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81.
《岩土力学》2017,(3)
鄂西渝东地区蕴藏着丰富的油气资源,纵向主要分布有侏罗系和志留系两套泥岩盖层,区域经历的抬升剥蚀过程会导致盖层破裂,影响油气保存。选取沉积于侏罗系沙溪庙组、桐竹园组以及志留系龙马溪组的3个典型区块泥岩,开展10~50MPa 5种围压下的三轴卸荷力学试验,探索卸荷对泥岩力学特性影响。研究表明:随卸荷围压增大,3类泥岩的卸荷效应均增强,侏罗系泥岩体现在卸荷变形增大,志留系泥岩主要体现在沿卸荷方向的侧向膨胀;对比常规三轴压缩试验中岩石破裂时的应力状态,卸荷得到的泥岩强度均上升,内摩擦角更大,泥岩侧压破裂系数呈负指数分布,随围压增大而减小,并且沉积时间短浅的泥岩在抬升剥蚀过程中更容易产生破坏;岩石破裂形态由岩石组构与应力环境共同决定,沙溪庙组泥岩的裂纹形态为单一剪切断面破坏,并且断口平缓,而桐竹园组泥岩与龙马溪组泥岩则随围压升高,由单一剪切断面向共轭剪切破坏过渡,其中桐竹园组泥岩断口平滑,龙马溪组泥岩断口则呈现锯齿状。 相似文献
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83.
The available data on K-Ar dating of Yenshanian granites in Zhejiang Province have been summarized in the present paper. Based on K-Ar isochron ages of the granites, in conjunction with geological evidence, three episodes of granitic magmatic intrusion are distinguished as follows: the first episode--160--135 m.y., the second-130-110 m.y. and the third--105--65 m.y. Furthermore, the tempo-spacial distribution of K-Ar ages and their geotectonic implieations are also discussed. 相似文献
84.
Geotectonically the Fengyang and Zhangbaling regions belong to the North China craton and the Dabie-Sulu oragene, respectively. Neo-Archean gneiss and amphibolite and metamor-phosed sea-facies sodic volcanic rocks axe the main outcrops in the two regions, respectively. The Zhangbaling terrane strike-skipped along the Tancheng-Lujiang fault zone in Mesozoic and Cenozo-ic eras and got close to the Fengyang terrane. Mesozoic Yanshanian intrusions occur broadly in thetwo regions. Gold-beating quartz veins occur in the metamorphic rocks in the Fengyang region and in the granodiorite and metamorphosed sea-facies sodic volcanic rocks in the Zhanghaling region.Generally, the formation of the auriferous quartz veins involved three stages. At the first stage,gold-poor sulfide quartz veins were formed; at the second stage gold-rich quartz sulfide veins wereformed; and at the third stage gold-poor barite and/or carbonate veins were formed. The 40^Ar/29^Ar step-heating plateau ages of the first-stage and the second-stage quartz aggregates from the Zhuding, Maoshan and Shangeheng gold deposits range between 116.1 0.6 Ma and 118.3 0.5 Ma and are pretty close to their least apparent ages and isoehronal ages, respectively. All plat-eau, least apparent and isoehronal ages range between 113.4 0.4 Ma and 118.3 0.5 Ma,which are considered as the formation age range of the quartz. It is reasonable and reliable to takethe 40^Ar/39^Ar age range of the quartz as the formation age range of gold-bearing quartz veins onthe basis of spatial relationship between gold-bearing quartz veins and their country rocks. Thegold deposits in the two regions were formed in Aptian, Cretaceous, when the Tancheng-Lujiangfault zone moved as a normal fault with slightly right-lateral strike-skip, was extensional and expe-rienced very strong magnmtic process. It is shown that the magnmtic hydrothermal fluid is a veryimportant part of the gold ore-forming hydrothermal fluid in the Fengyang and Zhanghaling re-gions. The formation of the gold ore deposits in the Fengyang and Zhanghaling regions had genetic relations with the extensional movement of the Tancheng-Lujiang fault zone and magmatic activities and took place under the extensional dynamic condition in Late Cretaceous. Therefore, the exten-sional movement of the Tancheng-Lujiang fault zone presented the energy and space for magmatic and gold ore-forming processes. 相似文献
85.
介绍了第31届国际地质大会有关地层学学术讨论的主要内容,包括地质年代表、生物地层学、事件地层学、层序地层学、磁性地层学、同位素地层学、综合地层学、沉积相与沉积古地理、生物古地理、构造古地理10个方面。这些研究可以明显反映出目前国际地层学研究的现状和发展趋势。地层学研究不断深入,特别是一些经典地区和关键层段的研究仍然在不断深入,这些经典地区和关键层段在研究理论和研究方法上的突破带动了整个地层学研究的发展;地层学研究领域不断扩大,服务范围也不断扩大,地层学与其它学科相互渗透,为地层学这门古老的学科注入了新的生命力;地层学各分支学科相互结合,向多学科综合研究的综合地层学方向发展。 相似文献
86.
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88.
东昆仑纳赤台群晚二叠世孢粉化石的发现及其意义 总被引:5,自引:0,他引:5
东昆仑造山带是我国西部一条规模宏大的造山带,它的形成时代及其演化格局涉及青藏高原构造格架和隆升机制研究的重要基础地质问题。它北隔柴达木盆地与祁连造山带相望,南与可可西里—羌塘地块为邻,西与西昆仑造山带相连,东与秦岭—大别造山带相接,地质位置极为重要。对东昆仑造山带形成的时代一直存在着不同的观点和认识,有人将其划为加里东期,也有人划为华力西期,造成这些分歧的关键是对纳赤台群的时代认识问题(李光岑等,1982)。纳赤台群是位于昆中断裂与昆南断裂之间的一套非均匀变质的地层,主要由灰绿色浅变质的复理石相的砂板岩、变砂岩和 相似文献
89.
内蒙古宁城盆地东南缘含道虎沟生物群岩石地层序列特征及时代归属 总被引:18,自引:3,他引:18
宁城盆地东南缘晚中生代岩石地层序列完整、连续,但该岩石地层序列及其所含生物群的地质年代归属问题还存在争议。含道虎沟生物群岩石地层剖面的发现和实测表明,研究区晚中生代地层序列从下至上由中侏罗世九龙山组—髫髻山组、晚侏罗世土城子组和早白垩世义县组组成。九龙山组—髫髻山组下部以沉积岩系为主,产道虎沟生物群,上部为中、基性火山岩,SHRIMP锆石U-Pb年龄为152Ma和164~165Ma。九龙山组—髫髻山组地层序列既为土城子组平行不整合覆盖,而且二者又同时被早白垩世义县组角度不整合覆盖。含道虎沟生物群的晚中生代岩石地层的地质年代早于热河生物群,为中侏罗世的产物,现暂将其统并为九龙山组—髫髻山组。 相似文献
90.
Paul COPPER 《《地质学报》英文版》2005,79(4):437-452
The Wangchengpo Frasnian section of Dushan County contains two atrypid brachiopod assemblages. The lower is characterized by the Atryparia (Costatrypa) dushanensis fauna that appears at the base of the Hejiazhai Member approximately in the falsiovalis to transitans conodont zones: the upper is characterized by the Radiatrypa yangi fauna, which appears in the Lujiazhai Member approximately correspondent with the hassi to Upper rhenana conodont zones. Atrypid brachiopods, together with other brachiopods from the Dushan section show that the Hejiazhai Member is of Frasnian age. Preliminary analyses of Frasnian atrypid brachiopods from sections of South China indicate that there are nine genera and subgenera including Atryparia (Costatrypa), Kyrtatrypa, Spinatrypa, lsospinatrypa, Spinatrypina, lowatrypa, Desquamatia (Desquamatia). Desquamatia (Seratrypa), and Radiatr)pa. Atrypid species diversity did not change much through the Frasnian. On a regional scale in South China, most atrypid species went extinct prior to the Frasnian/Famennian boundary. At any specific locality or section, these atrypids became extinct about 20-40 m below the Frasnian/Famennian (F/F) boundary, within the linguiformis conodont Zone, marking this as the major extinction level. Three new atrypid species are described: Atryparia (Costatrypa) dushanensis, lowatrypa pseudobodini, and Radiatrypa yangi. 相似文献