浙江省江郎山下白垩统方岩组沉积特征与物源分析

发布时间：2018-03-14 09:41

本文选题：江郎山　切入点：方岩组　出处：《东华理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：江郎山发育典型的老年期丹霞地貌景观,先后被评为世界自然遗产地和国家5A级旅游景区,本文对构成江郎山丹霞地貌的下白垩统方岩组进行了沉积构造、粒度特征、岩石地球化学特征研究,进而开展其物源分析。主要认识如下:(1)江郎山下白垩统方岩组岩石类型为砂岩、砾岩,砾石成分主要为中酸性火山岩,以凝灰岩为主(熔结凝灰岩、晶屑凝灰岩),其次为硅质岩,分选性普遍较差,砾石扁度介于1.01-4.17,球度为0.54-0.76,磨圆度为20.87%-24.7%。露头上粒序层理、叠瓦状构造和冲刷面构造十分发育。沉积类型以冲积扇和河流沉积为主,其粒度参数偏度、峰态、标准偏差指示该区水动力条件不稳定,流速多变但总体具有快速倾泄堆积的特点。(2)方岩组砂岩富硅酸盐矿物,碱性程度强,贫铝铁镁,亲铁元素偏低,亲石元素相对偏高,亲稀土相对富集而重稀土相对亏损,Eu的负异常明显,Sr值相对较低,稀土元素上不同岩石类型总体趋势基本相同,江郎山下白垩统方岩组的沉积物源主要来自南西和南东方向,风化母岩为中酸性火山岩,总体属于近源堆积。(3)白垩纪早期,区域背景由挤压环境变成拉张环境,江郎山所处的峡口盆地成为断陷盆地,接受附近侏罗系火山岩物质的沉积。在急速式的山洪环境中,峡口盆地堆积了大量砾岩、砂岩,形成多期次冲积扇。固结成岩后,区域抬升作用形成大量垂直断裂,胶结相对不坚固的砂岩在垂直断裂和风化剥蚀的作用下产生崩塌,而由多期次冲积扇堆积而成的这一部分砂砾岩得到保留。在内、外动力共同的作用下,最终形成现今的江郎山丹霞地貌景观。通过对该地貌景观的形成可以看出:丹霞景观地貌对岩相具有选择性,冲积扇相是形成丹霞地貌景观的物质基础。
[Abstract]:The typical Danxia landform landscape developed in Jianglang Mountain has been appraised as the World Natural Heritage site and the national 5A class tourist area. The sedimentary structure and granularity characteristics of the Lower Cretaceous Fangyan formation, which constitute the Danxia geomorphology of Jianglang Mountain, have been carried out in this paper. The rock types of the Lower Cretaceous calcite formation in Jianglang Mountain are sandstone, conglomerate and gravel mainly composed of intermediate-acid volcanic rocks and tuff (melt-formed tuff). The grained tuff, followed by siliceous rock, is generally poor in sorting, with gravel flatness between 1.01-4.17, sphericity between 0.54-0.76, and grinding roundness of 20.87-24.7.The grain sequence bedding, imbricate structure and scour surface structure on the outcrop are well developed. The sedimentary types are mainly alluvial fans and fluvial deposits. The granularity parameter bias, peak state and standard deviation indicate that the hydrodynamic conditions in this area are unstable, the velocity is variable, but generally has the characteristics of rapid dumping and accumulation.) the sandstone of the Fangyan formation is rich in silicate minerals, strong in alkalinity, poor in aluminum-ferric magnesium, and low in ferriphilic elements. The lithophile elements are relatively high, the relative enrichment of the lipophilic elements is relatively high, and the negative anomaly of the heavy rare earth elements is obviously lower than that of the depleted EU, and the general trend of different rock types on the rare earth elements is basically the same. The sediments of the Lower Cretaceous Fangyan formation in Jianglangshan mainly come from the direction of the south west and south east, and the aeolian parent rock is intermediate acid volcanic rock, which belongs to the near source accumulation. (3) in the early Cretaceous, the regional background changed from the compressional environment to the extensional environment. The Xiakou basin of Jianglang Mountain is a faulted basin, which accepts the deposition of the nearby Jurassic volcanic rocks. In the rapid mountain flood environment, the Xiakou basin accumulates a large number of conglomerates and sandstones, forming multi-stage alluvial fans, and after consolidation of diagenetic rocks, A large number of vertical faults were formed by regional uplift, and the relatively weak cemented sandstone collapsed under the action of vertical faults and weathering and denudation, while this part of sandy gravel, which was accumulated by multi-stage alluvial fans, was retained. Through the formation of the geomorphological landscape, it can be seen that the Danxia landscape is selective to the lithofacies, and the alluvial fan facies is the material basis for the formation of the Danxia landform landscape.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P534.53;P512.2

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