大庙斜长岩同位素地质年龄、稀土地球化学及其地质意义

大庙斜长岩的⁴⁰Ar/³⁹Ar年龄测定呈现出一条典型的马鞍型年龄谱,在中温阶段有二个明显的坪年龄1656±15 Ma和1029±7 Ma,结合其构造位置和全球斜长岩分布来看,它们分别代表了侵位年龄和后期热扰动的时代。密云奥长环斑花岗岩中角闪石的⁴⁰Ar/³⁹Ar坪年龄为1716±21 Ma。两者时空上密切相关,代表了裂谷作用初期非造山环境中双模式岩浆作用产物。斜长岩类和苏长岩之间稀土配分模式的相似性表明,它们明显为同一成因的岩浆分异系列的产物。     

Chronology of Sanbagawa metamorphism

By collating age data based on the fossil age of the protoliths, radiometric dating of the metamorphic minerals, and sedimentary records of erosion at the earth's surface, the history of the Sanbagawa metamorphism can be summarized as follows. (1) The pre-metamorphic sedimentary rocks (Carboniferous-Jurassic + Early Cretaceous?) became mixed and formed a thickened packet in the vicinity of an ancient trench through a variety of subduction-related tectono-sedimentary processes, probably in Early Cretaceous time (c., 130-120 Ma). (2) The subducted protoliths underwent progressive metamorphism reaching a maximum depth of c. 30 km in late Early Cretaceous time (c. 116 ± 10 Ma). (3) The high-P/T metamorphic rocks began to rise toward the surface (during the interval 110-50 Ma) with minimum estimates for the average cooling rate around 9-12°C/Ma and an average uplift rate around 0.4-0.5 mm/year. (4) Finally, at some stage after reaching the erosional surface, the high-P/T metamorphic rocks were covered unconformably by the middle Eocene (c. 50-42 Ma) Kuma Group. On the basis of the present chronological summary of the Sanbagawa metamorphism, the areal extent of the Sanbagawa metamorphism is also discussed with respect to the weakly metamorphosed subduction-accretion complex of the next tectonic belt to the south, the Northern Chichibu belt.     

天山地区地震韵律的初步探讨

根据新疆及苏联天山地区的地震目录和古地震研究成果,将整个天山地区的地震韵律划分为地震世、地震亚世、地震期、地震幕、地震阶五级,探讨了各级韵律的特征。估计了我国天山地区未来地震活动趋势。     

吉林延边地区屯田营组时代商榷

本文主要论述吉林省延边地区屯田营组时代。通过对屯田营组研究历史的回顾,从火山岩喷发—沉积序列和生物地层资料指出屯田营组时代为晚侏罗世,屯田营组与金沟岭组同是晚侏罗世两个火山旋回。     

洱海湖盆晚第四纪地层的14C年龄测定及洱海的演变

从大理洱海湖盆西部平原湖沼相地层的分布和相关的14C年龄测定以及文物考古资料,阐述了晚更新世中期以来洱海的演变。研究表明,距今5万年以来洱海西部古湖岸线是从西向东迁移的。期间曾有过几次摆动。引起洱海古湖岸线变迁的主导因素是点苍山断块的间歇性抬升和洱海湖盆的下沉,地质历史时期的气候干湿演变也起了重要作用     

The Darfur Dome,western Sudan: the product of a subcontinental mantle plume

Field investigations, K-Ar age determinations and chemical data were used to describe the development of an intraplate volcanic province, the Darfur Dome, Sudan. Magmatism started 36 Ma ago at a small subvolcanic complex (Jebel Kussa) in the center of the dome and was active in the same area between 26 and 23 Ma. Two major volcanic fields (Marra Mountains and Tagabo Hills) developed between 16 and 10 Ma. Volcanism started again at 6.8 Ma with a third volcanic field (Meidob Hills) and at 4.3 Ma in the Marra Mountains and with the reactivation of the center. Activity then continued until the late Quaternary. Having started in the center of the Darfur Dome, volcanism moved in 36 Ma 200 km towards the NNE and 100 km SSW No essential difference in the alkaline magma types (basanitic to phonolitic-trachytic, with different amounts of assimilation of crustal material) in the different fields, was observed. Magmatism is thought to have been produced by a rising mantle plume and volcanism was triggered by stress resolution along the Central African Fault Zone.     

东秦岭地区钼矿床的铼-锇同位素年龄及其意义

金属矿床的成矿年龄多年来一直是矿床地质工作者关注的问题之一。中国地质科学院岩矿测试技术研究所建立的铼－锇同位素定年实验室，为研究钼矿床的形成时代提供了新的手段。因辉钼矿是最主要的含铼矿物之一，且基本上不含普通锇，其中所含＾１８７Ｏｓ是由＾１８７Ｒｅ衰变而来，故放射成因＾１８７Ｏｓ的积累是矿物年龄及铼含量的函数。本文采用同位素稀释－等离子体质谱法，测定了东秦岭钼矿带中几个不同类型的大型钼矿床的Ｒｅ－     

吉林省北部西土山火山岩的地质特征及其形成的地质时代

本文以实际资料，叙述了西土山火山岩的地质、岩石化学、微量元素、稀土元素等方面的特征。与中国晚三叠世火山岩对比较吻合。且以较丰富的古生物及同位素年龄资料论证了西土山火山岩的地质时代属晚三叠世。     

京津地区长城系下伏变质岩系变质年龄及长城系底界年龄的厘定

长城系属中元古宇底部,其底界年龄一直存在争议。国内发表的数据在2000-1640Ma之间。通过分析以往数据,并据近年新资料,认为长城系底界年龄划在(1700±20)Ma是比较合理的。