摘要
对川东北普光一毛坝地区和通江地区的11个岩心和露头样品进行锆石、磷灰石（u—Th）／He定年分析，初步建立了He年龄一深度／温度动态演化模式，该地区磷灰石He封闭温度为85℃。川东北钻井岩心和剖面样品经历相同的热演化历程。该地区第三纪至第四纪为冷却抬升剥蚀主要时期，剥蚀速率约为74．8～172．5m／Ma，剥蚀厚度大约为2800～3000m，地温逐渐降低到磷灰石He封闭温度，直至达到现今温度，与青藏高原隆升引发的新构造运动在四川盆地的响应有关。普光5井等3200m以上中生界样品未经历过锆石He封闭温度，可能只有3200m以下的样品经历锆石He封闭温度，但所有样品都经历了磷灰石He封闭温度。根据锆石（U—Th）／He年龄大致推算出，川东北地区可能在晚侏罗世开始抬升，在晚侏罗世一早白垩世期间普光一毛坝地区和通江地区都处于缓慢抬升剥蚀阶段，只是普光一毛坝地区抬升剥蚀开始时间要早于通江地区。磷灰石和锆石He封闭温度和年龄揭示了该区动态热演化历史。该区在178．0Ma之前古地温大于170～1900C，随后地层继续抬升，古地温下降；在40．5～178．0Ma时，古地温为85—170℃；在0～40．5Ma时，现今地温小于85℃。
（U-Th）/He dating of apatite and zircon is performed on eleven core and outcrop samples from the Puguang-Maoba and Tongjiang areas in northeastern Sichuan Basin and the results are used to establish a dynamic evolution pattern for He age and depth/temperature. The closure temperature of the He in apatite in this area is at 85℃. The drilling core samples experienced the same thermal evolution history with the outcrop samples in the northeastern Sichuan Basin, where the Tertiary and the Quaternary were the main periods of cooling, uplifting and denudation. During these periods,the denudation rate was about 74. 8 -172.5 m/Ma,the maximum denudation thickness was 2 800 -3 000 m, the earth temperature gradually reduced to helium closure temperature of apatite, and finally to the current temperature. All these were related to the reaction of the Sichuan Basin to a new tectonic movement caused by the uplifting of the Qinghai-Tibet plateau. Cores sampled from the Mesozoic with a depth of less than 3 200 m in Well Puguan-5 did not undergo the closure temperature of zircon, only those gathered from a depth of more than 3 200 m might experience the closure temperature of zircon, but all the samples underwent the closure temperature of apatite. （U-Th）/He ages of zircon indicate that uplifting in the northeastern Sichuan Basin began in the Late Jurassic. During the Late Jurassic-Early Cretaceous,both the Puguang-Maoba area and the Tongjiang area were in gradual uplifting and denudation, but the uplifting and denudation in the Puguang-Maoba area began earlier than that in the Tongjiang area. （U-Th）/He ages and closure temperatures of apatite and zircon reveal the dynamic evolution of thermal history in the study area. Before 178Ma,the palaeo-geotemperature of the study area was above 170 -190℃, but lowered later along with the continuous uplifting. It was in the range of 85 - 170℃ during the 40.5 Ma - 178 Ma, and has lowered to less than 85℃ at present.
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2010年第3期277-287,共11页
Oil & Gas Geology
基金
国家重点基础研究发展计划(973计划)项目(2005CB422102)
国家重大专项(2008ZX05005-01-02)
关键词
(U—Th)/He年龄
封闭温度
抬升剥蚀
热史动态演化
热史模拟
南方海相层系
（U-Th）/He age, closure temperature, uplift and denudation, dynamic evolution of thermal history, thermal history simulation, marine sequence in South China
作者简介
秦建中（1957-），男，教授级高级工程师，油气地球化学与石油地质。
