摘要
结合塔里木北缘的库车拗陷和塔北隆起这两个构造单元的地温资料和岩石热物性参数,利用一维热传导方程,给出了塔里木北缘地区岩石圈的热结构。塔里木北缘地区平均地表热流为45mW/m~2左右,地幔热流约为20~24mW/m~2,莫霍面温度为514~603℃,热岩石圈厚度138~182km。在此基础上,根据该区地震测深剖面揭示的P波速度结构和岩石学,结合流变学模拟进一步确定了该区的岩石圈强度及其分布特征。研究结果表明,岩石圈的流变分层现象明显,整个上地壳和下地壳部分以脆性性质为主,下地壳底部才显韧性性质,壳下岩石圈地幔也表现为脆性性质,具有典型的“三明治”结构。此外,岩石圈强度也具有横向变化的特征,隆起区强度大于坳陷区强度;从南往北,强度依次降低,塔北隆起南部强度最大,库车坳陷强度最小。塔里木北缘地区岩石圈拉张背景下强度为4.77×10~(12)~5.03×10~(13)N/m,挤压背景下为6.5×10~(12)~9.40×10~(13)N/m,其脆-韧性转换深度在20~33km之间。塔里木北缘的岩石圈较冷且强度较大,岩石圈表现为刚性并以整体变形为主。该区地震活动性研究也表明了这一整体变形的地球动力学特征。
引文
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