青海木里三露天井田构造沉降史分析

摘要

According to drillhole and geological survey report of Sanlutian mining field in Juhugeng mining area, we inversed and analyzed the subsidence history of Sanlutian mining field by back-stripping method and dis-cussed the relationship between hydrate formation and tectonic evolution.The simulated results showed that the study area experienced four stages of subsidence and three stages of uplift since Carboniferous period as follows:subsiding slowly then rapidly with larger subsidence scope from Carboniferous to Late Triassic,uplifting and denudating in the end of Late Triassic by the late Indosinian movement,subsiding rapidly from Early Jurassic to Early Cretaceous,uplifting and denudating in Late Cretaceous by Yanshan movements,subsiding rapidly in Mi-ocene epoch,uplifting rapidly with the uplift of the Tibetan Plateau in Pliocene epoch,and subsiding rapidly in Quaternary period.The simulation result of subsidence history provides a quantitative or semi-quantitative value of parameters for the tectonic evolution in the study area.The control of the tectonic subsidence on the forma-tion of natural gas hydrate shows the two aspects,the maturity of source rocks and the formation of hydrate stable zone.%根据三露天井田的煤田钻孔和地质勘查报告等资料，应用回剥技术分析研究区从晚古生代石炭纪以来的沉降史及构造演化特征，讨论了水合物形成与构造演化的关系。模拟结果显示，研究区自石炭纪以来主要经历了4期沉降和3期抬升：石炭纪至晚三叠世，沉降由慢转快，沉降幅度较大；晚三叠世末期，由于晚印支运动影响构造抬升；早侏罗世至早白垩世，快速沉降；晚白垩世，燕山运动导致区域隆升；中新世发生较快速沉降；上新世受青藏高原隆升影响，快速隆升，随后第四纪又出现较快速沉降。沉降史模拟结果为研究区构造演化提供了定量或半定量的参数。三露天构造沉降对天然气水合物形成的控制作用体现在影响烃源岩成熟度和温压稳定带的形成两方面。