Volcanic eruption cycles division and characteristics in Huolinhe area of the central and southern Greater Khingan Mountain
Huolinhe area in the central and southern Greater Khingan Mountain has experienced strong volcanic ac-tivities since Mesozoic Era,and widely distributed intermediate acidic volcanic rocks were formed from Middle Ju-rassic to Early Cretaceous,which is a desirable area for evolution characteristics research of volcanic eruption during Mesozoic Era.The triple mapping method of"volcanic lithology and lithofacies,volcanic structure,and rock strata"was used in Huolinhe area to summarize and analyze the lithology,lithofacies,volcanic eruption cycles,and rhyth-mic characteristics.The result shows that the types of exposed rock types in this area can be divided into six catego-ries,including ordinary pyroclastic rocks,fused pyroclastic rocks,lava,sedimentary pyroclastic rocks and pyro-clastic sedimentary rocks,and latent volcanic rock.And there are eight types of lithofacies,including explosive fa-cies,pyroclastic flow facies,volcanic eruption collapse facies,overflow facies,volcanic eruption sedimentary faci-es,volcanic neck facies,intrusive facies,and subvolcanic lithofacies.The volcanic activity in this area can be di-vided into six volcanic eruption cycles:Xinmin period((163.7±1.7)～(160.0±4.0)Ma),Tamulangou period((164.2±4.1)～(159.7±2.7)Ma),Manketouebo period((163.4±1.3)～(157.0±1.1)Ma),Manitu period((151.4±2.6)～(144.0±2.8)Ma),Baiyingaolao period((141.7±1.3)～(128.6±1.4)Ma),and Meiletu period((133.4±1.5)～(127.7±1.4)Ma),corresponding to the six volcanic rock stratigraphic formation.Vol-canic activity was unstable in Huolinhe area during Middle Jurassic.A small amount of acidic volcanic debris erup-ted and were accompanied by many intermittent periods,followed by mainly calm overflow of neutral lava in the late phase.There was a strong eruption of acidic volcanic clastic rocks during Late Jurassic,accompanied by a small a-mount of medium acidic volcanic lava overflow.In the early stages of Early Cretaceous,the early stage volcanic ac-tivities were characterized by strong eruption of acidic volcanic clastic rocks,and the late stage volcanic activities were characterized by calm overflow of medium basic volcanic lava.The volcanic activities in this area could repre-sent the characteristics of the eruption cycles of Mesozoic volcanic rocks in the central and southern Greater Khingan Mountain.Therefore,the research result is of great significance to the reasonable division of the eruption cycles of Mesozoic volcanic rocks in the central and southern Greater Khingan Mountain,and could help promote in-depth comparative studies of volcanic rock combinations,volcanic activity characteristics,lithofacies construction,and volcanic stratigraphy in different regions.
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