关于蓟县型中、上元古界沉积环境及内蒙地轴的性质   总被引：7，自引：0，他引：7  

张炯飞  祝洪臣 《吉林地质》2000,19(4):11-16

内蒙地轴和燕辽坳都是华北地台北缘的二级大地构单元,本文在对蓟县型中、上元古界沉积环境和对内蒙地轴演化历史的初步研究基础上,认为蓟县型中、上元古界沉积盆地于长城－蓟县期,在北部与广海相连,属于陆表海发展,在青白口期,由于北部逐渐抬升,该沉积盆地才具有陆内盆地性质,内蒙地轴在长城－蓟县期总体处于水下环境,青白口爰开始抬升为古陆,其大规模抬升可能是在古生代或更晚。  相似文献   

Crustal contaminants in the Permian Oslo Rift, South Norway: constraints from Precambrian geochemistry     

Tom Andersen  Trine-Lise Knudsen 《Lithos》2000,53(3-4):247-264

During the late Paleozoic Oslo rifting event, the SW part of the Baltic Shield was penetrated by mantle-derived magmas from a depleted lithospheric or sublithospheric source. Along the way to their final emplacement, these magmas may have interacted with a heterogeneous continental crust, consisting of a mosaic of continental terranes, each with its unique composition and internal crustal history. Information on radiogenic isotope ratios and trace element distributions in the Precambrian terranes surrounding the rift can be used to define characteristic crustal components. These components may be used as endmembers in petrogenetic modelling of the Oslo Rift magmatic system. Based on available data, six endmember components can be identified, and (semi) quantitatively characterized in terms of Sr, Nd and Pb isotopes and selected trace elements. Data on the distribution of rock-types along the rift flanks allow estimates to be made of the relative importance of the components in different parts of the rift. Combining these data with petrological information may allow a realistic understanding of crust–magma interaction in the Oslo Rift magmatic system.  相似文献   

祁连山元古宙大陆溢流玄武岩   总被引：7，自引：0，他引：7  

夏林圻  夏祖春  徐学义  赵江天  杨合群  赵东宏 《地质论评》1999,45(7):1028-1037

祁连山西段大面积分布的元古宙浅海相火山岩系是大 陆裂 谷火山作用的产 物,属大陆溢流玄武岩系。岩石地球化学研究表明,它们具有高εNd值和低( 87Sr/86Sr)i值 ,系派生于岩石圈之下的地幔柱源,但也显示有岩石圈组分卷入的证据。它们的形成是地幔 柱岩石圈相互作用的结果,是北祁连山早古生代洋盆开启的前兆。  相似文献   

Palaeomagnetic study of Palaeoproterozoic granitoids from the Voronezh Massif, Russia     

A. G. Iosifidi  S. Bogdanova  A. N. Khramov  & G. Bylund 《Geophysical Journal International》1999,137(3):723-731

A palaeomagnetic investigation has been carried out of rocks from the eastern part of the Voronezh Massif, which constitutes, together with the Ukrainian Shield, the Sarmatian segment in the southern part of the East European Craton. The samples were collected in a quarry close to the town of Pavlovsk (50.4°N, 40.1°E), where a syenitic-granitic body intrudes Archaean units. U–Pb (zircon) dating has yielded an age of 2080  Ma for the intrusion.
  Two characteristic magnetic components, A and B, were isolated by thermal and alternating-field demagnetization. Component A was obtained from granites and quartz syenites (11 samples) and has a mean direction of D = 229°, I = 28°, and a pole position at 12°N, 172°E. This pole is close to a contemporary mean pole (9°N, 187°E) for the Ukrainian Shield, which implies that the Voronezh Massif and the Shield constituted a single entity at 2.06  Ga. These poles differ from contemporaneous poles of the Fennoscandian Shield, indicating that the relative positions of the two shields were different from their present configuration about 2100  Myr ago.
  A component B, isolated only in quartz monzonites (five samples), has a mean direction D = 144°, I = 49°, and a pole position at 4°N, 251°E, which is close to late Sveconorwegian (approximately 900  Ma) poles for Baltica. This suggests that the East European Craton was consolidated some time between 2080 and 900  Ma. Comparison with other palaeomagnetic data permit us to narrow this time span to 1770–1340  Ma.  相似文献   

湖南元古宙林家湾组和横路冲组的对比研究   总被引：2，自引：2，他引：0  

潘传楚 《大地构造与成矿学》1999,23(4):381-385

简单介绍了湖南元古宙论水铺群林家湾组正层型剖面和板溪群横路冲组正副层型剖面;对比了二组剖面的地层岩性和成岩时代及层位等特征;论证了沧水铺群林家湾组层位是合乎客观地质实际的;阐述了对湖南益阳沧水铺地区磨拉石一火山建造的划分对比讨论的重要意义。  相似文献   

武夷山西麓宁都地区基底褶皱构造式样初步探讨     

周仁元 《江西地质》1999,13(1):8-12

武夷山西麓宁都地区广泛分布一套成层有序的晚元古代浅变质岩系,长期以来被视为单斜构造。本文阐述了研究区基底褶皱的窨配置及褶皱式样,阐明了研究区的各紧密线状复式褶皱隶属区域大型复背斜的北翼,同时地基底褶皱的形成机制与后期改造作了地一步分析和探讨。  相似文献   

颗石藻与海洋、环境关系之探讨   总被引：3，自引：0，他引：3  

侯奎  陈镇东 《化工矿产地质》1999,21(1):31-39

笔者在20年的研究中相继发现,自中元古代和古生代以来海相钙质超微浮游生物－颗石藻的新属种达180余种,通过对颗石藻在海洋中分布状态与固碳特征的研究,证明颗石藻乃是海洋中重要的基础生产者,它和海洋碳酸盐及相关生物存在着密切的关系,其能借助光合作用,吸收海水中的CO2,而释放出氧气．对减少全球温室效应与保护地球生态环境平衡,有相当重要的贡献。  相似文献   

内蒙古中、上元古界地层的找金远景   总被引：10，自引：0，他引：10  

邵和明 《内蒙古地质》1999,(1)

内蒙古自治区境内,中、上元古界地层发育,其中所赋存的金属、非金属、贵金属矿产甚多。最近在中元古界朱拉扎嘎毛道组变质粉砂岩中所发现的微细浸染型金矿,是我局在元古界地层中寻找新类型金矿的一个突破,具有十分重要的意义。  相似文献   

辽西建平-喀左地区元古宙-古生代层序地层     

郭胜哲  张立东  鲍庆忠  董万德  王忠江 《地质通报》1999,18(3)

通过１∶５万区域地质调查工作,对建平—喀左地区元古宙—古生代地层做了岩石地层、生物地层、不整合界线地层和层序地层的多重划分与对比。进行了基本层序、沉积相和沉积环境的调查研究,将元古宙—古生代地层划分为１０个层序,归并为２个超层序,初步建立了岩石地层和年代地层格架。  相似文献   

Early Proterozoic palaeomagnetic data from the Pechenga Zone (north-west Russia) and their bearing on Early Proterozoic palaeogeography     

Trond H. Torsvik  Joseph G. Meert 《Geophysical Journal International》1995,122(2):520-536

  相似文献