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川东北元坝地区中生代构造与动态热演化史——磷灰石、锆石(U-Th)/He定年分析 被引量:25

Mesozoic tectonics and dynamic thermal history in Yuanba area of northeastern Sichuan Basin:application of (U-Th)/He dating of apatite and zircon
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摘要 通过对川东北元坝地区须家河组(T3x)—嘉定组(K1j)钻井岩屑样品镜质体反射率和锆石、磷灰石(U-Th)/He定年分析,建立了该区He年龄—深度/温度动态演化模式,推断出元坝地区磷灰石He封闭温度为95℃左右。元坝地区T3x-K1j中生代地层基本都经历了磷灰石He封闭温度(95℃);所有样品未经历锆石He封闭温度,T3x2-J1z地层部分样品可能经历了约170℃的最高古地温。元坝地区中生代地层在古近纪—新近纪(0.2~36.4 Ma)发生重大冷却抬升剥蚀,剥蚀速率约为109.9 m/Ma,K1j及以上地层最大抬升剥蚀厚度约为4 000 m。系统揭示了该区动态热演化历史,中生代地层最高古地温接近于170~190℃,随后地层发生抬升,古地温下降;在36~176 Ma之间时,古地温在95~170℃之间;在0~36 Ma时,现今地温小于95℃。 In Yuanba area of the northeastern Sichuan Basin,vitrinite reflectance and(U-Th)/He dating analyses of apatite and zircon in chip samples from the Xujiahe(T3x)-Jiading(K1j) Formations were carried out.A dynamic evolution model based on He age and depth/temperature was set up,by means of which we concluded that the He closure temperature of apatite was about 95 ℃.Most of the Mesozoic strata(T3x-K1j) in the study area experienced the He closure temperature of apatite(95 ℃) while no sample experienced the He closure temperature of zircon,and some samples from T3x2-J1z underwent the maxium palaeogeothermal of about 170 ℃.From Paleogene to Neogene(0.2-36.4 Ma),the Mesozoic strata in Yuanba area went through a severe cooling uplift and denudation with the denudation rate of 109.9 m/Ma.In K1j and the overlying strata,the maximum denudation thickness was about 4 000 m.The dynamic thermal evolution history in the study area was illustrated systematically as followed.In Mesozoic,the maximum palaeogeothermal of strata was 170-190 ℃.As strata upraise,palaeogeothermal decreased.From 36 to 176 Ma,palaeogeothermal was 95-170 ℃.From 0 to 36 Ma,the present geotemperature is below 95 ℃.
出处 《石油实验地质》 CAS CSCD 北大核心 2012年第1期19-24,共6页 Petroleum Geology & Experiment
基金 国家重点基础研究(973项目)(2005CB422102) 国家重大专项(2008ZX05005-01-02)
关键词 镜质体反射率 磷灰石和锆石U-Th/He定年 剥蚀厚度 热演化史 元坝地区 川东北 vitrinite reflectance U-Th/He dating of apatite and zircon denudation thickness thermal evolution history Yuanba area northeastern Sihuan Basin
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