| 6217铀矿床成因的同位素地质研究 |
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| 引用本文：.1986.An Isotope Geological Study On The Genfsis Of Thf 6217 Uranium Deposit[J].Mineral Deposits,5(2):54~62 |
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| An Isotope Geological Study On The Genfsis Of Thf 6217 Uranium Deposit |
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| Abstract:The 6217 uranium deposit is located along the contact zone between D granite and L granite, especially inside the D body. Calculations from U-Pb isotope data of pitchlende and uranium-bearing ore samples indicate that the U-Pb isochronic ages are 61.49Ma and 59.71Ma respectively, and the U-Pb three-stage model age is 69.05 Ma, revealing a metallogenic epoch between Late Cretaceous and Early Tertiary time. A study of the oxygen isotope composition shows that the δ18O vajues of hydrothermal solution range from +4.92‰ to +9.80‰ at pre-ore stage and from +4.07‰ to +8.49‰ at ore stage, suggesting that the ore-bearing solution is a mixture of magmatic water and meteoric water. At post-ore stage hydrothermal solution is derived from meteoric water, as can be concluded from itsδ18O values of -4.72-7.88‰, which is roughly consistent with theδ18O values of gallery water and meteoric water in the mining district.δ34S values of pyrite are -0.8 - +4.6‰ and δ13C values of calcite are -7.57 – 9.79‰, implying a probable derivation of sulfur and carbon from the magma. Lead isotope composition shows that the initial lead is a mixture of anomalous lead and common lead, which denotes a gradual entry of the radiogenic lead into the uranium-bearing solution at pre-ore stage. The calculation for gain or loss of uranium in percentage indicates that the country rocks lose uranium during the mineralization process by 27-67%. The t1 ages calcuated by the U-Pb three-stage model and the U-Pb episodic gain model are 560.87 Ma and 500.05 Ma respectively, which demonstrates that the uranium source is related to Cambrian metasedimentary sequence and that the 6217 ore deposit and the D granite probably have identical uranium derivation. It is believed therefore that the uranium of the ore deposit is derived from multiple sources: both from the leaching of uranium-rich D granite by the hydrothermal solution and from the uranium-rich post magmatic solution. |
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