Zircon U-Pb and oxygen isotope evidence for a large-scale 18O depletion event in igneous rocks during the Neoproterozoic

Zheng, Yong‐Fei; Wu, Yuan–Bao; Chen, Fukun; Gong, Bing; Li, Long; Zhao, Zi‐Fu

doi:10.1016/j.gca.2004.01.007

Cited by 496 publications

(323 citation statements)

References 118 publications

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“…The Neoproterozoic age of inherited zircons in the CB granite indicates that its source is a product of mid-Neoproterozoic rift magmatism along the northern margin of the South China Block. The similar origin has been inferred for the protoliths of UHP metaigneous rocks in the Dabie-Sulu orogenic belt [7,49,50]. These similarities in geochemistry and geochronology for the Late Triassic granites between Qinling and Dabie-Sulu imply that they have the same origin.…”

Section: Geodynamic Implicationssupporting

confidence: 72%

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Wang

Sun

et al. 2011

Chin. Sci. Bull.

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Mesozoic granitoids are widespread in the Qinling-Dabie-Sulu orogenic belt. Precise U-Pb dating on these granitoids can reveal the evolution of the continental collision orogen and thus provide information on the nature of magma sources. This study presents zircon LA-ICP-MS U-Pb dating and whole-rock geochemical analyses for two intrusions at Changba and Huangzhuguan in western Qinling. Zircon U-Pb ages for central and marginal phases of the Huangzhuguang intrusion are 214±1 Ma and 213±3 Ma, respectively. Zircons from the Changba intrusion yield a dominant cluster with an U-Pb age of 213±2 Ma. Collectively, these ages are younger than ages of 220 to 240 Ma for ultrahigh-pressure metamorphism due to the continental collision between the South China Block and the North China Block, corresponding to syn-exhumation magmatism. Some inherited zircons occur in the Changba intrusion, yielding a weighted mean of 206 Pb/ 238 U ages at 757±14 Ma. This indicates that the Changba intrusion has the crustal source of mid-Neoproterozoic ages and a tectonic affinity to the South China Block. Geochemically, the two intrusuons are both rich in LILE and LREE but depleted in HFSE and HREE, similar to arc-type igneous rocks. The Huangzhuguang intrusion exhibits linear correlations between SiO 2 and the other major oxides, implying chemical evolution from a cognate magma source. It contains mafic enclaves, suggesting possible mixing of felsic-mafic magmas. The Changba granite is rich in Si and K but poor in Fe and Mg as well as has a high value of Fe*, suggesting strong differentiation of granitic magma. Therefore, the two intrusions were derived from the Late Triassic anatexis of the continental crust of different compositions in the northern margin of South China Block. This process may be coupled with exhumation of the subducted continental crust in the stage of late collision.Qinling orogen, continental collision, granite, zircon U-Pb dating, whole-rock geochemistry, syn-exhumation magmatism Citation:Wang T G, Ni P, Sun W D, et al. Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature.

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Section: Geodynamic Implicationssupporting

confidence: 72%

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Wang

Sun

et al. 2011

Chin. Sci. Bull.

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“…Zircon grains of metamorphic origin frequently occur in UHP eclogite-facies metamorphic rocks, exhibiting shapes and structures that indicate significant dissolution of protolith zircon and subsequent overgrowth of metamorphic zircon (e.g., Liati and Gebauer 1999;Rubatto and Hermann 2003;Zheng et al 2004Zheng et al , 2007Sheng et al 2012Sheng et al , 2013. This indicates significant action of fluids on the protolith zircon at subsolidus to supersolidus conditions (Zheng, 2009).…”

Section: Action Of Subduction-zone Fluids Accessary Mineral Records Omentioning

confidence: 99%

Geochemistry of continental subduction-zone fluids

2014

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The composition of continental subduction-zone fluids varies dramatically from dilute aqueous solutions at subsolidus conditions to hydrous silicate melts at supersolidus conditions, with variable concentrations of fluid-mobile incompatible trace elements. At ultrahigh-pressure (UHP) metamorphic conditions, supercritical fluids may occur with variable compositions. The water component of these fluids primarily derives from structural hydroxyl and molecular water in hydrous and nominally anhydrous minerals at UHP conditions. While the breakdown of hydrous minerals is the predominant water source for fluid activity in the subduction factory, water released from nominally anhydrous minerals provides an additional water source. These different sources of water may accumulate to induce partial melting of UHP metamorphic rocks on and above their wet solidii. Silica is the dominant solute in the deep fluids, followed by aluminum and alkalis. Trace element abundances are low in metamorphic fluids at subsolidus conditions, but become significantly elevated in anatectic melts at supersolidus conditions. The compositions of dissolved and residual minerals are a function of pressure-temperature and whole-rock composition, which exert a strong control on the trace element signature of liberated fluids. The trace element patterns of migmatic leucosomes in UHP rocks and multiphase solid inclusions in UHP minerals exhibit strong enrichment of large ion lithophile elements (LILE) and moderate enrichment of light rare earth elements (LREE) but depletion of high field strength elements (HFSE) and heavy rare earth elements (HREE), demonstrating their crystallization from anatectic melts of crustal protoliths. Interaction of the anatectic melts with the mantle wedge peridotite leads to modal metasomatism with the generation of new mineral phases as well as cryptic metasomatism that is only manifested by the enrichment of fluid-mobile incompatible trace elements in orogenic peridotites. Partial melting of the metasomatic mantle domains gives rise to a variety of mafic igneous rocks in collisional orogens and their adjacent active continental margins. The study of such metasomatic processes and products is of great importance to understanding of the mass transfer at the slab-mantle interface in subduction channels. Therefore, the property and behavior of subduction-zone fluids are a key for understanding of the crust-mantle interaction at convergent plate margins.

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“…Reproducibility was better than ±0.1‰ (1σ). Detailed analytical procedures were reported in Zheng et al (2004) and Gong et al (2007). The O isotopic results of olivine and clinopyroxene crystals are listed in Appendix 2 and 3.…”

Section: Mineral O Isotope Analysis By Lf Techniquementioning

confidence: 99%

“…Zircon has a low oxygen diffusion rate and is resistant to surface alteration (e.g., Dai et al, 2011;Lackey et al, 2008;Valley, 2003;Valley et al, 2005). Oxygen isotopic compositions of zircon have been widely used to assess crustal growth and evolution (e.g., Hawkesworth and Kemp, 2006;Kemp et al, 2006), magmatic evolution of mafic intrusions (e.g., Dai et al, 2011;Valley, 2003;Yang et al, 2012b), and crustal recycling processes in subduction zones (e.g., Zheng, 2012;Zheng et al, 2004). Zircon usually crystallizes later in mafic magmas when they become Si-saturated (e.g., Hiess et al, 2009;Renna et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Formation of mafic magmas through lower crustal AFC processes — An example from the Jinan gabbroic intrusion in the North China Block

Guo

Wang

et al. 2013

Lithos

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Zircon U-Pb and oxygen isotope evidence for a large-scale 18O depletion event in igneous rocks during the Neoproterozoic

Cited by 496 publications

References 118 publications

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Geochemistry of continental subduction-zone fluids

Formation of mafic magmas through lower crustal AFC processes — An example from the Jinan gabbroic intrusion in the North China Block

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