干旱区生态环境知识资源中心(Arid): 六盘山地区下白垩统六盘山群乃家河组核形石形成的环境意义

Arid

	六盘山地区下白垩统六盘山群乃家河组核形石形成的环境意义
其他题名	The formation environment and genesis of the oncolite in Lower Cretaceous Liupanshan Group of Liupan Mountain area
	钟福平 1; 钟建华 1; 由伟丰 2; 边强 1; 刘吉善 3; 艾合买提江·阿不都热和曼 4; 张磊 4; 禚元杰 4; 王安东 4; 王金华 4; 孟玮 4
来源期刊	岩石矿物学杂志
ISSN	1000-6524
出版年	2010
卷号	29 期号:2 页码:206-212
中文摘要	六盘山寺口子水库下白垩统六盘山群乃家河组中发育了核形石,通过对其外部核心及纹层特征,以及核形石地球化学组分的研究,认为研究区核形石主要产于水动力较强的动荡水环境中,对捕捉和粘附碳酸钙质点作用相当明显,藻类自身的钙化和原地微生物引发的沉淀作用也可能是核形石的成因.经分析得到核形石的Sr/Ba值为4.87,CaO的含量达到了48.18%,总体上,研究区核形石在盐度高、温度较高、气候炎热、蒸发量大的干旱环境条件下形成.这些环境与研究区在该时期受燕山运动的影响,地壳整体抬升,湖盆发生萎缩的构造背景是相符的.
英文摘要	Oncolite is a kind of algae pack tablets composed of two parts, the core and cladding. It was the mucus secretion during the growth of algae in the process of capturing bonded debris materials and calcium carbonate particles and was formed through the core accretion as concentric patterned grains. On October 24, 2008, the authors found oncolites in Lower Cretaceous Naijiahe Formation of Liupanshan Group in a tunnel of Sikouzi Reservoir in the Liupan Mountain. The Lower Cretaceous strata in the study area are mainly composed of a set of purple, grayish green and gray mudstone, gray marl and light yellow muddy siltstone, with thin layered plas-ter between the marl. Oncolites occur in the upper part of Naijiahe Formation. A study of their external core and lamination characteristics suggests that they were formed mainly in a turbulent and high-energy water-environment. Geochemical compositions of the oncolites show that the debris was derived from land-based oxides such as SiO_2, Al_2O_3, Fe_2O_3, and FeO, whose values are all relatively low, with SiO_2 being 8.20%, Al_2O_3 being 2.77%, and (Fe_2O_3+FeO) being 3.00%. The content of these oxides in the lake depends on the amount of terrestrial detritus that entered the lake. In addition, the inflow of terrigenous detritus and vegetation cover are also related to the extent of weathering. The lower the degree of weathering or the better the covering, the lower the debris substance content. Therefore, the oncolites with relatively low SiO_2, Al_2O_3, Fe_2O_3, and FeO values indicate that during the same period the climate was relatively dry and the weathering was not strong. As only a small amount of clastic materials flowed into the lake and the lake water was relatively clean, a suitable water environment for the growth of algae and concolites were formed, and this also implies the close relationship between the influx of terrigenous clastic rocks and the growth of concolites. CaO content of concolites reaches 48.18%, indicating an obvious effects of the capturing and adhesion of calcium carbonate particles. Calcified algae itself and in situ precipitation of micro-organisms might also have been the causes for the formation of these concolites. The Sr/Ba value is 4.87, and the CaO content reaches 48.18%, suggesting that in the study area concolites were formed in a high salinity, high temperature, hot and strong evaporation arid environment. In Early Cretaceous, the region was affected by the Yanshanian movement, resulting in crustal uplift and lake atrophy. A study of the formation environment of these oncolites in Liupanshan area shows that their formation environment was consistent with the tectonic setting at that time.
中文关键词	核形石 ; 六盘山地区 ; 下白垩统 ; 乃家河组
英文关键词	oncolite Liupan Mountain area Lower cretaceous Naijiahe Formation
语种	中文
国家	中国
收录类别	CSCD
WOS类目	GEOLOGY
WOS研究方向	Geology
CSCD记录号	CSCD:3842480
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/225829
作者单位	1.中国人民解放军空军95338部队1大队, 衡阳, 湖南 421200, 中国; 2.中国石油化工有限公司石油勘探开发研究院, 北京 100083, 中国; 3.化工部郑州地质工程勘察院, 郑州, 河南 450011, 中国; 4.中国石油大学(华东)地球资源与信息学院, 东营, 山东 257061, 中国
推荐引用方式 GB/T 7714	钟福平,钟建华,由伟丰,等. 六盘山地区下白垩统六盘山群乃家河组核形石形成的环境意义[J],2010,29(2):206-212.
APA	钟福平.,钟建华.,由伟丰.,边强.,刘吉善.,...&孟玮.(2010).六盘山地区下白垩统六盘山群乃家河组核形石形成的环境意义.岩石矿物学杂志,29(2),206-212.
MLA	钟福平,et al."六盘山地区下白垩统六盘山群乃家河组核形石形成的环境意义".岩石矿物学杂志 29.2(2010):206-212.