This paper is the result of mineral exploration engineering.

Objective The Permian Cihai magnetite deposit produced in the Beishan area of Xinjiang is significantly different from the mafic-ultramafic rock bodies and deposits dominated by copper-nickel sulfides in the East Tianshan and Beishan area in the same era. Its unique geological characteristics and the uncertainty of the metallogenic mechanism have become the focus of attention in the geological community. This paper aims to deeply explore the metallogenic process and evolution history of the Cihai magnetite deposit.

methods Conduct systematic analysis and testing of in-situ major and trace elements of pyroxene, magnetite, ilmenite, and apatite in the Cihai magnetite ore, and carry out comprehensive research.

results As magnetite crystallizes, FeO, MgO, and Mg# of symbiotic pyroxene show continuous evolution, indicating that magnetite has undergone a gradual crystallization and separation process; the trace element distribution patterns of magnetite in Cainan and Cihai are almost the same and there is a transitional evolution, showing that it has undergone a continuous evolution process, further proving that magnetite is formed by gradual crystallization; for apatite in ore-bearing pyroxenite, its ΣREE has a good correlation with (Gd/Lu)_N, (La/Yb)_N and (La/Nd)_N, and the content of trace elements changes continuously, reflecting the crystallization differentiation trend of magma, also indicating that magnetite has undergone crystallization and separation; the formation temperature of magnetite is about 1100℃; a small number of melt inclusions (rich in Fe and rich in Si) with distinct compositions were identified in apatite within ore-bearing pyroxenite.

Conclusions The magnetite mineralization in the Cihai mining area is dominated by magmatic fractional crystallization, with local occurrence of liquid immiscibility..