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基于CSDP-2井的南黄海中部隆起构造热演化史研究
庞玉茂
学位类型博士
导师张训华
2017-05-12
学位授予单位中国科学院大学
学位授予地点北京
学位专业海洋地质专业 理学博士
关键词南黄海盆地 中部隆起 埋藏史 古地温 磷灰石裂变径迹 构造热演化史
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/m2,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/m2,而北部坳陷古新世早期可达71.7~75.5 mW/m2,最高可达80mW/m2
其他摘要The central uplift is the largest tectonic unit of the South Yellow Sea Basin (SYSB), which is not only the key study area of regional tectonic evolution, but also the potential area of current resource exploration. Based on the comprehensive description of drilling cores, experimental analysis, interpretation of logging and seismic data of the first deep whole-core drilling CSDP-2 well in central uplift of SYSB, the burial history and tectonic thermal evolution history have been studied by a serious of research methods and simulation techniques.
The first-stage drilling results of the CSDP-2 well have revealed the Neogene, Triassic, Permian, Carboniferous and Devonian. The burial history of central uplift has been studied based on the establishment of stratigraphic framework, seisimic interpretation and estimation of eroded thickness. Dominated by regional transgression during Carboniferous, the central uplift gradually turned into the stage of marine deposition after the late Devonian continental deposition, but the deposition rate was relatively lower. The deposition rate is significantly accelerated during the early Permian, then the alternative marine and continental deposition has formed because of regional uplift and regression at the end of early Permian. The study area suffered intense tectonic compression influenced by the Indosinia tectonic movement during Triassic. The detachment surface interlaid in the Permian argillaceous strata interval drilled by CSDP-2 may be the result of tectonic thrust during this period. The central uplift experienced strong denudation from the middle-late Cretaceous, and the eroded thickness is 1220m calculated by sonic-logging data and 1400m calculated by vitrinite reflectance. The general subsidence happened in Neogene and the unconsolidated sedimentary strata formed.
CSDP-2 well revealed the constant temperature zone at a depth of about 80m, of which the temperature is 15.8℃. The neutral point depth range is roughly in the vicinity of 1100m, and the average geothermal gradient is about 24.11~24.28℃/km. The thermal evolution history of the central uplift was studied by means of paleo-geothermal gradient method, fluid inclusion temperature measurement and apatite fission track (AFT) stochastic inversion. Results show that the paleotemperature of Paleozoic is about 40℃ at the end of Carboniferous and there is a significant temperature-rise process during the early Peimian and then tends to be steady. There is another short-term temperature-rise process at the end of Permian. The paleotemperature generally keep stable during Triassic and then rapidly rise from the late Triassic to early-middle Jurassic when the central uplift has not yet suffered large-scale uplift and denudation, and modeling results from vitrinite reflectance show that the highest paletemperature of Carboniferous and Permian can respectively reach 190℃ and 170℃ and the heat flow can reach 126 mW/m2. The maximum paleogeothermal gradient is about 59℃/km during this time, which is much higher than the present geothermal gradient. The paleotemperature and heat flow both began to decline from the late Jurassic followed by a slight rise, which is resulted from the rift development and rapid continental deposition during the early Cretaceous. During the mid-late Cretaceous, the denudation rate accelerated and resulted in the paleotemperature continuously decreased, and the paleo-heat flow began to decline until the end of Cretaceous when the rift development of the SYSB roughly finished. The AFT thermal history inversion results from the Permian samples show that it has not yet entered the annealing zone during the early Cretaceous, and the paleotemperature is about 100~140℃, corresponding to the results of fluid inclusion temperature measurement. The AFT inversion results reveal two distinct cooling events, the first happened from the late Cretaceous to the early Paleocene when the paleotemperature declined to about 80℃, and then followed by a slow cooling process until the late Oligocene when the other rapid cooling event happened and continued to the early Miocene. Since the Neogene, the paleotemperature slowly rised to the current level.
Based on the theory of advanced McKenzie extension model, the geodynamic modeling and traditional geothermometer simulation are integrated and applied to reconstruct the tectono-thermal evolution history of the northern depression of the South Yellow Sea Basin during Mesozoic-Cenozoic. Modeling results show that the central uplift and northern depression, which are both the secondary tectonic units of SYSB, experienced similar thermal evolution history since Cretaceous and characterized by the heat flow trend of rift basin, showing a distinct increase process during the rifting stage and a continus decrease process during the post-rifting stage. By contrast, the paleo-heat flow of the central uplift is generally lower than the north depression, the maximum value of the former can reach 70 mW/m2 at the end of the Late Cretaceous while the paleo-heat flow of north depression is about 71.7~75.5 mW/m2 during the early Paleocene and the highest is about 80mW/m2.
学科领域海洋地质学
语种英语
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/136596
专题海洋地质与环境重点实验室
作者单位1.中国科学院海洋研究所
2.青岛海洋地质研究所
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庞玉茂. 基于CSDP-2井的南黄海中部隆起构造热演化史研究[D]. 北京. 中国科学院大学,2017.
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