| Xiariduo rockbody is located at the most northern section of Yulong porphyry copper (molybdenum) belt or Xiariduo-Mamupu porphyry copper bet, and lies in the middle of Sanjiang tectonic zone, which belongs to the eastern region of Tethys-Himalayan tectonic domain, and is the turning parts of the construction line-from the EW to NS trending. Its special tectonic position makes Xiariduo rockbody has a metallogenic background.The main rock types are biotite-feldspars porphyry and quartz diorite porphyrite. The alteration of wall rock is mainly of K-silicate alteration, quartz-sericite alteration, skarnized, and propylitization. There are two types of dark enclaves, which are rich hornblende and biotite-rich. Two types of dark rim of enclaves are the result of the basic magma mixing with the host magma in different states:liquid and solid. An estimate of the equilibrium temperature of feldspars in the host rocks and the enclaves are790K and913K, and the geobarometer analysis of the hornblende shows2.01kbar, the hornblende’s equilibrium temperature calculated by the hornblende-plagioclase geothermometer is989.5K. This pressure is equivalent to the emplacement depth of7.92km. The biotite is magnesia mica, and its chemical composition shows a trend towards phlogopite. The biotite’s chemical composition also shows it originated from mantle, and this mantle source with the feature of high alkaline. The hornblende’s chemical composition show it belongs to magncsiohornblende, and also originated from mantle, but some hornblende has the features of metasomatic genesis. The inclusions in the rockbody with a wide range of homogenization temperature, and different types of inclusions show the feature of low salinity and multi-stages.According to the geochemical characteristics, the Xiariduo rockbody belongs to shoshonite series, and is characterized by high potassium and alkali richment, and has high CaO and MgO content, but with low content of CaO and TFeO. The rock has a lower content of REE, but enrich in LREE content, and with week negative Eu and Ce. This suggests the rock inherites the geochemical features of upper-mantle, but experience fluids metasomatism and contamination with crustal material, this also reflects that K-feldspar is not the magma source of K-rich mineral phase. In trace elements, the rock is rich in LILE, also has a high ration of Rb/Sr and Zr/Hf, but low in Ti/Eu and Ba/Rb ratio, this shows that the K-rich mineral phase in magma source is phlogopite, not the hornblende, and the source region have undergone the metasomatism by carbonate fluids. The Xiariduo rockbody also show some affinities with the adakite, but does not have the typical chemical composition of the adakite rock. The rock also has the characteristics of I-type granites, this also confirm that the magma is not only the product of partial melting of mantle material, but also experience the contamination with the crustal rocks and fluids metasomatism.Comparing the characteristics of petrography, mineralogy, geochemical, enclaves and inclusions of Xiariduo rockbody with ore-bearing porphyry in Yulong porphyry metallogenie belt, we can learn that the magma origin from low degree melting of the magnesia mica veins in mantle lithosphere, and experience the metasomatism of silicate-carbonate fluids and the hybridism of the melts, which are releasing from the subducted oceanic crust. Xiariduo rockbody were formed in continent-continent collisional setting. India-Asia continental’s relative sliding after the main collison formed a regional-scale strike-slip fault system along Jinsha River, and basin’s sinking and the mantle’s rising induced partial melting of the metasomatized lithospheric mantle, then emplaced in shallow crust and diagenesis, This is the petrogenic mechanism of the ore-bearing porphyry in Yulong porphyry metallogenic belt.It is showed by analysis and study for the metallogenetic specialization of the porphyry in Yulong porphyry metallogenic belt that Xiariduo rockbody has the same characteristics with the ore-bearing porphyry in Yulong brlt, and has significant differences with barren porphyry. And the rockbody has the potention of forming porphyry Mo(Cu) deposits. The "dirty" porphyry that discovered in the deep of Xiariduo rockbody is rich in metals, and may be the parent mineralization magma. This also indicates that the deep of the Xiariduo rockbody may be the the main ore bodies zone andy has the potention of the small intrusions to form large deposits, which provides a practice and reference with a certain theoretical basis for further ore prospecting of the intrusion. |
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