Genesis of the Late Cretaceous Longquanzhan Gold Deposit in the Central Tan-Lu Fault Zone, Shandong Province, China: Constraints from Noble Gas and Sulfur Isotopes

Minerals

Junhao Wei¹  Jun Tan¹  Huan Li¹  Wenjie Shi¹  Chuanpeng Liu²  Aiping Feng²  Jun Deng²  Yonglin Yao²  Jiantai Zhang² 

[1] School of Earth Resources, China University of Geosciences, Wuhan 430074, China;The 7th Institute of Geology & Mineral Exploration of Shandong Province, Linyi 276006, China;

关键词: noble gas isotope;    ore-forming fluid;    gold deposit;    Tan-Lu fault zone;    Shandong;   

DOI  :  10.3390/min11030250

来源: DOAJ

【 摘 要 】

The Longquanzhan deposit is one of the largest gold deposits in the Yi-Shu fault zone (central section of the Tan-Lu fault zone) in Shandong Province, China. It is an altered-rock type gold deposit in which ore bodies mainly occur at the contact zone between the overlying Cretaceous rocks and the underlying Neoarchean gneissic monzogranite. Shi et al. reported that this deposit formed at 96 ± 2 Ma using pyrite Rb–Sr dating method and represents a new gold mineralization event in the Shandong Province in 2014. In this paper, we present new He–Ar–S isotopic compositions to further decipher the sources of fluids responsible for the Longquanzhan gold mineralization. The results show that the δ³⁴S values of pyrites vary between 0.9‰ and 4.4‰ with an average of 2.3‰. Inclusion-trapped fluids in ore sulfides have ³He/⁴He and ⁴⁰Ar/³⁶Ar ratios of 0.14–0.78 Ra and 482–1811, respectively. These isotopic data indicate that the ore fluids are derived from a magmatic source, which is dominated by crustal components with minor mantle contribution. Air-saturated water may be also involved in the hydrothermal system during the magmatic fluids ascending or at the shallow deposit site. We suggest that the crust-mantle mixing signature of the Longquanzhan gold deposit is genetically related to the Late Cretaceous lithospheric thinning along the Tan-Lu fault zone, which triggers constantly uplifting of the asthenosphere surface and persistent ascending of the isotherm plane to form the gold mineralization-related crustal level magma sources. This genetic model can be applied, to some extent, to explain the ore genesis of other deposits near or within the Tan-Lu fault belt.

【 授权许可】

Unknown