The Lalingzaohuo molybdenum polymetallic deposit in the Qimantage metallogenic belt of Qinhai Province is a newly discovered skarn-por- phyry type deposit. Detailed studies on petrology, geochronology and element geochemistry of the granodiorites suggest that they are associated with the porphyry-type mineralization. The results show that： the age of porphyritic granodiorite is 242.6 ±3.4Ma, and the age of the peripheral fine-grained granodiorite is 250.4 ±4.0Ma. This may suggest they are multi-phase intrusions. The mineralization age is in agreement with porphyritic granodiorites. Major and trace elements analysis shows that the ore-bearing granodiorites belong to high-K calc-alkaline to shoshonitic series, I-type with crust-mantle source which has experienced significant fluid metasomatism. Field investigations show a large number of dark xenoliths contained in the Trassic grano- toids, with the evidence of magma underplating and mixing. In the middle Triassic, this area was just in the conversion stage from the oceanic subduction to collision orogeny in Eastern Kunlun, which can explain the fluid metasomatism and enrichment of the source region. The mechanism of crust-mantle mixing should be assciated with the subducted slab breaking. Delamination of the oceanic crust is a quick active process which coincides with the geolog- ical fact of the outbreak of the Triassic magmatism. At the same time, the mineralization intrusions show the characteristics of crust-mantle mixing sources and a higher degree of differentiation, which are the favorable conditions for molybdenum mineralization.
