Neoarchean Banded Iron Formations in the North China Craton: Geology, Geochemistry, and Its Implications

2016 ◽  
pp. 85-103
Author(s):  
Lianchang Zhang ◽  
Changle Wang ◽  
Mingtian Zhu ◽  
Hua Huang ◽  
Zidong Peng
Keyword(s):  
North China Craton ◽  
North China ◽  
Banded Iron Formations ◽  
The North ◽  
Iron Formations

Geochemical studies of banded iron formations (BIFs) in the North China Craton: a review

2017 ◽  
Vol 21 (6) ◽  
pp. 971-983 ◽  
Author(s):  
Inkyeong Moon ◽  
Insung Lee ◽  
Jung Hun Seo ◽  
Xiaoyong Yang
Keyword(s):  
North China Craton ◽  
North China ◽  
Banded Iron Formations ◽  
The North ◽  
Geochemical Studies ◽  
Iron Formations

Meso- and Neoarchean Banded Iron Formations and Genesis of High-Grade Magnetite Ores in the Anshan-Benxi Area, North China Craton

2017 ◽  
Vol 112 (7) ◽  
pp. 1629-1651 ◽  
Author(s):  
Yanpei Dai ◽  
Yudi Zhu ◽  
Lianchang Zhang ◽  
Mingtian Zhu
Keyword(s):  
North China Craton ◽  
North China ◽  
Regional Metamorphism ◽  
High Grade ◽  
Banded Iron Formations ◽  
Nd Isotope ◽  
The North ◽  
Metamorphic Fluids ◽  
Iron Deposits ◽  
Iron Formations

Abstract The Anshan-Benxi area in the North China craton has numerous occurrences of Algoma-type banded iron formations (BIFs) with subordinate high-grade magnetite ores. These ores provide insight into iron metallogenesis and early evolution of the North China craton. In this paper, we present Sm-Nd-Fe-O isotope, mineralogical, and structural data for four BIF-type iron deposits to place constraints on their depositional ages and formation mechanism. Previous SIMS and LA-ICP-MS zircon U-Pb dating results indicated a Mesoarchean age (ca. 3.10 Ga) for the Dagushan BIF and a Neoarchean age (ca. 2.55 Ga) for other regional BIFs (Dai et al., 2012, 2013, 2014). This is confirmed by Sm-Nd isochron ages of these BIFs, high-grade magnetite ores, and host metavolcanics, which yield two regression lines and match apparent ages of 3149 ± 85 Ma (MSWD = 1.2) for Dagushan, and 2671 ± 120 Ma (MSWD = 3.0) for the other three deposits. Our new chronological data thus suggest Meso- and Neoarchean BIF deposition and potentially significant BIF-type iron deposits at depth. The regional high-grade magnetite ores are all hosted in the BIFs that occur in the same orientation and have transitional boundaries between them. They also show similar Sm-Nd isotope compositions and magnetite rare earth elements + yttrium (REY) profiles, indicating that the Anshan-Benxi BIFs were most likely the source beds. The high-grade magnetite ores contain abundant pyrite and actinolite, with systematically lower δ56Fe values (0.67–0.40‰) when compared to the BIFs (1.88–0.64‰), suggesting a hydrothermal origin. In the field, some high-grade orebodies with schistose textures are adjacent to undeformed granitic plutons. This geologic relationship implies that the high-grade magnetite ores were formed earlier and probably did not result from magmatic hydrothermal fluids. Therefore we suggest that the Anshan-Benxi high-grade magnetite ores were most likely produced by infiltration of metamorphic fluids into primary BIFs, based on the following: (1) magnetite δ18O values within the high-grade magnetite ores (+2.5 to −0.6‰) are significantly lower than those in the BIFs (9.2–2.6‰); (2) magnetite (avg 0.39 ppm) and pyrite (avg 0.098 ppm) in the high-grade magnetite ores have much lower REY abundances than magnetite in the BIFs (avg 14.6 ppm); (3) skeletal quartz in the high-grade magnetite ores shows systematically higher FeOtolal contents (1.36–0.56 wt %) than those in laminated chert bands (0.06–0.00 wt %); and (4) hydrothermal zircons within the Nanfen BIF yield a U-Pb age of 2480 Ma, which is comparable to ca. 2.48 Ga regional metamorphism (Zhu et al., 2015). Furthermore, microstructural textures indicate a maximum regional deformation temperature of up to 500°C, which is lower than the plastic flow temperature (>600°C) of magnetite. Finite strain measurements and electron backscatter diffraction analyses suggest a general flattening deformation and similar crystallographic preferred orientation for all magnetite crystals. These structural features reveal that magnetite in the high-grade magnetite ores never experienced a separate tectonic event. Our microscopic studies also show that microfractures at the interfaces of BIF bands contain fragmented quartz crystals and are filled with abundant metamorphic minerals (e.g., actinolite and chlorite). Considering that the Anshan-Benxi high-grade magnetite ores are commonly adjacent to weak structural planes (e.g., faults), we propose that macro- and microscopic fractures probably provided channels for metamorphic fluids. Recent zircon U-Pb geochronology has indicated widespread BIF formation at ca. 2.55 Ga in the North China craton, corresponding to a pronounced peak in BIF deposition of other Precambrian cratons. It is thus implied that a global geologic event triggered the extensive occurrence of BIFs. We correlate the Neoarchean tectonic evolution of the North China craton with the 2.7 to 2.5 Ga Kenorland supercontinent. Significantly, planar distribution signatures of the North China craton BIFs indicate ca. 2.5 Ga cratonization through the amalgamation of at least seven microblocks that were welded by several Neoarchean greenstone belts. Hf-Nd isotope studies have highlighted the Archean episodic crustal evolution of the North China craton, and the Meso- and Neoarchean BIF deposition could have benefitted from these geologic processes. The Anshan-Benxi high-grade magnetite ores that formed at ca. 2.48 Ga were closely related to important metamorphic events during the North China cratonization process.

Neoarchean tectonics: insight from the deformation of the Archean basement of North China Craton

2020 ◽  
Author(s):  
Yongjiang Liu ◽  
Jing Li ◽  
Weimin Li ◽  
Sanzhong Li ◽  
Liming Dai
Keyword(s):  
North China Craton ◽  
Tectonic Evolution ◽  
North China ◽  
Shear Zones ◽  
Banded Iron Formations ◽  
The North ◽  
Detailed Structural Analysis ◽  
Ductile Shear Zones ◽  
Ductile Shear ◽  
Iron Formations

<p>The controversy over the Archean tectonic regimes has lasted several decades focusing around horizontal and vertical tectonics, the two classical tectonic models for Archean times. Thus, more studies of the early crustal growth and tectonic evolution are requisite for better understanding geodynamic regimes in the early Precambrian. The North China Craton is one of the major Archean to Paleoproterozoic cratons in the world and oldest craton in China, which preserves a large amount of ancient basement and abundant structures showing the early earth tectonics.</p><p>In this study, we have carried out detailed structural analysis of two down-slip ductile shear zones which developed in eastern Anshan area and provided an example for revealing of Neoarchean vertical tectonics in the study area. There were also develop many structures of dome and keel style in the North China Craton, such as Qian ’an, Qingyuan areas.</p><p>Based on abundant structural evidence and previous studies, we infer that the vertical tectonics is still the dominant model for Neoarchean crust growth and tectonic evolution in Anshan area. The formation of dome and keel structure, and the deformation of the down-slip ductile shear zones may have resulted from the sagduction of the banded iron formations and synchronous Archean granite dome emplacement, supporting a vertical tectonic regime in Archean times.</p>

Precambrian banded iron formations in the North China Craton: Silicon and oxygen isotopes and genetic implications

2014 ◽  
Vol 57 ◽  
pp. 299-307 ◽  
Author(s):  
Yanhe Li ◽  
Kejun Hou ◽  
Defang Wan ◽  
Zengjie Zhang ◽  
Guoliang Yue
Keyword(s):  
Oxygen Isotopes ◽  
North China Craton ◽  
North China ◽  
Banded Iron Formations ◽  
The North ◽  
Iron Formations

The mineralogy, mineral chemistry, and origin of the Wuyang banded iron formations, North China Craton

2019 ◽  
Vol 328 ◽  
pp. 111-127 ◽  
Author(s):  
Hong-Zhong Li ◽  
Jin Liang ◽  
Fei Yang ◽  
Ming-Guo Zhai ◽  
Lian-Chang Zhang ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Mineral Chemistry ◽  
Banded Iron Formations ◽  
Iron Formations

Neoarchean Algoma-type banded iron formations from Eastern Hebei, North China Craton: SHRIMP U-Pb age, origin and tectonic setting

2014 ◽  
Vol 251 ◽  
pp. 212-231 ◽  
Author(s):  
Chunming Han ◽  
Wenjiao Xiao ◽  
Benxun Su ◽  
Zhengle Chen ◽  
Xiaohui Zhang ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Tectonic Setting ◽  
Banded Iron Formations ◽  
Iron Formations
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