T100 Fundamental Insights from Field and Laboratory Studies Related to the Genesis and Ore-Forming Processes Associated with Granitoid Generation and Evolution to Their Related Alteration and Mineralization

Tuesday, 27 October 2020
5:30 PM - 8:00 PM
Meeting Rooms

TRACE ELEMENTS AND ISOTOPES OF SULFIDES IN PB-ZN ORES FROM LAOCHANG DEPOSIT, GEJIU DISTRICT, YUNNAN, CHINA: EVIDENCE FOR THE EXISTENCE OF EXHALATIVE SEDIMENTARY MINERALIZATION

Paper number: T100-3
Program: Technical Sessions
Time: 6:00 PM – 6:15 PM

Authors

  • Yuehua Zhao Presenting Author
    No.388 Lumo Road, Hongshan District, W School of Earth Resources, Wuhan
  • Shouyu Chen
    China University of Geosciences (Wuhan), Wuhan

Abstract

Laochang deposit is one of the important parts of the world-class Gejiu Sn-polymetallic deposit. Although there are many papers have been published to explain the ore genesis, controversy still exists. In this paper, the major and trace elements and S isotope of sphalerite and S, Pb isotopes of galena have been analyzed to explain the genesis of stratiform Pb-Zn ore. The Zn, S and Fe concentrations of sphalerites range from 44.51%~59.71%, 31.08%~33.06% and 6.33% ~18.90%, respectively, indicating that the sphalerite is marmatite. Trace elements exhibit that Fe, Mn, Cu, Ga, Cd and Sn are enrichment while Co, Ni, Ge, As, Ag, In, Sb and Pb are poor in the Laochang sphalerite. Time resolved laser ablation profiles reveal that Fe, Mn, Ga, Cd, In, As, Co and Ni are mainly present in solid solution or as nanoscale inclusions and Cu, Ag, Sb, Pb and Sn are present in both solid solution and mineral inclusions. The Cd concentrations, Zn/Cd and Ga/In ratios indicate that ore-formation temperature belongs to medium-high temperature. The sphalerite is rich in Ga and poor in Ge, which is similar to the SEDEX deposit Dabaoshan and Bainiuchang.

The measured δ34S values for sphalerite range from 0.8‰ to 3.7‰, while the galena δ34S values are between -1.2‰ and 0.3‰. The sulfur isotope compositions indicate that S has the characteristics of the sulfur of deep-seated magma source. The Pb isotopic compositions of galena yield 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values from 18.400 to 18.445, 15.656 to 15.694, and 38.478 to 38.968, respectively, indicating an upper crustal lead source with a little addition of mantle lead source. So, we conclude that the Laochang Pb-Zn deposit is of submarine exhalation sedimentary origin.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-350533

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.