三水盆地古近系(土布)心组黑色页岩中黄铁矿的形成及其控制因素   总被引：3，自引：0，他引：3  

刘春莲  董艺辛  车平  Franz T Fürsich  石贵勇  陈亮  严伟术 《沉积学报》2006,24(1):75-80

黄铁矿是富有机质沉积的特征矿物。根据TOC/S、TOC/DOP、S/Fe关系以及S TOC Fe多重线性回归分析结果对三水盆地古近系〖HT5”,6”〗土〖KG-*3〗布〖HT5”SS〗心组红岗段黑色页岩中沉积黄铁矿的形成及其控制因素进行了分析。土布心组红岗段黑色页岩的黄铁矿有成岩黄铁矿和同生黄铁矿两种成因组分。红岗段下部（亚段A）有机碳含量普遍较低,底部水体以弱氧化条件为主,硫酸盐还原作用发生于沉积物/水界面以下,黄铁矿为成岩成因,其形成主要受有机质的限制。红岗段中上部（亚段B和C）的沉积条件变化频繁,其有机碳含量变化幅度大。富有机质（TOC>4%）岩层形成于缺氧的底部水体条件下。水体中可含H2S,碎屑铁矿物在埋藏之前即与之在水体中反应形成同生黄铁矿。这一过程不受有机质的限制,而是受活性铁与H2S接触时间的限制。同时,由于大量淡水输入导致硫酸盐浓度的降低,从而对硫化物形成有一定的限制作用。对于低有机质（TOC<4%）样品,黄铁矿由同生和成岩组分组成。其中以成岩黄铁矿为主,其形成过程主要受有机质限制,而同生黄铁矿受铁矿物与H2S接触时间的限制。  相似文献   

New paleomagnetic evidences of paleogene tectonic rotation of the Qaidam Basin and adjacent region: mechanism and its tectonic implication     

Weimin Li  Yongjiang Liu  Zhiming Sun  Xiaohong Ge  Shoumai Ren  Junling Pei  Sihua Yuang  Xinzhuan Guo 《世界地质(英文版)》2006,9(1)

In order to better understand the tectonic evolution of the Qaidam Basin. The authors carried out a paleomagnetic study on 39 samples of 7 sites from Hongsanhan section, northwest Qaidam Basin. Stepwise thermo-demagnetization isolated a high-temperature component (HTC), which passes the fold and reversal tests at 95% confidence level. It suggests that the HTC should be primary. Unblocking temperature (about 685℃) and the experiment of isothermal remanence indicate that hematite is the mainly carrier of the remanence. A tilt-corrected mean direction is: Ds=7.1°, Is=38.5°, α95=7.4°. Corresponding to a palaeopole at, φ＝250.1°E, λ＝72.0°N, A95=6.8°, Compared with the reference APWP of Eurasia, the sampling area occurred a non-significant rotation (3.4°±5.5°) relative to Eurasia since Eocene due to the affect of left-lateral Altyn fault, Based on the paleomagnetic results of early Cretaceous and Teritary within the Qaidam block, we can obtained the mean clockwise rotations from the samples deposited from 160 Ma to 45 Ma is 24.5°±9.0°, and from 38 Ma to present is -0.5°±7.5° relative to present geomagnetism respectively. During the Mid Eocene (45～38 Ma) rotation phase, there should existing an important early tectonic event in northern part of the present-day Tibetan Plateau, which probably represents one of large-scale strike-slip events of the Altyn strike-slip fault.  相似文献   

Highlights of the Messel Oil Shale     

Stephan Schaal 《东北亚地学研究》2008,11(1):14-18

The Messel oil shale, Germany, was deposited in a maar crater that formed 47 million years ago. Since 1975 the Senckenberg Research Institute in Frankfurt am Main, has conducted systematic scientific excavations of this oil shale with much success. Besides plants and insects, more than 130 species of well - preserved fossil vertebrates like reptiles, fishes, birds and mammals have been found and have made Messel worldfamous. Some examples of these vertebrates are presented.  相似文献   

Carbon cycle variability in tropical Atlantic across two Early Eocene hyperthermals     

Shijun Jiang  Ying Cui  Yasu Wang 《地学前缘(英文版)》2021,12(2):521-530

Early Eocene hyperthermals are geologically short-lived global warming events and represent fundamental perturbations to the global carbon cycle and the Earth’s ecosystem due to massive additions of isotopically light carbon to the ocean-atmosphere system.They serve as ancient analogs for understanding how the oceanic carbonate system and surface-ocean ecosystem would respond to ongoing and future climate change.Here,we present a continuous carbonate record across the Eocene Thermal Maximum 2(ETM2 or H1,ca.54.1 Ma)and H2(ca.54 Ma)events from an expanded section at Ocean Drilling Program Site 1258 in tropical Atlantic.The abundant calcareous nannofossils and moderate carbonate content throughout the studied interval suggest this record was deposited above the calcite compensation depth(CCD),but below the lysocline and under the influence of terrestrial dilution.An Earth system model cGENIE is used to simulate the carbon cycle dynamics across the ETM2 and H2 to offer insights on the mechanism of the rapid warming and subsequent recovery in climate and ecosystem.The model suggests moderate changes in ocean pH(0.1–0.2 unit)for the two scenarios,biogenic methane from a rechargeable methane capacitor and organic matter oxidation from thawing of the permafrost.These pH changes are consistent with a recent independent pH estimate across the ETM2 using boron isotopes.The carbon emission flux during the ETM2 is at least an order of magnitude smaller than that during the Paleocene–Eocene Thermal Maximum(PETM)(0.015–0.05 Pg C yr^-1vs.0.3–1.7 Pg C yr^-1).The comparable pre-and post-event carbonate contents suggest the lysocline did not over deepen following the ETM2 at this tropical Atlantic site,indicating spatial heterogeneity in the carbonate system due to strong dilution influence from terrestrial weathering and riverine discharge at Site 1258.  相似文献   

藏东南始新世剑川盆地西缘沉积特征及构造意义          下载免费PDF全文

廖程  杨天南  梁明娟  信迪  董猛猛  薛传东 《岩石矿物学杂志》2021,40(4):729-746

印度-欧亚大陆碰撞作用形成了以西藏-喜马拉雅造山带为主体的正向碰撞带和以"三江"造山带为主体的斜向碰撞带,二者之间的现代分界线为喜马拉雅东构造结。剑川盆地是目前已确定的、位于斜向碰撞带最南端的始新世盆地。通过对盆地西缘4条剖面的详细沉积学研究,发现盆地充填过程分为2个阶段。钾质-超钾质火山活动(37～34 Ma)之前的充填物源自盆地西南侧,由冲积扇扇根、扇中亚相逐渐转变为三角洲平原亚相;火山活动之后的充填物源自盆地北西侧,形成冲积扇扇根、扇中亚相。结合盆地充填期间西侧基底构造变形特点,认为剑川盆地为始新世前陆盆地。始新世期间,剑川盆地与藏东、藏北诸多始新世前陆盆地一样,可能属于正向碰撞带的一部分,其与斜向碰撞带之间的界线位于剑川盆地以南。由于印度地块持续向北迁移,挤入到欧亚大陆内部,导致斜向碰撞带逐渐向北生长。  相似文献