To the south of Manzhouli,Hulunbuir,Inner Mongolia,experienced a tectonic regime transformation from compression to extension in the mid-Mesozoic.Based on systematic research of the volcanics,petrology,volcanic facies...To the south of Manzhouli,Hulunbuir,Inner Mongolia,experienced a tectonic regime transformation from compression to extension in the mid-Mesozoic.Based on systematic research of the volcanics,petrology,volcanic facies,chronology and geochemistry of rocks in the Buridun area,two stages of volcanics are identified.The first stage named the trachyte series was formed in the late Middle Jurassic(167-163 Ma),its eruption rhythm is pyroxene trachyandesite-trachyandesite-trachyte,and its origin rock is basic volcanics from thickened lower crust,with a tectonic setting in the collision orogeny after the closure of the Mongolia Okhotsk Ocean(MOO).The second stage is a bimodal volcanic rock,formed in the early Late Jurassic(163-160 Ma).The eruption rhythm of basic volcanics in this stage is basaltic andesite-basalt-olivine basalt,which comes from the metasomatized lithospheric mantle,the acidic volcanics of which being characterized by the eruption rhythm of sedimentary-explosive-overflow facies,which came from the partial melting of newly formed lower crust,and this shows the characteristics of A-type granite;the tectonic setting is extension of the lithosphere after collision and closure of the MOO.The changes in the formation age and tectonic setting of the two stages of volcanics demonstrate that the transition time from the compressive system to the extensional system south of Manzhouli is about 163 Ma.展开更多
The paper aims to reconstruct the eruption sequence of the permanent teeth of Lufengpithecus lufengensis. Eruption sequence here means the order of appearance of the tooth crowns out of the alveolar crypt. The permane...The paper aims to reconstruct the eruption sequence of the permanent teeth of Lufengpithecus lufengensis. Eruption sequence here means the order of appearance of the tooth crowns out of the alveolar crypt. The permanent dental developments of five juvenile mandibles are observed and analyzed via radiograph. Using such records as the stages of crown and root formation, location of the crown occlusion relative to the alveolar margin, and wear degrees of the erupted teeth, the eruption sequence of the mandibular permanent teeth of Lufengpithecus lufengensis is reasonably derived as M1 I1 I2 M2 P3 P4 C M3. This order is seen to differ very markedly from that in modern humans, and to be similar to that in apes.展开更多
基金financially supported by the Geological Survey program of China Geological Survey(Grant Nos.DD20189613,12120115031301)National Key Research and Development Program of China(Grant No.2019YFC0605202)。
文摘To the south of Manzhouli,Hulunbuir,Inner Mongolia,experienced a tectonic regime transformation from compression to extension in the mid-Mesozoic.Based on systematic research of the volcanics,petrology,volcanic facies,chronology and geochemistry of rocks in the Buridun area,two stages of volcanics are identified.The first stage named the trachyte series was formed in the late Middle Jurassic(167-163 Ma),its eruption rhythm is pyroxene trachyandesite-trachyandesite-trachyte,and its origin rock is basic volcanics from thickened lower crust,with a tectonic setting in the collision orogeny after the closure of the Mongolia Okhotsk Ocean(MOO).The second stage is a bimodal volcanic rock,formed in the early Late Jurassic(163-160 Ma).The eruption rhythm of basic volcanics in this stage is basaltic andesite-basalt-olivine basalt,which comes from the metasomatized lithospheric mantle,the acidic volcanics of which being characterized by the eruption rhythm of sedimentary-explosive-overflow facies,which came from the partial melting of newly formed lower crust,and this shows the characteristics of A-type granite;the tectonic setting is extension of the lithosphere after collision and closure of the MOO.The changes in the formation age and tectonic setting of the two stages of volcanics demonstrate that the transition time from the compressive system to the extensional system south of Manzhouli is about 163 Ma.
基金supported by National Science Foundation of China(40002003)
文摘The paper aims to reconstruct the eruption sequence of the permanent teeth of Lufengpithecus lufengensis. Eruption sequence here means the order of appearance of the tooth crowns out of the alveolar crypt. The permanent dental developments of five juvenile mandibles are observed and analyzed via radiograph. Using such records as the stages of crown and root formation, location of the crown occlusion relative to the alveolar margin, and wear degrees of the erupted teeth, the eruption sequence of the mandibular permanent teeth of Lufengpithecus lufengensis is reasonably derived as M1 I1 I2 M2 P3 P4 C M3. This order is seen to differ very markedly from that in modern humans, and to be similar to that in apes.
