Pb Isotope Mapping in the Tongbai-Dabie Orogenic Belt, Central China

Tongbai-Dabie orogenic belt in Central China is a part of the collisional belt between the Yangtze and North China cratons. It represents one of the most extensive ultrahigh-pressure （UHP） and high-pressure （HP） metamorphic rocks in the world. The Pb isotope mapping in this area is a significant method to constrain the crustal structure and tectonic evolution and to identify the tectonic boundaries within the vertical tectonic stack. Based on the Pb isotope compositions of the Dabie complex （DBC）, the Tongbai complex （TBC）, UHP and HP metamorphic rocks and associated foliated granites, the lower metamorphosed rocks from North Huaiyang （NHY） tectonic belt, and Cretaceous granites in the Tongbai-Dabie orogenic belt, we determined the Pb isotope geochemical map of the Tongbai-Dabie orogenic belt. The Pb isotope map shows that the Pb isotope compositions are similar within each geological body or lithotectonic unit, but the Pb isotope compositions of different lithotectonic units show systematic variations in the Tongbai-Dabie orogenic belt. The NHY tectonic belt contrasts strongly with the Tongbai-Dabie UHP.HP metamorphic belt in Pb isotope compositions. It is suggested that the line along the Xiaotian-Mozitan fault, the north limit of the Tongbai-Dabie UHP and HP metamorphic rocks, represents an important tectonic boundary. Within the Tongbai-Dabie HP -UHP metamorphic belt, to the south of Xiaotian-Mozitan fault, the vertical variations of Pb isotope compositions in different lithotectonic units and the spatial relationship among different major lithotectonic units have been constrained.

New Exploration of Tracking Deep Ancient Crustal Components: A Combined Analysis of Xenocrystic/Inherited Zircon Information within Different Genetic Types of Granitoids in Chinese Altai

Revealing deep composition information is crucial for systematic understanding of continental crust architecture.Deep exploration has become an important trend in the development of geoscience,and using magmatic rocks and their deep-source rock inclusions as‘rock probes’to trace the earth’s deep material information has been an effective way in recent years(e.g.,Mo,2011).

Zircon Hf Isotope Mapping for Understanding Crustal Architecture and Its Controls on Mineralization during Early Cretaceous in the Southern Great Xing'an Range,NE China

Voluminous Early Cretaceous granitoids and associated large-scale ore deposits are distributed within the southern Great Xing'an Range(SGXR),NE China.Based on previously published geochronology and zircon Hf-isotope data,Hf isotope mapping is undertaken to improve our understanding of crustal architecture and its controls on ore deposits.The ore-related Early Cretaceous granitoids were sourced predominantly from juvenile crust,with the involvement of variable proportions of ancient crustal materials.The crustal architecture,as inferred from Hf isotopic contour maps,indicates two distinct Hf isotopic domains in SGXR,including(1)a higher-ε_(Hf)(+7 to+11)juvenile crust containing minor ancient crustal material,and(2)a lower-ε_(Hf)(+2 to+6)juvenile crust containing a greater proportion of ancient crustal materials.The Hf isotopic maps identify links between crustal architecture and regional metallogeny.Copper deposits and other deposits with significant Cu production are restricted mainly to the higher-ε_(Hf)juvenile crustal regions in the northern and eastern SGXR.Deposits dominated by other metals(e.g.,Mo,Sn,W,Pb,Zn,and Ag)occur mainly in the lower-ε_(Hf)juvenile crustal regions in the southern and western SGXR.Interaction between juvenile crust-derived melts and ancient crustal components played an important role on the distribution of various ore metals.