基于U—Pb定年和团簇同位素测定的古老碳酸盐岩地层热演化史恢复及成藏过程重建

Recovery of thermal evolution history and reconstruction of accumulation process of ancient carbonate strata based on U-Pb dating and cluster isotope measurement

团簇同位素作为一种新的地质温度计,在与U-Pb定年一起使用的情况下,能为古老碳酸盐岩地层热历史恢复提供时间和温度坐标。依据U-Pb定年实验的结果,得出不同产状白云岩的成岩时间,并利用团簇同位素固态重排模拟,恢复不同产状白云岩的成岩温度。结果表明:①依据围岩的Δ_(47)固态重排模拟过程,目的层所经历的最大埋深温度约为216.5±5℃;②利用不同产状白云岩的成岩时间和温度数据,对前人根据岩石热导率和地层剥蚀量所恢复出的热演化史进行限定,从而使研究区的热演化史恢复由定性转变为定量;③以恢复出的热演化史为基础,依据流体包裹体捕获的均一温度判断,共有3期油气充注:第一期油气充注时间约为255~240 Ma,第二期油气充注时间约为160~120 Ma,第三期油气充注时间约为80~40 Ma。

As a new geothermometer, cluster isotopes, when used together with U-Pb dating, can provide time and temperature coordinates for the thermal history recovery of ancient carbonate strata. Based on the results of U-Pb dating experiment, the diagenetic time of different occurrence dolomites is obtained, and the diagenetic temperature of different occurrence dolomites is recovered by using solid state rearrangement simulation of cluster isotopes. The results show that:(1) According to the simulation process of ?47 solid rearrangement of surrounding rock, the maximum burial depth temperature of target layer is about 216.5±5 ℃. (2) Based on the diagenetic time and temperature data of dolomites of different occurrence, the thermal evolution history recovered by previous authors according to the thermal conductivity of rocks and the amount of strata denudation is defined, so that the thermal evolution history of the study area is changed from qualitative to quantitative.(3) Based on the recovered thermal evolution history and the homogeneous temperature captured by fluid inclusions, there are three stages of oil and gas charging. The first stage is about 255-240 Ma, the second stage is about 160-120 Ma, and the third stage is about 80-40 Ma.