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Sm-Nd isotopic geochronologyof the Yinachang Fe-Cu-REE deposit at Wuding,Yunnan Province and its genetic significance

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chinese Science Bulletin 2005年第18期50卷 2090-2096页

作者： yang yaomin tu guanzhi hu ruizhong shi xuefa institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China The Key Laboratory of Marine Sedimentology and Environmental Geology The First Institute of Oceanography SOA Qingdao 266061 China Northwest Geological Exploration Bureau CNNC Xi'an 710054 China

Sm-Nd isotope systematics of ores and fluorites places precise time constraints on REE mineralization of the Yinachang Fe-Cu-REE deposit in Yunnan Province which occur in the Proterozoic Kunyan group. The ore-related fluorites contain high abundant REE, and show a strong enrichment of LREE and a positive Eu anomaly, which is in marked contrast to post-ore fluorites that are HREE en-riched. The Sm-Nd isochron ages of the ores and fluorites are 1539±40 Ma and 1617±100 Ma, respectively, and calculated εNd(t) are ?4.6 and ?3.2. Accurate age determinations of the mineralization demonstrate that the REE mineralization took place during early Mesoproterozoic. Together with other geological evidence from the ore deposit, the primary REE-bearing ore-forming fluids are suggested to have been derived from the Enriched Mantle, and the Yinachang Fe-Cu-REE ore deposit is of volcanic exhalation- hydro-thermal sedimentary origin. This study also imply that the sudden large-scale REE mineralization in the Mesoprotero-zoic epoch may have been induced by alkaline-rich anoro-genic magmatism which occurred at marginal rifts of the continent in the Mesoproterozoic.

关键词：峡谷沉积物氟石同位素地球年代学

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