Geochemical characteristics of uranium-rich dispersed organic matter and their geological significance for uranium mineralization: A case study from the Ordos Basin
Fan Zhang , Yangquan Jiao , Liqun Wu , Hui Rong , Jianying Wang , Chengcheng Zhang
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引用次数: 0
Abstract
Geochemical characteristics of uranium minerals is an important content for uranium deposits, and is conducive to understand the formation mechanism, environment and genesis of sandstone-type uranium deposits. In the Diantou-Shuanglong uranium deposit from southern Ordos basin, carbonaceous debris (CD), dispersed organic matter, is widely distributed in sandstones from uranium-bearing strata, and is the dominant enrichment agent for uranium precipitation. The geochemical compositions of uranium-rich CD were investigated by using inductively coupled plasma mass spectrometry (i.e., ICP-MS) and scanning electron microscope-energy dispersive X-ray spectroscopy (i.e., SEM-EDS). The results show that element U bears a close relationship with elements W, Ta, Mo, Pb, Th, Bi, Mn, V, Ti, Co, Be, especially Mo, and Pb, indicating that these elements are rich in uranium-bearing minerals. The contents of rare-earth element (i.e., REE) and light rare-earth element (i.e., LREE) increase with the increasing uranium abundance, implying that REE primarily enrich in uranium minerals, especial for LREE. Moreover, LTEE (e.g., Nd) and Y are detected in uranium-bearing minerals. Besides, uranium-bearing CD exhibits similar REE geochemical characteristics and distribution patterns with the surrounding sandstones, indicating that they are homologous in sedimentary source, sedimentary environment, and tectonic background, and the CD is deposited during synsedimentary period. Given the distribution characteristics of trace element and REE, it is comprehensively inferred that the formation of uranium mineralization is not related to deep hydrothermal fluid below the lower crust, but is altered by the low-temperature hydrothermal fluid. Synsedimentary CD at the stage of low to medium thermal maturity is of certain adsorption and reduction, and is favorable for the precipitation and enrichment of uranium-bearing phase and the other trace element (e.g., Mo, V) similar in geophysical-chemical properties with U element, and the sedimentary environment is beneficial for preservation of uranium. It will be contributed to clarify the genesis of sandstone-type uranium deposit and to provide some guidance for the exploration of the uranium deposit in the studied area.
期刊介绍:
Journal of Geochemical Exploration is mostly dedicated to publication of original studies in exploration and environmental geochemistry and related topics.
Contributions considered of prevalent interest for the journal include researches based on the application of innovative methods to:
define the genesis and the evolution of mineral deposits including transfer of elements in large-scale mineralized areas.
analyze complex systems at the boundaries between bio-geochemistry, metal transport and mineral accumulation.
evaluate effects of historical mining activities on the surface environment.
trace pollutant sources and define their fate and transport models in the near-surface and surface environments involving solid, fluid and aerial matrices.
assess and quantify natural and technogenic radioactivity in the environment.
determine geochemical anomalies and set baseline reference values using compositional data analysis, multivariate statistics and geo-spatial analysis.
assess the impacts of anthropogenic contamination on ecosystems and human health at local and regional scale to prioritize and classify risks through deterministic and stochastic approaches.
Papers dedicated to the presentation of newly developed methods in analytical geochemistry to be applied in the field or in laboratory are also within the topics of interest for the journal.