Genesis and geological significance of sulfide bearing mafic enclaves and host syenite in Heishishan, East Kunlun: Evidence from geochronology, mineralogy, geochemistry and Sr-Nd-Hf isotopes

The Heishishan copper polymetallic deposit is located in Wulonggou area, middle part of the Eastern Kunlun Orogen Belt. Mafic microgranular enclaves (MMEs) are developed in quartz monzonite-syenite in the mining area, and sulfide is found in the MMEs. Zircon U-Pb dating of the syenite yields magmatic crystallization ages of 239.4 +/- 1.0Ma. The syenite samples are rich in Si and K, but depleted in Mg, Cr and Ni, and have obvious negative Eu abnormality, and enriched in large ion lithophile elements, and depleted in the high field strength elements. Furthermore, the syenite samples have enriched Sr-Nd-Hf isotopes. The MMEs are composed of plagioclase and amphibole, and amphibole cumulus crystal can be seen. The MMEs are characterized by depleted in Si, but rich in calcium, aluminum, alkali and iron. The Mg-# value of MMEs is 38.37. The MMEs have obvious Eu negative abnormality, weak fractionation of light and heavy rare earth elements. Combined with the similarity of mineral composition and petrographic characteristics of host syenite and MMEs, we believe that the MMEs and syenite come from the same magma chamber and belong to cognate origin MMEs. The MMEs are early separated crystallization phase of magma chamber, which were carried up to syenite melt by intermediate-acidic dike and emplaced into the shallow crust together. Based on geochemistry, isotopes and mineral composition, it is considered that syenite is the products of partial melting of water-bearing mafic rocks in the lower crust under low pressure. Sulfide is developed in the MMEs, and the sulfur content of the MMEs magma is much higher than that of the syenite magma, indicating that the early separated crystallization phase of the magma chamber took away the sulfur, making the sulfur content of the residual melt lowe