New paleoˉgeotherm om eters for the inversion of dynam ic therm al evolution history ofm arine sequences in South China

QIN  Jian-Zhong; WANG   Jie; QIU  Nan-Sheng-; BrentMcInnes

doi:10.11743/ogg20100303

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New paleoˉgeotherm om eters for the inversion of dynam ic therm al evolution history ofm arine sequences in South China
Vol. 31, Issue 3, Pages: 277-287(2010)
Online First：24 August 2010，

Published：2010
DOI： 10.11743/ogg20100303
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DOI：

QIN Jian-Zhong, WANG Jie, QIU Nan-Sheng-, et al. New paleoˉgeotherm om eters for the inversion of dynam ic therm al evolution history ofm arine sequences in South China[J]. 2010, 31(3): 277-287. DOI： 10.11743/ogg20100303.

摘要

对川东北普光-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-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—早白垩世期间普光-毛坝地区和通江地区都处于缓慢抬升剥蚀阶段，只是普光-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170～190℃，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℃。

Abstract

（UˉTh）/He dating of apatite and zircon is performed on eleven core and outcrop samples from the PuguangˉMaoba and Tongjiang areas in northeastern Sichuan Basin and the results are used to establish a dyˉnam ic evolution pattern forHe age and depth/temperature.The closure temperature of the He in apatite in this area is at85℃.The drilling core samples experienced the same thermal evolution historywith the outcrop samˉples in the northeastern Sichuan Basin，where the Tertiary and theQuaternarywere themain periods of cooling，uplifting and denudation.During these periods，the denudation rate was about74.8-172.5m/Ma，the maxiˉmum denudation thicknesswas2800-3000m，the earth temperature gradually reduced to helium closure temˉperature of apatite，and finally to the current temperature.All these were related to the reaction of the Sichuan