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The Jianshan banded iron formation (BIF) is embedded in Paleoproterozoic strata. The Jianshan BIF can be divided into oxide and silicate facies. The former consists mainly of quartz and magnetite, and the latter contains hornblende and actinolite. Geochemical analyses of the Jianshan BIF show that Al2O3 and TiO2 are quite scarce with no significant correlation, and the contents of incompatible elements and transition metal elements are low, indicating negligible involvement of terrigenous clastics during the deposition. The rare earth element (REE) curves reveal depletions in light REE, enrichments in heavy REE, and positive La, Y, and Eu anomalies, suggesting that the material source was a mixture of submarine hydrothermal fluid and seawater. Although the Ce anomalies are unobvious, the decoupling of Th and U and below-crustal Th/U ratios resulting from the oxidation of U4+, as well as the enrichment of heavy Fe isotopes, imply a rapid rise of oxygen content shortly after the Great Oxidation Event. The Jianshan BIF might deposit in a redox-stratified ocean. It might be an important possibility for the Jianshan BIF that Si deposition is likely attributed to oversaturation caused by a temperature drop of Si-rich hydrothermal fluids and that Fe deposition is probably due to rapid oxidization in the upper oxygenated layer of the redox-stratified ocean. [ABSTRACT FROM AUTHOR]

K-feldspar–quartz vein-type Au deposits, represented by the Hadamengou super-large Au deposit, are widely developed in the Archean high-grade metamorphic terrane in the western segment of the northern margin of the North China Craton. However, the formation processes of these Au deposits have long been debated, and their genetic relationship with magmatic activity remains unclear. In this study, by examining the geological and geochemical characteristics of the Hadamengou Au deposit and several related intrusions, we find that the Au–(Mo) mineralization system may be related to Indosinian alkaline magmatic activity. The Dongshadegai and Xishadegai intrusions, which are related to the formation of the Hadamengou Au deposit, formed in an Indosinian extensional tectonic environment, and both are characterized by high silica and alkaline contents and strong oxidizing properties, indicating that the parent magmas of these intrusions were capable of dissolving and transporting metallic elements during magma formation and evolution. The Indosinian Hadamengou Au deposit contains minerals such as magnetite and barite, and the H, O, S and Pb isotopic characteristics of this deposit indicate that the ore-forming fluids originated from magmatic–hydrothermal fluids and had oxidizing properties. These observations suggest the presence of an oxidized intrusion-related Au–(Mo) mineralization system in the studied metamorphic terrane. [ABSTRACT FROM AUTHOR]

Three NE-striking zoned polymetallic ore districts were found at the transition between the Shanhaiguan-Beizhen paleo-uplift and the Liaoxi depression at the midway point of the northern margin of the North China Plate. Although these deposits are located proximal to one another, they are metallogenic different and closely associated with the granite intrusions, and Au, Pb-Zn, and Mo are the major ore-forming elements. This paper investigates the rock/ore rare earth elements and trace elements and part of the whole-rock major elements of the Wenzhangzi Au-polymetallic deposit in western Liaoning Province. The results indicate that the andesite, granodiorite, and Au-rich polymetallic ore-forming fluids in the deposits exhibit the same crustal origin and closely associated with the Archean Au-rich crystalline basement. Granodiorite in the area tends to show a transition from quasi-aluminous to peraluminous → S-type granite, whereas the closely associated granite in the Yangjiazhangzi-Lanjiagou Mo metallogenic district is a differentiated I-type granite. These granites differ in age, with the former emplacing during the Mesozoic tectonic regime transition period and the latter emplacing during the intra-plate extrusion-uplift orogeny. [ABSTRACT FROM AUTHOR]