Second Language Acquisition （SLA） is influenced by many different factors. This paper attempts to discuss the age factor in SLA, particularly explores the learners＇ acquisition of accent. The author firstly introdu...Second Language Acquisition （SLA） is influenced by many different factors. This paper attempts to discuss the age factor in SLA, particularly explores the learners＇ acquisition of accent. The author firstly introduces the topic and reviews the literature on Critical Period Hypothesis （CPH）. Then, the optimal age to attain the native-like accent is discussed. Finally, the author describes some other elements that influence the acquisition of accent and draws a natural conclusion that the topic in this paper needs more profound research.展开更多
Magnetite separates from the Shaquanzi Fe-Cu deposit in the eastern Tianshan are used for Re-Os geochronological study. Re-Os data show that magnetite separates contain ca. 0.7 to 50.9 ppb Re and ca. 16 to 63 ppt Os. ...Magnetite separates from the Shaquanzi Fe-Cu deposit in the eastern Tianshan are used for Re-Os geochronological study. Re-Os data show that magnetite separates contain ca. 0.7 to 50.9 ppb Re and ca. 16 to 63 ppt Os. Eight samples yield a model 3 isochron age of （303 ±12） Ma （2or）, which is within uncertainty consistent with of the Re-Os date （295±7 Ma） of associated pyrite. Tectonic evolution shows that the Late Carboniferous Aqishan-Yamansu belt was a back-arc rift. Therefore, the Re-Os age of ca. 300 Ma indicates that the Shaquanzi Fe-Cu deposit may have formed in a back-arc extensional environment and was closely related to mantle-derived magmatism. The successful application of Re-Os magnetite geochronology in the Shaquanzi Fe-Cu deposit suggests that the purity of magnetite, relatively high Re and Os contents, and the closure of Re-Os systematic are base factors for a successful Re-Os geochronology. There would be a good prospect for Re-Os geochronology for magnet- ite.展开更多
文摘Second Language Acquisition （SLA） is influenced by many different factors. This paper attempts to discuss the age factor in SLA, particularly explores the learners＇ acquisition of accent. The author firstly introduces the topic and reviews the literature on Critical Period Hypothesis （CPH）. Then, the optimal age to attain the native-like accent is discussed. Finally, the author describes some other elements that influence the acquisition of accent and draws a natural conclusion that the topic in this paper needs more profound research.
基金financially supported by the National Basic Research Program of China(Grant No.2012CB416804)the ‘‘CAS Hundred Talents’’ Project from the Chinese Academy of Sciences(Grant No.KZCX2-YW-BR-09)to Qi Liang
文摘Magnetite separates from the Shaquanzi Fe-Cu deposit in the eastern Tianshan are used for Re-Os geochronological study. Re-Os data show that magnetite separates contain ca. 0.7 to 50.9 ppb Re and ca. 16 to 63 ppt Os. Eight samples yield a model 3 isochron age of （303 ±12） Ma （2or）, which is within uncertainty consistent with of the Re-Os date （295±7 Ma） of associated pyrite. Tectonic evolution shows that the Late Carboniferous Aqishan-Yamansu belt was a back-arc rift. Therefore, the Re-Os age of ca. 300 Ma indicates that the Shaquanzi Fe-Cu deposit may have formed in a back-arc extensional environment and was closely related to mantle-derived magmatism. The successful application of Re-Os magnetite geochronology in the Shaquanzi Fe-Cu deposit suggests that the purity of magnetite, relatively high Re and Os contents, and the closure of Re-Os systematic are base factors for a successful Re-Os geochronology. There would be a good prospect for Re-Os geochronology for magnet- ite.
