Temporal-spatial structure of shallow magma reservoir of giant porphyry metallogenic system——Evidence from 3000 m scientific deep drilling at Jiama deposit,Xizang
In recent years,the deep dynamic mechanism,magma evolution and ore source of porphyry system at colli-sion setting have been deciphered clearly,but the fine geological structure and evolution of shallow magma reser-voir(3～5 km)and its constraint mechanism on porphyry mineralization are still obscure.Here,take the Jiama gi-ant porphyry system in Xizang as an example,based on the 3000 m scientific deep drilling,and detailed core log-ging,to reveal the geological information of shallow magma reservoir at the Jiama porphyry system.At the same time,based on the crosscutting relationship of different intrusions and geochronology,the spatiotemporal struc-ture of the shallow magma reservoir of this metallogenic system is finely defined.Then,a multipulsed evolution model of magma chamber in the Miocene(～15 Ma)is established.Zircon SIMS U-Pb dating indicated that the dark quartz diorite porphyry emplaced at(14.9±0.1)Ma,slightly later than emplacement of the monzogranite por-phyry(15.534 Ma)and granodiorite porphyry(15.368 Ma).Its alteration and mineralization suggest that it is an important ore-forming intrusion.Finally,based on the temporal and spatial framework,mineralization and altera-tion characteristics of different intrusions in shallow magma reservoirs,as well as the widespread mafic micro-granular enclaves,abundant feldspar antecrysts and dissolution texture of quartz phenocryst in intermediate-felsic intrusive dykes,it is confirmed that there exist multiple magmatism,multiple hydrothermal evolution or continu-ous mafic magma feeding in the Jiama porphyry metallogenic system,and these process is the key factors control-ling copper polymetallic mineralization.
magma reservoirtemporal and special structureporphyry metallogenic systemJiamaXizang
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