青海南部杂多地区新建扎青组的地层层序及地质意义
The Stratigraphic Sequence and Geological Significance of New Zaqing Formation in Zaduo Area, South Qinghai
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摘要: 在青藏高原北羌塘盆地青海南部,青海省杂多县扎青乡地区的然者涌一带,发现以基性火山熔岩为主夹有中基性火山碎屑岩,具大陆板内裂谷拉斑玄武岩喷发特点的一套火山地层.该地层底部角度不整合接触覆盖在早中二叠世开心岭群诺日巴尕日保组、九十道班组之上,其上被晚三叠世结扎群甲丕拉组角度不整合覆盖.主要岩性为灰绿—灰紫色橄榄玄武岩、粗面玄武岩、玄武粗安岩及流纹岩、中基性火山角砾岩、角砾凝灰岩夹少量流纹岩和紫红色岩屑砂岩及细砾岩,其特征与峨眉山低钛玄武岩相似,具陆相喷发-沉积特征.区域对比在北羌塘地区具有独特地层特征,可与四川峨眉山玄武岩地层进行对比.而区域上该地区晚二叠世主要为一套海陆交互相含煤碎屑岩建造,未发现陆相火山岩出露,本文建立正式地层单位扎青组,以供参考,其时代暂归晚二叠—早三叠世.Abstract: A suit of volcanostratigraphic stratum consisted of many meta lava and some volcanics rocks which were possessed of erupting characters of tholeiiti basalts formed in Qiangtang basin in the Ranzheyong ways of Zhaqing area in Zaduo country,Qinghai.The relationship between the stratigraphic bottom and early-middle Permian Kaixinling Formation Nuo Ri Ba Ga Ri Bao Zu and Jiu Shi Dao Ban groups is unconformity of dip,and the volcanostratigraphic was covered with the late Triassic Jieza formation Jipila formation.The rock types of it include celadon-ash purple olivine basalt,aciculate basalt,basalt aciculate andesite,rhyolite,middle-mafic volcanic breccia,breccialuff and a few rhyolite,purple red debris sandst one and thinconglo merate,the character is as same as low Ti basalt of Emei Mountain.They were possessed of the charact eristics of continental erupting-sediment,there is unique character in region comparison,in north Qiangtang area,and can compare with Emei Mountain basalt stratig raphic.In the area,there was mostly a suit coal frag mental Formation and continental volcanics was not found,so we established Zhaqing formation for research,its era was the late Permian-early Triassic.
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