Sedimentary Record of the Proterozoic Changchengian Volcanic Events in Beijing and Its Neighbouring Area
-
摘要: 北京及邻区的中元古代大红峪组中发育着与火山事件有关的沉积相,主要包括两种基本类型:火山源硅质—陆源砂—碳酸盐岩混积相和火山碎屑重力流沉积,后者又可分为火山碎屑基浪沉积相和火山—沉积角砾碳酸盐岩混积相。初步分析表明,大红峪期大量的硅质沉积主要来自同期的水下火山活动;火山碎屑基浪沉积与火山口内残余热气冲破熔岩封堵而爆发泄出,造成一定范围的海水涌浪作用有关。Abstract: The volcanic rocks of the Proterozoic Dahongyu Formation mainly distribute in Pinggu County of Beijing and Jixian county of Tianjin about 600 km 2 with 718 m and 490 m of the maximum thickness in the both areas. More than 40 paleo carters were survived in the areas.The types of volcanic rocks mainly are potassic basalts and trachyte. Sedimentary facies related to volcanic event in the Middle Proterozoic Dahongyu Formation in Beijing and its neighboring area mainly include two basic types: siliceous sand carbonate mixed facies and pyroclastic gravity flow deposit, in which the later can be divided into pyroclastic basic surge and volcanic breccia-carbonate mixed deposit. Siliceous sand carbonate mixed facies: the rock types of this facies include white and light blue siliceous bearing quazites, light blue sandy silicalites, blue grey tuff, siliceous dolomites, intraclast shaped silicalites and geltexture silicalites. Siliceous sand carbonate mixed facies widely distribute in the NE basin axis inclined to the NW side. Preliminary results of analysis, according to characteristics of rocks, geochemistry and sedimentation, show that enormous siliceous sediments of the Dahongyu Formation mainly originated from the submarine volcanic eruption in the temporary time. Pyroclastic basic surges: Basic surges directly cover on basalts and occur around the paleo craters. They are composed of coarse sand grade pyroclastic rocks with large scale dune like cross bedding and poly grade bedding, fine sand silt grade pyroclastic rocks and tuff shales. The pyroclastic basic surge was caused by sea water surging in small range, which was related to release of remnant steam bursting to seal of volcanic craters. Volcanic breccia carbonate mixed facies: Volcanic breccia carbonate generally is single bed placed in between dolomites. In the beds breccia components are composed of sedimentary rocks (40~60%) and of basalts and tractytes (30~40%). According to analysis of sedimentary breccia content more than volcanic breccia, this facies probably formed under the condition bursting and returnning breccia mixed with submarine surface carbonates and water in the basin, as submarine gravity flow deposited around the places of the volcanic craters.
-
[1] 陈晋镳,张惠民,朱士兴.等蓟县震旦亚界的研究[A].见:中国地质科学院天津地矿所(主编),中国震旦亚界研究[C].天津:天津科技出版社,1980.56~114 [2] 王鸿祯,乔秀夫.中国元古代过构造单元及其边界性质.前寒武纪地质[J].1987,3:l~14 [3] 宋天锐,高健.北京十三陵前寒武系沉积岩[M].北京:地质出版社,1987.1~193 [4] 宋天锐,赵震,王长尧等.华北元古宙沉积岩[M].北京:北京科学技术出版社,1991.40~45 [5] 和政军,孟祥化,葛明.燕山地区长城纪沉积演化及构造背景[J].沉积学报,1994,12(2):10~19 [6] 任富根.蓟县长城纪火山-侵入岩浆活动问题[J].天津地矿所所刊,1986,16:109~122 [7] 邱家骧,廖群安.北京地区中元古代与中生代火山岩的酸度系列构造环境及岩浆成因[J].岩石矿物学杂志,1998,17(2):104~117 [8] 李昌年,邱家骧,杨眉.北京地区元古代火山作用及其构造环境讨论[A].见:李兆鼐,王碧香(主编),火山岩、火山作用及有关矿产[C].北京:地质出版社,1993.154~161 [9] 北京市地质矿产局.北京市区域地质志[M].北京:地质出版社,1991 [10] Morley C K, et al. Transfer zones in the East Afriean Rift system and their relevance to hydrocarbon exploration in rift [J]. AAPG, 1990, 74:1234~ 1253 [11] Gibbs A D. Structural styles in basin formation[A]. In:Tankard A J, Balkwill H R, eds. Extensional Tectonics and Stratigraphy of the North Atlantic Margins[C]. AAPG, Mem., 1989, 46:81~93 [12] 任启忠.伸展地区重要的调整构造传递断层[J].煤田地质与勘探,1990,(2):20~26 [13] 刘益丰,秦正永,王长尧.冀北燕山沉降带地层地球化学剖面研究[M].天津:天津科技翻译出版公司,1991.101~110 [14] Douthitt C B. The geochemistry of the stable isotopes of silicon[J].Geochimica et Cosmochimica Acta, 1982, 46(8):1449~1458 [15] Fisher R V. Base surge deposits (deposits of hydroclastic eruptions) [A]. In: Fisher R V, Schmincke H U, eds. Pyroclastic Rocks[C]. Heidelberg, Springer-Verlag, 1984, 247~257 [16] Fisher R V. Transport and deposition of a pyroclastic surge across an area of high relief:The 18 May 1980 eruption of Mount St. Helems [J]. Geol. Soc. Amer. Bull., 1990, 102:1038~1054
计量
- 文章访问数: 530
- HTML全文浏览量: 4
- PDF下载量: 425
- 被引次数: 0