The Qiangtang Basin,located in the central Tibetan Plateau,is an evaporate basin with deposited sodium salt and sylvite prospect.The recent discovery of salt springs with abnormally high sodium (Na+) and potassium (K+) contents in the Late Jurassic Xiali Formation provides an important clue for sylvite exploration.However,to date,there is little study about the paleo-environment of the Late Jurassic Xiali Formation,which largely constrain our understanding of key issues (such as formation conditions and possible layers of evaporates) in the Qiangtang Basin during late Jurassic.A high-resolution paleomagnetic analysis was performed on ～ 608 m thick of the Xiali Formation sediments in the Yanshiping section of the Qiangtang Basin to reconstruct the paleoclimatic history of the Qiangtang Basin during the Late Jurassic.At last,this study analyzed the integrated conditions of structure,climate and provenance with respect to the possible formation of potash and halite deposits in the Qiangtang Basin.The analysis of κ-T diagram,hysteresis loop and thermal demagnetization demonstrates that magnetite and hematite are the primary magnetic minerals.Magnetic parameters of the rocks show an obviously increased content of hematite,revealing that the upper member of the Xiali Formation formed under an arid climate.The comprehensive studies on tectonism,paleoclimate and provenance reveal that the upper member of the Xiali Formation was favorable for the formation of evaporites in the Qiangtang Basin during the Late Jurassic.%羌塘盆地位于青藏高原中部,是一个具有沉积钠盐、钾盐远景的蒸发岩盆地.最近在羌塘盆地上侏罗统夏里组中发现多处具有钾、钠异常的盐泉这一重要的找钾盐线索,然而目前对上侏罗统夏里组的古环境演变仍然不甚了解,限制了对晚侏罗世羌塘盆地的成盐(成钾)条件和可能的层位等重大科学问题的理解.因此本文以热磁分析为主,对羌塘盆地雁石坪地区上侏罗统夏里组沉积物进行高分辨率岩石磁学研究,并讨论其古环境意义.最后,根据成盐(成钾)理论,综合分析羌塘盆地上侏罗统夏里组成盐(成钾)的构造、气候和物源条件.κ-T曲线、磁滞回线和热退磁结果共同表明磁铁矿和赤铁矿是夏里组的主要载磁矿物;磁学参数分析表明夏里组上段赤铁矿含量相对增加,揭示夏里组上段形成于干旱气候环境;综合分析构造、气候和物源条件表明,羌塘盆地上侏罗统夏里组上段最为具备良好的成盐(成钾)条件.
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