Major influences on the evolution of the 2.67-2.1 Ga Transvaal basin, Kaapvaal craton
Major influences on the evolution of the 2.67-2.1 Ga Transvaal basin, Kaapvaal craton
复制标题
DOI：
10.1016/s0037-0738(01)00075-6
复制
发表时间：
2001-06-01
影响因子：
2.8
通讯作者：
Bumby, AJ
中科院分区：
文献类型：
--
作者：
Eriksson, PG;Altermann, W;Bumby, AJ
德兰士瓦是保存在Kaapvaal克拉通上的德兰士瓦超群的三个构造盆地之一。新太古宙-古元古代德兰士瓦盆地的演化主要受岩浆作用、古气候作用和海蚀作用的影响，板块构造作用零星存在。超群包括基底“原盆地”岩石，其次是黑礁组、Chuniespoort群和最上层比勒陀利亚群。原盆地单元的未成熟硅质和双峰火山岩反映了与c. 2.7 Ga Ventersdorp（超群）地幔柱有关的宽裂陷带。单个的原盆地序列是在断陷盆地中形成的，至少部分受Kaapvaal基底绿岩带取向的控制。岩浆期后、裂谷期后的热沉降发育了黑礁河板砂岩及其后的厚碳酸盐- bif表陆台地序列。伴随这种长期的热松弛而来的是次要的机械沉降。新太古代大气成分的强烈风化作用大大减少了弹性沉积，温室古气候进一步促进了碳酸盐沉积。由于全球岩浆事件或超大陆分裂导致的洋中脊生长增强，全球海平面上升也在Chuniespoort表盆演化中发挥了关键作用。比勒陀利亚群的沉积归因于两个旋回的裂谷作用和随后的热沉降作用。第一个旋回似乎反映了板块构造引起的裂谷作用，尽管由于第一次主要的全球冰川作用，海平面降低了，但一个表海淹没了裂谷盆地。第二个比勒陀利亚周期很可能与一次主要的大陆洪水玄武岩事件有关，热沉降使第二个可能更大的表海向卡普瓦尔克拉通北部推进。对板块构造在实质上是克拉通内的德兰西瓦盆地演化中相对次要的重要性的评价，在很大程度上取决于津巴布韦克拉通和卡普瓦尔克拉通碰撞的林波波造山运动的年龄；最近关于公元前2.0 Ga碰撞的证据支持了这样一个概念，即在德兰士瓦盆地演化过程中，灾难性的全球岩浆事件逐渐让位于板块构造。(C) 2001 Elsevier Science B.V.版权所有
The Transvaal is one of three structural basins of the Transvaal Supergroup preserved on the Kaapvaal craton. The evolution of the Neoarchaean-Palaeoproterozoic Transvaal basin is ascribed predominantly to magmatism, palaeoclimate and eustasy, with plate tectonics playing a sporadic role. The supergroup comprises basal 'protobasinal' rocks, followed by the Black Reef Formation, Chuniespoort Group and uppermost Pretoria Group. Immature siliciclastic and bimodal volcanic rocks of the protobasinal unit reflect a wide zone of rifting related to the c. 2.7 Ga Ventersdorp (Supergroup) mantle plume. Individual protobasinal successions were laid down in separate fault-bounded basins, controlled at least partially by greenstone belt orientations in the Kaapvaal basement.Post-magmatic, post-rifting thermal subsidence accommodated Black Reef fluvial sheet sandstones and the subsequent thick carbonate-BIF epeiric platform succession of the Chuniespoort Group. Subordinate mechanical subsidence accompanied this long-lived thermal relaxation. Intense weathering due to Neoarchaean atmosphere composition greatly reduced elastic sedimentation and the greenhouse palaeoclimate further encouraged carbonate sedimentation. Globally enhanced sea levels, due to enhanced mid-ocean ridge growth consequent upon either global magmatic events or supercontinent break-up, also played a pivotal role in Chuniespoort epeiric basin evolution.Pretoria Group sedimentation is ascribed to two cycles of rifting and subsequent thermal subsidence. The first cycle appears to reflect plate tectonically induced rifting, with an epeiric sea drowning the rift basin despite reduced sea levels due to the first major global glaciation. The second Pretoria cycle is most likely related to a major continental flood basalt event, with thermal subsidence allowing a second and probably larger epeiric sea to advance onto the northern Kaapvaal craton. Evaluation of the inferred relatively minor importance of plate tectonics in the evolution of the essentially intracratonic Transvaal basin depends to a large degree on the age assigned to the Limpopo orogeny during which the Zimbabwe and Kaapvaal cratons collided; recent evidence for a c. 2.0 Ga collision supports the concept that catastrophic global magmatic events gradually gave way to plate tectonics during Transvaal basin evolution. (C) 2001 Elsevier Science B.V. All rights reserved.