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Article: Paragenesis, stable isotopes, and molybdenite Re-Os isotope age of the Lala Iron-Copper deposit, Southwest China

TitleParagenesis, stable isotopes, and molybdenite Re-Os isotope age of the Lala Iron-Copper deposit, Southwest China
Authors
Issue Date2012
PublisherSociety of Economic Geologists, Inc.. The Journal's web site is located at http://www.segweb.org/publications/journal.aspx
Citation
Economic Geology, 2012, v. 107 n. 3, p. 459-480 How to Cite?
AbstractThe Lala Fe-Cu deposit in the Kangdian iron oxide copper-gold (IOCG) metallogenic province, SW China, is hosted in the Paleoproterozoic Hekou Group. This volcanic-sedimentary sequence has undergone upper greenschist-lower amphibolite facies metamorphism at ~850 Ma. The deposit contains more than 200 million metric tons (Mt) of Fe-Cu ores with an average grade of 13 wt % Fe and 0.92 wt % Cu. Orebodies are roughly strata bound but occur along foliation, lithologic contacts, and shear zones. The paragenetic sequence of the Lala deposit includes metamorphosed (I, II, and III) and unmetamorphosed (IV and V) stages. Stage I is characterized by extensively pervasive Na alteration, forming abundant albite but minor scapolite. Stage II occurs as massive and banded replacements, consists of Ti-V-poor magnetite and apatite with minor disseminated sulfide minerals, and was associated with pervasive K-Fe alterations forming K-feldspar, chlorite, and actinolite. Stage III occurs predominantly as bands and disseminations confined along foliations with minor veinlets crosscutting hosting rocks. This stage is characterized by abundant Fe-Cu-Mo sulfides intergrown with angular magnetite and minor titanite and allanite and is associated with alteration of carbonate, quartz, fluorite, and mica. Stage IV has an assemblage dominated by chalcopyrite with variable pyrite and bornite, occurring as veins of sulfides + quartz + calcite + biotite ± muscovite ± fluorite. Stage V occurs chiefly as veins of hematite ± calcite ± quartz and also results in extensive hematization. Stages II and III have fluids with high δ 18O (7.2-11.7‰) and δ 34S values (0-4‰), indicative of a magmatichydrothermal origin. However, the stage III fluids have δ34C values (~0.5‰) close to the least altered marble (0-2‰) of the hosting rocks, indicating a possible contribution of strata-sourced carbon. The stage IV fluids have δ34C values similar to and δ 18O (4.1-6.7‰) lower than the stage III fluids, and a wider range of δ 34S values (-9.0 to +10.5‰), consistent with significant contributions of strata-sourced sulfur. Fluids of the late barren vein stage (V) have relatively low δ34C (-4.0 to -2.4‰) and δ 18O values (-2.9 to +0.6‰), indicative of significant contributions of meteoric and oxidized fluids. Molybdenite from stage III has an Re-Os isotope age of 1086 ± 8 Ma, providing tight constraints on the timing of the main stage of mineralization. This age indicates that the Lala deposit is coeval with the ~1100 Ma intraplate magmatism in the western Yangtze Block. We propose that the majority of the Fe-Cu deposits in the Kangdian IOCG metallogenic province may have formed in an intraplate extensional setting, although it is possible that some of the deposits may have involved in multiple events including modification by the Neoproterozoic metamorphism forming the mineral assemblages of stage IV. © 2012 Society of Economic Geologists, Inc.
Persistent Identifierhttp://hdl.handle.net/10722/151371
ISSN
2015 Impact Factor: 2.487
References

 

DC FieldValueLanguage
dc.contributor.authorChen, WTen_US
dc.contributor.authorZhou, MFen_US
dc.date.accessioned2012-06-26T06:21:17Z-
dc.date.available2012-06-26T06:21:17Z-
dc.date.issued2012en_US
dc.identifier.citationEconomic Geology, 2012, v. 107 n. 3, p. 459-480en_US
dc.identifier.issn0361-0128en_US
dc.identifier.urihttp://hdl.handle.net/10722/151371-
dc.description.abstractThe Lala Fe-Cu deposit in the Kangdian iron oxide copper-gold (IOCG) metallogenic province, SW China, is hosted in the Paleoproterozoic Hekou Group. This volcanic-sedimentary sequence has undergone upper greenschist-lower amphibolite facies metamorphism at ~850 Ma. The deposit contains more than 200 million metric tons (Mt) of Fe-Cu ores with an average grade of 13 wt % Fe and 0.92 wt % Cu. Orebodies are roughly strata bound but occur along foliation, lithologic contacts, and shear zones. The paragenetic sequence of the Lala deposit includes metamorphosed (I, II, and III) and unmetamorphosed (IV and V) stages. Stage I is characterized by extensively pervasive Na alteration, forming abundant albite but minor scapolite. Stage II occurs as massive and banded replacements, consists of Ti-V-poor magnetite and apatite with minor disseminated sulfide minerals, and was associated with pervasive K-Fe alterations forming K-feldspar, chlorite, and actinolite. Stage III occurs predominantly as bands and disseminations confined along foliations with minor veinlets crosscutting hosting rocks. This stage is characterized by abundant Fe-Cu-Mo sulfides intergrown with angular magnetite and minor titanite and allanite and is associated with alteration of carbonate, quartz, fluorite, and mica. Stage IV has an assemblage dominated by chalcopyrite with variable pyrite and bornite, occurring as veins of sulfides + quartz + calcite + biotite ± muscovite ± fluorite. Stage V occurs chiefly as veins of hematite ± calcite ± quartz and also results in extensive hematization. Stages II and III have fluids with high δ 18O (7.2-11.7‰) and δ 34S values (0-4‰), indicative of a magmatichydrothermal origin. However, the stage III fluids have δ34C values (~0.5‰) close to the least altered marble (0-2‰) of the hosting rocks, indicating a possible contribution of strata-sourced carbon. The stage IV fluids have δ34C values similar to and δ 18O (4.1-6.7‰) lower than the stage III fluids, and a wider range of δ 34S values (-9.0 to +10.5‰), consistent with significant contributions of strata-sourced sulfur. Fluids of the late barren vein stage (V) have relatively low δ34C (-4.0 to -2.4‰) and δ 18O values (-2.9 to +0.6‰), indicative of significant contributions of meteoric and oxidized fluids. Molybdenite from stage III has an Re-Os isotope age of 1086 ± 8 Ma, providing tight constraints on the timing of the main stage of mineralization. This age indicates that the Lala deposit is coeval with the ~1100 Ma intraplate magmatism in the western Yangtze Block. We propose that the majority of the Fe-Cu deposits in the Kangdian IOCG metallogenic province may have formed in an intraplate extensional setting, although it is possible that some of the deposits may have involved in multiple events including modification by the Neoproterozoic metamorphism forming the mineral assemblages of stage IV. © 2012 Society of Economic Geologists, Inc.en_US
dc.languageengen_US
dc.publisherSociety of Economic Geologists, Inc.. The Journal's web site is located at http://www.segweb.org/publications/journal.aspxen_US
dc.relation.ispartofEconomic Geologyen_US
dc.titleParagenesis, stable isotopes, and molybdenite Re-Os isotope age of the Lala Iron-Copper deposit, Southwest Chinaen_US
dc.typeArticleen_US
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hken_US
dc.identifier.authorityZhou, MF=rp00844en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.2113/econgeo.107.3.459en_US
dc.identifier.scopuseid_2-s2.0-84860243114en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-84860243114&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume107en_US
dc.identifier.issue3en_US
dc.identifier.spage459en_US
dc.identifier.epage480en_US
dc.identifier.eissn1554-0774-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridChen, WT=55199302900en_US
dc.identifier.scopusauthoridZhou, MF=7403506005en_US

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