东南极泛非普里兹带:碰撞造山带还是板内造山带

The Pan-African Prydz Belt in East Antarctica: a Collisional Orogen or an Intraplate Orogen

东南极普里兹带是近几年在南极大陆上识别出的一条重要的泛非期构造带,因其成因涉及到冈瓦纳超大陆在寒武纪时的形成与演化问题,因此一直是国际地学界关注的焦点。但到目前为止,对于该造山带的构造属性还存在着不同的认识,有些人认为它是板内造山带,而另一些人认为它是两个大陆板块之间的碰撞带。其基本特征是普里兹带两侧为前泛非期不同性质的岩石圈单元,整个区域经历了早期中—下地壳挤压逆冲和晚期中—上地壳伸展垮塌的构造演化历史,区域麻粒岩相变质作用表现为近等热减压的顺时针p-t轨迹。此外,东南极克拉通与冈瓦纳其他块体在500Ma前的古地磁极移曲线并不一致。所以,尽管目前尚未发现蛇绿岩套、岛弧增生杂岩或高压变质岩等直接指相标志,但这些特征均反映了普里兹带是板间碰撞拼合的缝合带,而不是板内造山带,东南极地盾本身则是由不同块体在泛非期拼合而成的。

The Prydz Belt is one of the most important Pan-African mobile belts within the East Antarctic Shield. The belt provoked great interest to many geologists in recent years because it was related to the formation and evolution of the Gondwana suppercontinent during Cambrian. However, at present the tectonic attribute of the Prydz Belt remain highly debated. Some argue for an intraplate orogen, whereas others argue for a suture. In this paper, all the available data reported in the Prydz Bay-Grove Mountains area is presented and reviewed. The general features of the Prydz Belt are as follows. （1） It juxtaposed different terranes with different geological histories during the Pan-African tectonism. （2） It suffered from an earlier compressional deformation at low-to mid-crustal levels and subsequently followed by an extensional collapse at mid-to upper-crustal levels. （3） The whole Prydz Bay area recorded a clockwise p-t evolution with late near-isothermal decompression and anatexis. In addition, Paleomagnetic data showed that the apparent polar wander path for the India and Australo-Antarctic continental blocks did not form a spatially and temporally coherent pattern until c. 550 Ma. These features favor the Prydz Belt representing a collisional orogen between India and East Antarctica formed during the Pan-African period though there complex and high-pressure metamorphics. amalgamated by different terranes during the is no direct evidence such as ophiolite, island-arc accretionary Accordingly, the East Southern Antarctic shield was finally Pan-African period.