云南南涧新近系三营组特征及物源分析

发布时间：2018-03-11 10:53

本文选题：新近系　切入点：三营组　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：新近系三营组是1959年由云南地质局区调地质调查大队命名,其特征是由灰、深灰、褐灰、黄白等杂色泥岩(粘土岩)、粉砂岩、细-中粒砂岩与砾岩、砂砾岩及碳质泥岩夹煤层及菱铁矿小凸镜体组成,并夹有紫红色岩层。含哺乳动物、腹足类、植物、介形类及孢粉等化石。其中植物有Acer,Quercus,Celtis,Pinus等化石。底部一般具砾岩。不整合覆于北衙组、三号沟组或双河组等地层之上;上被第四系不整合覆盖。厚49-1331米。云南省南涧县三营组盆地位于哀牢山断裂带两侧,分别为南涧县城的南涧盆地和德苴乡至多依厂古建筑的德苴-多依厂盆地。经过详细的盆地实测地层剖面测制,得知南涧盆地主要发育为洪(冲)积扇-河流沉积相组合,其砾石组分不但有外来砾石,其砾石层中大的砾石很可能是其基底地层在外界条件下风化剥蚀形成的原位砾石,德苴-多依厂盆地主要以洪(冲)积扇-辫状河沉积相组合,其砾石风化严重,磨圆不好,且含有很明显的花岗岩砾石,其砾石物源很可能来自哀牢山构造带。通过对云南省南涧县哀牢山断裂带两侧的两个小型新近系三营组盆地共计5个露头测点的砾岩层砾性、砾度、砾态和砾向等的详细研究与分析,结合盆地基岩地层特点和周边构造带的岩性组合特征。对比了哀牢山断裂带两侧盆地的砾岩层组合特征,认为两者皆为半干旱-干旱古气候条件下形成的沉积盆地,其中南涧盆地具有快速堆积的特点,其砾石成分组合特征在盆地不同位置有较多的差异,反映了其物源供应条件较复杂;而德苴-多依厂盆地砾岩组合特征表明水动力条件相对南涧盆地弱,且砾石层砾石遭受了较强的物理化学作用。结合盆地基岩及周边地层岩性特点和砾石扁平面倾向统计,南涧盆地砾石主要来自盆地基底及周边高山,而德苴-多依厂盆地则主要是盆地内部的基底地层及其西缘的哀牢山构造带。为了进一步探讨两盆地物源的异同之处,对两盆地采集的碎屑锆石样品,分别进行了LA-ICP-MS碎屑锆石U-Pb测年,其中南涧盆地共得到碎屑锆石年龄62个,锆石年龄跨度介于222-1093Ma之间,这表示其物源组分复杂。在锆石U-Pb年龄谐和图上,可见锆石断续存在多个集中区,这个反映了锆石的原岩年龄,对锆石年龄进行频度统计,锆石年龄存在三个峰值,分别位于238Ma、436Ma、774Ma附近,在464-636Ma存在间断,对比研究区碎屑锆石测年数据,推测该盆地很可能存在3个或者更多的可能物源区。,德苴-多依厂盆地共得到碎屑锆石年龄80个,其测年结果则与南涧盆地大相径庭,其锆石测年高度集中在一个极小的区间(32.3-40Ma),这不仅表明该盆地物源区单一,同时也表明了其形成时间极短,沉积物搬运速度快速,在短时间内形成了这个盆地,结合目前德苴-多依厂盆地沉积物风化严重,且未见第四系沉积的现象,此盆地很可能经历了一个快速堆积而后急剧抬升的过程。
[Abstract]:The Sanying formation of the Neogene was named in 1959 by the Geological Survey Group of the Geological Bureau of Yunnan Province. It is characterized by mixed mudstone (clay rock, siltstone, fine to medium grained sandstone and conglomerate) with gray, deep ash, brown ash, yellow white, etc. Composed of gravelly and carbonaceous mudstone intercalated with coal seams and siderite, and intercalated with purplish red rocks, containing mammals, gastropods, plants, Ostracods and sporopollen fossils. Among them, there are Acera Quercus Celtis Pinus and other fossils. The bottom is usually conglomerate. The unconformity is on the formations of Beiya formation, No.3 Gou formation or Shuanghe formation. The basin of Sanying formation in Nanjian County, Yunnan Province is located on both sides of the Ailaoshan fault zone. The Nanjian basin in Nanjian county and the Deju-Duoyichang basin in Dejianxian in ancient buildings at most. Based on the detailed stratigraphic profiling of the basin, it is found that the Nanjian basin is mainly developed into a flood (alluvial) fan-river sedimentary facies association. There are not only foreign gravel in its gravel composition, but also the large gravel in its gravel layer is probably the in-situ gravel formed by weathering and denudation of its basement strata under external conditions. The Deju-Duichang basin is mainly composed of flood (alluvial) fan and braided river sedimentary facies. Its gravel weathered seriously, the grinding round is not good, and contains very obvious granite gravel, The gravel source is probably from the Ailaoshan structural belt. The gravel properties and graveliness of the two small Neogene Sanying formation basins on both sides of the Ailaoshan fault zone, Nanjian County, Yunnan Province, were measured at 5 outcrop sites. The characteristics of conglomerate assemblage on both sides of the Ailaoshan fault zone are compared by the detailed study and analysis of the gravel-state and gravel-direction, combined with the characteristics of the basement strata and the lithologic assemblages of the surrounding structural zones. It is considered that both of them are sedimentary basins formed under semi-arid and arid paleoclimate conditions, in which Nanjian basin is characterized by rapid accumulation, and the characteristics of gravel composition combination are different in different locations of the basin. The characteristics of conglomerate assemblage show that the hydrodynamic conditions are weaker than those in Nanjian basin. Combined with the lithologic characteristics of the basement and surrounding strata of the basin and the statistical analysis of the flat surface of the gravel, the gravel in the Nanjian basin mainly comes from the basement of the basin and the surrounding high mountains. The Deju-Duoyichang basin is mainly composed of the basement strata and the Ailaoshan tectonic belt in the western margin of the basin. In order to further explore the similarities and differences between the two basins, the samples of the detrital zircons collected from the two basins are studied. The U-Pb dating of LA-ICP-MS detrital zircons has been carried out respectively. A total of 62 zircon ages have been obtained in Nanjian Basin, and the zircon age span is between 222-1093 Ma, which indicates that its provenance components are complex. It can be seen that there are several concentration zones in zircon intermittently, which reflects the age of zircon. According to the frequency statistics of zircon age, there are three peaks of zircon age, located at about 238Ma-436Ma-774Ma, and discontinuous at 464-636Ma. By comparing the data of detrital zircon dating in the study area, it is inferred that there are probably three or more possible provenances in the basin. 80 zircon ages have been obtained in the Deju-Duichang basin, and the results are quite different from those in the Nanjian basin. The zircon dating height is concentrated in a very small interval of 32.3-40 Ma, which not only indicates that the source area of the basin is single, but also indicates that the basin was formed in a short time, with a very short time of formation and a rapid speed of sediment transport, resulting in the formation of the basin in a short period of time. Combined with the serious weathering of sediments in the Deju-Duoyichang basin and the absence of Quaternary sediments, the basin probably experienced a rapid accumulation and then a sharp uplift.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.6

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