东南极晚新元古—早古生代构造热事件及其在冈瓦纳超大陆重建中的意义

Late Neoproterozoic-Early Paleozoic Tectonothermal Events in East Antarctica: Implications for Amalgamation of the Gondwana Supercontinent

在东南极大陆内部及边缘发育3条晚新元古代—早古生代造山带,即东非造山带(南延部分)、普里兹造山带和罗斯造山带。东非造山带的南延部分主要出露于吕措—霍尔姆湾—毛德王后地—沙克尔顿岭地区,其内发育蛇绿岩、榴辉岩相超镁铁岩及逆冲—推覆构造,因而被解释为东、西冈瓦纳陆块拼合的缝合线。罗斯造山带主要出露于横贯南极山脉地区,其内保存有大陆裂解、洋壳俯冲和地体增生的地质纪录,代表冈瓦纳超大陆的活动大陆边缘。普里兹造山带主要出露于普里兹湾和登曼冰川,因其位于从前假设的统一东冈瓦纳陆块的内部,加之缺少蛇绿混杂岩、岛弧增生杂岩和高压变质岩(如蓝片岩或榴辉岩)等与大洋板块俯冲作用密切相关的岩石,所以当前存在着碰撞造山成因和板内改造成因两种不同的认识。普里兹造山带构造性质的确定不仅决定了冈瓦纳超大陆的汇聚过程和方式,也制约了罗迪尼亚超大陆的形成和演化过程。因此,开展普里兹造山带的研究对于揭示新元古代—早古生代的全球构造演化具有重要的科学意义。

Three late Neoproterozoic-early Paleozoic orogenic belts, East African Orogen, Prydz Belt and Ross Orogen, occur in East Antarctica. The East African Orogen extends southward to the Lützow-Holm Bay-Dronning Maud Land-Shackleton Range area. The area is interpreted as the southern part of the suture between East and West Gondwana blocks due to the appearance of ophiolites, eclogite-facies ultramafic rocks and thrust-nappe structures. The Ross Orogen is exposed in the Transantarctic Mountains and is considered as the active margin of the Gondwana supercontinent. The geological records of continental break-up, oceanic crustal subduction and terrane accretion are preserved in the orogen. The Prydz Belt occurs in the Prydz Bay and Denman Glacier, and is located in the interior of a previously proclaimed unified East Gondwana. The absence of subduction-related rocks, such as ophiolite suite, arc accretionary complex and high-pressure blueschist and eclogite, resulted in the argument that the Prydz Belt represents whether a collisional zone or an intraplate reworking belt. The determination of the nature of the Prydz Belt would constrain not only the amalgamation scenario of the Gondwana supercontinent, but also the reconstruction pattern of the Rodinia supercontinent. Therefore, the Prydz Belt is the key to understand the global tectonic evolution during the Neoproterozoic to early Paleozoic.