北川龙门山区泥盆系土桥子组灰岩—泥灰岩韵律层成因机制研究

发布时间：2018-05-08 19:38

本文选题：灰岩—泥灰岩韵律层 + 地化特征　；参考：《成都理工大学》2017年硕士论文

【摘要】：韵律层一直是地层学家和古气候学家重点研究对象,是研究高分辨率旋回地层学的重要载体。在我国灰岩—泥灰岩韵律层的研究主要集中在华南地区,且研究主要集中在灰岩—泥灰岩韵律层的差异成岩作用方面,而关于灰岩—泥灰岩韵律层的全面研究则比较少见。在龙门山区泥盆系土桥子组最大海泛面两侧,发育有三套特征明显的灰岩—泥灰岩韵律层。运用土桥子组灰岩—泥灰岩韵律层的野外剖面实测、薄片观察和地球化学特征,重点研究其成因机制。根据野外实测剖面资料和沉积特征,分析得出土桥子组主要发育三种沉积相类型:碳酸盐台地、碳酸盐缓坡和盆地相。这三种沉积相类型在土桥子组沉积演化上交替出现。通过对常量元素SiO_2、Fe_2O_3、FeO、Al_2O_3、TiO_2、CaO、MgO、K_2O、Na_2O、MnO和P_2O_5的分析,表明灰岩、泥灰岩在常量元素的化学组成上基本呈现一致的趋势。CaO、SiO_2和Al_2O_3在灰岩、泥灰岩中占有很大的比重,其余常量元素所占比重则很低。对微量元素V、Cr、Co、Ni、Cu、Zn、As、Rb、Sr、Zr、Cd、Ba、Th和U的分析表明,灰岩与泥灰岩的微量元素组成及比例也存在极大的相似性。通过分析灰岩、泥灰岩的酸不溶物、烧失剩余物跟各元素的相关性,发现SiO_2、Al_2O_3、K_2O、MnO、TiO_2和Cr等的含量与酸不溶物含量都呈很大的相关性。尤其是SiO2与酸不溶物的相关性达到了0.93。并在此基础上,分析元素的来源,为研究灰岩—泥灰岩韵律层提供可靠的元素基础。通过古氧相U/Th、古盐度Sr/Ba、古水深MnO、古气候Sr/Cu等分析,研究灰岩—泥灰岩韵律层形成时的古环境与古气候。认为灰岩—泥灰岩韵律层形成于炎热气候下的贫氧海相高水位体系域沉积环境。古气候和差异成岩作用是灰岩—泥灰岩韵律层的主要成因,其中在较大的宏观尺度上古气候的韵律和波动控制着韵律层的古环境和地球化学特征,而在较小的微观尺度上差异成岩作用进一步控制和影响着韵律层地球化学特征的分异性和韵律性。
[Abstract]:Prosodic layer has been the important research object of stratigraphers and paleoclimatologists and an important carrier of high resolution cyclic stratigraphy. In China, the study of lime-marl rhythms is mainly concentrated in South China, and the study is mainly focused on the differential diagenesis of lime-marl rhythms, but the comprehensive study on lime-marl rhythms is rare. On the two sides of the largest flooding surface of the Devonian Tuqiao formation in Longmen Mountain area, there are three sets of distinct lime-mudstone rhythms. Based on the field profile, thin section observation and geochemical characteristics of the lime-marl rhythmic layer of Tuqiao formation, the genetic mechanism is emphatically studied. Based on the field measured profile data and sedimentary characteristics, it is concluded that three types of sedimentary facies are mainly developed in Tuqiao formation: carbonate platform, carbonate gentle slope and basin facies. These three types of sedimentary facies alternately appeared in the sedimentary evolution of Tuqiao formation. Based on the analysis of the main element SiO2SiFe2O3S / SiOSiO2 / Al2O3TiO2TiO2CaOTiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2TiO2Ti@@ The analysis of trace elements such as the trace elements V _ (C _ (C) _ (CoA) _ (Cu) ~ (2 +) Zn ~ (2 +) ~ (2 +) ~ (2 +) ~ (2) ~ (2 +) ~ (2 +) ~ (2) ~ (2) ~ (2) ~ (2 +) Rbsrbszr@@ By analyzing the correlation between acid insoluble matter, burning residue and various elements in limestone and marl, it is found that the contents of SiO2Al2O3, MnO2O2 and Cr are closely related to the content of acid-insoluble substance. In particular, the correlation between SiO2 and acid insoluble was 0.93. On this basis, the source of elements is analyzed to provide a reliable element basis for the study of lime-marl rhythms. The paleoclimate and paleoclimate during the formation of lime-mudstone rhythmic layer were studied by the analysis of paleo oxygen phase U / T, paleosalinity Sr / Ba, ancient water depth MNO and paleoclimate Sr/Cu. It is considered that the rhythmic layer of limestone and marl was formed in the sedimentary environment of oxygen-poor marine high water level system tract in hot climate. Paleoclimate and differential diagenesis are the main genesis of lime-marl rhythm layer, in which the rhythm and fluctuation of paleoclimate control the paleoenvironment and geochemistry of the rhythmic layer at large macro scale. The differential diagenesis further controls and affects the differentiation and rhythm of the geochemical characteristics of the prosodic strata on a small microscopic scale.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P534.44

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