四川盆地晚奥陶世—早志留世碳硫同位素分馏动力学模型构建  

A Kinetic Model for Carbon and Sulfur Fractionation from the Late Ordovician to the Early Silurian in Sichuan Basin,China

作　　者：王泽唐 王超勇[2] 董再田 朱昱璇 WANG ZeTang;WANG ChaoYong;DONG ZaiTian;ZHU YuXuan(Xi’an University of Science and Technology,Collage of Geology and Environment,Xi’an,710054,China;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou,Jiangsu,221116,China;School of Mining,Liaoning Technical University,Fuxin,Liaoning 123000,China)

机构地区：[1]西安科技大学地质与环境学院,西安710054 [2]中国矿业大学资源与地球科学学院,江苏徐州221116 [3]辽宁工程技术大学矿业学院,辽宁阜新123000

出　　处：《沉积学报》2024年第6期2054-2065,共12页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41772129)。

摘　　要：【目的】晚奥陶世—早志留世过渡时期在全球出现的碳、硫同位素(δ^(13)C、δ^(34)S)显著偏移事件已得到广泛认可,但造成这些同位素发生偏移的原因仍存在较大争议,开展定量的数值模拟研究是解决该问题的途径之一。【方法】选取四川盆地在该时期沉积于不同区域的田林剖面和沙坝剖面共计47个页岩样品,分别进行了有机碳同位素(δ^(13)C_(org))、黄铁矿硫同位素(δ^(34)S_(py))测试,并结合Vensim 7.3.5系统动力学软件对其进行了模型重建和动力学分析。【结果】(1)赫南特冰期前期,当有机碳埋藏通量增加1.5~2.0倍、黄铁矿埋藏通量增加1.5~3.0倍时,即可出现C、S同位素的同步正偏现象,指示较高的初级生产力和广泛发育的铁质缺氧水体有利于沉积有机质与黄铁矿的埋藏,而冰后期火山活动的增强是δ^(13)C_(org)短时间内出现显著负偏移的必要条件;(2)赫南特冰期前期较低的海水硫酸盐浓度(约为5 mM)是δ34S出现正偏移的基础,冰后期陆源硫酸盐输入通量的增加是引起δ^(34)S_(py)负偏的主要影响因素。【结论】研究结果定量评价了δ^(13)C、δ^(34)S同步偏移的主要影响因素,对地质历史时期C、S同位素分馏过程动力学研究提供新的思路与定量预测模型。[Obective]The significant migration events of carbon and sulfur isotopes(δ^(13)C,δ^(34)S)in the global transition period from the Late Ordovician to the Early Silurian have been widely recognized,but the causes of these isotopes are still controversial.Quantitative numerical simulation is one of the ways to solve this problem.[Methods]A total of 47 shale samples from the Tianlin and Shaba sections,which were deposited in different regions of the Sichuan Basin during this period(23 samples from the Tianlin section,and 24 samples from the Shaba section),were selected for organic carbon(δ^(13)C_(org))and pyrite sulfur isotope(δ^(34)S_(py))analysis.The system dynamics software Vensim7.3.5 was used to reconstruct the model and analyze the dynamics.[Results]The main results are as follows:(1)Bothδ^(13)C_(org) andδ^(34)S_(py) exhibited synchronous positive shifts before the Hirnantian glacial period,reached the peak value in the Hirnantian glacial period,and then decreased.The synchronous positive deviation of C and S isotopes can occur when the burial fluxes of organic carbon were 1.5 to 2.0 times,and pyrite 1.5 to 3.0 times,that of the preglacial period.This indicates that the high primary productivity and widely developed anoxic water column of iron were beneficial to the burial of sedimentary organic matter and pyrite.During the Hirnantian glacial period,with the decreased primary productivity and increased oxygen content in water column,the burial flux of organic carbon and pyrite decreased gradually,and the carbon and sulfur isotopes were slightly negative.The intensity of volcanic activity mainly affects the migration of δ^(13)C,and the weakened volcanic activity was beneficial to the positive deviation of δ^(13)C,while the enhanced volcanic activity after the glacial period was the necessary condition for the significant negative deviation of δ^(13)C over a short time(0.5-1.0 Myr).(2)The lower seawater sulfate concentration(approximately 5 mM)in the early stage of the Hirnantian glacial period was the b

关 键 词：四川盆地 晚奥陶世 早志留世 碳同位素 硫同位素 动力学模型 

分 类 号：P534.4[天文地球—古生物学与地层学]