Mineralization characteristics and controlling factors of key metals of Re, Se, and Te in the Bainaimiao Cu-Au-Mo deposit, northern margin of North China Craton

Porphyry copper deposits are the most important source of critical minerals such as Re, Se, and Te. The Bainaimiao Cu-Au-Mo deposit is located in the eastern segment of the Central Asian Orogenic Belt (CAOB). The northern ore section exhibits porphyry-type alteration and mineralization characteristics, while the ore bodies in the southern ore section mainly occur as stratiform-like layers within the country-rock greenschist. There has long been debate regarding the genetic type of the Bainaimiao deposit. Through in-situ component analysis of different types of sulfides such as pyrite and chalcopyrite, combining with previous data and literatures, we propose that the Bainaimiao belongs to a porphyry deposit modified by later orogenic processes. The high Re content in molybdenite from the Bainaimiao deposit (109–1051 ppm, average of 627 ppm) may be controlled by factors likely its relatively low oxygen fugacity and the incorporation of terrigenous sedimentary components in the magma source. Chalcopyrite from different ore sections have high Se contents, averaging ca. 100 ppm, indicating that chalcopyrite is the primary host mineral for Se. The enrichment of Se is mainly achieved through coupled substitution between S 2 ⁻ and Se 2 ⁻. Tellurium concentrations are relatively low, primarily entering the chalcopyrite lattice as bismuth-tellurium mineral inclusions, which may be related to crustal contamination or the lack of competitive sulfides during Cu mineralization. Porphyry copper deposits in the CAOB have significant potential for mineralization of dispersed elements such as Re, Se, and Te. Future efforts should focus on study of mineralization processes and the comprehensive utilization and recovery of these key metal elements.