Extreme oxygen isotope signature of meteoric water in magmatic zircon from metagranite in the Sulu orogen, China: Implications for Neoproterozoic rift magmatism

Crustal recycling processes in generating the early Cretaceous Fangcheng basalts, North China Craton: New constraints from mineral chemistry, oxygen isotopes of olivine and whole-rock geochemistry

“…The Fangcheng basalts were erupted in the southeastern margin of the NCC, near the Sulu ultra-high pressure (UHP) metamorphic belt, the subducted Yangtze continental crust in the Triassic could be a possible candidate for the O range from −15 to +9‰ (Chen and Jahn, 1998;Ma et al, 2000;Tang et al, 2008;Yui et al, 1995;Zheng et al, 2007). Some metaigneous rocks in the Dabie-Sulu orogenic belt even exhibit anomalously negative δ…”

A perspective view on ultrahigh-pressure metamorphism and continental collision in the Dabie-Sulu orogenic belt

“…tremely negative δ 18 O values corresponding to the meteoric signature of cold paleoclimate, they occur not only in rock-forming minerals of UHP eclogite, granitic gneiss and quartz schist [21][22][23][24] , but also in granitic minerals such as garnet [25] and zircon [26] . The negative oxygen isotope anomalies arrive at the four world-record extremes with the most negative δ 18 O values for metamorphic minerals [12,27] , for intrusive minerals [25] , for zircon of magmatic origin [26,28,29] , and for zircon of metamorphic origin [29] . Therefore, the Dabie-Sulu UHP metamorphic rocks provide us a natural laboratory to study the physico-chemical changes that occurred during deep-subduction and exhumation of the continental crust.…”

“…The results show that majority of UHP metamorphic rocks have igneous protoliths with middle Neoproterozoic ages of 740 to 780 Ma [12,26,29,58,65,[78][79][80] and significant 18 O depletion ( Figure 7). Thus they have geotectonic affinity to the South China Block.…”

“…Combined studies of zircon U-Pb dating and Hf-O isotope analyses indicate that igneous protoliths of UHP metamorphic rocks are a product of mid-Neoproterozoic rift magmatism in the northern margin of the Yangtze Block [26,29,[80][81][82]89] . They are not only depleted in 18 O, but also consist of juvenile crust respectively in late Figure 7 The relationship between the protolith age and oxygen isotope ratio of zircons from metamorphic rocks in the Dabie-Sulu orogenic belt (data from Zheng et al [29,81] and Tang et al [26,80] ).…”

Discussion on the Neoproterozoic glaciations in the South China Block and their related paleolatitudes

“…Such low δ 18 O zircons occur widely along the Dabie-Sulu orogenic belt [8][9][10][11] , indicating that the large-scale 18 O depletion resulted from hydrothermal alteration of igneous rocks in rift tectonic zones due to interaction with meteoric water under low mean annual temperature environment. Further study [4] discovered the most negative δ 18 O values for garnet in the world from a Neoproterozoic granite in the Dabie-Sulu orogenic belt; coexisting zircon is also depleted in 18 O with an U-Pb age of 748±3 Ma.…”