羌塘盆地雀莫错沉降-堆积中心成因:热力衰减塌陷沉降

doi:10.11743/ogg20050203

摘要/Abstract

摘要：

在羌塘盆地东北部雀莫错地区侏罗系厚度巨大、层序齐全。其中,侏罗纪最早沉积的雀莫错组和最晚沉积的雪山组,现今地层残存厚度均超过1300m,分别属盆地内同期显著的局部沉降-堆积中心。这两期沉降-堆积中心的发育背景和演化过程颇为相似,即前期均有热力-岩浆活动的证据和与之有关的隆起背景;随后,早期沉积较薄甚至遭受剥蚀的隆起区发生快速沉降,接受巨厚沉积。这种隆、坳特征在时间上前后相随、上下叠置的特别现象,为热力作用形成的构造所特有。这一特征是雀莫错地区经历了(1)早期深部热力-岩浆作用上拱、岩浆喷溢,地壳表浅层隆升剥蚀,和(2)晚期深部热力衰减冷却,表浅层塌陷沉降之全过程的表现和记实。近年完成的航磁和大地电磁测深资料所反映出的深部结构方面证明此热力塌陷构造的存在。上侏罗统雪山组有机质镜质体反射率(R₀)高达1.63%～1.83%,为中生代热异常的发生提供了证据。雪山期塌陷沉降型火山机构的热力衰减塌陷和伴随的岩浆活动,一直间断延续到晚白垩世-早第三纪初。随后,该区始发生抬升冷却。

关键词: 热力塌陷, 沉降-堆积中心, 雀莫错, 羌塘盆地, 侏罗纪, 青藏高原, 岩浆活动

Abstract:

Jurassic is very thick and has a complete sequences in Quemocuo area, northeastern Qiangtang basin.The Quemocuo Formation and Xueshan Formation, the earliest and latest Jurassic deposits,both presently have a remaining thickness of over 1300m, representing the apparent local subsidence-accumulation centers of the times in the basin. These two subsidence-accumulation centers have very similar development background and evolution process, i.e. there are the evidences of early-stage thermal-magmatic activity and relevant uplifting backgrounds, subsequently, the uplifted areas where the early deposits being thin or even denuded have subsided rapidly and accumulated very thick deposits. The special phenomena that uplifts and depressions occur successively in time and are superimposed vertically are characteristic of structures having been formed by thermal activity.This unique feature shows that Quemocuo area has experienced two geologic processes:(1) humping up of deep thermal-magmatic activity, magmatic eruption, and uplifting and denudation of superficial and shallow crust in early stage; (2) thermal attenuation and cooling down at depth and caving in and depression of superficial and shallow crust in late stage. The deep structures revealed by aeromagnetic survey and magnetotelluric depth sounding data acquired in recent years verify the existence of this thermal subsidence structure. The vitrinite reflectance(R₀)of Upper Jurassic Xueshan Formation ranges from 1.63%to 1.83%, providing evidences for the Mesozoic thermal anomaly. The thermal attenuation and accompanying magmatic activities had lasted till Late Cretaceous-Early Tertiary. Later, this area was uplifted and cooled down.

Key words: thermal caving in, subsidence-accumulation center, Quemocuo, Qiangtang basin, Jurassic, Qinghai-Tibet plateau, magmatic activity

中图分类号:

TE111.1

刘池洋,杨兴科,任战利,等. 羌塘盆地雀莫错沉降-堆积中心成因:热力衰减塌陷沉降[J]. 石油与天然气地质, 2005, 26(2): 147-154. doi: 10.11743/ogg20050203 Liu Chiyang,Yang Xingke,Ren Zhanli,et al. Genesis of subsidence-accumulation centre in Quemocuo area of Qiangtang basin:caving-in subsidence with thermal attenuation[J]. Oil & Gas Geology, 2005, 26(2): 147-154. doi: 10.11743/ogg20050203

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