元古宙真核藻类演化及环境控制因素     

张凤廉  王华建  张水昌  邓胜徽  叶云涛  邓焱  王晓梅  吕丹  卢远征  吕怡潼 《地质学报》2021,95(5):1334-1355

宜居地球、地外生命探索以及资源勘查等的需求使真核生物的早期溯源和演化趋势研究成为国际热点.根据已发现实体化石、分子化石和分子钟证据,将元古宙真核藻类演化划分为环境准备(2.45～1.70 Ga)、缓慢发展(1.70～0.80 Ga)、剧烈波动(0.80～0.64 Ga)、快速辐射(0.64～0.54 Ga)四个阶段.元...  相似文献   

四川江油马鞍塘中晚三叠世沉积相及层序地层分析          下载免费PDF全文

赵玉峰  赵兵 《沉积与特提斯地质》2008,28(2):96-99

本文对四川江油马鞍塘中晚三叠世地层剖面进行了详细描述,根据岩石组合特征,结合全国岩石地层清理方案将其划分为天井山组和马鞍塘组[1].对天井山组和马鞍塘组进行了详细的沉积相及垂向变化规律研究,并将其划分为四个层序(相当于三级层序),同时讨论了各层序的体系域特征[2].  相似文献   

The Grenvillian Songshugou ophiolite in the Qinling Mountains, Central China: Implications for the tectonic evolution of the Qinling orogenic belt   总被引：6，自引：0，他引：6  

Yun-Peng Dong  Mei-Fu Zhou  Guo-Wei Zhang  Ding-Wu Zhou  Liang Liu  Qi Zhang 《Journal of Asian Earth Sciences》2008,32(5-6):325

The Qinling Mountains in Central China mark a gigantic composite orogenic belt with a complex tectonic evolution involving multiple phases of rifting and convergence. This belt separates the North China and South China Blocks and consists of the South and North Qinling terranes separated by the Shangdan suture. The suture is marked by the Grenvillian Songshugou ophiolite along the southern margin of the North Qinling terrane, which is key to understanding the Proterozoic tectonic evolution of the belt. The ophiolite consists of highly metamorphosed ultramafic and mafic rocks. Three groups of meta-basalts are present: group 1 rocks are LREE depleted and have a MORB compositional affinity. Their low Ta/Yb ratios (<0.1) are consistent with high degrees of partial melting of a depleted asthenospheric mantle. Rocks of group 2 have higher TiO₂ (1.63–2.08 wt%) and Ta/Yb ratios (>0.12), and display slight enrichment of LREE, suggesting that the original magmas were derived from a depleted mantle source mixed with some enriched material. Samples from group 3 are enriched in LREE and other incompatible elements (Ti, Zr, Ta, Nb), suggesting derivation from an enriched mantle source, possibly a plume. All the basalts have high εNd(t) (+4.2 to +6.9), variable εSr(t) and high ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios for given ²⁰⁶Pb/²⁰⁴Pb ratios. These characteristics are compatible with formation at a mid-ocean ridge system above an anomalous Dupal mantle region. The mafic rocks have a Sm–Nd whole-rock isochron age of 1030 ± 46 Ma.The Songshugou ophiolite was emplaced onto the southern margin of the North Qinling terrane, an active continental margin from the Meso-Proterozoic to Neo-Proterozoic.  相似文献   

南秦岭元古宙板内火山作用特征及构造意义   总被引：18，自引：2，他引：18  

徐学义  夏祖春  夏林圻 《岩石矿物学杂志》2001,20(3):255-262

南秦岭元古宙火山岩主要由两大类岩石构成，一类为SiO245%-57%的基性火山岩系，另一类为SiO267%-78%的酸性火山岩系，主要岩石类型为细碧岩、玄武岩和石英角班岩、流纹岩。基性火山岩整体上属拉斑玄武岩系列，酸性火山岩属钙碱系列。火山岩强烈富集稀土元素，尤其是轻稀土元素，酸性火山岩和基性火山岩有相似的稀土元素特征，显示了源区特征的不同。基性火山岩富集强不相容元素，相对亏损Nb和Ti, 成于大陆裂谷环境，具有大陆拉斑玄武岩的特征。同位素特征表明基性火山作用与地幔柱活动密切相关。南秦岭的中、晚元古代大陆拉张及由古地幔柱活动所引发的陆裂火山岩浆活动是古秦岭洋打开的先兆。  相似文献   

Proterozoic sutures and terranes in the southeastern Baltic Shield interpreted from BABEL deep seismic data     

T. Abramovitz  A. Berthelsen  H. Thybo 《Tectonophysics》1997,270(3-4):259-277

A hitherto unknown terrane and its bounding sutures have been revealed by a combined study of normal-incidence and wide-angle seismic data along the BABEL profile in the Baltic Sea. This Intermediate Terrane is situated between a Northern Terrane of Svecofennian age and a Southwestern Terrane of Gothian age. It is delimited upwards by two low-angle and oppositely dipping sutures and occupies mainly middle and lower crustal levels with a width of 300 km at Moho level. The 1.86 Ga suture against the Northern Terrane is imaged by a prominent almost continuous NE-dipping crustal reflection from 3.5 to 14 s twt over 175 km. Where it downlaps on the Moho, sub-Moho velocities change from 8.2 to 7.8 km/s (±0.2) over less than 25 km. A relatively strong, NE-dipping normal-incidence and wide-angle reflection at 19–23 s twt indicates that the suture extends into the upper mantle. The pervasive NE-dipping reflection fabric of the Intermediate Terrane is interpreted as shear zones that developed during collision and possibly were reactivated by later events. High Poisson's ratios suggest a mafic composition or high fluid content. The 1.86 Ga collision was probably succeeded by continental break-up and removal of an unknown continent, except for the Intermediate Terrane. Subsequent formation of an east-dipping subduction zone further to the west led to the emplacement of 1.81-1.77-Ga-old granitoids in the southern part of the Transscandinavian Igneous Belt. The 1.65-1.60 Ga suture against the Southwestern Terrane is defined by a semi-continuous band of strong SW-dipping reflections between 3 and 8 s twt over 65 km, which are interpreted as a low-angle thrust zone along which Gothian crust overrode the Intermediate Terrane. The identification of three individual seismic terranes in the southeastern part of the Baltic Shield provides new evidence for Palaeoproterozoic plate tectonic processes.  相似文献   

湖北京山中元古界打鼓石群沉积特征及其构造古地理意义   总被引：1，自引：0，他引：1  

熊兴斌  陈忆元 《地球科学》1991,16(5):489-495

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青海祁漫塔格地区野马泉花岗闪长岩LA-ICP-MS锆石U-Pb年龄及其地质意义   总被引：1，自引：1，他引：0  

宋忠宝  张雨莲  贾群子  陈向阳  江磊  何书跃  李金超  杨涛  全守村  张晓飞  栗亚芝  唐卓 《地质通报》2016,35(12):2006-2013

青海东昆仑复合造山带西段的祁漫塔格地区是一个特征显著的侵入岩浆构造带,同时也是重要的多金属成矿带。野马泉铁铜多金属矿是该区较为典型的接触交代矽卡岩型矿床。利用LA-ICP-MS锆石U-Pb定年方法,获得该矿区与野马泉铁铜矿床有关的花岗闪长岩体的成岩年龄为226±2Ma;该结果与前人利用辉钼矿Re-Os法获得的矽卡岩型铜钼多金属矿石和矽卡岩型钼矿石的等时线年龄一致,因此本文厘定野马泉矿区成岩成矿时代为中—晚三叠世。  相似文献   

An Updated Review of the Middle-Late Jurassic Yanliao Biota: Chronology, Taphonomy, Paleontology and Paleoecology   总被引：1，自引：1，他引：0  

XU Xing  ZHOU Zhonghe  Corwin SULLIVAN  WANG Yuan  REN Dong 《《地质学报》英文版》2016,90(6):2229-2243

The northeastern Chinese Yanliao Biota (sometimes called the Daohugou Biota) comprises numerous, frequently spectacular fossils of non-marine organisms, occurring in Middle-Upper Jurassic strata in western Liaoning, northern Hebei, and southeastern Inner Mongolia. The biota lasted for about 10 million years, divided into two phases: the Bathonian-Callovian Daohugou phase (about 168-164 million years ago) and the Oxfordian Linglongta phase (164-159 million years ago). The Yanliao fossils are often taphonomically exceptional (many vertebrate skeletons, for example, are complete and accompanied by preserved integumentary features), and not only are taxonomically diverse but also include the oldest known representatives of many groups of plants, invertebrates, and vertebrates. These fossils have provided significant new information regarding the origins and early evolution of such clades as fleas, birds, and mammals, in addition to the evolution of some major biological structures such as feathers, and have demonstrated the existence of a complex terrestrial ecosystem in northeast China around the time of the Middle-Late Jurassic boundary.  相似文献   

塔里木盆地沙雅隆起北部一元古宙潜山气藏地震解析、地层特征与时代研究          下载免费PDF全文

韩强  李宗杰  王超  杨子川  闫亮  孟庆龙  李弘艳  赵渊 《中国地质》2016,(2):486-499

文章利用钻井岩心、岩石薄片、测井、地震资料对塔里木盆地沙雅隆起北部三道桥气田潜山的地层格架、岩石岩相特征进行分析,并通过钻井岩心样品的锆石U-Pb年代学和野外地质露头地层对比研究,对这套潜山地层的时代进行了限定。研究结果表明三道桥潜山是一套厚度在700~800 m,浅变质的海相碎屑岩-碳酸盐岩沉积,3个碎屑锆石样品的最小谐和年龄为(1522±16)Ma,表明其沉积或成岩时代应不早于中元古代。该潜山是迄今为止塔里木盆地内获得工业油气的最古老的潜山。  相似文献   

辽东早元古代碳酸盐岩的地质地球化学特征     

王仲会  马青 《吉林大学学报(地球科学版)》1991,(1)

辽东半岛早元古宙坳拉槽内靠近优地槽一侧,分布着一套复杂碳酸盐岩系,其下部和海底拉斑玄武岩呈沉积接触,或薄互层状共存,与火山凝灰岩互层。底部碳酸盐岩主要为钙型,向上过渡为钙镁型碳酸盐,其中含有数层由海底喷气作用形成的硅质岩,上部的硅质条带状碳酸盐岩中含有条带状、条纹状喷气沉积的硫化物。碳酸盐岩系顶部为厚层质纯镁质碳酸盐岩,局部含巨厚层状菱镁矿。岩系中碳酸盐岩、硅质岩、金属硫化物的稀土特征和铁锰指数具有一致性。铅同位素研究表明它们源于下地壳。有证据显示:碳酸盐岩系是在一定水深条件下由沉积作用形成的。这和碳氧同位素碳研究的结果吻合。种种特征表明这套复杂的碳酸盐岩系具有其独特性,可能暗示着一种特殊的碳酸盐岩形成方式。  相似文献