Constraints on crustal evolution and gold metallogeny in the Northwestern Jiaodong Peninsula, China, from SHRIMP U-Pb zircon studies of granitoids

The northwestern part of the Jiaodong Peninsula, or the Zhao-Ye Gold Belt, contains the largest lode-gold deposits in China, which are spatially related to several suites of intrusive granitoids. Previous attempts to provide constraints on the timing of gold mineralization and its tectonic setting, through studies of the granitoids, have led to conflicting data, dependant on the isotopic methodology used, and resultant genetic and tectonic models for their setting are equivocal. SHRIMP U-Pb studies of complexly zoned zircons of the Linglong, Luanjiahe and Guojialing granitoid suites suggest that the Jiaodong Peninsula is underlain by Precambrian basement with components up to 3.4 Ga old. Inherited zircons of early Mesozoic age indicate that this basement was reworked at 250-200 Ma, probably during a collisional orogeny involving the North China Craton and South China Craton. The Linglong, Luanjiahe and Guojialing suites were derived from this early Mesozoic basement between 165 and 125 Ma, and were probably emplaced as post-collisional granitoids, the latest intrusions (at 125 Ma) coinciding broadly with superplume activity or a major plume breakout event in the Palaeo-Pacific Plate. Importantly, if lode-gold mineralization is essentially a single event, as indicated by similar hosting structures and deposit characteristics, it can be dated between about 126 Ma, the age of the youngest granitoid cut by gold-bearing quartz veins, and 120 Ma, the age of one of a swarm of post-mineralization feldspar-porphyry dykes. Thus, as in most other metallogenic provinces which host so-called mesothermal lode-gold deposits, gold mineralization was late in the orogenic cycle, probably late- or post-accretion, and closely followed the emplacement of the latest major plutonic phase in the development of a series of anomalously voluminous granitoid batholiths. (C) 1998 Elsevier Science B.V. AU rights reserved.