The formation and evolution of the Songpan-Garze fore-arc basin, western Sichuan
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摘要: 地处柴南缘昆中蛇绿杂岩带与羌塘地块北缘可可西里-金沙江古缝合线之间的松潘-甘孜褶皱带(包括东昆仑构造带),其主体应属古特提斯洋晚石炭世-晚三叠世时期向其北侧的柴达木古陆南缘俯冲过程中在活动陆缘弧-沟间隙之间增生形成的一个大型弧前构造带。具有由弧前盆地沉积楔和基底增生杂岩构成的双重结构特点,其形成与冈瓦纳大陆北缘若尔盖"三角"地块的楔入及俯冲带向南迁移有关。大致经历了晚石炭世-早三叠世狭窄弧前盆地和中晚三叠世宽阔弧前盆地两个主要演化阶段。Abstract: The Songpan-Garze fold zone, western Sichuan is a triangular tectonic zone located on the junction of the Qaidam landmass and Qiangtang landmass, and bounded by central Kunlun ophiolitic melange zone to the north, Hoh Xil-Jinshajiang suture zone to the south, Longmenshan fault to the east, and extended into the Karakorum Mountains to the west. The megagiant fore-arc fold zone 2500 km long in the EW direction and 150-500 km wide in the NS direction consists dominantly of tremendous (>10 km) Triassic flysch complexes,that are built up of fore-arc basin sedimentary rock series and basement accretionary complexes. It is inferred that the fold zone resulted from the accretion of the Palaeo-Tethys in the areas between active continental marginal arcs and trenches during its collision towards the southern margin of the Qaidam landmass north of it during the Late Carboniferous to the Late Triassic, or may owe its origin to the wedging of the triangular Zoige landmass on northern Gondwanaland and southward migration of the subduction zone. The Songpan-Garze fore-arc tectonic zone has evolved from a narrower fore-arc basin during the Late Carboniferous to the Early Triassic to a broad fore-arc basin during the Middle and Late Triassic.
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