鄂尔多斯盆地晚三叠世早期物源分析
Source Analysis During the Early Late Triassic in Ordos Basin
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摘要: 通过对鄂尔多斯盆地晚三叠世早期古水流方向及沉积物扩散方向、轻重矿物组合特征及稀土元素地球化学特征等的分析,发现延长组沉积早期古水流方向明显具有从湖盆四周向中心汇聚的特征,并可从轻重矿物组合上可以划分出5个物源方向,即东北、东、南、西南和西北方向,其中东北、西南和西北物源是主要物源方向.以东北方向物源明显占优势,南物源影响范围较小为特征.延长组早期沉积的母岩主要为太古宙的复杂变质岩系及下元古界的变火山-沉积岩系.其中,盆地东北部物源来自古阴山及大青山提供的稳定物源,因此三角洲沉积大面积发育;西南物源主要来自秦祁褶皱造山带的早古生界片麻岩、花岗岩类,以距离源区近,沉积物粒度明显比东北物源区粗为特征.Abstract: Based on directions of palaeo-flow, mineral combination characteristic and REE characteristic in Ordos Basin, directions of palaeo-flow of the early Yanchang Formation comesfrom circum to center, and five source directions can be found, which are northeast, ea st, south, southwest and northwest directions. The mainsource directions are northeast, southwest and northwest directions. The northeast source obviously dominates, and influencearea of south source is narrower. The main parent rock of the early Yanchang Formation is complex metamorphic rock of A rchean and metavolcanic rock-sed imentary rock system. The northeast source comes from the sustained source offered by the old Yinshan and the Daqingshan, so delta deposit develops grossly. The south source mainly comes from gneiss and granide of early Palaeozoic in the Qinling and Qilianshan fold orogenic zone, the characteristics of which are close to the provenance and sediment size obviously wider than the northeast source.
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Key words:
- Ordos Basin /
- the early Late Triassic /
- palaeo-flow direction /
- mineral combination /
- REE pattern
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