243 D2. Economic Geology (Posters)

Wednesday, 7 November 2018
9:00 AM - 6:30 PM
Halls J-K

GEOLOGY, RE-OS AND U-PB GEOCHRONOLOGY AND SULFUR ISOTOPE OF THE DONGGEBI PORPHYRY MO DEPOSIT, XINJIANG, NW CHINA, CENTRAL ASIAN OROGENIC BELT

Paper number: 243-6
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Donggebi porphyry Mo deposit in the eastern section of the Eastern Tianshan Orogenic Belt in the Central Asian Orogenic Belt contains Mo metal reserves of 0.5 Mt. The deposit is hosted in Early Carboniferous metasedimentary rocks, namely; metasandstone, meta-sandy mudstone . Multiple hydrothermal activities have resulted in propylitic, phyllic, and argillic alteration in this deposit. Four stages (I-IV) of hydrothermal activity are identified. Stage I is represented by a mineral assemblage of K-feldspar, quartz and wolframite. Stage II consists of quartz + magnetite+pyrite ± chalcopyrite veinlets/veins with phyllic halos. Stage III consists of quartz + molybdenite + pyrite ± galena ± sphalerite ± chalcopyrite veins that are commonly related to phyllic alteration in the altered rocks. Stage IV has an assemblage of calcite+gypsum. Molybdenite mainly occurs in Stages III. Re-Os dating results for molybdenite samples from these two stages yielded an isochron age of 234.2 ± 1.6 Ma (2σ, MSWD = 0.25, n = 8). Porphyritic granites have a SIMS U-Pb zircon age of ∼236 Ma and it was probably related to the Triassic felsic magmatism in this area. Values of δ34S of sulfides range from 1.5‰ to 3.8‰, with an average value of 2.81 ± 2.24‰ (n = 22), reflecting a deep sulfur source. Most molybdenite samples have high δ34S values (≥3.36‰) relative to other sulfide minerals (i.e., pyrite and chalcopyrite) of Stages I to III (δ34S = 1.5–3.8‰, n = 18). Based on the geological history and spatial-temporal distribution of the granitoids, it is proposed that the Mo deposits in the eastern part of the East Tianshan Orogenic Belt formed in a post-collision extensional setting in the Early Mesozoic.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-317545

© Copyright 2018 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.