山西平朔井工三矿煤系角砾岩特殊成因探讨

The origin of coal measure breccia in Jinggong No.3 Coal Mine, Pingshuo, Shanxi

  • 摘要: 平朔井工三矿煤系角砾岩成因和产状特殊,与煤层关系密切。通过补勘钻孔岩心观测,结合区域地质和以往钻孔资料分析,详细描述研究区角砾岩的成分、结构和构造特征,圈定角砾岩的层位、厚度和分布状况。发现平朔井工三矿角砾岩成分复杂、大小不一,其中泥岩砾径最大可达1.20 m以上,以棱角状为主,分选性极差;角砾岩体顶底界面明显,临近或出现在煤层中,横向连续性差。角砾岩破坏了煤层的连续性,总体北多南少,分布有限,呈透镜状产出,长轴指向西北物源区;垂向上,角砾岩自下而上减少。研究认为,聚煤期植物锚固作用强大,陆源边坡及碎屑受植被禁锢,只能在限定的范围内垂向加积,累积成边坡较陡的碎屑库;泥炭沼泽表层为植被泥炭交织在一起的泥炭网,底部深度降解的膏状泥炭提供了有利的滑移面。突发事件导致物源区边坡和角砾质碎屑库崩塌,冲越到泥炭网上,撕裂成“泥炭筏”,被泥炭筏载运移,断续沉积,并遭受改造。角砾岩成因及分布规律对煤层成因及厚度变化、煤炭资源/储量估算与开采具有重要指导意义。煤系、特别是煤层中沉积角砾岩的成因用泥炭筏载运移模式解释可能更为合理。

     

    Abstract: The genesis and occurrence of coal measure breccia in Jinggong No.3 Coal Mine of Pingshuo are special and closely related to the coal seams. Through core observation of supplementary drilling, combined with regional geology and analysis of previous drilling data, the composition, structure and structural characteristics of breccia in the study area are described in detail, and the horizon, thickness and distribution of breccia are delineated. It is found that the composition of breccia in Jinggong No.3 Coal Mine of Pingshuo is complex, and the size of breccia is different. The maximum diameter of mudstone is more than 1.20 m, which is mainly angular, and the sorting is very poor. The top and bottom interface of breccia is obvious, which is close to or appears in the coal seam, and the transverse continuity is poor. Breccia destroys the continuity of coal seam, with more in the north and less in the south, and its distribution is limited. It occurs in lenticular shape, and its long axis points to the northwest provenance. Vertically, breccia decreases from bottom to top. The results show that plant anchorage is strong in the coal accumulation period, terrigenous debris and side slope are confined by vegetation and accumulated vertically within a limited range, forming a debris reservoir with steep slope. Peat net interwoven with vegetation and peat is on the surface of peat swamp, and paste peat with deep degradation at the bottom provides a favorable slip surface. The unexpected events lead to the collapse of the slope and breccia reservoir in the provenance area, rush over the peat net, be teared into a peat raft and transported by the peat raft, intermittently deposit, and be transformed. The distribution law and genesis of breccia is of great significance genesis and thickness variation of coal seam, estimation and exploitation of coal resources/reserves. It may be more reasonal to explain the genesis of coal measures sedimentary breccia with peat raft transport model.

     

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