石油学报 ›› 2012, Vol. 33 ›› Issue (2): 213-224.DOI: 10.7623/syxb201202005

• 地质勘探 • 上一篇    下一篇

中扬子地区当阳复向斜中生代以来的构造抬升和热史重建

李天义 1 何 生 1 何治亮 2 沃玉进 2 周 雁 2 王芙蓉 1 杨兴业 1   

  1. 1中国地质大学构造与油气资源教育部重点实验室 湖北武汉 430074;2中国石油化工股份有限公司石油勘探开发研究院 北京 100083
  • 收稿日期:2011-08-05 修回日期:2011-11-18 出版日期:2012-03-25 发布日期:2012-05-17
  • 通讯作者: 李天义
  • 作者简介:李天义,男,1982年6月生,2007年毕业于中国地质大学(武汉),2009年至今在中国地质大学(武汉)攻读矿产普查与勘探专业博士学位,研究方向为海相油气地质与含油气盆地热史分析。
  • 基金资助:

    国家自然科学基金重点项目(No.40739904)、国家自然科学基金面上项目(No.41072093)和国家重大科技专项(2011ZX05005-002)资助。

Reconstruction of tectonic uplift and thermal history since Mesozoic in the Dangyang synclinorium of the central Yangtze area

LI Tianyi 1 HE Sheng 1 HE Zhiliang 2 WO Yujin 2 ZHOU Yan 2 WANG Furong 1 YANG Xingye 1   

  • Received:2011-08-05 Revised:2011-11-18 Online:2012-03-25 Published:2012-05-17

摘要:

综合运用锆石及磷灰石裂变径迹、镜质体反射率资料以及盆地模拟技术对中扬子地区当阳复向斜中生代以来的构造抬升和古地温演化进行了研究和重建。砂岩样品的锆石和磷灰石裂变径迹表观年龄分别为107~126 Ma和9.8~54 Ma,分别反映早白垩世燕山期、始新世至中新世喜马拉雅期的两次重要构造抬升及剥蚀冷却事件。侏罗系与白垩系、古近系与新近系之间的不整合面上、下镜质体反射率错开现象以及现今地表镜质体反射率异常偏高,也证实了两次抬升剥蚀冷却事件的存在。研究表明,区内当深3井和建阳1井的上三叠统-下侏罗统在早白垩世早期(约137 Ma)达到最大古地温190~210℃,造成锆石裂变径迹退火,至早白垩世末晚白垩世初(约97 Ma)剥蚀冷却至近地表20~40℃;晚白垩世至古近纪沉积使该套地层又一次埋深增温至140~165℃,造成磷灰石裂变径迹完全退火;喜马拉雅期再次构造抬升及剥蚀冷却至现今70~90℃。研究区古近系经历的最高古地温为100~120℃和现今40~50℃。研究区中生代古热流相对稳定,热流值相对较低为53.5 mW/m2;晚白垩世古热流逐渐增大,古近纪达到最高59 mW/m2;其古地温梯度分别为中生代36.3~43.0 ℃/km和新生代30.2~37.8℃/km,现今降低至28.9℃/km。早白垩世和始新世至中新世的最大剥蚀厚度分别约为4800 m和2400 m,由此可认为,当阳复向斜应该存在较大厚度的侏罗系,最大厚度可能达5000 m。

关键词: 磷灰石和锆石裂变径迹, 镜质体反射率, 构造抬升, 热史重建, 当阳复向斜, 中扬子地区

Abstract:

Reconstruction of the tectonic uplift and thermal history since Mesozoic in the Dangyang synclinorium of the central Yangtze area was made by means of apatite and zircon fission track thermochronology, vitrinite reflectance and basin modeling. Analyses of the zircon and apatite fission track data(107~126 Ma and 9.8~54 Ma) suggested that twice enormous tectonic uplift and cooling events occurred in the study area, one in the Early Cretaceous Yanshan stage and the other during the Eocene to Miocene Himalayan stage. The abruption of vitrinite reflectance values around Jurassic-Cretaceous and Paleogene-Neogene unconformities and abnormally high vitrinite reflectance values of the present land surface also gave evidence for the occurrence of these two events. Study results show that the Upper Triassic-Lower Jurassic formations in wells Dangshen-3 and Jianyang-1 had a maximum paleotemperature of 190~210 ℃ at the beginning of Early Cretaceous(~137 Ma), resulting in a zircon fission track annealing; the formations then cooled down to a near surface temperature of 20~40 ℃ due to the uplift and erosion of strata at the end of Early Cretaceous and the beginning of Late Cretaceous(~97 Ma); during Late Cretaceous to Paleogene(around 45 Ma), the strata had been deeply reburied with paleogeothermal values up to 140~165 ℃, leading to a complete apatite fission track annealing. Finally, the strata uplifted and were eroded again in the Himalayan stage, with paleotemperatures reduced to the present-day values of 70~90 ℃. Therefore, the maximum geotemperature that Paleogene strata in the study area have ever experienced was 100~120 ℃ and their present-day geothermal values range between 40~50 ℃. The heat flow of the study area was relatively steady in Mesozoic, with a lower value around 53.5 mW/m2, it began to increase from Late Cretaceous and had the highest value of 59 mW/m2 in Paleogene. The geothermal gradient for Mesozoic and Cenozoic strata in the study area is 36.3~43.0 ℃/km and 30.2~37.8 ℃/km, respectively, while the present-day geothermal gradient decreases to 28.9 ℃/km. The model indicates that the maximum erosion thickness of Early Cretaceous and Eocene to Miocene strata in the study area is about 4800 m and 2400 m, respectively. Consequently, the Dangyang synclinorium must have received enormous Jurassic sediments, and the maximum thickness of the Jurassic formation is likely to reach 5000 m.

Key words: fission track of apatite and zircon, vitrinite reflectance, tectonic uplift, reconstruction of thermal history, Dangyang synclinorium, central Yangtze area