梵净山群沉积地质特征与原型盆地分析

发布时间：2018-01-28 05:53

本文关键词： 梵净山群浊积岩弧后伸展岩石大地构造新元古代　出处：《地球学报》2017年04期 　论文类型：期刊论文

【摘要】：梵净山群出露于江南造山带西北端,为一套浅变质火山、碎屑岩系,其上亚群主要由深海、半深海浊积岩系组成,自下而上划分为铜厂组、洼溪组和独岩塘组。铜厂组主体由浊积扇相和盆地相组成,洼溪组则主要由浊积扇扇中、扇根亚相组成。进一步的沉积相序研究揭示,自回香坪组至铜厂组、洼溪组,沉积环境总体呈一先海进、后海退的沉积旋回,显示裂陷扩张过程。铜厂组和洼溪组浊流成因的小型斜层理位态研究揭示,前积层优选方位指向北、北东,证实沉积物来自其南,向北扩散。浊积砂岩骨架颗粒统计结果表明,石英含量占23%~34%,且主要为单晶石英,而长石含量占14%~23%,岩屑含量占39%~50%,岩屑以火山岩屑为主。骨架颗粒统计图解揭示其物源为岩浆弧。基于上述,并结合回香坪组火山岩大地构造属性研究,提出并确定梵净山群上部碎屑岩系的原型盆地形成于弧后裂陷,板块构造环境为初始边缘海。
[Abstract]:The Fanjingshan Group is a set of shallow metamorphic volcanoes and clastic rock series. Its upper subgroup is mainly composed of deep-sea, semi-deep-sea turbidite series, and is divided into Tongchang formation from bottom to top. The main body of Tongchang formation is composed of turbidite fan facies and basin facies, while the waxi formation is mainly composed of turbidite fan and fan root subfacies. Further study of sedimentary facies sequence reveals that from Huixiangping formation to Tongchang formation. The sedimentary environment of the Waxi formation shows a sedimentary cycle of first advance and backward of the sea, showing the process of rift expansion. The study on the small oblique stratigraphic position of turbidity in Tongchang formation and the Waxi formation reveals that the preferred direction of the front accumulation is north. In the north and east, it is confirmed that the sediment originated from the south and spread northward. The statistical results of the turbidite sandstone skeleton grain show that the quartz content is 23%, and the quartz content is mainly single crystal quartz, while the feldspar content accounts for 14% and 23%. The lithoclastic content accounts for 39% and 50% of which is dominated by volcanic debris. The statistical diagram of skeleton grain reveals that its source is magmatic arc. Based on the above, the geotectonic properties of volcanic rocks of Huixiangping formation are studied. The prototype basin of the upper clastic rock series of the Fanjingshan Group is proposed and determined to be formed in the back-arc rift and the plate tectonic environment is the initial marginal sea.
【作者单位】：中国地质大学(北京)地球科学与资源学院;中国地质科学院地质研究所;
【基金】：中国地质调查局项目(编号:1212011120115)资助~~
【分类号】：P512.2;P548
【正文快照】： 江南造山带是上扬子陆块与华夏陆块间的缝合带,主体为一条北东东—南西西向延展的新元古代变质基底岩系(水涛,1987)。梵净山群发育于江南古陆的西北端,主体出露于黔东北的梵净山地区,是江南造山带的重要地层单元。梵净山群在江南造山带中的构造古地理位置是一个广泛讨论而又悬

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