Table1_Using Clumped Isotopes to Reconstruct the Maximum Burial Temperature: A Case Study in the Sichuan Basin.DOCX

For strata that have experienced continual burial in the early stage and uplift in the late stage, the present-day temperature is lower than the maximum burial temperature (MBT), which is a key parameter for studying the hydrocarbon generation history of source rocks in petroliferous basins. In this paper, a new method for reconstructing the MBT is proposed based on the solid-state reordering model of carbonate clumped isotopes (Δ47). The MBT reconstructed using the Δ47 was compared with the MBT constrained using the traditional Easy%Ro model. The clumped isotope temperature (TΔ47) of the Permian micritic limestone from the Xibeixiang outcrop (about 62°C) is much higher than its initial formation temperature (20–25°C), suggesting that the limestone experienced partial solid-state reordering during the late burial process. The MBT of the calcite obtained from the solid-state reordering model is 139–147°C, which is quite similar to the MBT determined using the Easy%Ro model (139.5–147.5°C). TΔ47 of the Permian and Triassic limestone and calcite cements in the Puguang gas field are 150–180°C, while TΔ47 of the micritic dolostone is about 70°C, suggesting that the Δ47 of the limestone and calcite cements experienced complete solid-state reordering and the dolostone only experienced partial solid-state reordering. The MBT of the dolomite determined using the solid-state reordering model is 200–220°C, which is also similar to the MBT determined using the Easy%Ro model (202–227°C). Therefore, the case studies from the Sichuan Basin suggest that Δ47 can be used to reconstruct the MBT of ancient carbonate strata lacking vitrinite and detrital zircon data. However, different types of carbonate samples should be used to reconstruct the MBT for strata that have experienced different temperature histories. Micritic limestone and very finely crystallized dolostone can be used to reconstruct the MBT of strata that have experienced MBTs of <150–200°C and >200–250°C, respectively.

对于经历早期持续埋藏、晚期抬升的地层，其现今温度低于最大埋藏温度（maximum burial temperature, MBT）——该参数是研究含油气盆地烃源岩生烃史的核心参数。本文基于碳酸盐团簇同位素（Δ47）的固态重排模型，提出了一种重建最大埋藏温度的新方法。将利用Δ47重建得到的最大埋藏温度，与传统Easy%Ro模型约束得到的最大埋藏温度进行对比分析。对西贝巷露头二叠系微晶灰岩测得的团簇同位素温度（TΔ47）约为62℃，远高于其初始形成温度（20~25℃），表明该灰岩在晚期埋藏过程中发生了部分固态重排。基于固态重排模型计算得到的方解石最大埋藏温度为139~147℃，与Easy%Ro模型测定的结果（139.5~147.5℃）高度吻合。普光气田二叠系、三叠系灰岩及方解石胶结物的团簇同位素温度介于150~180℃，而微晶白云岩的团簇同位素温度约为70℃，这表明灰岩与方解石胶结物的Δ47已发生完全固态重排，而白云岩仅发生了部分固态重排。基于固态重排模型得到的白云岩最大埋藏温度为200~220℃，同样与Easy%Ro模型测定的结果（202~227℃）相近。因此，四川盆地的案例研究表明，对于缺乏镜质体与碎屑锆石数据的古碳酸盐地层，Δ47可用于重建其最大埋藏温度。但针对经历不同温度演化历史的地层，需选用适配的碳酸盐样品开展最大埋藏温度重建：微晶灰岩与极细晶白云岩可分别用于重建最大埋藏温度低于150~200℃、高于200~250℃的地层的最大埋藏温度。