Yaqu Intrusion In Hualong Qinghai: Petrogenesis And Mineralization And It's Structural Response

Riyue-Hualong ultrabasic rocks lies in the southern part of Qilian orogenic belt. Since the th late 70s of 20th century, after we found the Lashuixia copper-nickel sulfide deposit, this region has become the focus of domestic and foreign geologists. In Riyue-Hualong rock band, Yaqu rock is more representative. This paper according to systematically research the petrography, crystal chemistry, rare earth elements, trace elements and S and Re-Os isotopic geochemistry of Yaqu rock body, scientifically demonstrates its magmatic process, magma nature and mantle source district features. Based on these researches we get some initial understanding as follows:1. The Yaqu intrusion is mafic-ultramafic rocks,the main rock types are amphibole gabbro-norite, quartz diorite, biotite gabbro, the quantity of ultrabasic rock is few, the main ore-bearing rocks are gabbro-norite and diorite, each lithofacies is the result of mineral crystal by the same source magma; the main rock-forming minerals are pyroxene, plagioclase, hornblende and biotite.2. The REE partitioning pattern is LREE enrichment, the Eu anomaly is a distinct negative, and enriches LILE, correspondingly depleted HFSE.3. The magma source is enriched mantle, and the source matter is composed by metasomatic lithosphere mantle matter. Its formation age is 440.74±0.33 Ma.4. A majority of magma which forms the rock body is not the primary magma, it mainly composed by different evolution degree magma, When the magma is in the course of rising it should be hybridized a little by the crust substance. The S isotop,Re-Os isotope geochemical character and petrochemical data show that crustal contamination and the fractionation of pyroxene and Plagioclase in the magma revolution process of Yaqu intrusion and the accession of silicon-rich crustal rock composition may be the main factors leading to S-saturation and sulfide segregation in deep crust.