摘要:
兰坪—思茅盆地是中国西南部重要的成盐、成钾盆地,其大地构造位置处于东特提斯构造域,因此,特提斯的形成和演化对盆地成盐潜力、成盐规模和盐类分布规律有重要的影响.这种影响主要体现在:(1)古特提斯闭合之后,相关地块或地体上可残留陆表海,除了在相关地块内形成海相沉积盆地之外,海水还可能作为盐类物源补给迁移至相邻的沉积盆地;(2)兰坪—思茅盆地岩盐的物源除了来源于古特提斯闭合后的残留海,中特提斯期间的海侵作用也是重要补给形式,此外还受火山活动的影响;(3)新特提斯闭合后,印度板块与欧亚大陆碰撞,使兰坪—思茅盆地内发育大量走滑拉分和逆冲推覆构造,古代岩盐的赋存位置和形式发生了调整改造.总之,特提斯构造演化可以从提供盐类沉积的物源、控制盆地可容空间的大小、限制沉积盆地的边界和调整古代岩盐的分布等方面影响兰坪—思茅盆地的成盐、成钾条件.所以,对特提斯构造演化清晰的认识不仅能够为理解兰坪—思茅盆地成盐、成钾的机理提供帮助,还能为部署钾盐勘探方案、预测钾盐有利成矿区提供参考.
Abstract:
The Lanping-Simao basin, whose geotectonic position is in the Eastern Tethyan tectonic domain, is an important salt-forming and potash-forming basin in Southwest China. Therefore, the formation and evolution of Tethys has an important influence on the potential of salt formation, the scale of salt formation and the distribution of salts. This effect is mainly reflected in three aspects: (1) Apart from the formation of marine sedimentary basin in the relevant blocks, epicontinental sea could be retained in the relevant blocks or terranes after the closure of Paleo-Tethyan, and its water might also be used as a salt source to migrate to adjacent sedimentary basins. (2) The salt provenance originated from the transgression in the Meso-Tethys period, besides the residual sea after the closure of Paleo-Tethys, which in turn was affected by the volcanic activity. (3) Large strike slip and thrust nappe structures were developed in Lanping-Simao basin, with the collision of India and Eurasia plate after the closure of the Neo-Tethys. As a result, the location and form of ancient salt rock were adjusted and reconstructed. In summary, the salt and potassium-forming conditions of Lanping-Simao basin might have been influenced by the Tethyan tectonic evolution, with the providing of salt deposit provenance, the control of accommodation space of the basin, the limitation of boundary of sedimentary basin and the adjustment of ancient salt rock distribution. Therefore, a clear recognition of the evolution of Tethys can not only provide help for understanding the mechanism of salt-forming and potassium-forming in Lanping-Simao basin, but also for the deployment of potash exploration plan and the prediction of the favorable potash mining area.
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