中国南方二叠纪古海洋锶同位素演化

本文以贵州罗甸沫阳二叠系剖面为研究对象，通过对海相碳酸盐岩的锶同位素组成变化的研究，探讨了中国南方二叠纪古海洋锶同位素组成特点、演化及其地质意义。     

西藏南部中白垩世的锶、硫同位素组成及其古海洋地质意义

讨论了西藏南部中白垩世海相碳酸盐锶同位素组成和黑色页岩中黄铁矿硫同位素组成的主要特征及其古海洋地质意义。主要结论是:①该区中白垩世海相碳酸盐的锶同位素组成在0．7084～0．7090之间,大陆壳来源的锶占28%～30%,陆源物质输入的影响高于其它地区;火山熔岩中锶的同位素组成为0．7095,高于同期玄武岩的平均值,火山熔岩中大陆壳来源的锶约为65．2ｘ10-6,占总锶量的34%左右,火山熔岩形成过程中,同化了大量的壳源物质。②该区中白垩世黑色页岩中的黄铁矿的硫同位素组成为27‰～31．6‰,它来源于同期海水硫酸盐,且系中晚期成岩作用的产物,不同时间、不同沉积环境中形成的黄铁矿,其δ34S值差异明显,它们动态地反映成岩作用中环境的演化过程。     

羌塘盆地那底岗日地区中侏罗世碳酸盐岩碳、氧、锶同位素与古海洋沉积环境

本文首次利用碳酸盐岩C,O,Sr稳定同位素探讨了羌塘盆地那底岗日地区中侏罗世海洋沉积环境的演变。测试结果表明,该区中侏罗世碳酸盐岩δ     

新生代气候变化与陆地硅酸盐岩风化和海洋Sr同位素研究

新生代全球气候自始新世55Ma以来在逐渐变冷。陆地硅酸盐岩在造山带和高原地区通过加速化学风化，消耗了大气中的CO2温室气体造成了新生代气候变冷。目前关于陆地硅酸盐岩风化与海洋Sr同位素关系的研究，主要存在两种观点：一种认为海水Sr同位素变化可作为全球地表化学风化的替代性标志；另一种观点认为全球并不存在平均地表风化这种说法，海水Sr同位素在地质历史中的演化是主要与某种地质构造事件或岩石类型的风化有关。我国应当不失时机地加快对源于喜玛拉雅山地的恒河－布拉马普特拉河进行研究，以进一步揭示陆地硅酸盐岩风化与海洋Sr同位素变化的关系。     

锶同位素地层学研究进展

锶同位素地层学（SIS）根据地质历史中的任何时间全球范围内海水的 锶同位素组成都是均一的，海水87Sr/86Sr比值随时间变化这一基本原理，利用代表原始海水的海相碳酸盐（以及磷酸盐和硫酸盐）的87Sr/86Sr比值确定海相地层的年代，研究海平面变化，造山运动，古气候等全球事件，在地层学，沉积学，石油地质学和矿床学等领域中有着广泛的应用前景，同位素地层学已在世界范围内得到地质学家的普遍关注，并已获得迅速的发展，国内的有关研究则刚刚起步，锶同位素地层学研究的难点主要在于对样品成岩蚀变的挖掘和分析技术上，同时还需要有良好的地层学研究基础，在样品选择上应充分考虑其原始组分的抗成岩蚀变能力，锶同位素地层学的研究需要地层学家，沉积学家和地球化学家的共同努力。     

中国东南沿海中—新生代玄武岩微量元素和Nd—Sr—Pb同位素研究

本文对中国东南沿海不含幔源包体的中生代玄武岩和含幔源包体的新生代玄武岩进行了微量元素和Nd-Sr-Pb同位素对比研究。中生代玄武岩呈Ta,Nb和Hf负异常,低Ce/Pb,Nb/U比值和高La/Nb比值,与岛弧火山岩和陆壳岩石的微量元素特征相类似,说明在岩浆生成和上升过程中,幔源组分受到了陆壳组分的混染。新生代玄武岩呈Ta,Nb正异常和Pb负异常,高Ce/Pb,Nb/U比值和低La/Nb比值,与海岛玄武岩（OIB）相类似,Nd-Sr同位素成分与夏威夷玄武岩类似,因而它们未受明显的陆壳混染。^143Nd/^144Nd与^206Pb/^204Pb之间的负相关关系和^87Sr/^86Sr与^206Pb/^204Pb之间的正相关关系说明本区新生代玄武岩起源于中等亏损程度的软流圈地幔,并与EMII富集地幔组分发生了混合。     

青藏高原的隆起与海洋锶同位素组成的演化

近年来,随着构造隆升驱动气候变化假说的提出,青藏高原的隆起受到越来越多的关注,并将之与大陆化学风化速率及海洋锶同位素的演化紧密联系。围绕青藏高原的隆升及其环境与气候效应,对海洋锶同位素组成的演化特征及其影响因素的较为全面而详细的论述表明:将青藏高原的隆升与全球气候变化、大陆化学风化速率及海洋锶同位素组成的演化相联系,也许是解决目前关于海洋锶同位素组成的演化及其物源问题的重要手段,根据海洋锶同位素的演化历史来研究全球气候变化规律及青藏高原的构造演化历史将是本研究领域的重点。     

青藏高原的隆起与海洋锶同位素组成的演化

近年来,随着构造隆升驱动气候变化假说的提出,青藏高原的隆起受到越来越多的关注,并将之与大陆化学风化速率及海洋锶同位素的演化紧密联系.围绕青藏高原的隆升及其环境与气候效应,对海洋锶同位素组成的演化特征及其影响因素的较为全面而详细的论述表明:将青藏高原的隆升与全球气候变化、大陆化学风化速率及海洋锶同位素组成的演化相联系,也许是解决目前关于海洋锶同位素组成的演化及其物源问题的重要手段,根据海洋锶同位素的演化历史来研究全球气候变化规律及青藏高原的构造演化历史将是本研究领域的重点.     

海水的氯同位素组成特征

本研究采用基于Cs2 Cl+离子的正热电离质谱法测定了海水中的氯同位素组成。结果表明海水的3 7　Cl 3 5Cl值基本上是均一的 ,平均值为 0 .3190 93,变化范围为 0 .318782～ 0 .3192 2 1。相对于某一标准海水的表面海水的δ3 7Cl值与包括海水温度、盐度、经纬度在内的所有因素基本无关。但不同深度的海水的δ3 7Cl值随深度而降低 ;δ3 7Cl值也显然与大陆注入水和区域有关。     

Dolomitization by hypersaline reflux into dense groundwaters as revealed by vertical trends in strontium and oxygen isotopes: Upper Muschelkalk,Switzerland

The Trigonodus Dolomit is the dolomitized portion of the homoclinal ramp sediments of the Middle Triassic Upper Muschelkalk in the south‐east Central European Basin. Various dolomitizing mechanisms, followed by recrystallization, have been previously invoked to explain the low δ¹⁸O, high ⁸⁷Sr/⁸⁶Sr, extensive spatial distribution and early nature of the replacive matrix dolomites. This study re‐evaluates the origin, timing and characteristics of the dolomitizing fluids by examining petrographic and isotopic trends in the Trigonodus Dolomit at 11 boreholes in northern Switzerland. In each borehole the ca 30 m thick unit displays the same vertical trends with increasing depth: crystal size increase, change from anhedral to euhedral textures, ultraviolet‐fluorescence decrease, δ¹⁸O_VPDB decrease from ?1·0‰ at the top to ?6·7‰ at the base and an ⁸⁷Sr/⁸⁶Sr increase from 0·7080 at the top to 0·7117 at the base. Thus, dolomites at the top of the unit record isotopic values similar to Middle Triassic seawater (δ¹⁸O_VSMOW = 0‰; ⁸⁷Sr/⁸⁶Sr = 0·70775) while dolomites at the base record values similar to meteoric groundwaters from the nearby Vindelician High (δ¹⁸O_VSMOW = ?4·0‰; ⁸⁷Sr/⁸⁶Sr = >0·712). According to water–rock interaction modelling, a single dolomitizing or recrystallizing fluid cannot have produced the observed isotopic trends. Instead, the combined isotopic, geochemical and petrographic data can be explained by dolomitization via seepage‐reflux of hypersaline brines into dense, horizontally‐advecting groundwaters that already had negative δ¹⁸O and high ⁸⁷Sr/⁸⁶Sr values. Evidence for the early groundwaters is found in meteoric calcite cements that preceded dolomitization and in fully recrystallized dolomites with isotopic characteristics identical to the groundwaters following matrix dolomitization. This study demonstrates that early groundwaters can play a decisive role in the formation and recrystallization of massive dolomites and that the isotopic and textural signatures of pre‐existing groundwaters can be preserved during seepage‐reflux dolomitization in low‐angle carbonate ramps.     

Tectono-sedimentary events and geodynamic evolution of the Mesozoic and Cenozoic basins of the Alpine Margin,Gulf of Tunis,north-eastern Tunisia offshore

The structural pattern, tectono-sedimentary framework and geodynamic evolution for Mesozoic and Cenozoic deep structures of the Gulf of Tunis (north-eastern Tunisia) are proposed using petroleum well data and a 2-D seismic interpretation. The structural system of the study area is marked by two sets of faults that control the Mesozoic subsidence and inversions during the Paleogene and Neogene times: (i) a NE-SW striking set associated with folds and faults, which have a reverse component; and (ii) a NW–SE striking set active during the Tertiary extension episodes and delineating grabens and subsiding synclines. In order to better characterize the tectono-sedimentary evolution of the Gulf of Tunis structures, seismic data interpretations are compared to stratigraphic and structural data from wells and neighbouring outcrops. The Atlas and external Tell belonged to the southernmost Tethyan margin record a geodynamic evolution including: (i) rifting periods of subsidence and Tethyan oceanic accretions from Triassic until Early Cretaceous: we recognized high subsiding zones (Raja and Carthage domains), less subsiding zones (Gamart domain) and a completely emerged area (Raouad domain); (ii) compressive events during the Cenozoic with relaxation periods of the Oligocene-Aquitanian and Messinian-Early Pliocene. The NW–SE Late Eocene and Tortonian compressive events caused local inversions with sealed and eroded folded structures. During Middle to Late Miocene and Early Pliocene, we have identified depocentre structures corresponding to half-grabens and synclines in the Carthage and Karkouane domains. The north–south contractional events at the end of Early Pliocene and Late Pliocene periods are associated with significant inversion of subsidence and synsedimentary folded structures. Structuring and major tectonic events, recognized in the Gulf of Tunis, are linked to the common geodynamic evolution of the north African and western Mediterranean basins.     

A pulse of the Earth:A 27.5-Myr underlying cycle in coordinated geological events over the last 260 Myr

We performed spectral analyses on the ages of 89 well-dated major geological events of the last 260 Myr from the recent geologic literature.These events include times of marine and non-marine extinctions,major ocean-anoxic events,continental flood-basalt eruptions,sea-level fluctuations,global pulses of intraplate magmatism,and times of changes in seafloor-spreading rates and plate reorganizations.The aggregate of all 89 events shows ten clusters in the last 260 Myr,spaced at an average interval of～26.9 Myr,and Fourier analysis of the data yields a spectral peak at 27.5 Myr at the≥96％confidence level.A shorter period of～8.9 Myr may also be significant in modulating the timing of geologic events.Our results suggest that global geologic events are generally correlated,and seem to come in pulses with an underlying～27.5-Myr cycle.These cyclic pulses of tectonics and climate change may be the result of geophysical processes related to the dynamics of plate tectonics and mantle plumes,or might alterna-tively be paced by astronomical cycles associated with the Earth's motions in the Solar System and the Galaxy.     

晚中生代地球表层重大地质事件的陆地环境剧变与生物群演替响应

晚中生代时期华北东北部发育燕辽生物群、热河生物群和阜新生物群陆地生物群。它们的快速演变过程和华北克拉通上同时期发育的岩石圈减薄、大面积强烈岩浆活动、变质核杂岩及伴随的伸展盆地等地球表层重大地质事件并行发生,表现着地壳表层系统圈层间的相互作用和响应。生物群的繁盛与灭绝与地球表层大规模岩浆-火山活动(髫髻山组—张家口组和大北沟组—义县组)发育时代高度协同一致。地球表层重大地质事件直接或间接地控制或改造着地球表层古地理和古生态环境,生物群只得调整自身去适应环境和生态背景的改变。火山-岩浆活动改变着地质-生态环境,生物群都紧密联系多期次火山-岩浆活动,化石也都被埋葬在沉积-火山碎屑岩中。华北克拉通破坏重大地质事件发生响应于全球变化和统一地球表层系统。盆地沉积充填序列、特殊陆相环境沉积建造、特殊环境沉积物等记录了响应的古地理、古环境变化与响应。陆地生物群分布、演化、更替与精确定年,脊椎-无脊椎生物(化石)埋葬特征,生物演化速率、消长关系和生物群(组合)更替的形式和性质,以及脊椎动物骨骼、牙齿的常量、微量元素、H-B-C-N-O-S和C-O-Sr等地球化学特征的研究可以恢复和重建古地理、古生态环境和古生态系统。     

吉林省晚印支期—燕山期成矿事件年谱的拟建及特征

吉林省铁、镍、钒、钛、钨、钼、金、银、铜、铅、锌、锑等内生金属矿产主要是晚印支—燕山期成矿事件的产物,已有测年数据拟建的成矿事件年谱所显示的结构特征表明：①、可划分出230～180 Ma、180～130 Ma、130～100 Ma三个时段和六个亚时区;②、180 Ma±、130 Ma±、100 Ma±的三大成矿峰期,均处于早期盆地闭合,新期盆地打开的转换期;③、三大成矿峰期由老而新主矿种由钼—金（银）—铜的演化。上述特征受该地质时期区域构造-岩浆作用和岩石圈的演化所制约。     

川东地区早三叠世碳、锶同位素演化及地质意义

早三叠世作为地球发展史上一个高度的反常时期,人们对其关注程度远不及二叠纪/三叠纪界线。海相碳酸盐的碳、锶同位素组成与演化是了解重大突变期的生态环境事件和地球过程的重要切入点。根据前人公布的川东地区早三叠世锶、碳同位素数据,绘制同位素演化散点图,根据曲线的演化特征以及不同地区的对比,分析其控制因素和地质过程。研究表明,川东地区早三叠世锶同位素演化曲线单调上升,具有很高的全球一致性,由河流注入到海水的高放射成因的锶含量增加是加剧87Sr/86Sr比值单调上升的主要原因。碳同位素演化曲线在短时间内发生的一系列高频率、大幅度波动,大量的磷酸盐注入海洋使菌藻类大量繁殖,海洋的初级生产力增强,有机碳埋藏量增大,使δ13C偏高。甲烷水合物吸收与释放等暂时性效应不是引起曲线来回波动的主要因素,海洋水体倒转等持续性效应可以很好地解释曲线异常,但对其驱动机制有待进一步研究。此外δ13Ccarb和δ13Corg的同步研究并参考早寒武世是下一步研究的重点。     

Weathering processes in the Indus River Basin: implications from riverine carbon, sulfur, oxygen, and strontium isotopes

This study deals with the major ions and isotope systematics for C, O, S, and Sr in the Indus River Basin (IRB). Major ion chemistry of the Indus, and most of its headwater tributaries, follow the order Ca²⁺>Mg²⁺>(Na⁺+K⁺) and HCO₃⁻>(SO₄²⁻+Cl⁻)>Si. In the lowland tributaries and in some of the Punjab rivers, however, (Na⁺+K⁺) and (SO₄²⁻+Cl⁻) predominate. Cyclic salts, important locally for Na⁺ in dilute headwater tributaries, constitute about 5% of the annual solutes transported by the Indus. Weathering of two lithologies, sedimentary carbonates and crystalline rocks, controls the dissolved inorganic carbon (DIC) concentrations and its carbon isotope systematics throughout the Indus, but turbulent flow and lower temperatures in the headwaters, and storage in reservoirs in the middle and lower Indus promote some equlibration with atmospheric carbon dioxide. Combined evidence from sulfur and oxygen isotopic composition of sulfates refutes the proposition that dissolution of these minerals plays a significant role in the IRB hydrochemistry and suggests that any dissolved sulfates were derived by oxidation of sulfide minerals.

In the upper Indus, silicate weathering contributes as much as 75% (or even higher in some tributaries) of the total Na⁺ and K⁺, declining to less than 40% as the Indus exits the orogen. In contrast, about two-thirds of Ca²⁺ and Mg²⁺ in the upper Indus (over 70% in some tributaries) and three-fourth in the lower Indus, are derived from sedimentary carbonates. The ⁸⁷Sr/⁸⁶Sr ratios tend to rise with increasing proportions of silicate derived cations in the headwater tributaries and in the upper and middle Indus, but are out of phase or reversed in the lower Indus. Finally, close to the river mouth, the discharge weighted average contribution of silicate derived Ca²⁺+Mg²⁺ and silicate derived Na⁺+K⁺ are, respectively, about one-fourth and two-thirds of their total concentrations.     

黄淮海平原晚新生代重大地质事件

晚新生代以来,青藏高原的隆升导致中国地貌格局、古气候系统及晚新生代沉积体系发生巨变。青藏高原以东至边缘海的广大区域形成统一水系,将巨量沉积物搬运至中国东部连续堆积形成黄淮海平原。太行山的隆升、边缘海陆架的沉降,黄河的贯通及晚第四纪大规模海侵等,深刻改造了黄淮海平原的自然环境,至今仍然影响其社会经济的发展,成为重要的科学问题。针对这些事件的研究,对于理解晚新生代黄淮海平原的形成和演化具有重要意义,也可为缓解该地区目前紧张的人地关系提供理论基础。对晚新生代黄淮海平原形成发育的构造地貌过程、黄河贯通和晚第四纪海侵等重大事件研究现状进行了综合分析,认为：①青藏高原隆升是黄淮海平原当今地貌及海陆格局形成的根本原因;②黄河贯通对黄淮海平原地表过程、水系演化及源-汇体系带来深远影响;③沿海地区晚更新世以来3次重要的海侵事件及相关的海陆相互作用,不但造成了沉积环境的变化,还形成了下切河谷特殊地貌景观;④晚新生代黄淮海地区重大地质事件的时间节点是中新世和晚第四纪。系统总结了黄淮海平原在构造-气候相互作用、地貌动态演化和年代学研究中存在的问题,认为未来亟需对黄淮海平原开展多学科系统性的工作。     

2.5Ma以来大陆风化强度的演变

本次研究得出了２．５ＭａＢＰ以来洛川剖面黄土－古土壤序列的酸不深物＾８７Ｓｒ／＾８６Ｓｒ、Ｒｂ／Ｓｒ、磁化率和沉积速率的变化曲线。黄土和古土壤酸不深物＾８７Ｓｒ／８６Ｓｒ、Ｒｂ／Ｓｒ和磁化率的变化具有类似的阶段性和周期性,这与晚新生代以来古气候的主要变化以及行星轨道参数相一致。研究证明,黄土和古土壤酸不深物＾８７Ｓｒ／＾８６Ｓｒ值得化学风化强度的替代指标,沉积速率是物理风化强度的替代指标。自２．５