首页|Age and genesis of the Lamahanshan Ag-Pb-Zn deposit, southern Great Xing'an Range, northeastern China: Constraints from sphalerite Rb-Sr dating, fluid inclusions and H-O-S-Pb isotopes
Age and genesis of the Lamahanshan Ag-Pb-Zn deposit, southern Great Xing'an Range, northeastern China: Constraints from sphalerite Rb-Sr dating, fluid inclusions and H-O-S-Pb isotopes
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NSTL
Elsevier
The Lamahanshan deposit in the eastern Central Asian & nbsp;Orogenic Belt & nbsp;(CAOB) is a newly-discovered Ag-Pb-Zn vein deposit in the southern Great Xing'an Range (GXR). Vein-type Ag-Pb-Zn orebodies are mainly hosted in the & nbsp;fracture zones & nbsp;of gneissic & nbsp;plagiogranite,& nbsp;granite & nbsp;porphyry, and quartz porphyry.& nbsp;Mineralization & nbsp;comprises four stages: (I) quartz-magnetite, (II) quartz-pyrite-chalcopyrite, (III) quartz-polymetallic & nbsp;sulfides, and (IV) quartz +/-& nbsp;sphalerite. Sphalerite Rb-Sr dating yielded an isochron age of 137.7 & nbsp;+/-& nbsp;6.1 & nbsp;Ma, coeval with the regional Late Jurassic-Early Cretaceous Pb-Zn polymetallic mineralization. Three types of & nbsp;fluid inclusions & nbsp;(FIs), namely vapor-rich two-phase (LV-type), liquid-rich two-phase (VL-type), and daughter mineral-bearing three-phase (SL-type), are distinguished at Lamahanshan. Stage I and II contain all FI types with homogenization temperatures (T-h) of 383-418 & nbsp;degrees C and 350-392 & nbsp;degrees C and & nbsp;salinities & nbsp;of 0.9-38.1 & nbsp;wt% and 0.7-35.0 & nbsp;wt%, respectively, whereas stage III contain VL- and LV-type FIs with T-h & nbsp;=& nbsp;318-349 & nbsp;degrees C and salinity & nbsp;=& nbsp;0.7-10.5 & nbsp;wt%. Only VL-type FIs occur in stage IV, with T-h & nbsp;of 271-320 & nbsp;degrees C and salinities of 4.3-7.8 & nbsp;wt%. The microthermometric and H-O isotope data (delta O-18(H2O)& nbsp;=& nbsp;-9.4 to 0.9 parts per thousand and delta D & nbsp;=& nbsp;-137.0 to -124.7 parts per thousand) indicate that the ore-forming fluids were initially magmatic with later & nbsp;meteoric water & nbsp;incursion. Fluid boiling, cooling, fluid-rock reactions, and meteoric water mixing were the major ore precipitation mechanisms at Lamahanshan. The sulfide S (delta S-34 & nbsp;=& nbsp;4.0-6.7 parts per thousand), Sr ((Sr-87/Sr-86)(i)& nbsp;=& nbsp;0.698957-0.700069), and Pb (Pb-206/Pb-204 & nbsp;=& nbsp;17.230-18.193,& nbsp;Pb-207/Pb-204 & nbsp;=& nbsp;15.440-15.627, and & nbsp;Pb-208/Pb-204 & nbsp;=& nbsp;37.664-38.407) isotopes also support that the metals were magmatic-derived. Integrating the available geological, mineralization, fluid inclusion, and H-O-S-Sr-Pb isotope evidence, we propose that the Lamahanshan deposit shares many similar features with distal magmatic-hydrothermal vein-type ores, and was formed in an extensional setting related to the & nbsp;Early Cretaceous & nbsp;Paleo-Pacific & nbsp;subduction & nbsp;rollback.
Central Asian Orogenic BeltGreat Xing'an RangeLamahanshan Ag-Pb-Zn depositFluid inclusionH-O-S-Sr-Pb isotopesPORPHYRY MO DEPOSITLEAD-ZINC VEINSINNER-MONGOLIAU-PBORE GENESISNE CHINAPOLYMETALLIC DEPOSITSTABLE-ISOTOPERE-OSGEOCHEMICAL CHARACTERISTICS
NSTL
Elsevier
