Isotopic Geochemistry of Metallogeny for the Largest Paleokarst Uranium Deposit in China

Min Maozhong; Wang Xiangyun; Shen Baopei; Wen Guangdou; Fan Tao

A uranium deposit is the largest paleokarst type U deposit in loth scale and tonnage in China. Thedeposit is formed below a fossil cave and in a faulting}olution breccia system in the Lower Carbonifer-ous limestone. The temperature of mineralizing fluids ranges from 1810℃to 1500 ℃Four U一Pb ages forpitchblende and whole rock ores, 135, 131, 119 and 65 Ma, have been determined, which are obviouslyyounger than those of the wall rocks. Sulfur isotope data show that the δ³⁴ S values of pyrites from theores range from 1.00 ‰to一15. 3‰with a mean value of一6.87‰,closel to those of pyrites fromthe wall rocks(1. 00‰一15.60‰，mean- 7.06‰)，suggesting that the wall rocks are the source ofsulfur for mineralization. The five analyzed samples of calcites from the ores have δ¹³ Cvalues between 0.34‰and-3.19‰(mean一1.50‰).The similarity between the average carbon isotope composition of the ores(一1.50‰)and the wall rocks(0.53‰)is interpreted to result from an isotope exchange between the wall rock and mineralizing fluid. The lead isotope composition of pyrites from the ores andwhole}ock of Lower Carboiferous sugggests that the source of lead and urarnum in the deposit is vari-ous in strata of the ore field.The value of δ¹⁸O and δ^Dfor mineralizing fluids range from 1.5‰o 7.3‰ and from一30.4‰to一84.9‰,of metamorphic and meteoric waters.respectively, indicating that the mineralizing fluid is a mixed waterThe mineralizing process is clowly related to development historyof regional tectordic movemnets and multi-episode paleokarstification. Thus, it is named as hydrothermalreworked paleokarst type uranium deposit.

Isotopic Geochemistry of Metallogeny for the Largest Paleokarst Uranium Deposit in China

1 Department of Earth Sciences Nanjing University Nanjing 210008;

2 No.303 Geological Party Bureau of Geology and Lxploration of Central-Ruth China Hunan 425808

Received Date: 1995-03-29

Publish Date: 1997-03-10

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Abstract: A uranium deposit is the largest paleokarst type U deposit in loth scale and tonnage in China. Thedeposit is formed below a fossil cave and in a faulting}olution breccia system in the Lower Carbonifer-ous limestone. The temperature of mineralizing fluids ranges from 1810℃to 1500 ℃Four U一Pb ages forpitchblende and whole rock ores, 135, 131, 119 and 65 Ma, have been determined, which are obviouslyyounger than those of the wall rocks. Sulfur isotope data show that the δ³⁴ S values of pyrites from theores range from 1.00 ‰to一15. 3‰with a mean value of一6.87‰,closel to those of pyrites fromthe wall rocks(1. 00‰一15.60‰，mean- 7.06‰)，suggesting that the wall rocks are the source ofsulfur for mineralization. The five analyzed samples of calcites from the ores have δ¹³ Cvalues between 0.34‰and-3.19‰(mean一1.50‰).The similarity between the average carbon isotope composition of the ores(一1.50‰)and the wall rocks(0.53‰)is interpreted to result from an isotope exchange between the wall rock and mineralizing fluid. The lead isotope composition of pyrites from the ores andwhole}ock of Lower Carboiferous sugggests that the source of lead and urarnum in the deposit is vari-ous in strata of the ore field.The value of δ¹⁸O and δ^Dfor mineralizing fluids range from 1.5‰o 7.3‰ and from一30.4‰to一84.9‰,of metamorphic and meteoric waters.respectively, indicating that the mineralizing fluid is a mixed waterThe mineralizing process is clowly related to development historyof regional tectordic movemnets and multi-episode paleokarstification. Thus, it is named as hydrothermalreworked paleokarst type uranium deposit.

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Isotopic Geochemistry of Metallogeny for the Largest Paleokarst Uranium Deposit in China

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