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

Mesozoic tectonics and dynamic thermal history in Yuanba area of northeastern Sichuan Basin：application of（U-Th）/He dating of apatite and zircon

王杰 秦建中 刘文汇 陶成 腾格尔

Wang Jie Qin Jianzhong Liu Wenhui Tao Cheng Tenger

中国石油化工集团公司油气成藏重点实验室, 江苏, 无锡, 214151 2. 中国石油化工股份有限公司石油勘探开发研究院无锡石油地质研究所, 江苏, 无锡, 214126

SINOPEC Key Laboratory of Petroleum Accumulation Mechanisms, Wuxi, Jiangsu 214151, China 2. Wuxi Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214151, China

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109.9m/Ma,K1j及以上地层最大抬升剥蚀厚度约为4000m。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0～36Ma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 4000 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℃.

国家重点基础研究(973项目)(2005CB422102);国家重大专项(2008ZX05005-01-02)

https://doi.org/10.11781/sysydz201201019