb)/w(Ta) 和 w(Zr)/w(Hf) 比值,右斜式稀土配分模式,Nb、Ta、Ti亏损,但是它们均表现了Nd T_DM＝2.54～2.72 Ga和明显的正ε_Nd(t)值。这些地球化学特征表明其钙碱性花岗质岩浆形成于晚太古代大洋岛弧环境,来源于弧下玄武质初生地壳的部分熔融,并经历了一定程度的结晶分异。由于晚太古代洋壳向大洋岛弧俯冲、脱水,引起上覆地幔楔的部分熔融形成弧下初生地壳玄武质物质,这些弧下玄武质物质在少于37km环境下部分熔融形成五台山晚太古代钙碱性花岗质岩浆。     

华北克拉通北缘早白垩世岩石圈减薄: 钾玄岩的Pb同位素证据

内蒙古四子王旗地区出露的早白垩世玄武岩属于钾玄岩。岩石富集大离子亲石元素（LILE）、轻稀土元素（LREE）,亏损高场强元素（HFSE）,其地球化学特征总体与洋岛玄武岩(OIB)相似。w(Rb)/w(Nb)、w(K)/w(Nb)、w(Zr)/w(Nb)、w(Th)/w(Nb)和w(Th)/w(La)比值主要落在EM1-OIB范围内。w(²⁰⁶Pb)/w(²⁰⁴Pb)、w(²⁰⁷Pb)/w(²⁰⁴Pb)和w(²⁰⁸Pb)/w(²⁰⁴Pb)分别变化在17.18～17.81, 15.40～15.50和37.54～38.05之间,岩石的Pb同位素组成接近EM1型地幔端元。随着Pb含量(质量分数)的增加,Pb同位素比值几乎没有变化,表明四子王旗钾玄岩没有经历明显的地壳物质混染。钾玄质母岩浆源于软流圈地幔的减压低度部分熔融。四子王旗钾玄岩是华北克拉通岩石圈减薄事件的产物。     

柴西北缘鄂博梁地区下干柴沟组泥岩地球化学特征及古环境

以柴达木盆地西北缘鄂博梁地区为例,通过痕量元素及稀土元素分析测试,结合沉积综合柱状图,探讨古近系下干柴沟组的古盐度、古气候和古氧化-还原条件等变化特征。样品具有明显的Eu负异常及轻微的Ce负异常,氧化-还原指标Ni/Co、V/Cr、U/Th一致指示氧化条件,古气候指标Sr/Cu值与Sr、Rb/Sr值指示的气候温湿变化趋势一致,古气候条件与Sr/Ba、Th/U判断出的古盐度变化相符合。古近纪青藏高原隆升高度较低且范围有限,鄂博梁地区下干柴沟组沉积期处在温暖湿润的淡水环境。     

广东乳源地区棋梓桥组—天子岭组碳酸盐岩地球化学特征及其古环境意义

通过运用对沉积环境反应敏感的Sr、Ba、Cu、Fe、Mn、Ca、Ni、V等元素,结合δ¹³C_V-PDB、δ¹⁸O_V-PDB数据及沉积学特征,对粤北韶关盆地乳源地区泥盆系棋梓桥组—天子岭组的古盐度、古气候、古水深、氧化-还原性等古环境参数进行综合研究。结果表明：棋梓桥组Z值普遍较低(121.56～123.34),Sr/Ba值(质量分数之比)变化明显(4.77～24.66),沉积时期古温度为17.49～25.49℃,Fe/Mn值为13.12～38.45,Sr/Cu值为6.41～32.64,V/(V+Ni)值均大于0.54,古水深曲线与沉积相特征显示为一次海平面升降旋回;天子岭组Z值较高(125.53～128.12),沉积时期古温度平均为20.54℃,具有异常高的Sr含量,Fe/Mn平均值为44.22,V/(V+Ni)值均大于0.54,古水深曲线与沉积相特征显示4次海平面升降旋回。研究区的弗拉斯阶(天子岭组)整体继承了吉维特阶(棋梓桥组)的海侵格局,由西向东海域面积进一步扩大,海平面升降旋回性增强,气候向...     

微量元素在地质沉积环境中的应用

在地球化学相分析中,用微量元素比值及分布特点可明显地将陆相沉积和海相沉积环境区分开,利用硼的含量及锶钡(Sr/Ba)和钙镁(Ca/Mg)比值,可以判断沉积岩的沉积环境同时利用微量元素计算古气侯指数"C"值,可追溯古环境.在此应用等离子发射光谱仪(PE3000型全谱直读)对南疆塔里木盆地库车河进行微量元素分析,探讨了库车河的沉积环境及其古气候特征.     

青藏高原东北缘古降水重建与人类活动

青藏高原东北缘的自然环境对全球变化响应敏感,重建全新世中晚期的降水对过去全球变化研究具有意义.本文利用现代表土孢粉、化石孢粉和现代气候数据,采用GIS和现代类比法,重建了全新世中晚期百年分辨率的降水序列,并探讨了其与人类活动的关系.重建结果表明:6.3~5kaBP为典型湿润期,降水充沛,并在6.09kaBP达到最大值465mm,比现代降水量高约210mm;5~3.9kaBP为亚湿润期,平均降水量比现代高约65mm,但整体降水量在波动中下降;3.9~2.9kaBP为波动期,降水量急剧下降,较前一阶段减少约79mm;2.9kaBP以来降水量较为稳定,平均降水量与现代相当;其中有6个干湿事件,湿事件为6kaBP、4.1kaBP、1.6kaBP,干事件为4.9kaBP、3.8kaBP、2.8kaBP.降水量变化与植被覆盖和史前文化变迁关系密切.     

新疆柯坪大湾沟奥陶系顶部-志留系底部化学地层特征讨论

新疆塔里木盆地奥陶系-志留系界线可能在柯坪县大湾沟剖面柯坪塔格组下段顶部-中段底部的泥岩夹白云岩地层内穿过,化学地层分析将有助于该界线问题的解决。对系统采集的72个样品进行ICP测试和数据对比、校正,w(Ce)/w(La) 化学地层分析结果表明,柯坪塔格组下段-中段界线层可细分为3个化学地层段,化学波动趋势可能反映了古水体氧化-还原度的变化,其与生物化石的变化趋势可对比,出现的异常峰可能与峡东奥陶系-志留系界线附近的异常相对应。     

龙门山甘溪土桥子组灰岩-泥灰岩韵律层地球化学特征研究

龙门山甘溪土桥子组发育多套灰岩-泥灰岩韵律层,其地球化学特征对其形成时的古环境、古气候具有重要的指示意义。在对土桥子组最大海泛面之上沉积的一套灰岩-泥灰岩韵律层进行野外详细描述与系统采样的基础上,对其中的37对74层灰岩-泥灰岩韵律层的常量、微量元素进行分析测试与研究。通过古氧相U/Th、古盐度Sr/Ba、古水深Mn O、古气候Sr/Cu等分析,认为该灰岩-泥灰岩韵律层形成于炎热气候下的贫氧海相高水位体系域沉积环境。古气候和差异成岩作用是灰岩-泥灰岩韵律层的主要成因,其中在较大的宏观尺度上古气候的韵律和波动控制着韵律层的古环境和地球化学特征,而在较小的微观尺度上差异成岩作用进一步控制和影响着韵律层地球化学特征的分异性和韵律性。     

内蒙古大青山石拐盆地侏罗系元素地球化学特征及沉积环境指示意义

研究内蒙古大青山石拐盆地侏罗纪的古气候、古水深和古盐度等环境信息。对石拐盆地侏罗系13件细粒沉积岩样品进行了主元素和痕量元素地球化学测试,分析了古沉积环境演化特征。研究表明:①古盐度指标Li、Sr、Ga和Sr/Ba值指示五当沟组、召沟组和大青山组为淡水沉积环境,长汉沟组为淡水—微咸水环境;②古氧化-还原指标U/Th、V/Cr、Ni/Co和V/(V+Ni)值指示研究区为氧化环境,其中召沟组为弱氧化环境,石拐群向大青山组氧化程度逐渐增强;③古水深计算指示五当沟组、长汉沟组和大青山组为浅水环境,召沟组为浅水—半深水环境;④古气候指标(古气候指数、化学蚀变指数、Rb/Sr和Sr/Cu值)指示古气候由石拐群的暖湿气候向大青山组的半干热气候转变。研究区随着气候变得越加炎热干旱,蒸发作用加强,水体变浅,盐度逐渐升高,氧化作用越来越强。     

洞穴石笋氧同位素古气候重建应用

近年来,应用洞穴次生碳酸盐稳定氧、碳同位素进行古气候研究得到了迅速的发展,尤其是利用石笋中1δ8O与δ13C重建不同地区不同时间尺度下的古气候环境,为全球气候的变化提供了许多新的有意义的认识.然而,当前在利用石笋氧同位素进行古气候重建,特别是对1δ8O的解译过程中仍存在诸多不确定性,尤其是δ18O与温度、降水的联系不统一问题.该文从洞穴石笋δ18O与温度、降水的相关关系以及不同时间尺度下所指示的气候意义等角度对当前洞穴石笋气候学中氧同位素的应用进行了总结分析.     

Paleotemperature changes over the past 3000 years in eastern Beijing,China:A reconstraction based on Mg/Sr records in a stalagmite

The Mg/Sr ratio in a stalagmite,whic is directly proportinonal to DMg/Ca,the solid-liquid distribution coefficient of Mg,is proposed as a geochemical thermometer to estimate paleotemperature changes,The paleotemperature change in eastern Beijing over the past 3000 years has been reconstructed by using this thermometer in the stalagmite ZFFS-1 from Jingdong Cave,The records can be divided into two periods:3000-2000 aBP,cool and wet ,the air temperature averaging 9.8℃;and 2000aBP-present, hot and dry,the air temperature being 1℃ higher than the mean value (11.7℃) of the past 3000 years ,During 500-200 aBP,the air temperature was about 1.2℃ lower than that of the present,corresponding to the Little Ice Age Europe Like δ^18O and δ^C ,Mg/Sr (or DMg/Ca) reflects and obviously warming trend of the past 200 years,These results are supported by historic recods.     

A high-resolution stalagmite O-C isotope record from Nanjing and its rapid response to climatic events

Here we discussed rapid response of the cave temperature and vegetation to the four Dansgaard-Oeschger cold and warm cycles during 50-40 kaBP based on results of oxygen and carbon stable isotopic compositions from a stalagmite in Tangshan, Nanjing. It is found that the amount of C₃ vegetation relative to C₄-type declines during the D-O warm events, indicating the decrease of the effective meteoric precipitation. Compared with O-isotope records of the Greenland ice core, the stalagmite record displays a very similar pattern to Greenland ice core record over the decade-century time scale, suggesting that the changes of the East Asian monsoon climate are in accordance with the high-latitude polar climate in the short-term time scale. The age of the ice-rafted H5 event in the stalagmite record, however, preceded that of Greenland ice cores by 2 ka. This out of phase between the remote areas cannot be yet proven because the two time scales were determined from different dating methods.     

Speleothem Mg,Sr and Ba records during the MIS 5c-d,and implications for paleoclimate change in NE Sichuan,Central China

Trace metals of Mg, Sr and Ba in a stalagmite (SZ2) collected from Suozi Cave in NE Sichuan, Central China, were analyzed with ICP-AES. The stalagmite was dated to have developed between 120 and 103 ka BP. Results indicate that the Mg/Ca, Sr/Ca and Ba/Ca ratios of SZ2 varied between (9500-14700) 10 6 , (54-123) 10 6 and (31-82) 10 6 , respectively. The three records displayed significant millennial scale variations, which correlate with changes in past climate and environment. Lower values of Mg/Ca ratios and higher values of Sr/Ca and Ba/Ca ratios of SZ2 occurred during relatively cold-dry marine isotope stage (MIS) 5d, while the opposite trend was observed during relatively warm-humid MIS 5c. Trace metals in speleothems can be affected by distribution coefficients or trace metal concentrations in solutions from which speleothems precipitate. Temperature is suggested to be the dominant controller of Mg/Ca ratios in SZ2, whereas the Sr/Ca and Ba/Ca ratios may have been influenced by surface soil and atmospheric dust activities and prior calcite precipitation in Suozi Cave. Further investigations are warranted as to whether Sr/Ca and Ba/Ca ratios were affected by temperature and growth rate of the speleothem. The shifts of Mg/Ca, Sr/Ca and Ba/Ca records in SZ2 during the transition from MIS 5d to 5c apparently were earlier than the oxygen isotope record ( 18 O) of the same stalagmite. This possibly indicates (1) that atmospheric dust activity (the mechanism affecting SZ2 Sr/Ca and Ba/Ca ratios) is closely related to temperature, and (2) that temperature changes (dominated by solar insolation) precedes change in speleothem 18 O records which are controlled by both summer monsoons and winter temperatures.     

川东北宋家洞石笋氧碳同位素及锶含量突变分析

通过对宋家洞石笋SJ3的氧碳同位素及锶含量进行Mann-Kendall test突变分析,得出以下结论:(1)氧同位素值记录了末次冰盛期向Heinrich Event 1时期的转变;(2)碳同位素值和锶含量记录了由H1冷期向BФlling-AllerФd暖期的转变;(3)碳同位素值和锶含量指示了在19.8～15.3ka时当地的东亚夏季风和冬季风呈正相关关系,在15.3～14.8 ka呈负相关关系,表明石笋SJ3记录了古气候环境的冷干、暖湿变化,且不同气候指标对环境变化的敏感度不同。     

矾山碱性杂岩体中发现碳酸岩

矾山杂岩体是中心型碱性超基性岩——碱性岩侵入体。它由三期侵入岩组成,在三期岩石形成之后有碳酸岩和正长岩脉形成。碳酸岩主要岩石类型包括：黑云母方解石碳酸岩、正长石—黑云母方解石碳酸岩、黄铁矿—方解石碳酸岩等。碳酸岩锶的含量为3364×10^-6～19263×10^-6, 钡的含量为323×10-6～378×10^-6。碳酸岩的稀土元素∑REE为323×10^-6～551×10^-6, 其δEu值0.99～1.1,(La/Yb)_N为291.9～759.4。碳酸岩的δ¹⁸O值是+8.6×10^-3～+10.2×10^-3, δ¹³C为-4.9×10^-3。根据上述事实认为碳酸岩的物质源自岩浆。     

新疆巴里坤湖 9.0cal.ka BP来沉积物地球化学元素分布特征与古气候环境演化

根据中国西北干旱区巴里坤湖BLK-1剖面沉积物的地化元素分析,采用SPSS因子分析法提取了对沉积环境变化敏感的地化元素和氧化物组分. 在 R、Q 型因子分析的基础上,结合沉积物的硅铁铝率（SiO2/（Al2O3+Fe2O3））、淋失系数（SiO2/（MgO+K2O））、CaO/MgO以及腐殖化度等指标,提取出古气候环境信息. 初步研究结果表明:近9.0cal ka BP以来,巴里坤湖地区气候环境仍以干旱化为主,全新世期间出现过多次不同程度的干湿变化,经历了5个气候阶段:9.0～7.5cal kaBP期间,气候干旱;7.5～5.8cal kaBP期间,气候温暖湿润,为研究区全新世最佳适宜期;5.8～3.0cal kaBP期间,气候干旱;3.0～1.0cal kaBP期间,气候湿润;1.0～0cal kaBP期间,气候干旱.     

Abnormal overpressure distribution and natural gas accumulation in foreland basins,Western China

Shizitan in Jixian County, Shanxi Province, is a site of transitional period from Paleolithic to Neolithic. The dating and the sporopollen analysis show that the middle reaches of the Yellow River where the site is located had been maintaining a steppe environment during 35.1-9.4 kaBP, in which, 35.1-17 kaBP belonged to the last glacial. With cold and dry climate, this period featured a desert steppe environment. In the late of this period, the area had a cold and half-humid steppe environment. The 17.0-11.9 kaBP belonged to the early- and mid-period of the last deglaciation. Mild and half-arid steppe alternates with mild and half-arid steppe, with a small amount of deciduous broadleaf species. During the period of 11.9-10.5 kaBP, cold and dry glacial climate appeared once more, featuring a desert steppe environment. During 10.5-9.4 kaBP, it is mild and half-arid, and later transited toward warm and half-humid. The early phase of this period featured a steppe environment and the later transited into a steppe environment with fairly more deciduous broadleaf species. Microlith, a mark of a transitional period from Paleolithic to Neolithic, was distributed mainly in 17.0-11.9 kaBP. The relatively warm, half-arid and fluctuating steppe environment in the early and medium period of the last deglaciation made a contribution to the appearance and development of Microlithic culture.     

A very strong summer monsoon event during 30-40 kaBP in the Qinghai-Xizang (Tibet) Plateau and its relation to precessional cycle

Guliya ice core records, high lake-level records in the Qinghai-Xizang Plateau and at its north side as well as vegetation succession records indicated that during the period of 30-40 kaBP, namely the later age of the megainterstadial of last glacial period, or the marine oxygen isotope stage 3, the climate of the Qinghai-Xizang Plateau was exceptionally warm and humid, the temperature was 2-4℃ higher than today and the precipitation was 40% to over 100% higher than the current average, all these suggested the existence of an exceedingly strong summer monsoon event. It has been inferred that the occurrence of such an event was attributed, on the one hand, to the stronger summer low pressure over the Plateau, which strengthened the attraction to the summer monsoon; on the other hand, to the vigorous evaporation of the tropic ocean surface, which promoted the moisture-rich southwest monsoon to flow over the Qinghai-Xizang Plateau. The background responsible for the formation of the very strong summer monsoon was that the period of 30-40 kaBP was just in the strong insolation stage of the 20ka precessional cycle, when the Qinghai-Xizang Plateau received extraordinary strong solar radiation and thus enlarged the thermodynamical contrast between the Plateau and the mid-south part of the Indian Ocean.     

Coral Sr thermometer simplified from Sr/Ca thermometer

Cubic sub-samples obtained from a Porites coral slice collected from Xisha Islands, South China Sea, were weighed with precise micro-balance. The Sr and Ca concentrations were analyzed with isotope dilution thermal ionization mass spectrometry. Our results demonstrate that Ca concentrations in all samples are very uniform ( mean = 9.52mmol/g, la = 0.02mmol/g) ; Sr concentrations and Sr/Ca ratios are well correlated (correlation coefficient r = 0.9968) . It implies that the Sr thermometer can replace Sr/Ca thermometer and the determination of Ca can be omitted. This can save up to 50% time and cost, and more importantly, paleoclimate study using coral proxy can now be carried out in routine Sr isotope laboratories.