Baotoudong syenite pluton is located to the east of Baotou City, Inner Mongolia, the westernmost part of the Trias- sic alkaline magmatic belt along the northern margin of the North China Craton （NCC）. Zircon U-Pb a...Baotoudong syenite pluton is located to the east of Baotou City, Inner Mongolia, the westernmost part of the Trias- sic alkaline magmatic belt along the northern margin of the North China Craton （NCC）. Zircon U-Pb age, petrological, miner- alogical and geochemical data of the pluton were obtained in this paper, to constrain its origin and mantle source characteris- tics. The pluton is composed of nepheline-clinopyroxene syenite and alkali-feldspar syenite, with zircon U-Pb age of 214.7±1.1 Ma. Diopside （cores）-aegirine-augite （rims）, biotite, orthoclase and nepheline are the major minerals. The Bao- toudong syenites have high contents of rare earth elements （REE）, and are characterized by enrichment in light rare earth ele- ments （LREE） and large ion lithophile elements （LILE; e.g., Rb, Ba, Sr）, depletion in heavy rare earth elements （HREE） and high field strength elements （HFSE）. They show enriched Sr-Nd isotopic compositions with initial 87Sr/86Sr ranging from 0.7061 to 0.7067 and eNd（t） values from -9.0 to -11.2. Mineralogy, petrology and geochemical studies show that the parental magma of the syenites is SiO2-undersaturated potassic-ultrapotassic, and is characterized by high contents of CaO, Fe2O3, K2O, Na2O and fluid compositions （H2O）, and by high temperature and high oxygen fugacity. The syenites were originated from a phlogopite-rich, enriched lithospheric mantle source in garnet-stable area （〉80 km）. The occurrence of the Baotoudong sye- nites, together with many other ultrapotassic, alkaline complexes of similar ages on the northern margin of the NCC in Late Triassic implies that the lithospheric mantle beneath the northern margin of the NCC was previously metasomatized by melts/fluids from the subducted, altered paleo-Mongolian oceanic crust, and the northern margin of the craton has entered into an extensively extensional regime as a destructive continental margin in Late Triassic.展开更多
Climate warming has been more pronounced in the Arctic than elsewhere, resulting in a recent rapid glacial retreat. Over 85% of the Almajallojekna glacier has disappeared over the last 115 years and it is one of the f...Climate warming has been more pronounced in the Arctic than elsewhere, resulting in a recent rapid glacial retreat. Over 85% of the Almajallojekna glacier has disappeared over the last 115 years and it is one of the fastest retreating glaciers in Sweden. In 2011 and 2012, at 18 sites in the vicinity of the remaining glacier network, we sampled arthropods and related the species richness, abundance and proportion of herbivores to altitude （ranging from 824 to 1,524 m.a.s.1.） and the age of the site （ranging from 0 to 〉 115 years）. Temperature was measured at six sites and the average annual air temperature ranged from -3.7℃ to 1.1℃. In total, we recorded 3,705 arthropods from 117 species in nine different taxonomic groups. The most abundant and species-rich group was Coleoptera （1,381 individuals, 41 species） followed by Araneae （1,050 individuals, 15 species） and Macrolepidoptera （732 individuals, 17 species）. Only at lower altitudes did the abundance and species richness of arthropods increase with increasing age of the site. The results were consistent among the studied taxonomic groups and when controlling for sam- piing intensity using two different approaches. The proportion of herbivores decreased with increasing age of the site and with increasing altitude. Clearly, altitude appears more important than the age of the site and, at higher altitudes, abundance, species richness and herbivory are low [Current Zoology 60 （2）： 203-220, 2014].展开更多
基金the National Natural Science Foundation of China (Grant No. 41302038) Institute of Geology, Chinese Academy of Geological Sciences (Grant No. J1205)
文摘Baotoudong syenite pluton is located to the east of Baotou City, Inner Mongolia, the westernmost part of the Trias- sic alkaline magmatic belt along the northern margin of the North China Craton （NCC）. Zircon U-Pb age, petrological, miner- alogical and geochemical data of the pluton were obtained in this paper, to constrain its origin and mantle source characteris- tics. The pluton is composed of nepheline-clinopyroxene syenite and alkali-feldspar syenite, with zircon U-Pb age of 214.7±1.1 Ma. Diopside （cores）-aegirine-augite （rims）, biotite, orthoclase and nepheline are the major minerals. The Bao- toudong syenites have high contents of rare earth elements （REE）, and are characterized by enrichment in light rare earth ele- ments （LREE） and large ion lithophile elements （LILE; e.g., Rb, Ba, Sr）, depletion in heavy rare earth elements （HREE） and high field strength elements （HFSE）. They show enriched Sr-Nd isotopic compositions with initial 87Sr/86Sr ranging from 0.7061 to 0.7067 and eNd（t） values from -9.0 to -11.2. Mineralogy, petrology and geochemical studies show that the parental magma of the syenites is SiO2-undersaturated potassic-ultrapotassic, and is characterized by high contents of CaO, Fe2O3, K2O, Na2O and fluid compositions （H2O）, and by high temperature and high oxygen fugacity. The syenites were originated from a phlogopite-rich, enriched lithospheric mantle source in garnet-stable area （〉80 km）. The occurrence of the Baotoudong sye- nites, together with many other ultrapotassic, alkaline complexes of similar ages on the northern margin of the NCC in Late Triassic implies that the lithospheric mantle beneath the northern margin of the NCC was previously metasomatized by melts/fluids from the subducted, altered paleo-Mongolian oceanic crust, and the northern margin of the craton has entered into an extensively extensional regime as a destructive continental margin in Late Triassic.
文摘Climate warming has been more pronounced in the Arctic than elsewhere, resulting in a recent rapid glacial retreat. Over 85% of the Almajallojekna glacier has disappeared over the last 115 years and it is one of the fastest retreating glaciers in Sweden. In 2011 and 2012, at 18 sites in the vicinity of the remaining glacier network, we sampled arthropods and related the species richness, abundance and proportion of herbivores to altitude （ranging from 824 to 1,524 m.a.s.1.） and the age of the site （ranging from 0 to 〉 115 years）. Temperature was measured at six sites and the average annual air temperature ranged from -3.7℃ to 1.1℃. In total, we recorded 3,705 arthropods from 117 species in nine different taxonomic groups. The most abundant and species-rich group was Coleoptera （1,381 individuals, 41 species） followed by Araneae （1,050 individuals, 15 species） and Macrolepidoptera （732 individuals, 17 species）. Only at lower altitudes did the abundance and species richness of arthropods increase with increasing age of the site. The results were consistent among the studied taxonomic groups and when controlling for sam- piing intensity using two different approaches. The proportion of herbivores decreased with increasing age of the site and with increasing altitude. Clearly, altitude appears more important than the age of the site and, at higher altitudes, abundance, species richness and herbivory are low [Current Zoology 60 （2）： 203-220, 2014].
