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U-Pb zircon age, geochemical and isotopic characteristics of carbonatite and syenite complexes from the Shaxiongdong, China

Xu, Cheng; Campbell, Ian; Allen, Charlotte M; Chen, Yanjing; Huang, Zhilong; Qi , Liang; Zhang, Guishan; Yan, Zaifei

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The Qinling is an important orogenic belt, which formed by the joining of the North China and South China blocks. The Shaxiongdong carbonatite-syenite complexes were emplaced at the southern margin of South Qinling and border the South China block. LA-ICPMS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) zircon U-Pb geochronology constrains the syenite emplacement age to be 441.8 ± 2.2 Ma, which is significantly earlier than the collision of the South China block and South Qinling...[Show more]

dc.contributor.authorXu, Cheng
dc.contributor.authorCampbell, Ian
dc.contributor.authorAllen, Charlotte M
dc.contributor.authorChen, Yanjing
dc.contributor.authorHuang, Zhilong
dc.contributor.authorQi , Liang
dc.contributor.authorZhang, Guishan
dc.contributor.authorYan, Zaifei
dc.date.accessioned2015-12-08T22:18:24Z
dc.identifier.issn0024-4937
dc.identifier.urihttp://hdl.handle.net/1885/31327
dc.description.abstractThe Qinling is an important orogenic belt, which formed by the joining of the North China and South China blocks. The Shaxiongdong carbonatite-syenite complexes were emplaced at the southern margin of South Qinling and border the South China block. LA-ICPMS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) zircon U-Pb geochronology constrains the syenite emplacement age to be 441.8 ± 2.2 Ma, which is significantly earlier than the collision of the South China block and South Qinling along the Mianlue suture (200-240 Ma) near where the complexes reside. Trace-element abundances and C-O-Sr-Nd-Pb isotopes for the carbonatites and calcite separates indicate an igneous origin. They and associated syenites show overlaps of initial 87Sr/86Sr ratios (0.7029-0.7033, 0.7030-0.7032) and εNd (2.8 to 4, 2.5 to 6 for syenites and carbonatites, respectively), which implies that the carbonatites may derive from a carbonated alkali silicate melt. However, the rocks are composed dominantly of calcite. They have markedly lower Th, Nb, Zr and P contents compared to average calciocarbonatites worldwide. Calcites from the carbonatites are also characterized by low REE contents and relatively flat REE patterns. This indicates that the carbonatites are calcite-rich cumulates, which were produced from a residual liquid derived from an intensively fractioned carbonatite magma. In addition, the syenites are characterized by negative Pb and no Nb anomalies. They show lower Sr isotopes and higher εNd than syn/post-orogen related granites emplaced in the Qinling. This indicates that the complexes formed in a rifting environment. It is noted that Sr and Nd isotopic compositions from the carbonatites and syenites are close to HIMU mantle source values. Variations in 207Pb/206Pb (0.785-0.842) and 208Pb/206Pb (1.954-2.110) ratios from the calcites best fit a model involving mixing HIMU and EM1 components. Therefore, plume activity may play an important role in the complex generation and tectonic evolution of the South China block. Geological support for this deduction is the presence of numbers of Silurian dyke swarms. We hypothesize that the upwelling plume metasomatizing the continental lithosphere resulted in the South Qinling separating from South China block along the Mianlue suture during the early Paleozoic period.
dc.publisherElsevier
dc.sourceLithos
dc.subjectKeywords: ablation; carbonatite; emplacement; geochronology; inductively coupled plasma method; isotopic composition; laser method; mantle source; rifting; suture zone; syenite; uranium-lead dating; zircon; Asia; China; Eurasia; Far East; Hubei; North China Block; Calcite cumulates; Carbonatite and syenite complexes; Plume; Rifting environment; South China block; South Qinling
dc.titleU-Pb zircon age, geochemical and isotopic characteristics of carbonatite and syenite complexes from the Shaxiongdong, China
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume105
dc.date.issued2008
local.identifier.absfor040203 - Isotope Geochemistry
local.identifier.absfor040303 - Geochronology
local.identifier.ariespublicationu4047674xPUB82
local.type.statusPublished Version
local.contributor.affiliationXu, Cheng, Chinese Academy of Sciences
local.contributor.affiliationCampbell, Ian, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationAllen, Charlotte M, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationChen, Yanjing, Peking University
local.contributor.affiliationHuang, Zhilong, Chinese Academy of Sciences
local.contributor.affiliationQi , Liang, Chinese Academy of Sciences
local.contributor.affiliationZhang, Guishan, Chinese Academy of Sciences
local.contributor.affiliationYan, Zaifei, Chinese Academy of Sciences
local.description.embargo2037-12-31
local.bibliographicCitation.startpage118
local.bibliographicCitation.lastpage128
local.identifier.doi10.1016/j.lithos.2008.03.002
dc.date.updated2015-12-08T08:16:07Z
local.identifier.scopusID2-s2.0-51649102290
local.identifier.thomsonID000260993100011
CollectionsANU Research Publications

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