川西北碧口地块中新生代隆升及构造扩展特征  

Meso-Cenozoic Uplift and Tectonic Expansion of the Bikou Block,Northwest Sichuan

作　　者：金文正[1,2] 白万奎 王俊鹏 叶治续[5] JINWen-Zheng;BAIWan-Kui;WANG Jun-Peng;YE Zhi-Xu(School of Energy Resources,China University of Geosciences,Beijing 100083,China;State Key Laboratory for Petroleum Resource and Prospecting,Beijing 102249,China;Geophysical Research Institute of Sinopec Shengli Oilfield Branch,Dongying 257000,Shandong,China;Hangzhou Institute of Petroleum Geology,PetroChina,Hangzhou 310023,Zhejiang,China;Jidong Oilfield Branch Company,PetroChina,Tangshan 063200,Hebei,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]油气资源与探测国家重点实验室,北京102249 [3]中国石化胜利油田分公司物探研究院,山东东营257000 [4]中国石油杭州地质研究院,浙江杭州310023 [5]中国石油天然气股份有限公司冀东油田分公司,河北唐山063200

出　　处：《华南地质》2023年第1期24-36,共13页South China Geology

基　　金：国家自然科学基金项目(41002072);油气资源与探测国家重点实验室开放课题基金(PRP/open-1307)。

摘　　要：青藏高原东北缘的向东构造扩展特征是地质热点问题之一,为了精确厘定该扩展速率及变化特征,本文对碧口地块及其东西两侧地层的磷灰石和锆石样品开展了裂变径迹测定和分析。结果表明:磷灰石裂变径迹长度在11.5~12.6μm之间,绝大部分磷灰石和锆石裂变径迹年龄分别为古近纪(66.9~45.4 Ma)和侏罗纪—早白垩世(201.5~105.9 Ma)。研究区热史演化总体上具有阶段性,其中碧口地块构造隆升具一致性,而东侧地区热史演化相似且明显滞后于碧口地块,即碧口地块在27~15 Ma之间急剧隆升,而东侧区域不同位置随后在12 Ma和4 Ma开始发生急剧构造隆升。这种构造隆升时间差异是因为碧口地块在随青藏高原地块向东南构造挤压过程中,构造应力向东南方向传递且发生构造扩展所致,构造扩展速率由西至东递减显著,由碧口地块内部的20 km/Ma逐渐降至四川盆地边缘的1.40 km/Ma。构造扩展速率受到地层岩性及构造变形样式等多种因素影响,碧口地块内部的构造扩展速率大约是东侧区域的12倍,构造扩展至四川盆地边缘逐渐减弱并在盆地内消失。The eastward tectonic expansion of the northeast margin of the Qinghai-Tibet Plateau is one of the important geological issues.In order to accurately determine the expansion rate and its variation,fission track measurement and analysis has been carried out on apatite and zircon samples from the strata of Bikou Block and its east and west sides,the results of which show that the fission track length of apatite is between 11.5μm and 12.6μm,and most of the fission track ages of apatite and zircon are distributed in Paleogene(45.4-66.9 Ma)and Early Jurassic-Cretaceous(105.9-201.5 Ma),respectively.The thermal history evolution can be generally phased,in which the tectonic uplift of Bikou Block is consistent,while the thermal history evolution in the east is similar and obviously lags behind Bikou Block,that is,Bikou block rises sharply between 27 Ma and 15 Ma,then the sharp tectonic uplift occurred at different locations in the eastern region betwteen 12 Ma and 4 Ma.This differential tectonic uplift is due to the tectonic stress transmitted to the southeast resulting in tectonic expansion in the process of tectonic compression of Bikou block with the Qinghai-Tibet Plateau Block to the southeast,and the tectonic expansion rate decreases significantly from west to east,from 20 km/Ma in the Bikou Block to 1.40 km/Ma in the edge of Sichuan Basin.The rate inside the Bikou Block is about 12 times that in the east,which is affected by many factors such as formation lithology and structural deformation styles.The tectonic expansion gradually weakened on the edge of Sichuan Basin and then disappeared.

关 键 词：磷灰石 锆石 裂变径迹 扩展速率 碧口地块 青藏高原 

分 类 号：P597.3[天文地球—地球化学]