本文選題：黏土礦物 + 化學(xué)風(fēng)化指數(shù)(CIA)��； 參考：《中國地質(zhì)大學(xué)》2017年博士論文

【摘要】：二疊紀(jì)末(~250Ma)發(fā)生了地史時(shí)期最具災(zāi)難性的集群滅絕事件,約90%的海洋生物種、70%的陸地脊椎動(dòng)物及絕大數(shù)陸地植物在這次事件中消亡。盡管歷經(jīng)幾十年的不懈努力,這次地史上最大生物滅絕事件的觸發(fā)機(jī)制及滅絕機(jī)制至今未有最終定論。目前最廣為接受的是以二疊紀(jì)末-三疊紀(jì)初強(qiáng)烈的火山活動(dòng)為最終觸發(fā)機(jī)制、其派生產(chǎn)物——?dú)夂颦h(huán)境惡化(包括全球變暖、海陸酸化等)為滅絕機(jī)制的假說。然而假說是否成立,仍需沉積記錄的直接驗(yàn)證,其第一步即是全面系統(tǒng)地查明二疊紀(jì)-三疊紀(jì)之交全球氣候變化、尋找海陸酸化的地質(zhì)證據(jù),然后才可能在精確的年齡框架內(nèi)探討氣候環(huán)境與火山活動(dòng)、生物滅絕之間的時(shí)間序列關(guān)系與因果關(guān)系。對(duì)于P-Tr之交古環(huán)境氣候演變,目前最大的進(jìn)展是生物成因氧同位素定量恢復(fù)古氣溫的研究,其結(jié)果證明了晚二疊世末全球氣候變暖的事實(shí)。然而氣候環(huán)境變化的其它方面,如氣候變干還是變濕、化學(xué)風(fēng)化作用增強(qiáng)還是減弱,是否存在酸化等問題還廣受爭(zhēng)議。因此本論文就針對(duì)以上問題,擬通過對(duì)華南4條海相剖面(揚(yáng)子地臺(tái)北緣:上寺、甘溪;揚(yáng)子地臺(tái)南緣:新民、東攀)和1條陸相剖面(揚(yáng)子地臺(tái)西緣滇東魯貝)進(jìn)行高分辨率黏土礦物及CIA等指標(biāo)的綜合分析研究,以期為探明華南P-Tr之交古氣候環(huán)境演變提供證據(jù)支持。本文研究過程及取得結(jié)論如下:(1)通過對(duì)各研究剖面穩(wěn)定主微量元素比值(如Al2O3/TiO_2、Zr/Hf,Zr/Sc、Nb/Ta、Th/Sc等)、稀土元素配分模式(和TOC)的縱向變化及對(duì)比得出:揚(yáng)子北緣上寺、甘溪剖面物源成分及縱向變化相似,但自N.changxingensis帶向上變化不顯著;揚(yáng)子南緣新民剖面和東攀剖面物源成分相差較大,前者更偏基性,后者偏酸性,且前者在P-Tr界線上下具有較為明顯的物源變化,而后者幾乎無變化;魯貝剖面物源為峨眉山玄武質(zhì),縱向無變化,物源較穩(wěn)定。(2)通過X射線粉晶衍射分析(XRD)、掃描電鏡/透射電鏡(SEM/TEM)觀察以及巖石熱解分析(Rock-eval)等手段綜合判斷華南黏土礦物組合特征及其影響因素。結(jié)果表明黏土礦物組合具有明顯的地域性:揚(yáng)子北緣P-Tr剖面黏土礦物組成以伊利石+伊蒙混層為主,綠泥石含量在二疊系頂部開始出現(xiàn)并向三疊系增加,上寺剖面界線附近另含蛭石礦物;揚(yáng)子南緣P-Tr剖面黏土礦物組成復(fù)雜,以伊利石質(zhì)+綠泥石質(zhì)礦物為主,伊蒙、綠蒙、綠蛭等混層礦物發(fā)育,東攀剖面P-Tr界線及其之上含蛭石;滇東魯貝剖面黏土礦物亦以伊利石質(zhì)+綠泥石質(zhì)礦物為主,含少量高嶺石和蛭石;揚(yáng)子南緣、滇東魯貝剖面黏土礦物組成較揚(yáng)子北緣富含綠泥石質(zhì)礦物,其原因主要是物源富鎂鐵質(zhì),這與它們距離峨眉山玄武巖較近及晚二疊世末揚(yáng)子南緣發(fā)育大量海相玄武巖有關(guān)。同時(shí),綜合各剖面巖石裂解分析、有機(jī)質(zhì)鏡質(zhì)體反射率Ro、火山粘土巖伊蒙混層中伊利石層片含量(上寺最低:50-60%;東攀、魯貝剖面中等:70-80%;甘溪、新民最高:90%)以及SEM/TEM觀察,筆者認(rèn)為各剖面黏土礦物明顯受成巖作用影響,但影響程度各不相同:揚(yáng)子北緣剖面以蒙脫石的伊利石化為主,上寺剖面轉(zhuǎn)化程度最低,成巖作用程度最小,同時(shí)非混層礦物伊利石和綠泥石在揚(yáng)子北緣不受成巖作用主導(dǎo);揚(yáng)子南緣剖面成巖作用則以蒙脫石的伊利石化和綠泥石化為主,且成巖轉(zhuǎn)化在二疊系碳酸鹽巖層位更高,東攀剖面是研究剖面中唯一仍含R0型伊蒙混層的剖面,其原因可能是該剖面缺乏蒙脫石轉(zhuǎn)化所需的K+;滇東魯貝剖面黏土礦物成巖作用亦以蒙脫石的綠泥石化和伊利石化為主,成巖轉(zhuǎn)化在二疊系較為粗粒的層位及三疊系比較顯著。(3)評(píng)估了成巖作用影響后,整體上華南P-Tr之交黏土礦物蘊(yùn)含向上逐漸干旱化的氣候趨勢(shì),但各區(qū)域表現(xiàn)形式不盡相同:揚(yáng)子北緣剖面綠泥石在二疊系頂部出現(xiàn)并向三疊系逐漸增加、伊利石結(jié)晶度亦從二疊系向三疊系增加;揚(yáng)子南緣東攀剖面R0型伊蒙混層、高嶺石向上逐漸減少、伊利石結(jié)晶度反而略有略增加;滇東魯貝剖面則表現(xiàn)在高嶺石向上逐漸減少,并伴隨煤層/線的向上減薄消失、好溫喜濕Gingantopteris植物群被相對(duì)更適應(yīng)干旱氣候的Peltaspermum盾籽類為主體的植物面貌所代替。但總體上,氣候在P-Tr附近的干旱化是循序漸進(jìn)的,直至界線之上約0.08Ma才出現(xiàn)干旱化的快速加強(qiáng)。(4)為探究華南P-Tr之交化學(xué)風(fēng)化強(qiáng)度變化,筆者計(jì)算了各剖面化學(xué)風(fēng)化指數(shù)CIA,結(jié)果表明揚(yáng)子北緣剖面CIA受碳酸鹽含量影響很大,其值與CaO及方解石含量呈明顯的此消彼長的變化關(guān)系,表明CIA在揚(yáng)子北緣剖面應(yīng)用受化學(xué)沉積影響大;而揚(yáng)子南緣新民剖面除了碳酸鈣含量影響CIA的應(yīng)用外,過多的火山物質(zhì)也是限制CIA應(yīng)用的一大原因,因此也無法用來恢復(fù)化學(xué)風(fēng)化強(qiáng)度變化。相比之下?lián)P子南緣東攀剖面與滇東魯貝剖面樣品以細(xì)粒碎屑巖為主,生物化學(xué)碳酸鹽組分極少,物源保持一致且后期成巖改造影響小,因此是較為合適的CIA應(yīng)用剖面。結(jié)果顯示,東攀剖面CIA值域在75-90之間,而魯貝剖面CIA二疊系則近100,均有從二疊系到三疊系減小的趨勢(shì),但從二疊系至P-Tr界線附近減小程度微弱,表明化學(xué)風(fēng)化作用雖有減弱,但不明顯或基本無變化;而化學(xué)風(fēng)化的快速減弱在P-Tr界線之上的三疊系底部(距P-Tr界線約0.08Ma),該變化在魯貝剖面有記錄,海相東攀剖面三疊系因采樣地層較短樣品較少,沒有到達(dá)對(duì)比于魯貝剖面CIA快速降低的層位,因此無此記錄。(5)為驗(yàn)證黏土礦物得出的氣候干旱化,本文還增加了魯貝剖面環(huán)境磁學(xué)特征的實(shí)驗(yàn),結(jié)果表明該剖面P-Tr界線之下磁性礦物以主要形成于溫暖潮濕氣候環(huán)境中的磁鐵礦為主,三疊系中赤鐵礦(和磁赤鐵礦)等主要形成和保存于高溫干旱、氧化環(huán)境中的磁性礦物取代磁鐵礦的主導(dǎo)地位,與前人在海相上寺、峽口及東攀剖面進(jìn)行的磁學(xué)實(shí)驗(yàn)得出相同的結(jié)論,結(jié)合黏土礦物及CIA數(shù)據(jù)變化,筆者認(rèn)為至少在華南,三疊系紅層應(yīng)為高溫干旱氣候條件下的產(chǎn)物,其磁性礦物轉(zhuǎn)變亦主要為沉積初期氣候環(huán)境變化的產(chǎn)物,而不是有些學(xué)者認(rèn)為的僅代表后期成巖作用中磁性礦物氧化的結(jié)果。(6)魯貝剖面CIA在三疊系東川組并非完全處于低值,而間歇性的出現(xiàn)極高值,這些高值恰好對(duì)應(yīng)更細(xì)粒的泥巖-粉砂巖同時(shí)相對(duì)于沉積的絕大部分細(xì)砂巖來說含有更多的磁鐵礦、具有更高的磁化率。這些泥巖-粉砂巖層位表明在三疊紀(jì)高溫干旱氣候大背景下氣候具有短暫間歇性的強(qiáng)降雨時(shí)期,具有明顯的季風(fēng)性氣候特點(diǎn)。而在二疊系,無論CIA還是磁化率在二疊系均沒有如此巨大的變化,因此季風(fēng)性氣候在三疊紀(jì)相對(duì)于二疊紀(jì)是明顯加強(qiáng)的。這從華南各沉積剖面三疊系的巖性旋回性比二疊系更明顯也可見一斑。(7)火山活動(dòng)CO_2氣體大量釋放及高溫能夠促進(jìn)硅酸鹽礦物的化學(xué)分解,化學(xué)風(fēng)化作用增強(qiáng),因此目前地學(xué)界廣泛“想當(dāng)然地”認(rèn)為在廣泛且強(qiáng)烈的火山活動(dòng)的大背景下,化學(xué)風(fēng)化作用在P-Tr之交應(yīng)是增強(qiáng)的;然而另一方面,P-Tr之交Pangea大陸特殊的分布格局使得季風(fēng)性氣候十分盛行,其特點(diǎn)是總體降水少、干旱,間歇有短期強(qiáng)降水,因此總體上是抑制化學(xué)風(fēng)化作用的。因此,筆者認(rèn)為,P-Tr之交及早三疊世氣候濕潤或干旱取決于火山活動(dòng)影響與季風(fēng)性氣候兩者之間的博弈。而就本論文研究結(jié)果顯示,至少在當(dāng)時(shí)的華南地區(qū),氣候總體是向干旱轉(zhuǎn)變的,表明大陸聯(lián)合引起的季風(fēng)性氣候可能略占上風(fēng)。(8)本文提出了華南P-Tr剖面中可用于反映陸地酸化的指標(biāo)——蛭石、HIM礦物。蛭石是一種膨脹性2:1型黏土礦物,在自然界中多形成于偏酸性的沉積環(huán)境中(pH范圍一般在4-6),是弱酸性土壤中常見的黏土礦物類型。HIM礦物是一種膨脹性黏土礦物間層被“島嶼狀”羥基鋁/鎂/鐵等聚合物充填的特殊黏土礦物,其形成及穩(wěn)定pH較蛭石偏低。在本論文上寺、東攀、魯貝剖面中,蛭石(和HIM礦物)僅存在于跨越各剖面P-Tr界線附近層位,且與碳同位素負(fù)偏及陸源物質(zhì)/炭屑大量輸入具有很好的對(duì)應(yīng)性。因此,筆者認(rèn)為二者的出現(xiàn)可能指示了陸地生態(tài)系統(tǒng)崩潰、植被破壞,大量偏酸性土壤物質(zhì)輸入沉積盆地的現(xiàn)象。另外蛭石、HIM礦物的出現(xiàn)與碳同位素負(fù)偏較好的對(duì)應(yīng)性,因此酸化很可能是P-Tr之交強(qiáng)烈的火山活動(dòng)釋放大量酸性氣體的結(jié)果。(9)關(guān)于華南P-Tr之交氣候環(huán)境變化與生物滅絕之間的關(guān)系,根據(jù)本文的研究結(jié)果,筆者認(rèn)為氣候干旱化在二疊紀(jì)末-早三疊世最早期是循序漸進(jìn)且不顯著的,直到界線之上才出現(xiàn)迅速加強(qiáng),但植物滅絕層位附近廣泛發(fā)育的森林野火可能是造成陸地植物滅絕及生態(tài)崩潰的一大原因。另一方面,滅絕界線附近的迅速升溫則可能是導(dǎo)致海陸生物滅絕的主要原因。但更精細(xì)的研究仍在進(jìn)行以期檢驗(yàn)溫度驟升是否真正為生物滅絕的主要原因。同時(shí),就全球范圍來看,酸化證據(jù)目前在不同地域、甚至不同剖面與滅絕層位關(guān)系也是不一致的,酸化是否是生物滅絕的直接原因還有待于進(jìn)一步驗(yàn)證。
[Abstract]:At the end of the Permian period (~250Ma), the most catastrophic mass extinction event occurred in the history of the earth, about 90% of the marine species, 70% of the terrestrial vertebrates and the great number of terrestrial plants died out in this event. Despite the unremitting efforts of decades of unremitting efforts, the triggering mechanism and extinction mechanism of the largest biological extinction event in the earth's history have not been the most. The most widely accepted theory is that the most widely accepted triggering mechanism is the volcanic activity of the early Permian Late Triassic, and its production, the hypothesis of the extinction mechanism of climate and environment (including global warming, sea and land acidification, etc.). However, whether the hypothesis is established or not, the direct verification of sedimentary records is still needed, and the first step is a comprehensive system. To find out the global climate change at the Permian Triassic period and find the geological evidence for the acidification of the sea and land, then it is possible to explore the time series relation and causality between the climate environment and the volcanic activity, the extinction of the organisms in the exact age frame. The biggest progress is the biogenic oxygen same at present in the evolution of the Paleoenvironment of P-Tr. The results of the quantitative restoration of the paleo temperature by the position element have proved the fact that the global climate warming at the end of the Late Permian. However, other aspects of the climate and environment change, such as the climate change or the wetting, the chemical weathering enhancement or weakening, and the existence of acidification are still widely disputed. 4 southern marine sections (the northern margin of the Yangtze Platform: Shangsi, Gan Xi, the southern margin of the Yangzi platform: Xinmin, East Panzhihua) and 1 continental facies profiles (the western margin of the Yangtze platform) in the comprehensive analysis of high resolution clay minerals and CIA, in order to provide evidence for the exploration of the evolution of the paleoclimate environment at the intersection of the Southern China P-Tr. The conclusions are as follows: (1) through the stability of the main trace elements ratio (such as Al2O3/TiO_2, Zr/Hf, Zr/Sc, Nb/Ta, Th/Sc, etc.) and the longitudinal variation and comparison of the distribution pattern of rare earth elements (and TOC), the source composition and longitudinal variation of the Gansu Creek profile are similar, but the upward variation of the N.changxingensis zone is not significant, and the south of the Yangtze is not significant. The source composition of the margin Xinmin section and the East Panzhihua section is quite different, the former is more basic and the latter is partial acid, and the former is more obvious in the P-Tr boundary, and the latter is almost unchanged. The source of the lube section is the basalt of Mount Emei, the longitudinal and the source is stable. (2) through the X ray powder diffraction analysis (XRD), scanning electricity Mirror / transmission electron microscopy (SEM/TEM) observation and rock pyrolysis analysis (Rock-eval) are used to synthetically determine the characteristics of Southern China clay mineral assemblage and its influencing factors. The results show that the clay mineral assemblage has a distinct regionality: the clay minerals in the P-Tr section of the northern margin of the Yangtze River are mainly illite + imimon, and the content of chlorite in the top of the Permian system. The P-Tr section of the southern margin of the Yangtze River is complex with a complex mineral composition of clay minerals in the southern margin of the Yangtze, with illite and green muddy minerals as the main mineral, imimon, green Mongolia and green leech, and the P-Tr boundary and the vermiculite in the East Panzhihua section. The main green and muddy mineral mineral contains a small amount of kaolinite and vermiculite, and the southern margin of the Yangtze River, the clay mineral composition of the Lubei section in the east of Yunnan is rich in green mudstone minerals in the northern margin of the Yangtze, mainly due to its MgO rich source, which is related to their close proximity to the Mount Emei basalt and the development of a large number of marine basalts at the southern margin of the Late Permian Yangtze. The analysis of rock cracking in each section, the reflectance of the organic vitrinite Ro, the illite content in the illite layer of the volcanic clay rock (the lowest: the upper Temple: 50-60%; the East climbing, the Lubei section medium: 70-80%; Gan Xi, the Xinmin highest: 90%) and the SEM/TEM observation, the author thinks that the clay minerals in each section are obviously influenced by the diagenesis, but the influence degree is different: Yang The northern margin of the sub section is dominated by illite in montmorillonite, with the lowest transformation degree in the Shangsi section and the smallest diagenesis. At the same time, the illite and chlorite are not dominated by the diagenesis in the northern margin of the Yangtze, and the diagenesis of the southern margin of the Yangtze River is mainly montmorillonite illite and green mud petrifaction, and the diagenesis is converted to Permian carbon. The strata of the acid salt rock are higher, and the East Panzhihua section is the only section of the R0 immont mixed layer in the study section. The reason may be that the section lacks the K+ required for the transformation of montmorillonite, and the clay mineral diagenesis of the eastern Yunnan Rubei section is mainly of the montmorillonite's Greenstone and illite petrochemistry, and the diagenesis is converted to the coarse-grained layers of the Permian and three fold. (3) (3) after evaluating the influence of diagenesis, the climate trend of the clay minerals in Southern China on the whole is gradually arid, but the forms in each region are different: the chlorite in the northern margin of the Yangtze River appears at the top of the Permian and gradually increases to the Triassic, and the illite crystallinity is also increased from the Permian to the Triassic. In the East Panzhihua section of the southern margin of the Yangtze River, the R0 imimon mixed layer, the kaolinite gradually decreases, and the illite crystallinity slightly increases; in the east of Yunnan, the profile of the kaolinite decreases gradually, with the upward thinning of the coal seam / line, and the good temperature and humid Gingantopteris plants are relatively adaptable to the Peltaspermum shield seed of the drought climate. On the whole, the drought of the climate in the vicinity of P-Tr is gradual, and the rapid strengthening of the droughts on the boundary is about 0.08Ma. (4) in order to explore the changes in the chemical weathering intensity of the Southern China P-Tr, the author calculated the chemical weathering index CIA of each section, and the result indicates that the CIA in the northern margin of the Yangtze is carbonated. Salt content has a great influence on the variation of the value of CaO and calcite content, which indicates that the application of CIA in the northern margin of the Yangtze River is greatly influenced by chemical deposition, and in addition to the application of calcium carbonate content in the Xinmin section of the southern margin of the Yangtze, excessive volcanic material is also a major reason for limiting the application of CIA, so it can not be used. To restore the change of chemical weathering intensity, the East Panzhihua section of the southern margin of the Yangtze River and the Lubei section in the southern margin of the Yangtze River are mainly fine grained clastic rocks, with few biochemical carbonate components, consistent source and late diagenetic transformation, so it is a more suitable CIA application section. The CIA Permian in the Lubei section is nearly 100, which decreases from Permian to Triassic, but decreases slightly from the Permian to the P-Tr boundary, indicating that chemical weathering has weakened, but not obvious or basically unchanged, and that the chemical weathering weakens at the bottom of the Triassic system above the P-Tr boundary (P-Tr boundary is about 0.08Ma). There is a record in the Lubei section, and the Triassic in the East Panzhihua section of the marine facies is less than the sample of short samples, and there is no comparison to the rapid reduction of CIA in the lube section. Therefore, there is no such record. (5) in order to verify the climate droughts obtained from clay minerals, this paper also increased the experiment of the environmental magnetic characteristics of lube's surface, and the results show that the section P-Tr The magnetic minerals under the boundary line are mainly magnetite formed in the warm and humid climate, and the Triassic hematite (and magnetite) is mainly formed and preserved in the high temperature and drought, and the magnetic minerals in the oxidizing environment replace the magnetite, and the magnetic experiments carried out with the predecessors in the upper monastery, the channel and the East Panzhihua section With the same conclusion, combined with clay minerals and CIA data changes, I think the red layer of the Triassic should be a product of high temperature and drought climate at least in Southern China, and its magnetic mineral transformation is also the product of the climate change at the early stage of the deposition, but not some scholars believe that the magnetic mineral oxidation in the late diagenesis is only a result of the formation of magnetic mineral oxidation. (6) the CIA section of the Ru Bei section is not completely at low value in the Triassic Dongchuan formation, but has a high value intermittently. These high values just correspond to more fine grained mudstone and siltstone with more magnetite and higher magnetization ratio relative to most of the fine sandstones. These mudstone siltstone layers indicate that the Triassic period was in the Triassic period. Under the high temperature and drought climate, the climate has a short period of intermittent strong rainfall and has a distinct monsoon climate characteristics. In the Permian, no matter the CIA or the susceptibility of the Permian in the Permian, the monsoon climate is obviously strengthened in the Triassic period relative to the Permian period. This is three overlapping sections in Southern China. The lithologic cyclicity of the system is more obvious than that of the Permian. (7) the mass release of CO_2 gas and the high temperature can promote the chemical decomposition of silicate minerals and enhance the chemical weathering. Therefore, the chemical weathering effect of chemical weathering in P-Tr is now widely considered in the field of extensive and intense fire mountain activities. On the other hand, on the other hand, the special distribution pattern of the Pangea continent at the turn of P-Tr makes the monsoon climate very prevalent, which is characterized by less overall precipitation, drought and short-term strong precipitation, which is therefore generally inhibited by chemical weathering. Therefore, the author considers that the early three fold climate wetness or drought depends on the early three fold climate or drought. A game between volcanic activity and monsoon climate, and the results of this study show that at least in the Southern China region at that time, the climate changed to drought in general, indicating that the monsoon climate caused by the continental union may have a slight upper wind. (8) this paper presents the indicators that can be used to reflect the acidification of the land in the Southern China P-Tr section. Vermiculite, HIM mineral. Vermiculite is an expansive 2:1 clay mineral, which is mostly formed in acidic sedimentary environment (pH range is generally in 4-6). It is a common clay mineral type in weak acid soil,.HIM mineral is a special clay filled clay mineral interlayer filled with "island" hydroxy aluminum / magnesium / iron and other polymers. Mineral, its formation and stability pH is lower than vermiculite. In this paper, the vermiculite (and HIM minerals) in the temple, East Panzhihua and Lubei sections in this paper only exist near the horizon of the P-Tr boundary across various sections, and have good correspondence with the negative carbon isotope bias and the heavy input of the terrestrial matter / carbon chips. The system collapse, vegetation destruction, a large amount of acidic soil material into the sedimentary basin. In addition, the vermiculite, HIM mineral appears to be in good correspondence with carbon isotopes, so acidification is likely to be the result of the release of a large number of acidic gases from the strong volcanic activity of P-Tr. (9) the climate change and biological extinction at the Southern China P-Tr According to the results of this study, the author believes that the early stage of climate droughts is gradual and not significant at the early stage of the Late Permian to the early three fold, and it is not very significant until the boundary, but the widespread forest wildfires near the plant extinction horizon may be a major cause of the extinction of the terrestrial plants and the ecological collapse. On the other hand, rapid warming near the extinction boundary may be the main cause of the extinction of the sea and sea, but more elaborate studies are still being carried out to test whether the sudden rise in temperature is the main cause of extinction. It is also inconsistent. Whether acidification is the direct cause of extinction is still to be further verified.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：P532;P59
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本文編號(hào)：2012816