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Jiaodong peninsula, located at the southeastern margin of the North China Craton, is well known for its rich endowment of super-large gold deposits. This region is also characterized by hundreds of intermediate – mafic dykes that cluster into several dyke swarms. In this study, we present zircon U-Pb ages which show that the timing of dyke emplacement as ca. 120 Ma, which followed the crystallization of the (quartz-) diorite porphyry at ca. 130 Ma. These ages coincide with the peak ages reported for magmatism and metallogeny in the central North China Craton. The various ages (2450–2570 and 154 Ma) from the inherited zircon crystals in these rocks suggest that substantial lower to middle crustal basement rocks and Jurassic granitoids were involved during dyke emplacement. The dyke swarms, varying between alkaline and subalkaline, are compositionally low-Si low-Ti lamprophyre and low-Si high-Ti dolerite porphyry in the western of the Jiaodong peninsula, whereas those in the eastern part are composed of both high-Si low-Ti and low-Si high-Ti lamprophyres. These features imply multiple sources for the dykes from convective asthenospheric mantle to ancient enriched lithospheric mantle with magma generation at different depths involving mixture of slab-derived hydrous fluids. The source magmas of the dykes were hydrous and enriched in volatiles as well as ore components, and their evolution occurred under high oxygen fugacity conditions. The relatively rapid emplacement and cooling of the dyke systems enabled the migration of fluids into ore-controlling faults or fractures. We envisage that the dyke swarms played an important role in generating the world-class gold mineralization of Jiaodong. [ABSTRACT FROM AUTHOR]

The Jiaodong type comprises a unique class of gold mineralisation which includes the Linglong type quartz-vein hosted and the Jiaojia type fracture-disseminated style deposits. Although the type area is in the Jiaodong Peninsula in NE China, where some of the world's richest gold reserves occur, we identify similar occurrences in other parts of China and elsewhere in the world under this category. The ore fluids migrated upwards forming quartz vein type of gold ore (Linglong type) wherever the ore-controlling fractures are at high angles. Fluid infiltration into the surrounding wall rocks and generation of the Jiaojia type disseminated style deposits resulted where the ore-bearing fluids encountered low angle fractures. On a regional scale, the Jiaodong type gold mineralisation occurs along the margins of reactivated cratons, within the interior of cratons along paleosuture zones, or along the junctions of micro-blocks, and is distinctly different from the classic orogenic gold in terms of their tectonic setting, ore characteristics and genetic history. Unlike skarn and porphyry type of deposits, the Jiaodong type gold deposits do not always show close spatial relationship with magmatic intrusives and some of the deposits occur distal to plutons (> 10 km). In this paper, we evaluate the salient geological, geochronological, geochemical and isotopic features of the Jiaodong type gold deposits and propose some general guidelines for gold prospecting. Based on case studies, we predict that the gold lodes in the Jiaodong type mineralised zones might extent vertically up to 3000 m with only minor mineralogical and geochemical variations. [ABSTRACT FROM AUTHOR]

The Mesozoic lithospheric destruction of the North China Craton (NCC) in eastern China with a concomitant large-scale crustal exhumation has been widely accepted. However the specific timing, magnitude and rate of exhumation remain elusive. The widely outcropping episodes of Mesozoic granitoids in the Jiaodong Peninsula provide an excellent natural case for crustal exhumation research. Application and comparison of two Al-in-hornblende barometers and experimental Qz-Ab-Or phase diagram indicate that oxygen fugacity could affect pressure estimation of granitoids and the Al-in-hornblende barometers derived from the AS95 (referring to Anderson and Smith, 1995) has the potential to estimate pressures of granitoids emplaced at 1–2 kbar. The Qz-Ab-Or phase diagram can be used to constrain the emplacement pressures of granitoids on the premise of selecting suitable geochemical data. Our results demonstrate a rapid crustal exhumation event between ∼160 and 115 Ma, i.e., approximately 10 km for the Jiaobei terrane and 7 km for the ultra-high pressure metamorphic terrane, reflecting heterogeneous exhumation possibly in response to the lithospheric destruction of the NCC. [ABSTRACT FROM AUTHOR]