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LA-MC-ICP-MS U-Pb dating of low-U garnets reveals multiple episodes of skarn formation in the volcanic-hosted iron mineralization system, Awulale Belt, Central Asia

Yan Shuang, Renjie Zhou, Niu Hecai, Yuexing Feng, Ai Duc Nguyen, Zhao Zhenhua, Yang Wubin, Dong Qian and Jianxin Zhao
LA-MC-ICP-MS U-Pb dating of low-U garnets reveals multiple episodes of skarn formation in the volcanic-hosted iron mineralization system, Awulale Belt, Central Asia
Geological Society of America Bulletin (October 2019) 132 (5-6): 1031-1045

Abstract

Volcanic-hosted iron deposits of the eastern Awulale metallogenetic belt in Central Asia possess a reserve of over 1.2 billion tons of iron ores and constitute one of the most important basements for high-grade iron resources in China. Skarns are widespread in these deposits and closely associated with iron mineralization. The ages of these skarns are unclear, and their genesis remains debated, preventing further investigation into their metallogenic processes. We focused on garnets in nine ore-bearing skarns from three large-scale iron deposits (Chagangnuoer, Dunde, and Beizhan) in the eastern Awulale belt. U-Pb dating was conducted on these garnets using our in-house reference material, the Taochong garnet (TC-13, Pb-Pb isochron age: 126.2+ or -2.3 Ma, initial (super 207) Pb/ (super 206) Pb ratio: 0.845+ or -0.022). Laser-ablation-multicollector-inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) was employed in the garnet U-Pb dating, and high-precision U-Pb ages (0.3%-1.6%) were obtained, highlighting the advantages of LA-MC-ICP-MS in dating low-U minerals. The garnet U-Pb ages of the nine skarn samples fall into three groups, i.e., 329.0+ or -5.1 to 326+ or -3.3 Ma (2 samples), 316.3+ or -2.9-311.2+ or -2.4 Ma (6 samples), and 295.6+ or -1.0 Ma (1 sample), implying three episodes of skarn alteration in the volcanic-hosted iron mineralization system. The first and second episodes of skarns formed as a result of contact metasomatism between coeval volcanic rocks and limestone, and they have economically important iron mineralization. The third was likely caused by a local postcollision granitic intrusion, but its metallogenic potential deserves further assessment.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 132
Serial Issue: 5-6
Title: LA-MC-ICP-MS U-Pb dating of low-U garnets reveals multiple episodes of skarn formation in the volcanic-hosted iron mineralization system, Awulale Belt, Central Asia
Affiliation: Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, Key Laboratory of Mineralogy and Metallogeny, Guangzhou, China
Pages: 1031-1045
Published: 20191014
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 72
Accession Number: 2019-095257
Categories: Economic geology, geology of ore depositsGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2019339
Illustration Description: illus. incl. 3 tables, geol. sketch maps
N43°08'60" - N43°19'60", E84°22'00" - E85°05'60"
Secondary Affiliation: University of Queensland, AUS, AustraliaBeijing Research Institute of Uranium Geology, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201950
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