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Zircon U-Pb dating and stable isotopic compositions for constraining the genesis of the Chagangnuoer magnetite deposit in western Tianshan, NW China

Citation

Hong, W and Zhang, Z and Baker, MJ and Jiang, ZS and Duan, S, Zircon U-Pb dating and stable isotopic compositions for constraining the genesis of the Chagangnuoer magnetite deposit in western Tianshan, NW China, Ore Geology Reviews: Journal for Comprehensive Studies of Ore Genesis and Ore Exploration, 121 Article 103478. ISSN 0169-1368 (2020) [Refereed Article]

Copyright Statement

© 2020 Elsevier B.V. All rights reserved.

DOI: doi:10.1016/j.oregeorev.2020.103478

Abstract

The Chagangnuoer magnetite deposit in western Tianshan (NW China) is hosted by submarine volcanic rocks and marble lens, with a resource of >220 Mt Fe at 38 wt%. Two major orebodies FeI and FeII are current in production. Pervasive garnet skarn, magnetite, actinolite–epidote, and marble zones are developed at Chagangnuoer. Paragenetic sequences are divided into garnet–pyroxene (I), magnetite–pyrite ± chalcopyrite (II), actinolite–epidote–K-feldspar (III), garnet ± tremolite ± scapolite (IV), magnetite ± hematite (V), actinolite–epidote (VI), and sulfide–calcite–quartz (VII) stages. A diorite beneath the FeII and a granodiorite with skarn alteration have zircon U-Pb ages of 329 ± 2 and 317 ± 4 Ma, respectively. These intrusions have high potassic to shoshonitic, metaluminous affinities, and significant Nb, Ta, Ti and Sr anomalies. Stage II magnetite has δ18OV-SMOW compositions of 1.9–3.5‰, higher than Stage V magnetite (0.5–2.1‰), indicating a hydrothermal fluid source of magmatic origin. The δ18O values of garnet, actinolite, epidote and quartz range from 4.1 to 12.2‰. Stage VII calcite has δ13CV-PDB of −2.0 to −0.8‰ and δ18O of 8.9 to 9.9‰, lower than for the marble (average δ13C + 2.3‰, δ18O 12.8‰). δ34SV-CDT compositions for pyrite and chalcopyrite from Stages II and VII vary between 0.8 and 13.1‰. The isotopic compositions imply that minor non-magmatic sources (e.g., marine carbonate, seawater, and meteoric water) have been circulated into hydrothermal fluids producing the skarn alterations and associated iron mineralization. The early-stage skarn alteration and main Fe mineralization relate to the emplacement of diorite stock at depth, whereas the late-stage skarn-magnetite assemblages are intimately associated with the granodiorite. The Chagangnuoer deposit is concluded to be magnetite skarns formed by magmatic-hydrothermal fluids that emanated from the dioritic and granodioritic magmas intruding above a sub-arc mantle wedge and that metasomatized intensely with the Carboniferous andesitic-rhyolitic volcanic rocks and carbonate.

Item Details

Item Type:Refereed Article
Keywords:Volcanic-based Fe deposit, iron skarn, stable isotopes, Awulale Iron Metallogenic Belt, Western Tianshan
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and metamorphic petrology
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Mineral exploration
Objective Field:Mineral exploration not elsewhere classified
UTAS Author:Hong, W (Mr Wei Hong)
UTAS Author:Baker, MJ (Dr Michael Baker)
ID Code:151830
Year Published:2020
Web of Science® Times Cited:1
Deposited By:CODES ARC
Deposited On:2022-08-05
Last Modified:2022-09-08
Downloads:0

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