【作者】 胡广；

【导师】 胡文瑄；

【作者基本信息】 南京大学 ， 能源地质学， 2012， 博士

【摘要】 中国东南部晚中生代地层主要以侵入岩、火山岩为主,实际上,在这套侵入岩和火山岩为主的地层中还广泛发育一套碎屑沉积岩。目前对于这些黑色泥页岩的具体形成时间、形成环境和生烃潜力还少有报道。本次研究以下白垩统黑色泥页岩为重点,在全区挑选了11条典型下白垩统剖面,进行了放射性年代学、沉积学、地球化学等多学科综合研究,得出以下几点初步认识：(1)中国东南部下白垩统黑色泥页岩主要发育层位为浙江省永康群中的馆头组和浙江沿海地区的石浦群,江西省火把山群中的石溪组,福建省的坂头组和广东省的水底山组。对这些层位典型剖面锆石U-Pb定年研究后发现浙东沿海的石浦群应该与浙东的九里坪上段,馆头组以及朝川组下段对比；江西省石溪组的开始沉积时间和浙江馆头组大体相当,建议将江西的火把山群与浙江永康群对比。对于福建坂头组,永安盆地的坂头组开始年龄为144±2Ma,而崇安盆地坂头组的开始沉积年龄为116±2Ma。因此建议将崇安盆地坂头组与永安盆地吉山剖面第21-32层对比,可与馆头组和朝川组对比。(2)全区来看下白垩统黑色泥页岩可以分成上下两套,其中早白垩世早期黑色泥页岩主要分布于广东和闽西地区,以广东大亚湾水底山组和福建永安坂头组下部黑色泥页岩最为典型,形成时间为134+2Ma；早白垩世晚期黑色泥页岩分布相对普遍,典型的例如浙江馆头和石浦群、江西的石溪组和福建的坂头组。形成时间在113±3Ma到100±2Ma之间。(3)针对广泛发育的早白垩世晚期那套黑色泥页岩,我们对其沉积环境进行了岩石学、古生物学和地球化学综合研究,发现这套黑色泥页岩均受海侵的影响。海侵的西界终止于武夷山山脚,而北界至少到达28°N。古太平洋向西俯冲导致的中国东南部快速断陷沉降是早白垩世海侵的主要原因,当然高的早白垩世海平面也是海侵的必要条件。(4)对浙江石浦和福建崇安两条典型剖面中黑色泥页岩的总有机碳含量、总氮含量以及有机碳同位素分析发现晚期这套黑色泥页岩中至少可以识别出五次碳同位素负偏事件SI～SV和CI～CV。其中事件SIV、SV、CIV和CV中黑灰色泥岩段中有机质含量和有机碳同位素的负偏主要受控于高等植物的输入。而对于事件SⅠ～SⅢ和CⅠ～CⅢ,控制其碳同位素负偏的原因可能是大气二氧化碳库的扰动。与北特提斯洋盆和太平洋平顶山OAE1b对比研究结果表明负偏事件SⅠ～SⅢ和CⅠ～CⅢ不仅在时间与OAE1b吻合,且在碳同位素变化趋势和模式上极其相似。(5)对中国东南部下白垩统黑色泥页岩的生烃潜力研究表明,两套黑色泥页岩的有机质丰度总体达到中等—好的烃源岩标准,并且早期优于晚期；有机质类型以Ⅲ型为主,晚期好于早期；有机质热演化总体大部分进入成熟-高成熟演化阶段,部分受火山作用影响的处于过成熟演化阶段。早期粤北地区成烃潜力较大；而晚期浙江沿海和闽西地区的潜力较大。更多还原

【Abstract】 A set of clastic sedimentary rocks, particularly black shales, developed widely in the upper Mesozoic, which is dominated by igneous rocks in southeastern China. However, the ages, sedimentary environments, and hydrocarbon potential of these black shales have not been studied in detail. In this work,11typical Lower Cretaceous sections outcropped black shales were investigated. Multidiscipline researches are concentrated on them including radiometric dating, sedimentology, and geochemistry and so on. Five preliminary conclusions were drawn.The formations that contain black shales are the Guantou Formation and the Shipu Group in Zhejiang Province, the Shixi Formation in Jiangxi Province, the Bantou formation in Fujian Province, and the Shuidishan Formation in Guangdong Province. The zircon U-Pb dating on these formations indicated that the Shipu Group is comparable to the upper Jiuliping, Guantou, and the lower part of Chaochuan formations, and the age of the base of Shixi Formation is roughly isochronous to the Guantou Formation in Zhejiang Province. The age of the base of Bantou Formation in the Yong’an basin of Fujian Province is144±2Ma, whereas, the age of the Bantou Formation in the Chong’an Basin is about116±2Ma. Thus we suggested that the Bantou Formation in the Chong’an section should correlate with the beds from No.21to32of the Yong’an section, and is comparable to the Guantou and Chaochuan formations in Zhejiang Province.The results of radiometric dating and stratigraphic research demonstrate that there are in general two sets of black shales, i.e., the lower part and the upper part of Lower Cretaceous. The lower part of Lower Cretaceous black shales are distributed regionally in Guangdong and Fujian provinces, which are represented by the Bantou Formation and the Shuidishan Formation. Their sedimentary ages are134±2Ma and144±2Ma, respectively. The upper part of Lower Cretaceous black shales develop widely in Fujian, Zhejiang, and Jiangxi provinces, i.e., the Bantou, Guantou, and Shixi formations. They were deposited from113±3Ma to100±2Ma.Comprehensive researches of petrography, paleontology and geochemistry were conducted to the upper part of Lower Cretaceous black shales. Results indicated that the black shales were influenced by marine transgression. The northern boundary of transgression extends at least to the28°N, while its western boundary is limited to the southeastern side of the Wuyi Mountains. The regional tectonic subsidence that stimulated by the raped westward subduction of the Paleo-Pacific plate accompanying with the overall high sea level is the main driving force for the transgression.Organic carbon isotope, total organic carbon, and total nitrogen were also analyzed for those black shales from the Shipu and Chong’an sections. At least five δ13Corg negative excursion events (events SI-SV for the Shipu section, events CI-CV for the Chong’an section) can be recognized in both sections. Relevant analyses of TOC, N/C ratios, and δ13Corg suggested that the events SIV, SV, CIV, and CV were caused by regional factors such as an increase in terrestrial plant detritus, whereas events SⅠ-SⅢ and CⅠ-CⅢ might result from global factors. The tentative correlation between the δ13Corg negative excursions SⅠ-SⅢ, CⅠ-CⅢ, and OAE1b in Tethys and Pacific implied that they are similar in stratigraphic carbon isotope. It suggests that the OAElb might be global events, and the black shales SI-SIII and CⅠ-CⅢ in costal southern China should be the equivalents to OAE1b. They are all the products of the disturbance of carbon isotope of CO2reservoir in the global ocean-atmosphere system.By detailed organic geochemical analyses including organic matter abundance, type and maturity of the Lower Cretaceous black shales in Southeastern China, the source rock features of the strata were revealed. The organic matter abundance of the sources reaches the medium to good quality hydrocarbon source rock standards, and the lower part of Lower Cretaceous is better. The organic matter type is mainly III, with types II and I also being found. The type of the upper part of Lower Cretaceous is better. The thermal maturity of most samples is mature to high mature, with some in mature stage by little influence of volcanic. Thus, a relatively comprehensive hydrocarbon resource evaluation indicates that the favorable regions are in the north of Guangdong Province for the early Lower Cretaceous and in the coastal region of Zhejiang Province and the west of Fujian Province for the late Lower Cretaceous.更多还原