基于CSDP-2井的南黄海中部隆起构造热演化史研究

发布时间：2018-06-29 00:09

本文选题：南黄海盆地 + 中部隆起　；参考：《中国科学院大学(中国科学院海洋研究所)》2017年博士论文

【摘要】：中部隆起作为南黄海盆地面积最大的构造单元,是区域构造演化研究的关键区域,也是当前盆地资源调查的潜力区。基于南黄海中部隆起的第一口全取心深钻CSDP-2井,通过系统的岩心描述、分析测试、测井及地震解释等综合分析,采用多种研究方法和模拟技术,对中部隆起的埋藏史和构造热演化史进行了研究。CSDP-2井第一阶段钻探依次揭示新近系、三叠系、二叠系、石炭系及泥盆系部分地层。在地层格架建立、地震解释及剥蚀量计算的基础上,恢复了地层埋藏史。研究表明,中部隆起区在晚泥盆纪陆相沉积基础上,石炭纪开始海侵并转为海相沉积为主,但沉积速率较低,二叠纪早期沉积速率显著加快,早二叠世末期区域隆升及海退形成典型的海陆交互相沉积,进入三叠纪受印支运动影响,中部隆起处于挤压构造背景之下,CSDP-2井在二叠系泥岩段钻遇的地层滑脱面,推断为该期逆冲构造作用的结果,中-晚白垩世开始,中部隆起长期处于隆升剥蚀阶段,声波时差法计算的剥蚀厚度为1220m,镜质体反射率法估算的剥蚀厚度为1400m,直至新近纪时期全区的整体拗陷沉降,开始发育了一套未固结的松散沉积层。CSDP-2井测井揭示的恒温带深度约为80m,温度为15.8℃,中性点深度大致在1100m附近,现今地温梯度平均值变化范围在24.11~24.28℃/km。通过古地温梯度法、流体包裹体测温及磷灰石裂变径迹随机反演等对中部隆起热演化史进行了研究。结果显示晚古生界在石炭纪末期古地温在40℃左右,早二叠世有一期显著的升温过程并随后趋于平稳。至二叠纪末期存在短暂升温过程,三叠纪整体较为稳定,快速的升温过程出现在晚三叠世至早中侏罗世,此时中部隆起尚未发生大规模隆升剥蚀作用,地层厚度大,镜质体反射率模拟得到的石炭系最高古地温可达190℃,二叠系最高古地温可达170℃,最高古热流可达126mW/m~2,古地温梯度法计算得到的二叠系最高古地温梯度为59℃/km,远高于现今地温梯度。晚侏罗世开始的区域抬升引起古地温及热流均呈下降趋势,但早白垩世期间的盆地整体裂陷发育及陆相沉积速率的加快引起古热流及古地温小幅回升,至中-晚白垩世剥蚀速率加快,古地温持续降低,而古热流直到白垩纪末期盆地裂陷发育基本结束之后才开始下降。二叠系砂岩样品磷灰石裂变径迹热史反演结果显示其早白垩世期间尚未进入部分退火带,古地温约为100~140℃,与包裹体测温结果一致。热史反演结果反映两期明显的快速降温过程,自晚白垩世至古新世早期为一期冷却事件,古地温下降到约80℃,之后为缓慢降温过程,至渐新世末期进入另一期快速冷却过程,并持续到中新世早期。新近纪以来,古地温缓慢升高至现今地温状态。基于改进的McKenzie拉张模型理论,将地球动力学模拟技术与传统古温标法相结合,对南黄海北部坳陷进行构造热演化史研究,表明中部隆起和北部坳陷作为同属南黄海盆地的二级构造单元,其白垩纪以来的热史演化趋势具有一致性,整体表现为伸展断陷盆地的热史演化趋势特征,即裂陷期古热流逐渐增高,进入裂后期古热流开始降低,差异在于中部隆起古热流整体较北部坳陷低,前者晚白垩世末期最高约为70 mW/m~2,而北部坳陷古新世早期可达71.7~75.5 mW/m~2,最高可达80mW/m~2。
[Abstract]:The central uplift, which is the largest structural unit in the South Yellow Sea basin, is the key area for the study of regional tectonic evolution and the potential area of current basin resource investigation. The first full coring deep drilling CSDP-2, based on the central uplift of the South Yellow Sea, has been analyzed by comprehensive analysis of core description, analysis and testing, logging and seismic interpretation. Research methods and simulation techniques have been carried out on the burial history of the central uplift and the history of tectonic thermal evolution. The first stage drilling of.CSDP-2 well has revealed the Neogene, the Triassic, Permian, Carboniferous and Devonian parts. On the basis of the establishment of the stratigraphic framework, the seismic interpretation and the calculation of the amount of denudation, the history of the buried strata has been restored. On the basis of Late Devonian continental facies deposits in the middle uplift area, the Carboniferous period began to transgression and converted to marine sediments, but the deposition rate was lower, and the early Permian sedimentary rate was significantly accelerated. The regional uplift and sea retreat formed typical marine intercontinental sedimentary facies at the end of the early Permian, and the middle uplift was influenced by the Triassic Indosinian movement. Under the background of extrusion structure, the detachment surface of the formation of CSDP-2 well in the Permian mudstone section is deduced as the result of the thrust structure in this period. From the middle Late Cretaceous, the central uplift was long in the uplift and erosion stage, the thickness of the denudation calculated by the acoustic wave time difference method was 1220m, and the denudation thickness estimated by the vitrinite reflectance method was 1400m until recently. The whole depression subsidence of the whole region began to develop a set of unconsolidated loose sedimentary layer.CSDP-2 well logging revealed that the depth of the constant temperature zone was about 80m, the temperature was 15.8 degrees C, the depth of the neutral point was approximately 1100m, and the average variation range of the geothermal gradient was at 24.11~24.28 C / km. through the paleo geothermal gradient method and the fluid inclusions. The thermal evolution history of the middle uplift was studied by random inversion of apatite fission track. The results showed that the Paleozoic Paleozoic at the end of the Carboniferous period was about 40 C, and the early Permian period had a significant warming process and then tended to be stable. The course appeared from the late three fold to the early Middle Jurassic. At this time, the central uplift has not yet occurred large scale uplift and denudation, the thickness of the strata is large, the highest paleo temperature of the Carboniferous system obtained by the vitrinite reflectance simulation can reach 190 degrees C, the highest paleo temperature of the Permian system can reach 170 C, the highest paleo heat flow can reach 126mW/m~2, and the Permian system obtained by the paleo geothermal gradient method is calculated. The highest paleo geothermal gradient is 59 /km, far higher than the present geothermal gradient. The uplift of the late Jurassic caused the decline of the paleotemperature and heat flow, but the development of the overall rifting and the acceleration of the continental deposition rate during the early Cretaceous period caused the paleo heat and the paleo geotemperature to rise slightly, and the erosion rate of the middle Late Cretaceous accelerated and the ancient land was in the ancient land. The temperature continued to decrease, and the paleo heat flux began to decline until the end of the Cretaceous period. The inversion of the thermal history of the apatite fission track in the Permian sandstone sample shows that the early Cretaceous has not yet entered a part of the annealing zone, and the paleo geotemperature is about 100~140 C, which is in accordance with the results of the enveloped temperature measurement. The inversion results of thermal history reflect the results of the inversion of thermal history. Two distinct rapid cooling processes, from the late Cretaceous to the early Palaeocene epoch as one stage cooling event, descended to about 80 degrees C, and then slowly cooled down to another stage of the Oligocene to the early stage of the middle Miocene. Since the Neocene, the Paleogene temperature has been slowly rising to the present geothermal state. Based on the improved M CKenzie stretching model theory, combining the geodynamic simulation technique with the traditional paleo thermo scale method, studies the tectonic thermal evolution history of the northern depression of the South Yellow Sea. It shows that the central uplift and the northern depression are the two level tectonic units of the South Yellow Sea basin, and the thermal history evolution trend since the Cretaceous period is consistent, and the overall performance is extension. The thermal history trend of the basin is characterized by the gradual increase of the paleo heat flow in the period of the rifting period and the decrease of the paleo heat flow in the late stage of the crack. The difference lies in the lower paleo heat flow in the central uplift than the northern depression, the former is about 70 mW/m~2 at the end of the late Cretaceous, and the Paleocene in the northern depression can reach 71.7~75.5 mW/m~2, up to 80mW/m~2..
【学位授予单位】：中国科学院大学(中国科学院海洋研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P542;P736.1

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