Multi-Phase Hydrothermal Fluid Events in the Giant Lannigou Gold Deposit, SW China: Insights from Calcite Sm–Nd Age, Trace Elements, and C-O-Sr Isotopes
Author:
Li Piyou12ORCID, Hu Yuzhao12ORCID, Tian Zhendong3, Guan Shenjin12ORCID, Fan Huijun4
Affiliation:
1. Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, China 2. South-West Institute of Geological Survey, Geological Survey Center for Nonferrous Metals Resources, Kunming 650093, China 3. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China 4. The First Gas Production Plant, PetroChina Changqing Oilfield Company, Jingbian 718500, China
Abstract
The Nanpanjiang basin hosts the world’s second-largest concentration of Carlin-type gold deposits. To decipher the origin and evolution of hydrothermal fluid, this study conducted Sm–Nd dating, in-situ trace element, and C-O-Sr isotopic analyses on three types of calcite samples from the giant Lannigou gold deposit in the Nanpanjiang basin, SW China. The type-I calcite, intergrown with Au-bearing arsenian pyrite, has an Sm–Nd isochron age of 213 ± 7 Ma (MSWD = 0.81), indicating that gold mineralization occurred in Late Triassic. The type-II calcite, which coexists with high-maturity bitumens and cut through the main-stage gold orebodies, yields an Sm–Nd age of 188 ± 14 Ma (MSWD = 0.34), representing a post-ore hydrocarbon accumulation event. The type-I and type-II calcite samples have low REE contents (5.28–51.6 ppm) and exhibit MREE-enriched and LREE-/HREE-depleted patterns. Combined with their identical C-O-Sr isotopes, we suggest that hydrothermal fluids responsible for the precipitation of type-I and type-II calcite samples were derived from a mixed metamorphic fluid and meteoric water source. In contrast, the type-III calcite samples, associated with realgar and orpiment, have distinct Mn, Sr, and As contents, REE patterns, and C-O-Sr isotopic composition from the type-I and II calcites, suggestive of different fluid sources. Based on our and previously published data, we propose that the fluid evolution, gold mineralization, and hydrocarbon accumulation in the Nanpanjiang basin are closely related to the Indosinian and Yanshanian orogenies in South China.
Funder
National Natural Science Foundation of China Entrusted Project of China Gold Group Jinfeng Mining Co., Ltd.
Subject
Geology,Geotechnical Engineering and Engineering Geology
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