准东北石炭系火山岩岩石学、地球化学及Lu异常研究

发布时间：2018-01-03 06:13

本文关键词：准东北石炭系火山岩岩石学、地球化学及Lu异常研究　出处：《中国矿业大学》2016年博士论文　论文类型：学位论文

【摘要】：准噶尔盆地东北地区位于中亚增生造山带(CAOB)的关键部位,经历了多阶段不同性质的演化和变革。火山岩岩石学和地球化学研究对地球深部信息提取、限定构造演化背景、反演岩浆演化过程具有重要意义。本论文以准噶尔盆地东北部乌伦古坳陷和陆梁隆起为重点研究区,以英2井、乌参1井、滴北1井、滴北2井等油气探井钻遇的石炭系火山熔岩、火山碎屑岩为研究对象,系统分析了钻井岩芯、录井岩屑、地球化学、测井和地震等资料,开展了大量岩石薄片鉴定和主量元素、微量元素等地球化学测试,探讨了该区石炭系火山岩岩石学特征及火山岩源区与构造背景,发现了在该区石炭系火山岩样品中存在的显著Lu富集异常特征,开展了Lu元素富集异常限定的微量元素与稀土元素地球化学模拟,并讨论了其地质意义。研究工作取得如下主要成果和认识:通过岩石学研究,将准噶尔盆地东北部石炭系火山岩划分为火山熔岩类、火山碎屑岩类、火山沉积岩类三个岩石类型和爆发相、喷溢相、火山通道相和火山-沉积相四个岩相类型。有机地球化学信息指示乌伦古坳陷早石炭世处于局限海环境;在早石炭世晚期,沉积水体发生显著咸化,且缺乏陆源有机质的加入;在乌伦古坳陷下石炭统识别出了浮岩状熔积岩,是早石炭世晚期乌伦古坳陷存在海底岩浆侵入的直接证据;通过对沉积背景的研究,将本区火山-沉积相进一步划分为自碎火山岩沉积亚相、扇三角洲沉积亚相、风暴沉积亚相和水下扇沉积亚相四种亚相。火山-沉积相的研究对该区的地质勘探具有重要启示。Rb、U、Ba、Sr和Pb等流体活动性元素与HFSE、REE流体不活动性元素的比值较好地反映了源自俯冲板片的活动性元素富集程度。本区石炭系火山熔岩样品具有较低的Sr/Nd比和U/Th比,意味着地幔源区受来自俯冲板片的流体的影响较小;样品中Y含量较高,Sr/Y较低,明显不同于俯冲洋壳部分熔融产生的埃达克熔体,表明俯冲洋壳熔体对本区火山熔岩地球化学组成的贡献小;而本区石炭纪样品具有较低Ba/Th和较高的Th、Pb含量,同时具有较低的Ce/Th和Ce/Pb比值,表明本区石炭系火山熔岩样品受俯冲板片沉积物熔体影响较大。研究区样品具有相对较高的镁含量,同时微量元素和稀土元素分布模式与Setouchi和Ryukyu中部高镁安山岩类似。综上所述,本区石炭系火山熔岩源区受到俯冲板片上沉积物熔融产生的俯冲板片沉积物熔体的影响较大。微量元素地球化学特征与构造环境判别图解指示,准噶尔盆地东北部石炭系火山岩形成于大陆岛弧构造环境。准噶尔盆地东北地区石炭纪火山岩样品具有显著的重稀土元素Lu富集异常,这种显著的Lu富集异常在国内外都很罕见。重稀土元素具有极为相近的化学性质,在岩浆演化过程中较为稳定。Lu富集异常为我们提供了研究岩浆演化过程的重要信息。根据对本区石炭系火山熔岩源区信息的研究,对研究区英2井石炭系火山熔岩样品进行了微量元素与稀土元素地球化学模拟。模拟结果与样品地球化学特征符合较好,证实了俯冲板片沉积物熔体加入了地幔源区,并对该区石炭系火山岩样品的物质组成做出了贡献。因此Lu富集异常可以作为石炭纪准噶尔盆地卡拉麦里缝合线及其沿长线附近俯冲沉积物熔体加入岛弧火山岩岩浆源区的重要识别指标。
[Abstract]:In the northeastern Junggar basin is located in the central accretionary orogenic belt (CAOB) is the key part, multiple stages of the different nature of evolution and change. The deep information of petrology and geochemistry of the volcano on earth extraction, defined tectonic background, inversion of magma evolution has important significance. This paper takes Junggar basin in the northeast of ancient Wulun depression and Luliang Uplift as the key research area, to the British 2 black and 1 wells, wells, Dibei 1 wells, 2 wells of oil and gas in Dibei drilled Carboniferous volcano lava and volcano clastic rocks as the research object, systematic analysis of drilling cores, logging cuttings, geochemistry, logging and seismic the data, carried out a large number of rock slices identification and major elements, trace elements and geochemical testing, discusses the Carboniferous volcano rocks and source rocks and volcano tectonic background, found in the Carboniferous volcano rock In the presence of significant Lu enrichment anomaly, the trace elements and REE geochemical simulation of Lu enrichment anomaly defined, and discusses its geological significance. The research work made the following main achievements: through petrological study, the northeastern Junggar basin the Carboniferous volcano rocks into volcano lava and volcano clastic rock type, volcano sedimentary rocks of three types of rock and explosive facies, effusive facies, volcano and volcano - sedimentary facies Channel Four lithofacies types. Organic geochemical information indicating the Wulungu depression of Early Carboniferous in the restricted sea environment; in the late Early Carboniferous, significant sedimentary water salinization, and lack of terrigenous join organic matter; in the Wulungu depression of Lower Carboniferous identified pumice like peperite, is late Early Carboniferous Wulungu depression direct evidence for the existence of magma intrusion through the seafloor; sedimentary background The research in this area can be further divided into volcano - sedimentary facies autoclastic volcano sedimentary facies, fan delta subfacies, storm sedimentary subfacies and subaqueous fan subfacies four subfacies. Facies of volcano sedimentary has important implications for geological exploration in this area.Rb, U, Ba. Sr and Pb activities of fluid elements and HFSE, the ratio of REE fluid activity elements reflect the activity of the elements from the subducted slab. The enrichment degree of Carboniferous volcano lava samples with low Sr/Nd ratio and U/Th ratio, means that the mantle source region is less affected by fluid from subducted slab the Y content in the sample; high, low Sr/Y, significantly different adakitic melts from partial melting of subducted oceanic crust produced, showed that the subducted oceanic crust melt in this region the volcano lava geochemical composition contribution is small; while the region of Carboniferous samples with low Ba/Th and high Th, containing Pb At the same time, with the lower Ce/Th and Ce/Pb ratios, indicating that this region of Carboniferous volcano lava samples by subducted sedimentary melt influence. Samples of the study area has a relatively high content of magnesium, and trace elements and rare earth elements and the distribution patterns of central Setouchi and Ryukyu high Mg andesite is similar. In summary, the Carboniferous volcano the source of the lava area affected by the subducting slab on the sediment melt produced by subduction sediment melt greatly. Trace element geochemical characteristics and tectonic setting discrimination diagrams indicate that the Carboniferous volcano rocks in the northeastern Junggar basin formed in a continental island arc tectonic environment. The Carboniferous volcano rock samples in the northeastern Junggar basin has significant enrichment of heavy rare earth elements Lu this anomaly, significant Lu enrichment anomaly at home and abroad are very rare. The heavy rare earth elements have very similar chemical properties, in the magma The evolution of stable.Lu enrichment anomaly provides us with important information on the evolution process of magma. According to the study of the Carboniferous volcano lava information source, the study area well Ying 2 Carboniferous volcano lava samples of trace elements and REE geochemical simulation. The simulation results and the samples with geochemical characteristics well, that subducted sedimentary melt into the mantle source region, and the Carboniferous volcano rock samples of material composition and make a contribution. So Lu can be used as enrichment anomaly in Junggar Basin Carboniferous Kalamaili suture and the important index to identify long-term near subducted sedimentary melt into island arc volcano magma source region.

【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P588.14

【参考文献】