鄂尔多斯盆地北部中侏罗统直罗组岩石地球化学特征及其地质意义
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P619.14;P512.2

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国家重点研发计划(2023YFC2906701); 地球深部探测与矿产资源勘查国家科技重大专项(2025ZD1006801)


Lithogeochemical characteristics of the Middle Jurassic Zhiluo Formation in the northern Ordos Basin and its geological significance
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    摘要:

    内蒙古杭锦旗地区是鄂尔多斯盆地北缘重要的产铀地区之一,具有优越的成矿地质条件和找矿前景。本文对杭锦旗地区X7-6井中侏罗统直罗组岩芯进行了沉积学、岩石学和地球化学分析,系统地研究了有利于铀富集成矿的条件。研究结果表明,直罗组下段为辫状河沉积,主要为灰色厚层砂岩和薄层泥岩夹薄层煤,富含炭屑和黄铁矿,而上段发育曲流河及三角洲相沉积,以紫红色粉砂岩和泥岩为主;地球化学分析结果显示样品具有轻稀土元素富集、重稀土元素亏损的右倾型配分模式;化学蚀变指数CIA值在54 ~77之间,表明直罗组经历了中等风化作用;古环境和古气候判别指标Sr/Cu、U/Th、V/Cr 、Ni/Co、V/(V+Ni)和Sr/Ba值显示直罗组沉积时古水体为富氧的淡水环境,古气候经历了从干湿交替向干旱-半干旱的演变;直罗组源区构造背景为大陆岛弧,源岩以上地壳长英质岩石为主。上述沉积环境、构造背景、古气候和物源特征为该地区直罗组铀富集成矿提供了有利的地质条件。

    Abstract:

    The Hangjinqi area in Inner Mongolia is one of the significant uranium-bearing regions in the northern Ordos Basin, with favorable geological conditions and promising exploration prospects for mineralization. This paper conducts sedimentological, petrological and geochemical analyses on the core samples of the Middle Jurassic Zhiluo Formation from the borehole X7-6 in the Hangjinqi area, systematically studying the conditions conducive to uranium enrichment and mineralization. The research results show the lower section of the Zhiluo Formation comprises braided river deposits, mainly composed of the thick-bedded gray sandstone and thin mudstone interbedded with thin coal seams, rich in carbonaceous debris and pyrites, while the upper section is characterized by meandering river and deltaic sedimentation, dominated by purple-red siltstone and mudstone.The geochemical characteristics exhibit a "right-inclined" pattern with enrichment of light rare earth elements and depletion of heavy rare earth elements. The chemical index of alteration (CIA) values rangs from 54 to 77,indicating moderate chemical weathering of the Zhiluo Formation during deposition. The paleoenvironmental and paleoclimatic discrimination indicators Sr/Cu, U/Th, V/Cr, Ni/Co, V/(V+Ni), and Sr/Ba values suggest that the paleowater system during the deposition of the Zhiluo Formation was an oxygen-rich freshwater environment, and the paleoclimate underwent a transition from alternating dry and wet conditions to arid and semi-arid conditions. The tectonic setting of source areas of the Zhiluo Formation are continental arcs, and the provenances are primarily composed of the upper crustal felsic rock. The sedimentary environments, tectonic setting, paleoclimate and provenance characteristics can provide favorable geological conditions for uranium enrichment and mineralization in the Zhiluo Formation of the Hangjinqi area.

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李宗谚,王涛,彭楠,等, 2026. 鄂尔多斯盆地北部中侏罗统直罗组岩石地球化学特征及其地质意义[J]. 岩石矿物学杂志, 45(3):584~602.
LI Zong-yan, WANG Tao, PENG Nan, et al, 2026. Lithogeochemical characteristics of the Middle Jurassic Zhiluo Formation in the northern Ordos Basin and its geological significance[J]. Acta Petrologica et Mineralogica, 45(3): 584~602.

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  • 收稿日期:2025-09-29
  • 最后修改日期:2026-03-19
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  • 在线发布日期: 2026-05-20
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