ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    秦岭造山带凤县–山阳地区富钴–镍钠长角砾岩年代学研究及地质意义

    Geochronology Study and Geological Significance of Cobalt-Nickel-Rich Albite Breccia in the Fengxian-Shanyang, Qinling Orogenic Belt

    • 摘要: 秦岭造山带内沿凤县–山阳断裂两侧分布大面积钠长角砾岩,这些钠长角砾岩的钴、镍等元素含量普遍较高,因此具有良好的研究价值。笔者通过野外地质考察发现与钠长岩有关的镍钴矿床、矿化点共6处(商南县博鱼沟钠长角砾岩、商南县过凤楼白云石钠长角砾岩、商南县开河白云石钠长角砾岩、商南县开河铁白云石方解石钠长角砾岩、山阳县桐木沟铁白云石钠长角砾岩和柞水县凤凰镇水滴沟白云石钠长角砾岩)。对此开展系统的岩石学、锆石U-Pb年代学和锆石微量元素研究,研究表明:这些富钴–镍钠长角砾岩主要呈浅灰白色和青灰色,块状构造,可见角砾状构造,部分区域可见黄铁矿、方解石、石英及钠长石脉。钠长角砾岩样品的锆石多呈现自形–半自形,年龄集中分布在375~543 Ma、665~959 Ma和963~1155 Ma,其年龄峰值分别对应早泥盆世、志留纪、奥陶纪、新元古代、中元古代、古元古代。综合研究表明,这些富钴–镍的钠长角砾岩年龄和该区泥盆系地层年龄一致,不同时期壳源沉积物对泥盆纪钠长角砾岩沉积过程均有贡献,成岩后期的岩浆–热液作用对镍–钴矿有明显的富集作用,综上所述,研究区出露的钠长角砾岩具有钴–镍矿化的潜力。

       

      Abstract: In the Fengxian-Shanyang, Qinling orogenic belt, there are large amounts of albites breccia that show the obvious enrichment of cobalt and nickel elements, which therefore are important for the ore probe. In this paper, a total of 6 albite breccia related to Co-Ni deposits and mineralization points have been found through field geological investigation (Boyugou albite breccia in the Shangnan County, Guofenglou dolomite-bearing albite breccia in the Shangnan County, Kaihe dolomite-bearing albite breccia in the Shangnan County, Kaihe iron-dolomite- and calcite-bearing albite breccia in the Shangnan County, Tongmugou iron-dolomite-bearing albite breccia in the Shanyang County and Shuidigou dolomitbearing albite breccia in the Fenghuang Town of the Zhashui County). Systematic studies of petrology, zircon U-Pb chronology, and zircon trace elements display that these cobalt-nickel-rich albite breccia are mainly grayish white and bluish gray with massive structure and brecciated structure, and some areas occasionally exist the pyrite, calcite, quartz and albite veins. The zircons of albite breccia are mostly idiomorphic and semi-idiomorphic, and their ages are concentrated in 375~543 Ma, 665~959 Ma, and 963~1155 Ma. Their age peaks are corresponding to the Early Devonian, Silurian, Ordovician, Neoproterozoic, Mesoproterozoic, and Paleoproterozoic. The comprehensive studies demonstrate that the zircon ages of these cobalt-nickel-rich albite breccia are consistent with the age of Devonian strata. Crust-derived sediments of different periods are contributed to the sedimentary process of Devonian albite breccia, and the later magmatic -hydrothermal processes are responsible for the enrichment of nickel-cobalt breccia deposits. In conclusion, the albite breccia exposed in the study area has the potential for cobalt-nickel mineralization.

       

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