辽东宽甸钴矿勘查区变基性岩地球化学特征和年代学研究
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P588.3

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国家自然科学基金项目(92062214);国家重点研发计划(2022YFC2903502);中国地质调查项目(DD20242528);中国地质科学院基本业务费项目(JB2304)


Whole-rock geochemistry and geochronology of meta-basic rocks from the cobalt exploration area in Kuandian, eastern Liaoning Province
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    摘要:

    以辽东宽甸钴矿勘查区南辽河群里尔峪组变基性岩为研究对象,通过全岩地球化学组成和锆石年代学研究,讨论了里尔峪组变基性岩形成的构造背景以及钴的来源。地球化学分析结果显示,钻孔中变基性岩为正斜长角闪岩,具有一致的稀土元素配分模式,弱Eu负异常,显示E-MORB的地球化学特征。详细的矿物化学分析和地质温压计算结果表明,含辉石斜长角闪岩(ZK2-1)记录了峰期高角闪岩相变质温压条件, p= 0.82~1.00 GPa和t=712~751℃;(含辉石)斜长角闪岩(ZK1-1和ZK3-1)记录了峰后退变质阶段的温压条件,分别为p=0.42~0.81 GPa和t=688~759℃、p= 0.59~0.85 GPa和t=703~739℃。锆石SHRIMP U-Pb定年结果表明,变基性岩中变质锆石记录的年龄为1 857~1 850 Ma。综合宽甸地区变基性岩地球化学和年代学结果,推测其原岩为古元古代中期拉斑玄武岩,形成于伸展环境,并且在其形成过程中岩浆经历了显著的地壳物质混染,暗示古元古代中期打开的洋盆规模可能有限。通过与南、北辽河群变基性岩全岩地球化学特征对比研究,认为宽甸地区变基性岩不是钴矿化的主要成矿物质来源,有关钴矿化的物质来源仍需进一步研究。

    Abstract:

    In this study, the whole-rock geochemistry and zircon U-Pb ages are reported for the meta-basic rocks of the Li’eryu Formation of the South Liaohe Group from the cobalt exploration area in Kuandian. These data provide a significant insight into the tectonic background, as well as the source of cobalt. Geochemical features of the meta-basic rocks in boreholes show that they are orthorhombic amphibolite, and have similar rare-earth elements (REEs) patterns, with slightly negative Eu anomalies. REEs and trace elements compositions have affinity to those of E-MORB. Based on the mineral compositional analyses and p-t estimates using conventional geothermobarometers, the clinopyroxene-bearing amphibolite (ZK2-1) records p-t conditions of p=0.82~1.00 GPa and t= 712~751℃, which probably constrained the peak high amphibolites-facies stage. The metamorphic p-t conditions of (clinopyroxene-bearing) amphibolite (ZK1-1 and ZK3-1) are p= 0.42~0.81 GPa, t= 688~759℃ and p=0.59~0.85 GPa, t=703~739℃, respectively, which represent the conditions of the retrograde stage. The metamorphic zircon from the meta-basic rocks yield the SHRIMP U-Pb ages of 1 857~1 850 Ma. The integrated study of geochemistry and zircon U-Pb dating reveals that their protoliths of the meta-basic rocks are mid-Paleoproterozoic tholeiitic basalt and formed in an extended tectonic environment. Their protoliths underwent significant crustal assimilation imply that the scale of the mid-Paleoproterozoic oceanic basin may be limited. By comparing the geochemical characteristics of meta-basic rocks in the North and South Liaohe groups, it is believed that meta-basic rocks in the Kuandian area are not the main source of cobalt mineralization. The material sources of cobalt mineralization still needs further research.

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廉涛,孙莉,王舫,等, 2024. 辽东宽甸钴矿勘查区变基性岩地球化学特征和年代学研究[J]. 岩石矿物学杂志, 43(5):1281~1301.
LIAN Tao, SUN Li, WANG Fang, et al, 2024. Whole-rock geochemistry and geochronology of meta-basic rocks from the cobalt exploration area in Kuandian, eastern Liaoning Province[J]. Acta Petrologica et Mineralogica, 43(5): 1281~1301.

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  • 收稿日期:2024-03-29
  • 最后修改日期:2024-08-25
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  • 在线发布日期: 2024-09-25
  • 出版日期: 2024-09-25