台湾海岸山脉同造山盆地古热流值的估算:基于镜质体反射率约束下的一维盆地模拟  

Estimation of Paleo-geothermal Flow of the Synorogenic Basin in the Coastal Mountains,Eastern Taiwan:One-dimensional Basin Simulation Under the Constraint of Vitrinite Reflectance Measurements

作　　者：赵武 单业华[1,3] 胡斯敏[1,2] 郑剑 ZHAO Wu;SHAN Yehua;HU Simin;ZHENG Jian(State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;Innovation Academy of Earth Science,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广东广州510640 [2]中国科学院大学,北京100049 [3]中国科学院地球科学研究院,北京100029

出　　处：《大地构造与成矿学》2023年第4期750-762,共13页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(4197020422)资助。

摘　　要：台湾东部海岸山脉上新世‒更新世同造山盆地记录了北吕宋岛弧与欧亚板块之间的斜向碰撞过程。目前关于该盆地的构造属性存在着两种绝然不同的认识,即“热”的弧前盆地和“冷”的碰撞盆地。本文采集了海岸山脉南部泰源向斜西翼更新统八里湾组泥岩样品,测量了其有机质的镜质体反射率(Ro)。Ro测量值的最小值、最大值和平均值与相对埋深之间的相关系数分别是0.76、0.43和0.67,反映出样品中同生镜质体在数量上远超过原生镜质体。由于同生镜质体和原生镜质体无法简单区分,本文将最小值和平均值分别作为原生镜质体平均镜质体反射率的下界和上界,采用一维盆地模拟技术计算出在给定剥蚀厚度和热流值的范围下的理论镜质体反射率。通过对比理论和实测镜质体反射率,我们发现:①八里湾组所有地层段与中段、上段在镜质体反射率(Ro)的偏差上具有不同的特征,意味着在中段开始沉积时下段卷入到褶皱冲断带中;②对于上段获得盆地剥蚀厚度解的下限是3.2~4.8 km,对应的热流值小于0.68~1.00 HFU(36.84~41.87 mW/m^(2)),表明同造山盆地是一个“冷盆”。The Neo-Pleistocene synorogenic basin in the coastal mountains of the eastern Taiwan recorded the oblique collision between the North Luzon Island Arc and the Eurasian Plate.At present,there are two completely different hypotheses about the tectonic properties of the basin,namely“hot”forearc basin and“cold”collision basin.The vitinite reflectance(Ro)of organic matters in the Baliwan Formation of the Pleistocene series in the western wing of the Taiyuan syncline in the southern Coastal Mountains was measured.The correlation coefficients between the minimum,maximum and average values of the measured values and the relative burial depth were 0.76,0.43 and 0.67,respectively,indicating that the amount of the syngenic vitrinites in the samples far exceeded that of the primary vitrinite.Because it is simply impossible to distinguish the two,this paper takes the minimum value and the average value as the lower and upper bounds of the average Ro value of the primary vitrinite,and calculates the theoretical Ro value within a given denudation thickness and heat flow value by using one-dimensional basin simulation technique.By comparing the theoretical and measured Ro values,we find that:(1)The deviation of Ro values of all members of the Baliwan Formation from the middle and upper members is different,which means that the lower member of Baliwan Formation is involved in the fold and thrust belt;(2)The estimated basin denudation thickness for the upper member is no more than 3.2 to 4.8 km,and the corresponding heat flow value is less than 0.68 to1.00 HFU,indicating that the synorogenic basin is a“cold basin”.

关 键 词：同造山盆地 盆地模拟 镜质体反射率 古热流 

分 类 号：P588[天文地球—岩石学]