沉积学报2025，Vol.43Issue(6)：1968-1977,10.DOI:10.14027/j.issn.1000-0550.2024.015
四川邻水地热井含膏盐段岩屑碳氧同位素特征
Carbon and Oxygen Isotope Characteristics of Rock Debris in the Salt-bearing Section of Geothermal Well in Linshui County,Sichuan Province
摘要
Abstract
[Objective]Carbon and oxygen isotopes are important geochemical indices of carbonate rocks,play an important role in revealing the characteristics of sedimentary and diagenetic fluids,and have become one of the basic means to study carbonate rocks.At present,a large number of studies on carbon and oxygen isotopes in limestone-dolomite have been conducted globally,but there are few studies on carbon and oxygen isotopes in sulfate-carbonate.In the sulfate-carbonate stage of the sedimentary sequence,there are still carbon and oxygen elements that can be tested,which makes this study possible.There are currently studies on carbon and oxygen isotopes of the plaster salt section of Huaying Mountain and the plaster bearing strata of Reichenhall Formation,Australia,but these studies are few and concentrated on surface samples.It is of great theoretical significance to study carbon and oxygen isotopes of drilling gypsum salt samples.[Methods]In the process of drilling a geothermal well in Doubei Village,Gaotan Town,Linshui County,and Sichuan,to the east of Huaying Mountain in Sichuan Basin,carbon and oxygen isotopes of paste salt interbedding cuttings of Jialingjiang-Lekoupo Formation were studied.[Results](1)The δ13CPDB ranges from-4.68‰ to-0.12‰,with an average value of-2.86‰.The δ18OPDB of paste salt interbedding cuttings in the Dao-bei geothermal well ranges from-15.47‰ to-2.56‰,with an average value of-9.13‰,and the Z-value is lower than 120,which is inconsistent with the characteristics of marine sediments.The δ13CPDB and δ18OPDB values were significantly lower than that of the Triassic paste salt formation in Huaying Mountain and the Reichenhall paste salt formation in Australia;(2)According to the two calculation methods,the formation temperature is 28.18℃-111.71℃,the average value is 68.45℃and 4.54℃-78.21℃,the average value is 38.91℃.The former was close to the present temperature of the formation,but the latter was lower,which may be related to the selection of δ18O in the calculation formula.[Conclusions]The carbon and oxygen isotopes of the underground salt-salt strata in this area are mainly affected by the thermochemical sulfate reduction(TSR)in the deep-buried stage before the formation fold and the massive inflow of surface fresh water after the formation fold,fracture and uplift.The high formation tempera-ture and exchange of organic carbon before fold and the desalting of surface water after fold and fracture are the fundamental reasons for the low δ13C and δ18O of the gypsum salt layer in this area.However,there may be a little freshwater action and influence during the depositional stage.关键词
邻水县/地热井/碳氧同位素/TSR作用/地表水Key words
Linshui county/geothermal well/carbon and oxygen isotopes/thermochemical sulfate reduction(TSR)/surface water分类
天文与地球科学引用本文复制引用
LIU JianQing,HUANG CongJun,ZHU HuaPing,HE Li,RAN Jing..四川邻水地热井含膏盐段岩屑碳氧同位素特征[J].沉积学报,2025,43(6):1968-1977,10.基金项目
中国地质调查局地质调查项目(DD20221733,DD20230322)[Geological Survey Project of China Geological Survey,No.DD20221733,DD20230322] （DD20221733,DD20230322）
