Although volcanogenic massive sulfide (VMS) deposits always form in extensional settings, many have been reworked by metamorphism, deformation, and the circulation of hydrothermal fluids during subsequent accretionary events. The genesis of VMS deposits has been well documented, however, the mechanisms that rework the mineralization have been relatively poorly constrained. An understanding of these mechanisms, though, is critical to the development of robust mineral deposit models as they are capable of remobilizing ore-forming metals. The Xitieshan Pb–Zn deposit, located in Qinghai Province, western China, is the third largest Pb–Zn deposit in China, with a total Pb–Zn metal reserve of 6.4 million tons. The occurrence of laminated and non-laminated orebodies in the Xitieshan deposit make it an ideal candidate to i) constrain the effects of metamorphic and hydrothermal processes on remobilization of metals in these base-metal systems, and ii) assess the genetic nature of this deposit. This is accomplished here by integrating new S isotope data and trace-element chemistry of sulfides from laminated ores with previous information on regional and deposit geology, and deformation characteristics preserved by the mineralized system. The S isotope composition of pyrite and sphalerite grains from laminated ores are consistently positive and range from 2.08 ‰ to 5.81 ‰, indicative of mixing of reduced sulfur from three distinct sources — volcanic rocks, seawater and thermochemical reduced sulfate, which is typical of VMS deposits globally. Greigite (Fe3S4) grains in laminated ores exhibit oscillatory zonation with respect to Cu, Co, Mn, Sb, and Tl concentrations; such compositional variations indicate that at least some of the primary VMS mineralization characteristics have been preserved despite subsequent reworking by metamorphism, deformation, and hydrothermal circulation. Combined with the results of previous studies, a two-stage genetic model is proposed for the formation and modification of the Xitieshan Pb–Zn deposit — i) initial formation of the primary Pb–Zn mineralization with minor of Cu, and ii) subsequent metamorphism and hydrothermal reworking of the deposit, which did not completely destroy the textural and chemical characteristics of the primary mineralization.

Trace element

Ore genesis

δ34S

genetic model

Base metal

10.1016/j.oregeorev.2022.105103

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Updating the Geologic Barcodes for South China: Discovery of Late Archean Banded Iron Formations in the Yangtze Craton

Scientific Reports (2017)

Hui Ye Chang–Zhi Wu Tao Yang M. Santosh Xizhu Yao

Abstract Banded iron formations (BIFs) in Archean cratons provide important “geologic barcodes” for the global correlation of Precambrian sedimentary records. Here we report the first finding of late Archean BIFs from the Yangtze Craton, one of largest Precambrian blocks in East Asia with an evolutionary history of over 3.3 Ga. The Yingshan iron deposit at the northeastern margin of the Yangtze Craton, displays typical features of BIF, including: (i) alternating Si-rich and Fe-rich bands at sub-mm to meter scales; (ii) high SiO 2 + Fe 2 O 3total contents (average 90.6 wt.%) and Fe/Ti ratios (average 489); (iii) relative enrichment of heavy rare earth elements and positive Eu anomalies (average 1.42); (iv) and sedimentary Fe isotope compositions (δ 56 Fe IRMM-014 as low as −0.36‰). The depositional age of the BIF is constrained at ~2464 ± 24 Ma based on U-Pb dating of zircon grains from a migmatite sample of a volcanic protolith that conformably overlied the Yingshan BIF. The BIF was intruded by Neoproterozoic (805.9 ± 4.7 Ma) granitoids that are unique in the Yangtze Craton but absent in the North China Craton to the north. The discovery of the Yingshan BIF provides new constraints for the tectonic evolution of the Yangtze Craton and has important implications in the reconstruction of Pre-Nuna/Columbia supercontinent configurations.

Banded iron formation

Supercontinent

Protolith

Rodinia

10.1038/s41598-017-15013-4

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Citations (33)