Yanshanian (Late Mesozoic) ore deposits in China – An introduction to the Special Issue

Abstract

The Late Jurassic-Cretaceous Yanshanian Orogeny (or “Yenshan Movement”), one of the most important tectonothermal events, is first recognized in China, especially eastern China. This Late Mesozoic orogeny, which was initiated most likely by a Mesozoic tectonic switch, strongly reworked or destructed the older continental lithospheres or cratonic keels that are manifested by alternating compressive and extensional deformation, voluminous igneous rocks, and a variety of characteristic magmatic-hydrothermal mineral systems. Despite its first discovery and definition in Yenshan-Yinshan area of North China craton, the Yanshanian Orogeny probably is of global tectonic, magmatic and metallogenic significance. However, there have been hot debates on the precise starting time, accurate duration or time-interval, detailed processes and evolution linked to deep lithospheres, tectonic nature, and geodynamic mechanism(s) of the Yanshanian Orogeny, which inevitably have hindered the understanding of the genesis, mineralizing processes and geodynamic mechanism of the Late Mesozoic magmatic-hydrothermal mineral systems.This Special Issue captures some of the latest research results on the Yanshanian ore deposits that are involved into a few main Mesozoic metallogenic belts or provinces, from northeast to southwest China, including: (1) the Jiaodong Peninsula metallogenic province in the North China Craton, (2) the Middle-Lower Yangtze River Valley metallogenic belt in the central eastern China, (3) the Jiangnan and (4) the Nanling metallogenic belts in the South China Block, (5) the southeastern China Coast metallogenic belt, and (6) the Sanjiang metallogenic belt in southwest China. Through a multidisciplinary study, this Special Issue re-investigated and re-evaluated the relationship between the Late Mesozoic magmatic-hydrothermal mineral systems and the Yanshanian tectonothermal events in the studied metallogenic belts or provinces. A few important contributions to the topic in this Special Issue (Yanshanian metallogeny) are summarized as followings: (1) A new ore-deposit type, i.e. the “intracontinental reactivation” type, has been suggested to interpret the genesis of those Au-(polymetallic) deposits that are hosted within older metamorphic rocks and related to the Late Mesozoic basin-and-range extensional settings; (2) Late Mesozoic re-activation of the preexisting structures by the Yanshanian tectono-thermal event(s) might be an important mechanism controlling the Yanshanian large-scale mineralization; (3) A-type granites formed by partial melting of the Mesoproterozoic crust, but with inputs from mantle-derived melt are also favorable for Sn mineralization, in addition to S-type and I-type granites as previously recognized; (4) Calculated oxygen fugacities (ƒO2) of granitic magmas based on chemical compositions of primary biotite have been confirmed to be effective proxy for distinguishing Cu-Au-Mo-W-Sn-Pb-Zn mineralized granites from barren granites; (5) A significant epoch of W–Sn magmatic-hydrothermal ore system at ca. 145–135Mahas been identified in the southeastern China Coast metallogenic belt; and (6) In addition to traditional structural geology, mineralogy, petrology, geochemistry and geochronology, new analytical techniques (e.g. Cu isotopes) and data treatment method (e.g., Bi-dimensional empirical mode decomposition) can be used to provide more constraints for deep exploration.