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31.
华南阿伦尼格世几丁虫生物地层与古生物地理 总被引:14,自引:0,他引:14
本文系统介绍了湖北宜昌黄花场及浙江常山黄泥塘剖面Arenig统几丁虫分布发育规律,指出华南地区Arening统的几丁虫自下向上可划分为Conochitinasymmetrica,Eremochitinabaculata,Eremochitinabrevis-Conochitinalangei,Conochitinapirum,Rhabdochitinaturgida等生物带。讨论了华南地区这一时期 相似文献
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近十余年来,在华北地台太古宙花岗岩-绿岩带金矿的研究中,获取了许多有关地层、岩石金丰度值的资料。早期获取的资料因化验分析方法灵敏度不高且样品中常常包含矿化、蚀变和构造破碎的岩石等原因而使其金丰度值偏高。最新的数据采用了高灵敏度化验分析方法且剔除了矿化、蚀变和破碎的岩石样品,计算出的金丰度值均明显低于或接近于地壳金丰度值。结合其它研究成果,提出绿岩带有关金矿矿源是多源的(变质的、岩浆的),甚至是深源的(下地壳或上地幔)认识。 相似文献
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如实记述了1995年度中国大陆及边邻MS≥7.0地震活动的时、空演变与华北(φN30°~φN42°,λE105°~λE125°)地震活动等有关的试验预报的实况。对过去的预报办法提出了一些改进意见。 相似文献
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Using data from the intensive observation period (May–June 2000) of the NWC-ALIEX (The Field Experiment on Interaction between Land and Atmosphere in Arid Region of North-west China), the characteristics and mechanisms of some key land-surface process over Gobi in a typical arid region of north-west China are analyzed and several parameters of land-surface processes are calculated. The weighted mean of the surface albedo over a typical arid region of the Dunhuang Gobi is calculated using the relative reflection as a weighting factor, and its value is 0.255 ± 0.021. After removing the influence of precipitation, the mean soil heat capacity over a typical arid region of the Dunhuang Gobi is 1.12 × 106 J m-3 K-1,which is smaller than that observed in the Heihe (China) River basin Field Experiment (HEIFE). The mean soil heat diffusivity and conductivity are about half of those observed in HEIFE. 相似文献
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Problem on development control of marine source bed hold in Chinese petroleum industry progression. The Hongshuizhuang Formation,Tieling Formation and Xiamaling Formation in the Middle and Upper Proterozoic are important hydrocarbon source beds in northern North China, and investigation of their sedimentary environments and the controls has great significance for petroleum exploration in North China. Based on sedimentology (sequence stratigraphy), palaeoecology, sedimentary geochemistry, and sedimentary palaeogeography, their development pattern is discussed. All these studies indicate that the development controls of the hydrocarbon source beds include a favorite palaeogeographic location, exceeding propagation of biomes in low and middle latitudes, anoxic environments, enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter in the marine carbonates. 相似文献
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IntroductionUnderstandingthemechanismofcontinentalearthquakesisveryimportantforseismichaz-ardpreventionandearthquakeprediction.Themodernseismotectonictheoryandtheideaofearthquakepredictionaredevelopedmainlyfromthestudiesoninterplateearthquakes,whicharedifficulttoexplainthephenomenaofintraplateearthquakes,suchasthecontinentalearthquakesoccurredinChinesemainland.Whiletheinterplateearthquakesoccurredalongtheplatebounda-ries,theintraplateearthquakesdistributediffuselyintheinterioroftheplates.Thus… 相似文献
40.
Fu-yuan Wu Simon A. Wilde Guang-liang Zhang De-you Sun 《Journal of Asian Earth Sciences》2004,23(5):781
Northeastern (NE) China is a well-documented example of a collisional zone characterized by widespread post-orogenic granites and mafic–ultramafic complexes. Based on a study of the Hongqiling and Piaohechuan Cu–Ni sulfide-bearing mafic–ultramafic complexes in central Jilin province, we present geological, petrological, geochemical and geochronological data which indicates their post-orogenic origin.The Hongqiling complex comprises pyroxenite, olivine websterite, lherzolite, gabbro and leucogabbro. Zircon U–Pb SHRIMP analyses on a leucogabbro of the Hongqiling complex yield a weighted mean 206Pb–238U age of 216±5 Ma. The Piaohechuan complex is composed of gabbro, pyroxenite and dolerite, exposed as dikes. A plagioclase-bearing pyroxenite has a U–Pb zircon weighted mean 206Pb–238U age of 217±3 Ma, identical to that of the Hongqiling complex. These ages are coeval with the emplacement of A-type granites in the area, but slightly younger than the regional metamorphism (240 Ma) and syn-orogenic granitic magmatism (246±4 Ma). This suggests that these mafic–ultramafic complexes are post-orogenic in origin. The age data also indicated a short period of lithospheric stabilization of about 30 Ma after cessation of orogenic activity.Geochemical investigation indicates that the primary mafic magma was a lithospheric mantle-derived basalt resulting from the upwelling of asthenosphere due to lithospheric delamination during post-orogenic processes. The magmatic source was contaminated by a small amount of crustal material, and subsequent crystal fractionation resulted in the Cu–Ni mineralization.The widespread occurrence of mafic–ultramafic complexes in the Xing'an–Mongolian Orogenic Belt of NE China and in the Altay–Tianshan–Junggar Orogenic Belt of Northern Xinjiang indicates that mafic intrusions are an important magmatic suite that evolved during post-orogenic processes. Portions of this mafic magma could have underplated the lower crust, and served as the heat source for associated late-stage granitic magmas. 相似文献