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Article: Mantle-derived gaseous components in ore-forming fluids of the Xiangshan uranium deposit, Jiangxi province, China: Evidence from He, Ar and C isotopes

TitleMantle-derived gaseous components in ore-forming fluids of the Xiangshan uranium deposit, Jiangxi province, China: Evidence from He, Ar and C isotopes
Authors
KeywordsChina
He, Ar and C isotopes
Mantle-derived volatiles
The Xiangshan U deposit
Issue Date2009
PublisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/chemgeo
Citation
Chemical Geology, 2009, v. 266 n. 1-2, p. 86-95 How to Cite?
AbstractThe Xiangshan U deposit, the largest hydrothermal U deposit in China, is hosted in late Jurassic felsic volcanic rocks although the U mineralization post dates the volcanics by at least 20 Ma. The mineralization coincides with intrusion of local mantle-derived mafic dykes formed during Cretaceous crustal extension in South China. Ore-forming fluids are rich in CO 2, and U in the fluid is thought to have been dissolved in the form of UO 2 (CO 3) 2 2- and UO 2 (CO 3) 3 4- complexes. This paper provides He and Ar isotope data of fluid inclusions in pyrites and C isotope data of calcites associated with U mineralization (pitchblende) in the Xiangshan U deposit. He isotopic compositions range between 0.1 and 2.0Ra (where Ra is the 3He/ 4He ratio of air = 1.39 × 10 - 6) and correlates with 40Ar/ 36Ar; although there is potential for significant 3He production via 6Li(n,α) 3H(β) 3He reactions in a U deposit (due to abundant neutrons), nucleogenic production cannot account for either the 3He concentration in these fluids, nor the correlations between He and Ar isotopic compositions. It is more likely that the high 3He/ 4He ratios represent trapped mantle-derived gases. A mantle origin for the volatiles of Xiangshan is consistent with the δ 13C values of calcites, which vary from - 3.5‰ to - 7.7‰, overlapping the range of mantle CO 2. The He, Ar and CO 2 characteristics of the ore-forming fluids responsible for the deposit are consistent with mixing between 3He- and CO 2-rich mantle-derived fluids and CO 2-poor meteoric fluids. These fluids were likely produced during Cretaceous extension and dyke intrusion which permitted mantle-derived CO 2 to migrate upward and remobilize U from the acid volcanic source rocks, resulting in the formation of the U deposit. Subsequent decay of U within the fluid inclusions has reduced the 3He/ 4He ratio, and variations in U/ 3He result in the range in 3He/ 4He observed with U/ 3He ratios in the range 5-17 × 10 3 likely corresponding to U concentrations in the fluids < 0.2 ppm. © 2008 Elsevier B.V. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/129165
ISSN
2015 Impact Factor: 3.482
2015 SCImago Journal Rankings: 2.346
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorHu, RZen_HK
dc.contributor.authorBurnard, PGen_HK
dc.contributor.authorBi, XWen_HK
dc.contributor.authorZhou, MFen_HK
dc.contributor.authorPeng, JTen_HK
dc.contributor.authorSu, WCen_HK
dc.contributor.authorZhao, JHen_HK
dc.date.accessioned2010-12-23T08:33:13Z-
dc.date.available2010-12-23T08:33:13Z-
dc.date.issued2009en_HK
dc.identifier.citationChemical Geology, 2009, v. 266 n. 1-2, p. 86-95en_HK
dc.identifier.issn0009-2541en_HK
dc.identifier.urihttp://hdl.handle.net/10722/129165-
dc.description.abstractThe Xiangshan U deposit, the largest hydrothermal U deposit in China, is hosted in late Jurassic felsic volcanic rocks although the U mineralization post dates the volcanics by at least 20 Ma. The mineralization coincides with intrusion of local mantle-derived mafic dykes formed during Cretaceous crustal extension in South China. Ore-forming fluids are rich in CO 2, and U in the fluid is thought to have been dissolved in the form of UO 2 (CO 3) 2 2- and UO 2 (CO 3) 3 4- complexes. This paper provides He and Ar isotope data of fluid inclusions in pyrites and C isotope data of calcites associated with U mineralization (pitchblende) in the Xiangshan U deposit. He isotopic compositions range between 0.1 and 2.0Ra (where Ra is the 3He/ 4He ratio of air = 1.39 × 10 - 6) and correlates with 40Ar/ 36Ar; although there is potential for significant 3He production via 6Li(n,α) 3H(β) 3He reactions in a U deposit (due to abundant neutrons), nucleogenic production cannot account for either the 3He concentration in these fluids, nor the correlations between He and Ar isotopic compositions. It is more likely that the high 3He/ 4He ratios represent trapped mantle-derived gases. A mantle origin for the volatiles of Xiangshan is consistent with the δ 13C values of calcites, which vary from - 3.5‰ to - 7.7‰, overlapping the range of mantle CO 2. The He, Ar and CO 2 characteristics of the ore-forming fluids responsible for the deposit are consistent with mixing between 3He- and CO 2-rich mantle-derived fluids and CO 2-poor meteoric fluids. These fluids were likely produced during Cretaceous extension and dyke intrusion which permitted mantle-derived CO 2 to migrate upward and remobilize U from the acid volcanic source rocks, resulting in the formation of the U deposit. Subsequent decay of U within the fluid inclusions has reduced the 3He/ 4He ratio, and variations in U/ 3He result in the range in 3He/ 4He observed with U/ 3He ratios in the range 5-17 × 10 3 likely corresponding to U concentrations in the fluids < 0.2 ppm. © 2008 Elsevier B.V. All rights reserved.en_HK
dc.languageengen_US
dc.publisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/chemgeoen_HK
dc.relation.ispartofChemical Geologyen_HK
dc.subjectChinaen_HK
dc.subjectHe, Ar and C isotopesen_HK
dc.subjectMantle-derived volatilesen_HK
dc.subjectThe Xiangshan U depositen_HK
dc.titleMantle-derived gaseous components in ore-forming fluids of the Xiangshan uranium deposit, Jiangxi province, China: Evidence from He, Ar and C isotopesen_HK
dc.typeArticleen_HK
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hken_HK
dc.identifier.authorityZhou, MF=rp00844en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.chemgeo.2008.07.017en_HK
dc.identifier.scopuseid_2-s2.0-68349127536en_HK
dc.identifier.hkuros177727en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-68349127536&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume266en_HK
dc.identifier.issue1-2en_HK
dc.identifier.spage86en_HK
dc.identifier.epage95en_HK
dc.identifier.isiWOS:000272870800012-
dc.publisher.placeNetherlandsen_HK
dc.identifier.scopusauthoridHu, RZ=7202640800en_HK
dc.identifier.scopusauthoridBurnard, PG=24754536900en_HK
dc.identifier.scopusauthoridBi, XW=7102242579en_HK
dc.identifier.scopusauthoridZhou, MF=7403506005en_HK
dc.identifier.scopusauthoridPeng, JT=8230916900en_HK
dc.identifier.scopusauthoridSu, WC=7402010379en_HK
dc.identifier.scopusauthoridZhao, JH=49061691300en_HK
dc.identifier.citeulike5458124-

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