2 D29. Investigations in Economic Geology

Sunday, 22 October 2017
8:00 AM - 12:00 PM
Skagit 5

N2-RICH FLUID IN THE VEIN-TYPE YANGJINGOU SCHEELITE DEPOSIT, YANBIAN, NE CHINA

Paper number: 2-6
Program: Technical Sessions
Time: 9:15 AM – 9:30 AM

Authors

Abstract

High nitrogen contents in geological environments are generally observed in nitrate deposits. However, in this study, nearly pure N2 (TN2 (L) =-151.2～-167.8℃, T(V)-~150.3℃) fluid inclusions were identified in W-mineralized quartz veins at the Yangjingou scheelite deposit, east of Yanbian area in NE China. Other fluid inclusion populations identified include N2–CO2, NaCl–H2O±N2 and CO2±N2-NaCl-H2O fluid inclusions; no hydrocarbon components were detected. The host rocks consist of the Wudaogou group metamorphic series and the lithology is mainly Ca-rich mica. Subhedral sulfides occur in early disseminated W-mineralization quartz veins, or have partially replaced early scheelite. ThN2 and ThN2-H2O values indicate that N2 fluid trapping P-T ranges from 315℃ to 410℃ and 80 MPa to 350 MPa. O and H isotope data suggest that mineralizing fluids were composed of mixed magmatic and metamorphic water and the δ15N values of N2-rich inclusions indicate that fluid-rock interaction occurred within a metamorphic environment. The nitrogen-rich fluid is closely associated with scheelite precipitation. During thermal decomposition and fo2-increase, which occurred synchronously with retrograde metamorphism and magmatic activity, large amounts of N2 has liberated from NH4+ bearing micas, which accumulated in quartz scheelite veins.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-301306

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