The Grenvillian and Pan-African orogens: World's largest orogenies through geologic time, and their implications on the origin of superplume
The Grenvillian and Pan-African orogens: World's largest orogenies through geologic time, and their implications on the origin of superplume
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DOI：
10.1016/j.gr.2008.01.001
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发表时间：
2008-08
影响因子：
6.1
通讯作者：
S. Rino;Y. Kon;W. Sato;S. Maruyama;M. Santosh;Dapeng Zhao
中科院分区：
文献类型：
--
作者：
S. Rino;Y. Kon;W. Sato;S. Maruyama;M. Santosh;Dapeng Zhao
新元古代的地球主要是由格伦维和泛非造山作用形成的。其中，格伦维尔造山带长期以来被认为是全球规模的造山事件的次要性质，而泛非造山带已被广泛认识到在许多大陆片段，虽然不是在亚洲的主要部分。根据年代学信息的锆石从主要河口横跨几个重要的地形的地球仪，我们在这里表明，格伦维尔造山带的大陆地壳的形成作出了重大贡献。在0.6 Ga和0.8 Ga之间的时间段标志着泛非造山带黎明时的高潮。这一时期形成的陆壳主要集中在泛非造山带，分布于地球仪。这些地区分布在地球仪的半个半球，在它们迁移形成劳亚大陆后，面积逐渐缩小。全球河口砂中锆石年龄的标准化频率分布清楚地表明，新元古代（0.9- 0.6Ga）和格伦维尔期（1.3- 1.0Ga）的峰值是最大的。这意味着广泛的俯冲，因此活跃的板块构造，可能已经通过这些时期运作。锆石的研究还揭示了格伦维尔造山带的新区域，特别是在现在被厚的古生代沉积盆地覆盖的大陆上。根据本研究中确定的格伦维尔造山带的新位置，并使用的分布模式作为一个标志层，我们提出了修订的古地理配置的Rodinia和冈瓦纳超大陆。结果表明，新元古代是地球地壳形成最活跃的时期。Rodinia拼合之后形成的冷盆地在Rodinia的北方边缘形成一个盆地链，成为地幔隆起的场所，导致超大陆拼合体的裂陷和分离。在冈瓦纳大陆形成后，大陆向北移动。540 Ma，并在250 Ma以来扩大了超大陆盘古大陆的北方。基于这些结果，我们还评估了超级大陆在超级地幔柱形成机制中的作用，解决了核幔边界上方最冷的地幔在数亿年的时间内变成最热的地幔之谜。泛非俯冲形成的板片墓地可以通过P波层析成像成像。我们假设冈瓦纳大陆下D”层的高速异常现在已经转化为低V区，从而产生非洲超级地幔柱。固体地球在中生代的构造历史似乎是由格伦维尔奥伦卡形成的石板墓地控制的。1.0佐治亚州
The Neoproterozoic Earth was shaped largely by the Grenvillian and Pan-African orogenies. Out of these, the Grenvillian orogeny has long been regarded to be of minor nature in terms of global-scale orogenic episodes, whereas the Pan-African orogeny has been widely recognized in many continental fragments, although not in major parts of Asia. Based on chronological information in zircons from major river mouths across several important terrains of the globe, we show here that the Grenvillian orogeny contributed significantly to the formation of the continental crust. The time period between 0.6 Ga and 0.8 Ga marked the climax at the dawn of the Pan-African orogeny. Continental crust formed in this period is concentrated in the Pan-African orogenic belts widely across the globe. These regions were widespread over the half hemisphere of the globe, and were subsequently reduced in size after they moved to form Laurasia. The normalized frequency distribution of zircon ages from river-mouth sand over the world clearly demonstrates that Neoproterozoic and (0.9–0.6 Ga) and Grenvillian (1.3–1.0 Ga) peaks define the largest population. This means that extensive subduction, and hence active plate tectonics, might have operated through these periods. The zircon study has also brought to light new regions of the Grenvillian orogenic belts, particularly in the continents which are now covered by thick Phanerozoic sedimentary basins. Based on the new locations of Grenvillian orogens identified in this study, and using the distribution patterns as a marker bed, we propose revised paleogeographic configurations of the Rodinia and Gondwana supercontinents. Our results demonstrate that the Neoproterozoic was the most active period of crust formation in the Earth. The cold basins, formed right after the assembly of Rodinia, exhibit a basin chain fringing the northern periphery of Rodinia, which turned into sites of mantle upwellings and led to the rifting and separation of the supercontinental assembly. The continents then moved northwards after the formation of Gondwana at ca. 540 Ma, and enlarged the northern half of the supercontinent Pangea since 250 Ma. Based on the results, we also evaluate the role of supercontinents in the mechanism of generation of superplumes addressing the enigma that the coldest mantle right above the Core–Mantle Boundary turns to the hottest one over a period of several hundreds of million years. Slab graveyard formed by the Pan-African subduction can be imaged through P-wave tomography. We postulate that the high-velocity anomaly in the D” layer underneath Gondwana has now transformed to the low-V regions to generate the African superplume. The tectonic history of solid Earth in the Phanerozoic seems to be controlled by the slab graveyards formed by the Grenvillian orogeny ca. 1.0 Ga.