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青藏高原东缘一直被普遍认为是一个吸收印度—欧亚大陆碰撞变形的调节带。本文所获得的最新SHRIMP锆石U-Pb测年结果显示:青藏高原东缘具有更加复杂的地质历史。测年结果表明,高原东缘最古老的前寒武纪结晶基底形成于古元古代(2401~1912Ma)。这一古老基底首先受到中元古代构造热事件(1361~1040Ma)的影响,随后受到新元古代与弧岩浆活动有关构造热事件(791~817Ma)的强烈改造。松潘—甘孜复理石杂岩的基底是亲洋壳型的,形成于晚新元古代的大陆裂解作用(681~655Ma)。高原东缘的前寒武纪微地块可能是由这次裂解作用从扬子或青藏地块拉裂出去形成的。这些微陆块先增生拼贴于东冈瓦纳大陆、然后又从中裂离,并最终卷入高原东缘的特提斯构造演化过程中。伴随东冈瓦纳大陆裂解,高原东缘古特提斯洋于石炭纪至二叠纪早期拉开(328~292Ma),经早中生代弧-陆碰撞作用闭合(224~213Ma)。中侏罗世这一地区发育显著的构造岩浆活动(175Ma),但其动力学背景仍不十分清楚。晚白垩世岩浆活动(97Ma)可能是印度板块初始俯冲阶段的产物。新生代岩浆作用(18Ma)与陆-陆碰导致的大规模走滑断层作用所引起的同熔作用有关。
The eastern edge of the Qinghai-Tibet Plateau has long been widely regarded as an adjustment belt that absorbs the collision-deformation of India-Eurasia continent. The latest SHRIMP zircon U-Pb dating obtained in this paper shows that the eastern margin of the Tibetan Plateau has a more complicated geological history. The dating results show that the Oligocene Precambrian crystalline basement formed in the eastern margin of the plateau formed in the Paleoproterozoic (2401-1912 Ma). This ancient base was first strongly influenced by Mesoproterozoic tectono-thermal events (1361-1040 Ma) and was subsequently strongly altered by Neoproterozoic-tectono-thermal events related to arc magmatism (791-817 Ma). The base of the Songpan-Garze flysch complex is an oceanic oceanic type that formed during the Neoproterozoic continental cleavage (681-655 Ma). Precambrian microfacies on the eastern edge of the plateau may be formed by the cleavage of the Yangtze block or the Qinghai-Tibet block. These micro-alluvians first proliferated and collapsed to the East Gondwanaland, then split again and eventually became involved in the Tethyan tectonic evolution along the eastern edge of the plateau. Along with the dissolution of the East Gondwanaland, the Gt Tertis Ocean in the eastern margin of the plateau opened in the early Carboniferous to Permian (328 ~ 292Ma) and closed (224 ~ 213Ma) by the Meso-Mesozoic-continental collision. The Middle Jurassic has significant tectonomagmatic activity (175 Ma) in this area, but its kinetic background is still not clear. Late Cretaceous magmatism (97 Ma) may be the product of the initial subduction of the Indian plate. The Cenozoic magmatism (18Ma) is related to the same melt effect caused by the large-scale strike-slip faults caused by land-continent collision.