Jurassic Intra-plate Basaltic Magmatism in Southeast China: Evidence from Geological and Geochemical Characteristics of the Chebu Gabbroite in Southern Jiangxi Province     

XIE Guiqing  MAO Jingwen  HU Ruizhong  LI Ruiling  JIANG Guohao  CAO Jinjian  ZHAO Junhong State Key Laboratory of Geological Process  Mineral Resourses  China University of Geosciences  Beijing  Institute of Mineral Resources  Chinese Academy of Geological Sciences  Beijing Institute of Geochemistry  Chinese Academy of Sciences  Guiyang  Guizhou Earth Science Department  Sun Yat-Sun University  Guangzhou  Guangdong 《《地质学报》英文版》2005,79(5):662-672

Geochemical and isotopic investigations have been carded out on the Chebu gabbroite in southern Jiangxi Province, southeast China and these results are compared with gabbro bodies along the coast of Fujian Province in order to understand their magma sources and tectonic implications. The Chebu intrusion formed at the beginning of the Middle Jurassic （172~4.3 Ma）. These rocks are Ti-rich and Al-poor in major elements, characterized by strong enrichment in large-ion lithophile elements （LILE） and moderate enrichment in high field strength elements （HFSE） and light rare-earth elements CLREE）, without pronounced Nb or Ta anomalies. Age-correlated Sr-Nd isotope ratios show moderately high ranges of （^87Sr/^86Sr）i from 0.7065 to 0.7086 and 0.5124 to 0.5125 of （^143Nd/^144Nd）i. The geochemical characteristics of the Chebu gabbroite suggest that it is notably different from island-arc basalt and similar to intra-plate basaltic rocks. By combining interpretations of its geological and geochemical characteristics and the regional geological development history, the Chebu gabbroitic intrusion is thought to be the product of asthenosphere upwelling and rapid lithosphere extension during a transition of tectonic systems in southeast China. The tectonic environment and source characteristics of the intrusion are different from Cretaceous gabbro bodies along the coast of Fujian Province, The former formed in a tectonic environment of rapid intra-plate lithospheric extension and the source characteristics were of a weakly enriched primitive mantle, whereas the latter originated mainly in a volcanic-magmatic arc extensional tectonic environment and the nature of the source was an enriched mantle with more subduct subducted components.  相似文献   

Threshold for initiation of motion of unimodal and bimodal sediments     

Shaileshkumar B.PATEL  Prem Lal PATEL  Prakash Devidas POREY 《国际泥沙研究》2013,28(1):24-33

Experimental data,obtained from previous studies,on Critical Tractive Stress(CTS) of non-uniform sediments, have been used to verify the adequacy of existing relationships for CTS of non-uniform bimodal sediments.Keeping in view the performance of such relationships,a new relationship for computation of dimensionless CTS of individual size fraction of non-uniform unimodal and bimodal sediments has been proposed in the form of power law.The coefficient and exponent of the proposed power law have been empirically correlated with sediment characteristics for available sediment data.The proposed relationship has been validated with independent flume and field data to assess their applicability for unimodal and bimodal sediments.  相似文献