Metallogenic epoch of the Xiarihamu magmatic Ni-Cu sulfide deposit in eastern Kunlun orogenic belt and its prospecting significance

Abstract：The superlarge Xiarihamu magmatic Ni-Cu sulfide deposit is located in eastern Kunlun orogenic belt of Qinghai Province. The study of its mineralization, lithology, geodynamic mechanism and tectonic setting is very important for further prospecting breakthrough in eastern Kunlun orogenic belt. This paper discusses the tectonic setting of the mineralization in Xiarihamu magmatic Ni-Cu deposit through the dating of Xiarihamu mafic-ultramafic intrusion, and further indicates the prospecting significance and potentiality of eastern Kunlun region. Most magmatic sulfides were found in peridotites and pyroxenites through drilling, and the Ni-bearing ultramafic intrusion orebody is different from the gabbro in the formation time. The zircon U-Pb ages of barren olivine-pyroxenite from Xiarihamu ultramafic intrusion drilling core are 412.9±1.8 Ma（MSWD=1.2）and 410.9±1.6 Ma（MSWD=3.1）, about 20 Ma younger than the age of gabbro. It is revealed that parent magma had the island arc magma characteristics, as shown by systematic olivine composition and Fo value study of Xiarihamu ultramafic intrusion drilling core samples. Based on these data, together with the age of eclogite in this region, the authors preliminarily hold that the magma source of Xiarihamu ultramafic intrusion had the characteristics of eastern Kunlun island arc. There occurred sulfide immiscibility of silicate magma with the upwelling of the partial melting magma, and the differentiated magma intruded into the structurally weak location of post collision in eastern Kunlun orogenic belt and formed the superlarge Xiarihamu magmatic Ni-Cu deposit. The crustal contamination of S played a very important role in forming the Ni orebody. This understanding is of great prospecting significance and research value for mineralization evaluation and potentiality exploration around other mafic-ultramafic intrusions in eastern Kunlun orogenic belt.