川东地区早三叠世碳、锶同位素演化及地质意义     

刘超飞  程晨  张得鲁  李晋芳  范玖琳 《岩石矿物学杂志》2015,34(2):219-226

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。  相似文献   

河南西峡晚白垩世恐龙蛋化石壳微量元素组成及其对恐龙灭绝的指示意义   总被引：2，自引：1，他引：1  

汪晓伟  姚肖永  徐学义 《岩矿测试》2015,34(5):520-527

恐龙蛋化石是探索恐龙生存和灭绝的重要研究材料,目前对恐龙蛋化石的研究集中在生物学和埋藏特征方面。本文利用电感耦合等离子体发射光谱法(ICP-OES)对采自河南西峡晚白垩世的12枚恐龙蛋化石壳及部分围岩进行分析测试,研究其生命微量元素组成及其与恐龙灭绝的关系。结果表明,恐龙蛋壳中缺乏碳氮磷硫等有机质元素,而主要由钙铝镁铁钾等生命必需元素和锶锰钡镧锌硼钒钴铱等微量元素组成,其中锶和铱均具有明显的超高异常,这可能与地外撞击事件引起生态环境的急剧变化有关。元素的组合规律表明西峡盆地晚白垩世应为干旱、半干旱的气候环境,来自于环境中异常含量的锶和铱共同作用使这一时期该地区大量的恐龙蛋在恐龙体内遭受污染,发育孵化机能受到影响,成为导致盆地内恐龙灭亡的主要原因之一。这一发现为探讨恐龙生活环境变化、灭绝原因以及揭示晚白垩纪古气候提供了重要依据。  相似文献   

淄博市淄川区饮用天然矿泉水赋存条件与形成机理研究          下载免费PDF全文

吴立新 《山东国土资源》2014,30(6)

淄博市淄川区饮用天然矿泉水按照含水层性质可划分为松散岩类孔隙水、碳酸盐岩类裂隙岩溶水和岩浆岩类构造裂隙水3大类。区内29眼井泉监测点饮用天然矿泉水检测结果显示,研究区存在锶型、锂型和锶锂复合型3种类型矿泉水。从水岩作用角度分析了矿泉水中锶和锂的来源,认为研究区广泛分布寒武纪碳酸盐岩,石灰岩尤其是鲕状灰岩中丰富的锶元素,是锶矿泉水形成主要的物源条件之一;地下水沿灰岩裂隙岩溶运动为矿泉水的形成创造了重要的水动力条件;研究区腐殖质经低矿化近中性的大气降水淋滤后,形成富含腐殖酸的偏酸性溶液入渗地下,对地下岩层产生溶解、溶滤作用,随着溶解过程的进行,岩石中的锶元素大量进入地下水中。  相似文献   

川东兴隆场地区长兴组白云岩地球化学特征及流体来源   总被引：1，自引：0，他引：1  

成晓啭  李平平  邹华耀  王广伟  陈棡 《地质学报》2013,87(7):1031-1040

四川盆地东部长兴组—飞仙关组礁滩相储层为重要的天然气勘探目的层,优质储层的岩性多为白云岩,且主要分布于开江-梁平陆棚的东西两侧。川东兴隆场地区位于开江-梁平陆棚西侧有利相带的东南端,长兴组白云岩层段为该区主力产气层,且白云岩主要分布在台地边缘礁滩相等易于发生暴露的高能沉积相带。明确了白云岩宏观分布的控制因素,以岩石结构及Mg/Ca值和有序度为基础,结合岩石地球化学特征,对川东兴隆场地区上二叠统长兴组白云岩成因进行分析。研究结果表明兴隆场地区长兴组白云岩是在埋藏条件下,同层位的泥晶灰岩及泥灰岩中封存的浓缩海水通过压实作用排挤进入碳酸盐沉积物交代灰岩形成的。有如下证据:①飞仙关组沿缝合线发育的自形白云石化学组成(CaO含量均值30.94%,MgO含量均值20.76%)与长兴组白云石化学组成(CaO含量均值30.51%,MgO含量均值21.28%)相近,表明二者成因及白云化流体具有相似性,推断压实流体可能为长兴组白云岩白云化流体;②长兴组白云岩δ13C介于1‰～2.5‰之间,δ18O介于-6‰～-4‰之间,分布在同期古海水的δ13C(0～5.8‰)、δ18O(-7.5‰～-3.5‰)变化范围内,并与全球典型埋藏白云岩δ13C、δ18O分布区间一致,说明白云化流体具有同期海水性质,且形成于埋藏成岩环境中;③长兴组白云岩的87Sr/86Sr值(0.707108～0.707507)覆盖在了川东北晚二叠世海水Sr同位素(0.706620～0.707742)的变化范围内,证明白云化流体来源于同期海水;④长兴组白云岩稀土元素表现为LREE亏损、HREE富集的海水稀土元素特征,表明白云化流体具有海源流体的性质;⑤长兴组碳酸盐岩Fe含量均较低(<2000×10-6),但长兴组白云岩相对于灰岩具有较高的Mn含量(69×10-6～90×10-6,均值为76×10-6)和较强的阴极发光性,反映了白云岩形成于埋藏的还原环境中。  相似文献   

Aragonite stromatolitic buildups from Santorini (Aegean Sea,Greece): Geochemical and palaeontological constraints of the caldera palaeoenvironment prior to the Minoan eruption (ca 3600 yr bp)     

Pere Anadón  Carles Canet  Walter L. Friedrich 《Sedimentology》2013,60(5):1128-1155

The pyroclastic deposits of the Minoan eruption (ca 3600 yr bp ) in Santorini contain abundant xenoliths. Most of these deposits are calcareous blocks of laminated‐botryoidal, stromatolite‐like buildups that formed in the shallow waters of the flooded pre‐Minoan caldera; they consist of (i) light laminae, of fibrous aragonite arranged perpendicular to layering, and (ii) dark laminae, with calcified filaments of probable biological origin. These microstructures are absent in the light laminae, suggesting a predominant inorganic precipitation of aragonite on substrates probably colonized by microbes. Internal cavities contain loose skeletal grains (molluscs, ostracods, foraminifera and diatoms) that comprise taxa typical of shallow marine and/or lagoon environments. Most of these forms are typical of warm water environments, although no typical taxa from hydrothermal vents have been observed. Past gasohydrothermal venting is recorded by the occurrence of barite, pyrolusite and pyrite traces. The most striking features of the stable isotopic data set are: (i) an overall wide range in δ¹³C_PDB (0·16 to 12·97‰) with a narrower variation for δ¹⁸O_PDB (?0·23 to 4·33‰); and (ii) a relatively uniform isotopic composition for the fibrous aragonite (δ¹³C = 12·40 ± 0·43‰ and δ¹⁸O = 2·42 ± 0·77‰, n = 21). The δ¹³C and δ¹⁸O values from molluscs and ostracods display a covariant trend, which reflects a mixing between sea water and a fluid influenced by volcano‐hydrothermal activity. Accordingly, ⁸⁷Sr/⁸⁶Sr from the studied carbonates (0·708758 to 0·709011 in fibrous aragonite and 0·708920 to 0·708991 in molluscs) suggests that the aragonite buildups developed in sea water under the influence of a hydrothermal/volcanic source. Significant differences in trace elements have been detected between the fibrous aragonite and modern marine aragonite cements. The caldera water from which the fibrous aragonite crusts formed received an input from a volcano‐hydrothermal system, probably producing diffuse venting of volcanogenic CO₂ gas and of a fluid enriched in Ca, Mn and Ba, and depleted in Mg and probably in Sr.  相似文献   

Source area and seasonal 87Sr/86Sr variations in rivers of the Amazon basin          下载免费PDF全文

Roberto V. Santos  Francis Sondag  Gérard Cochonneau  Cristelle Lagane  Pierre Brunet  Karina Hattingh  Jeane G. S. Chaves 《水文研究》2015,29(2):187-197

We report the results of a detailed study of dissolved Sr isotopes in the Solimões and Beni‐Madeira Rivers of the Amazon basin. This study developed data collected over 8 years indicating large spatial and temporal variations in dissolved Sr isotopes among the rivers of the Amazon basin. The large ⁸⁷Sr/⁸⁶Sr variations were found to be correlated with the geology of the source areas of the suspended sediments. The Beni‐Madeira River displays a high average ⁸⁷Sr/⁸⁶Sr ratio and large ⁸⁷Sr/⁸⁶Sr fluctuations during the hydrological cycle. This large average value and fluctuations were related to the presence of Precambrian rocks and Ordovician sediments in the source area of the suspended sediment of the river. In contrast, the Solimões River displays a narrow range of Sr isotope ratio variations and an average value close to 0.709. This river drains mostly Phanerozoic rocks of northern Peru and Ecuador that are characterized by low Sr isotope ratios. The isotopic fluctuations in the Beni‐Madeira River were observed to propagate downstream at least as far as Óbidos. This signal is characterized by an inverse relationship between the concentration of elemental Sr and its isotopic ratios. We further demonstrate that the Sr isotopic composition and content in the Beni‐Madeira River is controlled by suspended sediments derived from the Andes. Despite draining areas underlain by Precambrian rocks and having high ⁸⁷Sr/⁸⁶Sr ratios, such rivers as the Negro and Tapajós play a minor role in the total Sr budget of the Amazon basin. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Proterozoic biotite Rb–Sr dates in the northwestern part of the Yilgarn Craton,Western Australia     

W. G. Libby  J. R. De Laeter  R. A. Armstrong 《Australian Journal of Earth Sciences》2013,60(6):851-860

Rb–Sr dating of biotite in the northwestern corner of the Yilgarn Craton identified four areas with distinctive age ranges. Biotite in the northwestern area, which includes the Narryer Terrane and part of the Murchison Terrane, yields reset Rb–Sr dates of ca 1650 Ma. In the western area, along the margin of the craton, biotite has been reset to 629 Ma. Eastward of these areas, mainly in the Murchison Terrane, the modal biotite date is near 2450 Ma, though because of a skewed distribution the mean date is closer to 2300 Ma. Dates in a transition zone between the western and eastern areas range broadly between 2000 and 1000 Ma, averaging about 1775 Ma. The western area and the transition zone are continuous with analogous areas south of the limits of the present study. The 1650 Ma dates in the northwestern area are probably related to plutonic and tectonic activity of similar age in the Gascoyne Province to the north. They may represent cooling after thermal resetting during tectonic loading by southward thrust‐stacking of slices of Narryer Terrane and allochthonous Palaeoproterozoic volcanic arc and backarc rocks during the Capricorn Orogeny. This episode of crustal shortening resulted from the collision of the Yilgarn and Pilbara Cratons to form the West Australian Craton. The dates reflect cooling associated with subsequent erosion‐induced rebound. The 2450 Ma biotite dates of the eastern area are similar to biotite dates found over most of the Yilgarn Craton and represent a background upon which the later dates have been superimposed. The origin of dates in the western area is unknown but may be related to an associated dolerite dyke swarm or to possible thrusting from the west. There is some evidence of minor later intrusion of felsic hypabyssal rock between 2000 and 2200 Ma and localised shearing in the Narryer area at about 1350 to 1400 Ma. One small area near Yalgoo with biotite Rb–Sr dates near 2200 Ma may be cogenetic with the Muggamurra Swarm of dolerite dykes.  相似文献   

碳酸盐岩中锶元素地球化学特征及其指示意义   总被引：7，自引：0，他引：7  

倪善芹  侯泉林  王安建  琚宜文 《地质学报》2010,84(10):1510-1516

应用锶指示古环境的方法很多,其中以锶的含量和与Sr配对的相应的元素比值作为指示剂,具有典型代表性。本文以北京下古生界碳酸盐岩为研究对象,采用ICP-MS分析技术测试了49件样品中Sr、Ba、Cu的含量。以锶的含量、Sr/Ba、Sr/Cu比值作为地化指标,深入探讨了锶的地球化学特征。系统的分析了Sr含量,Sr/Ba、Sr/Cu比值对不同的沉积环境的地质响应。指出从浅海环境到深海环境Sr含量及其相应的元素比值增加趋势明显,对沉积环境具有重要的指示作用。并且,Sr的分布还受到不同沉积旋回的影响,研究沉积作用对Sr分布的影响时,应在同一沉积旋回中进行。此外还深入研究了不同岩性、不同沉积旋回中Sr的分布特征,探讨了影响Sr分布的不同因素。归纳了锶对沉积环境的指示作用。就成岩作用对碳酸盐岩中锶分布的影响,结合前人的工作,进行了探索性的分析。  相似文献   

多金属矿床中方解石的地球化学特征反映的成矿流体性质          下载免费PDF全文

邹明亮  王琦  李剑  梁永东  李冉 《地质找矿论丛》2012,27(4):391-398

利用多金属矿床中不同阶段形成的方解石Fe,Mn,Sr的质量分数及C,O,Sr的同位素特征探讨成矿过程中的流体性质,并尝试对成矿机制及其过程进行定量模拟。分析表明:①成矿期形成的方解石中Fe,Mn的质量分数明显增高,大部分Mn的质量分数高于1%,是岩浆期后热液作用的反映,利用阴极发光强度可区分不同期次沉淀的方解石;②δ(13 C)和δ(18 O)的联合变化趋势可定性判别方解石的沉淀机制,结合流体中碳氧同位素背景值可对方解石及与之伴生的多金属矿物沉淀过程进行定量模拟;③不同成矿区具有特定的87Sr/86Sr值区间,该值可作为区分不同端元流体的有利依据。Sr-87Sr/86Sr体系可用于蚀变-成矿体系中的流体/岩石值以及不同来源流体中Sr贡献度的定量计算;④成矿过程均伴随有放射性成因锶加入,古老铝硅酸盐是成矿物质的主要母源。  相似文献   

次灵敏线直接比较火焰原子吸收光谱法测定工业碳酸锶的纯度     

严伟 《安徽地质》2009,19(3):204-206

研究了次灵敏线407．8nm原子吸收光谱法测定工业碳酸锶中碳酸锶含量的条件,建立了一种全新的分析方法,即在测定过工业碳酸锶的杂质含量后,用高纯物质配制与被测样品成分一致的工作溶液,与样品溶液比较测定。该方法要求两种溶液的基体;介质;酸度;释放剂尽量一致,并同时使用标准曲线法和直线比较法。该方法准确,简单,快速,同一样品八次测定结果的极差小于0.3％,相对标准标差为0．10％。测定结果与国标方法相吻合。  相似文献