新疆吉木薩爾凹陷二疊系蘆草溝組熱液噴流沉積特征及沉積環(huán)境
發(fā)布時間：2018-10-19 10:20
【摘要】：新疆吉木薩爾凹陷二疊系蘆草溝組(P21)是一套非常重要的致密油層。前人研究認(rèn)為蘆草溝組這套層位是正常的湖相沉積,發(fā)育湖相碎屑沉積和碳酸鹽沉積的過渡性巖類。根據(jù)研究團(tuán)隊多年來在準(zhǔn)噶爾盆地的研究,發(fā)現(xiàn)吉木薩爾凹陷所處盆地的東部地區(qū)從晚石炭世至中二疊世處于陸內(nèi)裂谷環(huán)境,且在沉積時期受到了巖漿熱液流體的影響,形成吉木薩爾凹陷特有的熱液噴流沉積環(huán)境。在該環(huán)境中除了發(fā)育正常沉積的陸源碎屑巖類外,還首次發(fā)現(xiàn)了與火山活動和巖漿活動相關(guān)的熱液噴流沉積巖(簡稱“噴積巖”)。熱液噴流沉積巖是與深源巖漿、熱液活動相關(guān)的巖石組合:紋層狀堿性-過堿性的中性(安山巖)凝灰?guī)r類和超基性(碳酸巖)凝灰?guī)r類,同時也發(fā)現(xiàn)了研究區(qū)內(nèi)有豐富的藻類和生物活動的跡象。本文對吉木薩爾凹陷二疊系蘆草溝組的巖石類型、礦物特征、沉積特征和形成環(huán)境進(jìn)行探討,得出以下認(rèn)識:(1)熱液噴流沉積巖主要分為五大類,以白云巖類和沉凝灰?guī)r類為主。區(qū)內(nèi)巖石沉積構(gòu)造類型多樣,主要發(fā)育水平層理和交錯層理,同時也發(fā)現(xiàn)包卷層理、泄水構(gòu)造等同生變形構(gòu)造,以及本區(qū)特殊的生物成因構(gòu)造。蘆草溝組發(fā)育的是一套與火山活動相關(guān)的沉凝灰?guī)r(火山碎屑巖)以及凝灰質(zhì)泥晶云巖、微生物白云巖等。通過巖石學(xué)、礦物學(xué)鑒定和綜合地球化學(xué)測試分析,認(rèn)為本區(qū)的礦物組合是在特殊環(huán)境下形成的,與巖漿地幔熱液、火山活動相關(guān)的熱液噴流沉積組合。(2)根據(jù)蘆草溝組巖石的地球化學(xué)實驗分析,得出以下結(jié)論:①碳、氧同位素實驗分析得出,研究區(qū)在沉積時期處于鹽度偏高,水循環(huán)較差,蒸發(fā)速度較快的湖泊環(huán)境中,且受到了熱液流體與湖水的混合作用。②根據(jù)主、微量元素實驗分析,通過樣品的釩(V)、鎳(Ni)、鍶(Sr)、鋇(Ba)以及氧化還原敏感元素比值,指示其處于鹽度較高、缺氧的陸相沉積環(huán)境。③稀土元素方面,樣品呈現(xiàn)輕稀土(LREE)較為富集右傾配分模式,且出現(xiàn)了較弱的Ce正異常和Eu負(fù)異常的特征,反映了處在一種弱氧化的、還原的偏堿性且形成溫度較低的沉積環(huán)境中。(3)蘆草溝組熱液噴流沉積巖層中存在一些不同于正常礦物的特殊生物形態(tài),部分很好的保存了生物結(jié)構(gòu)特征,且在生物死后被其他礦物所交代。常見到黃鐵礦化、膠磷礦化、硅化的生物形態(tài)以及一些生物的空腔和骨骼碎片。通過交代礦物的結(jié)構(gòu)和類型推測可能是介形蟲、三葉蟲等生物。這類生物主要出現(xiàn)在泥晶級的白云巖層中,與巖漿成因的方解石關(guān)系密切,猜測這類生物的存在也是與巖漿熱液活動相關(guān)的。
[Abstract]:The Permian Lucaogou formation (P 21) in Jimusar depression, Xinjiang is a very important compact reservoir. It is considered that the Lucaogou formation is a normal lacustrine sedimentary, lacustrine clastic deposit and carbonate sedimentary transitional rock. Based on the research conducted by the research team in Junggar Basin for many years, it was found that the eastern part of the basin in the Jimusar depression was in an intracontinental rift environment from the late Carboniferous to the Middle Permian, and was influenced by magmatic hydrothermal fluid during the sedimentary period. Forming the unique hydrothermal jet deposition environment in Jimusar sag. In addition to the normal sedimentary terrigenous clastic rocks, hydrothermal jet sedimentary rocks related to volcanic and magmatic activities were first discovered in this environment. Hydrothermal jet sedimentary rocks are rock assemblages related to deep magma and hydrothermal activity: lamellar alkaline-peralkaline neutral (andesite) tuff and ultrabasic (carbonate) tuff. At the same time, there are abundant signs of algae and biological activities in the study area. In this paper, the rock types, mineral characteristics, sedimentary characteristics and forming environment of the Permian Lucaogou formation in Jimusar depression are discussed, and the following conclusions are obtained: (1) hydrothermal jet sedimentary rocks are divided into five main types, dolomite and tuff. There are various types of sedimentary structures in the area, mainly developing horizontal bedding and staggered bedding. At the same time, cogeneration deformation structures such as enclosing bedding, drainage structure, and special biogenic structures in the area are also found. The Lucaogou formation has developed a set of sedimentary tuff (pyroclastic rock) associated with volcanic activity as well as tuffaceous mudstone and microorganism dolomite. Through petrology, mineralogical identification and comprehensive geochemical testing and analysis, it is concluded that the mineral assemblages in this area were formed under special circumstances, and were associated with magmatic mantle hydrothermal solution. (2) based on the geochemical analysis of the rocks of the Lucaogou formation, the following conclusions are drawn: 1 carbon and oxygen isotopic experiments show that the studied area is relatively high in salinity and poor in water cycle during the sedimentary period. In the lake environment with fast evaporation rate, the mixing of hydrothermal fluid and lake water was carried out. 2 according to the experimental analysis of main and trace elements, the vanadium (V), nickel (Ni), strontium (Sr), barium (Ba) and the ratio of redox sensitive elements were obtained. It is indicated that the samples are in a high salinity and anoxic terrestrial sedimentary environment. 3 the samples show a relatively enriched right-dip distribution pattern of light rare earth (LREE), and show the characteristics of weak Ce positive anomaly and Eu negative anomaly. It reflects that there are some special biological forms in the hydrothermal jet sedimentary strata of the Lucaogou formation which are different from the normal minerals in a weakly oxidized, reduced alkalinity and low temperature sedimentary environment. Some of the biologic features are well preserved and are accounted for by other minerals after the death of the organism. Pyrite mineralization, phosphate mineralization, silicification, and some biological cavities and bone fragments are common. The structure and types of metasomatic minerals may be ostracods and trilobites. This kind of organism mainly appears in mud-grained dolomite strata and is closely related to the calcite of magmatic origin. It is assumed that the existence of this kind of organism is also related to magmatic hydrothermal activity.
【學(xué)位授予單位】：西北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P618.13
，
本文編號：2280846
[Abstract]:The Permian Lucaogou formation (P 21) in Jimusar depression, Xinjiang is a very important compact reservoir. It is considered that the Lucaogou formation is a normal lacustrine sedimentary, lacustrine clastic deposit and carbonate sedimentary transitional rock. Based on the research conducted by the research team in Junggar Basin for many years, it was found that the eastern part of the basin in the Jimusar depression was in an intracontinental rift environment from the late Carboniferous to the Middle Permian, and was influenced by magmatic hydrothermal fluid during the sedimentary period. Forming the unique hydrothermal jet deposition environment in Jimusar sag. In addition to the normal sedimentary terrigenous clastic rocks, hydrothermal jet sedimentary rocks related to volcanic and magmatic activities were first discovered in this environment. Hydrothermal jet sedimentary rocks are rock assemblages related to deep magma and hydrothermal activity: lamellar alkaline-peralkaline neutral (andesite) tuff and ultrabasic (carbonate) tuff. At the same time, there are abundant signs of algae and biological activities in the study area. In this paper, the rock types, mineral characteristics, sedimentary characteristics and forming environment of the Permian Lucaogou formation in Jimusar depression are discussed, and the following conclusions are obtained: (1) hydrothermal jet sedimentary rocks are divided into five main types, dolomite and tuff. There are various types of sedimentary structures in the area, mainly developing horizontal bedding and staggered bedding. At the same time, cogeneration deformation structures such as enclosing bedding, drainage structure, and special biogenic structures in the area are also found. The Lucaogou formation has developed a set of sedimentary tuff (pyroclastic rock) associated with volcanic activity as well as tuffaceous mudstone and microorganism dolomite. Through petrology, mineralogical identification and comprehensive geochemical testing and analysis, it is concluded that the mineral assemblages in this area were formed under special circumstances, and were associated with magmatic mantle hydrothermal solution. (2) based on the geochemical analysis of the rocks of the Lucaogou formation, the following conclusions are drawn: 1 carbon and oxygen isotopic experiments show that the studied area is relatively high in salinity and poor in water cycle during the sedimentary period. In the lake environment with fast evaporation rate, the mixing of hydrothermal fluid and lake water was carried out. 2 according to the experimental analysis of main and trace elements, the vanadium (V), nickel (Ni), strontium (Sr), barium (Ba) and the ratio of redox sensitive elements were obtained. It is indicated that the samples are in a high salinity and anoxic terrestrial sedimentary environment. 3 the samples show a relatively enriched right-dip distribution pattern of light rare earth (LREE), and show the characteristics of weak Ce positive anomaly and Eu negative anomaly. It reflects that there are some special biological forms in the hydrothermal jet sedimentary strata of the Lucaogou formation which are different from the normal minerals in a weakly oxidized, reduced alkalinity and low temperature sedimentary environment. Some of the biologic features are well preserved and are accounted for by other minerals after the death of the organism. Pyrite mineralization, phosphate mineralization, silicification, and some biological cavities and bone fragments are common. The structure and types of metasomatic minerals may be ostracods and trilobites. This kind of organism mainly appears in mud-grained dolomite strata and is closely related to the calcite of magmatic origin. It is assumed that the existence of this kind of organism is also related to magmatic hydrothermal activity.
【學(xué)位授予單位】：西北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P618.13
，
本文編號：2280846
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