晚三叠世泛大陆的解体和中特提斯洋的形成

2025-03-15 14:52:03
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晚古生代形成的泛大陆的解体以中特提斯洋形成为先导。三叠纪—侏罗纪时(在西亚局部地段可能略早一些),在其原冈瓦纳大陆群北缘发生裂解,形成横贯东西的中特提斯。在东特提斯构造域,中特提斯洋分为南北两支,分别为雅鲁藏布江洋和班公湖-怒江洋,其间为冈底斯陆块,相当Ssengör的基莫里大陆(郝子文等,1983)。雅鲁藏布江洋相当Sengör,A.M.C.;Jeloji Bolümü(1991)的新特提斯。而班公湖-怒江洋则与他们所述的位于西亚和欧洲基莫里大陆和劳亚大陆之间,于晚古生代—中中生代期间消亡的古特提斯难以对应。

中特提斯不是古特提斯(指古生代—早中生代)的延续和发展(至少在东特提斯构造域是如此),在空间上它明显南移。它是二叠纪的泛大陆解体产物,属于从晚前寒武纪末的泛大陆解体,到二叠纪重组后再解体这一大陆裂-聚巨旋回(周期约600Ma)发展的另一旋回的开始。随着印度洋和南大西洋的形成,原来的冈瓦纳大陆群全面解体。这一解体作用至今仍在红海和南极洲进行。在南极洲罗斯海和威得尔海之间的东西半岛交接地带,正在形成一个横南极裂谷带(P.J.J.Kamp and P.G.Fitzgerald,1987)。

中特提斯除北支班公湖-怒江洋于晚侏罗世—早白垩世闭合外,其南支的扎格罗斯-雅鲁藏布江洋,并未完全闭合,部分转换、归并到印度洋之中。

三江特提斯构造带正是在这一全球构造形成的背景中形成演化。它地处泛华夏大陆群与冈瓦纳大陆群交接地带,历经了两次泛大陆解体旋回和原、古、中特提斯3大发展阶段。它的构造演化也是在全球大陆由南聚北散到北聚南散,自古生代以来大陆不断自南向北漂移过程中,通过裂-聚演变而完成的,其动力学机制,可能与地球质心向南迁移,南半球膨胀,泛大陆解体,并向北漂移有关;在自南向北输送大陆北移的软流圈的地幔对流中,除了垂向的地幔对流体外,可能存在大小不等水平涡旋,只有这样才能促使陆块的旋转和泛大陆的形成及形成后的立即解体(李兴振,1994;李兴振等,1995)。

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