The Songnen masiff is located to the east of the Central Asian Orogenic Belt. The existence and rather the scale and nature of the Precambrian crystalline basement is controversial. Based on recent study of zircon U-P...The Songnen masiff is located to the east of the Central Asian Orogenic Belt. The existence and rather the scale and nature of the Precambrian crystalline basement is controversial. Based on recent study of zircon U-Pb chronology, besides a minor number of Neoproterozoic strata, most of the so-called Precambrian metamorphic rock series, such as the Dongfengshan Group and the Zhangguangcailing Group, were formed in the Mesozoic and Paleozoic.展开更多
Objective Northeast China is located in a cold region with high latitude. In the mid-low mountain areas, the existence of Quaternary glacier as well as its range and nature are always controversial. The glacial paleo...Objective Northeast China is located in a cold region with high latitude. In the mid-low mountain areas, the existence of Quaternary glacier as well as its range and nature are always controversial. The glacial paleogeomorphology of Northeast China had been extensively studied and explored. The results revealed that Quaternary glaciers was developed in the northern part of Great Hinggan Ranges and Changbai Mountains. However, some scholars believed that the development of the Quaternary glaciers in China resulted from tectonic coupling and close relation with the elevation of mountains. In Northeast China, glaciation did not occur in any mid-low mountain areas during the Quaternary except the Changbai Mountains where the elevation is more than 2600 m. The question is whether glaciation occurred in the mid-low mountain areas of Northeast China during the Quaternary？ In order to clarify this question, this paper reports the Quaternary glacial remains of Tala Mountain, which were newly discovered in Ar Horqin Banner, lnner Mongolia and their age dating.展开更多
By using petrological,isotope chronological,and geochemical methods,the authors studied the volcanic rocks in the studied area,mainly including dacites and trachytes. The results show that they formed during the late ...By using petrological,isotope chronological,and geochemical methods,the authors studied the volcanic rocks in the studied area,mainly including dacites and trachytes. The results show that they formed during the late Early Cretaceous. Geochemically,the volcanic rocks are relatively enriched in large-ion lithophile elements( Rb,K,and Th) and depleted in high field strength elements( Nb,Ta,and Ti),and rich in light rare earth elements,and depleted in heavy rare earth elements. The fact indicates that the main body of the volcanic rocks in the Qushenla Formation was derived from the partial melting of lower crust. The lithological assemblages are characterized by continental high-K calc-alkaline and shoshonitic series,suggesting that the southward-subducting oceanic slab in southern Bangong Lake had break off and that the Bangong Lake-Nujiang Ocean had closed before 107 Ma. The main dynamic mechanisms for the genesis of this set of intermediate-acidic volcanic rocks were upwelling of the asthenosphere and partial melting of the lower crust caused by slab break-off.展开更多
基金supported by the China Geological Survey (grant No.12120113053900,DD20160048-04,DD20160343-08,DD20160343-09)
文摘The Songnen masiff is located to the east of the Central Asian Orogenic Belt. The existence and rather the scale and nature of the Precambrian crystalline basement is controversial. Based on recent study of zircon U-Pb chronology, besides a minor number of Neoproterozoic strata, most of the so-called Precambrian metamorphic rock series, such as the Dongfengshan Group and the Zhangguangcailing Group, were formed in the Mesozoic and Paleozoic.
基金supported by the China Geological Survey(grant Nos.DD20160048-04 and DD20179402-01 DD20179402-02)the National Natural Science Foundation of China(grant No.41702032)
文摘Objective Northeast China is located in a cold region with high latitude. In the mid-low mountain areas, the existence of Quaternary glacier as well as its range and nature are always controversial. The glacial paleogeomorphology of Northeast China had been extensively studied and explored. The results revealed that Quaternary glaciers was developed in the northern part of Great Hinggan Ranges and Changbai Mountains. However, some scholars believed that the development of the Quaternary glaciers in China resulted from tectonic coupling and close relation with the elevation of mountains. In Northeast China, glaciation did not occur in any mid-low mountain areas during the Quaternary except the Changbai Mountains where the elevation is more than 2600 m. The question is whether glaciation occurred in the mid-low mountain areas of Northeast China during the Quaternary？ In order to clarify this question, this paper reports the Quaternary glacial remains of Tala Mountain, which were newly discovered in Ar Horqin Banner, lnner Mongolia and their age dating.
基金Supported by project of National Natural Science Foundation of China(No.41172056)
文摘By using petrological,isotope chronological,and geochemical methods,the authors studied the volcanic rocks in the studied area,mainly including dacites and trachytes. The results show that they formed during the late Early Cretaceous. Geochemically,the volcanic rocks are relatively enriched in large-ion lithophile elements( Rb,K,and Th) and depleted in high field strength elements( Nb,Ta,and Ti),and rich in light rare earth elements,and depleted in heavy rare earth elements. The fact indicates that the main body of the volcanic rocks in the Qushenla Formation was derived from the partial melting of lower crust. The lithological assemblages are characterized by continental high-K calc-alkaline and shoshonitic series,suggesting that the southward-subducting oceanic slab in southern Bangong Lake had break off and that the Bangong Lake-Nujiang Ocean had closed before 107 Ma. The main dynamic mechanisms for the genesis of this set of intermediate-acidic volcanic rocks were upwelling of the asthenosphere and partial melting of the lower crust caused by slab break-off.
