Geochronology and Ore Genesis of the Niujuan-Yingfang Pb-Zn-Ag Deposit in Fengning,Northern North China Craton:Constraints from Fluid Inclusions,H-O-S Isotopes and Fluorite Sr-Nd Isotopes

• 来源期刊: 地球科学学刊（英文版）
• 年，卷（期）: 2021,（1）
• 所属期刊栏目: Special Colume on Mesozoic Magmatism,Gold Mineralization and Deep Exploration in East China
• 页码范围: 81-102
• 页数: 22页
• 语种: 英文

摘要

The Niujuan-Yingfang Pb-Zn-Ag deposit in northern North China Craton(NCC)is hosted at the contact zone between Permian biotite monzogranite and Hongqiyingzi Group migmatitic gneiss.The orebodies are structurally controlled by NE-trending F1 fault.Mineralization can be divided into three stages:(1)siliceous-chlorite-pyrite stage,(2)quartz-Ag-base metal stage,and(3)fluorite-calcite stage.Four types of fluid inclusions were identified,including:(1)liquid-rich aqueous inclusions,(2)vapor-rich inclusions,(3)liquid-rich,solid-bearing inclusions,and(4)CO2-bearing inclusions.Mi-crothermometric measurements reveal that from stage I to III,the homogenization temperatures range from 317 to 262 ℃,from 297 to 192 ℃,and from 248 to 151 ℃,respectively,and the fluid salinities are in the ranges from 1.1 wt.％to 6.5 wt.％,1.2 wt.％to 6.0 wt.％and 0.7 wt.％to 4.0 wt.％NaCl equiva-lents,respectively.Fluid boiling and cooling are the two important mechanisms for ore precipitation according to microthermometric data,and fluid-rock interaction is also indispensable.Laser Raman spectroscopic analyses indicate the fluid system of the deposit is composed of CO2-NaCI-H2O±N2.Me-tallogenic fluorites yielded a Sm-Nd isochron age of 158±35 Ma.The δ34SV-CDt values of sulfides range from-1.3％o to 6.3％o,suggesting that the sulfur may be inherited from the basement metamorphic ig-neous rocks.Hydrogen and oxygen isotopic compositions of quartz indicate a metamorphic origin for the ore-forming fluid,and the proportion of meteoric water increased during the ore-forming processes.Sr-Nd isotopes of fluorites show a crustal source for the ore-forming fluid,with primary metamorphic fluid mixed with meteoric water during ascent to lower crustal levels.Combined with the geological,metallogenic epoch,fluid inclusions,H-O-S and Sr-Nd isotopes characteristics of the deposit,we suggest that the Niujuan-Yingfang deposit belongs to the medium-low temperature hydrothermal vein-type Pb-Zn-Ag polymetallic deposit,with ore-forming fluids dominantly originated from metamorphic fluids.